Genotype environment interactions and genetic parameters in New Zealand Romney sheep : a thesis submitted for the degree of Doctor of Philosophy at Massey University, New Zealand

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(2) GENOTYPE-ENVIRONMENT INTERACTIONS AND GENETIC PARAMETERS IN NEW ZEALAND ROMNEY SHEEP. A t he s i s submi t t ed f o r the d e g r ee o f. Doc t o r o f P h i l o so phy at Ma s s ey Un iv e r s i t y New Z e a l and. SUBHASH CHANDER CHOPRA. 1 978.

(3) ii .. ABSTRACT. P e r forman c e r e cords o f 1 , 1 1 3 New Zealand Romney ewe hogge t s f rom two sub f locks ma i n t a ined on con t ro l (CSR) and i n t ens ive (HSR) s t o ck in g r a t e s were ana lysed .. The d a t a r e p r e s e n t e d the progeny o f 34 s i r e s and. we r e co l l e c t e d b e tween 1 9 6 7 and 1 9 74 inclus ive wh ich cove r ed four cons e c u t ive two-year s i re p e r iods .. The t r a i t s inve s t i ga t ed were hogge t l ive-we i gh t ( HLW ) , greasy f le e c e we igh t ( GFW) , c l ean wo o l we ight per un i t a rea (WA) , c l ean s c oured y i e ld (Y) , s t a p l e length ( SL ) , me an f i b re d i ame t e r (MFD ) , s t andard d e v i a t ion of the f ibre d i ame t e r ( S FD ) , qua l i t y numb e r (QN ) , c r imp s p e r c e n t ime ter ( CP C ) , t o t a l cr imp numb e r (TCN ) , char a c t e r ( CHG ) , t i p p in e s s ( T G ) , hand l e ( HG ) , lus t r e (LG ) , greasy co lour (GCG) , s c oured c o l o ur ( S C G ) , d i s c o l oured area ( DAG ) , cot t i ng (CG) , co t t ed area ( CAG ) and s oundn e s s ( SG ) . S tocking r a t e had s i g n i f icant e f f e c t on a l l the t ra i t s exc e p t ing MFD , SFD , TCN and HG .. H S R depre s s ed the t r a i t s inve s t iga t e d excep t i ng. Y , S FD , QN , CPC , HG , GCG , S CG , CG and CAG . w e r e an imp o r t a n t source o f va r i a t ion . e x c e p t on. l�W,. SFD , CHG and HG was sma l l .. Year e f f e c t s exc e p t in DAG. The inf luence o f b i r t h- r ank S t ocking r a t e x year. i n t e ract ions except in CPC , TCN , CHG , TG , HG , GCG and CAG we re imp o r t an t .. S i r e x s t o c k i n g r a t e in t e rac t ions we re s i gn i f i c an t in HLW ,. MFD , SFD , TCN and GCG only , whe r e a s s i r e x y ear i n t e r a c t ions we re s i gn i f icant in HLW , GFW , HG and SCG . S ire x s t ocking r a t e and s i r e. x. year i n t e r a c t ions we re i n c l uded in. d i f f e rent way s in some f o rmu lae for c a l c u l a t ion of he r i t ab i l i t y e s t ima t e s . The s e e s t ima t e s we re c a l cu l a t ed f rom p a t e rn a l h a l f - s i b analy s e s in C S R ,.

(4) iii .. The various e s t ima t e s f o r t h e d i f fe rent t ra i t s. HSR and comb ined d a t a .. we r e i n the f o l l owing ranges : H LW 0 . 2 1 - 0 . 7 2 , y. GFW 0 . 3 8 - 0 . 6 1 ,. WA 0 . 3 1 - 0 . 4 9 , 0 . 87 ,. 0 . 53 ,. SL 0 . 54 - 0 . 6 3 ,. MFD 0 . 3 4. S FD 0 . 3 5 - 0 . 6 6 ,. QN 0 . 4 6 - 0 . 7 2 ,. CPC 0 . 4 8 - 0 . 8 8 ,. TCN 0 . 6 5 - 1 . 0 9 ,. CHG 0 . 2 4 - 0 . 3 4 ,. TG 0 . 1 3 - 0 . 2 7 ,. HG 0 . 2 3 - 0 . 6 6 ,. LG 0 . 3 2 - 0 . 4 2 ,. GCG 0 . 2 2 - 0 . 4 4 ,. 0 . 19. SCG 0 . 1 0. -. --'. 0 . 39 ,. DAG 0 . 04. 0. 21 ,. CG 0 . 1 2. -. 0 . 67 ,. S G 0 . 00 - 0 . 2 2 .. CAG 0 . 1 8 - 0 . 53 ,. No s i gn i f i cant d i f f e renc e s b e t tve en the e s t ima t e s in the two s t o cking r a t e s exc e p t in CG and SG were ob s erved . t h e s e comp a r i sons. iS. The r e l evance o f. d i s cu s s e d i n t e rms o f s i re x s t ocking r a t e and. s ir e x year int erac t ion s .. In t ra- t r a i t gene t i c c o r r e l a t i ons be tween t h e two s t oc king r a t e s w e r e c l o s e t o un ity exc e p t in HLW ( P < 0 . 0 5) ;. Y , SFD , GCG , SCG ( 0 . 0 5< P < 0 . 1 ) .. Gene t i c c o r r e l a t ions b e twe en t r a i t s we re cal c u l a t e d by the p a t e rnal h a l f - s ib me thod .. The c o r r e lat ion coe f f i c i e n t s sugge s t t h a t t h e HLW. s e le c t ion r e s u l t s in h i gh e r f l e e c e we igh t , longer s t ap l e s , b e t t e r f l e e ce charac t e r , inc r e a s e d va r i a t ion i n f ib r e d i ame t e r , h i ghe r q ua l i ty S e l e c t ion f o r f l e e c e we igh t would. numb er and c r imp ing and mo r e lus t re .. r e s u l t in longer s t ap l e s , less cot t ing and less s u s c e p t Jb i l i t y to b r e ak and increased mean f ib r e d i ame t e r .. Co r r e l a ted re s p on s e s exp e c t ed w i t h. s e l e c t ion f o r f ineness a r e reduced s t ap l e leng t h , more c o t t ing an d l e s s s ound wo o l .. S e l e c t ion ·fo r TCN resul t s in f avourab le changes in H LW ,. GFW , TG , co t t ing , co lour and soundn e s s .. Favourab l e changes in y ie l d ,. c r imp ing , d i s c o loured area are exp e c t ed f o l l owing s e l e c t ion f o r whi t ene s s o f a mid s ide samp l e , whe r e a s GFW could d e c l ine ..

(5) iv .. App l i c a t ion s o f the r e s u l t s are d i s c u s s ed w i t h par t i cu l a r re f erence t o the role p l ayed by s i re. x. s t o cking r a t e and s i re. x. year i n t e ra c t ions. in the gene t i c imp roveme n t of cha r a c t e r s of economic imp o r t an c e in New Zea l and Romney sheep ..

(6) v.. AC KNOWLEDGEMENTS. I t is with s p ec i a l gra t i t ud e that I acknow l ed ge my s up e rvi s o r s , Pro f e s s o r A.L . Rae and Dr G . A . Wi c k h am f o r t h e i r immense h e l p , cons t an t encouragement , c on s t ruc t ive c r i t i c i sm and able coun s e l t hroughout t h e course o f this s t udy and t he p r eparat i o n o f t h i s t h e s i s .. G ra t e f ul a cknowled gement i s made t o t h e s t a f f o f Sheep Husb and ry Dep a r t men t and No . l Sheep Farm , Mas sey Un ive r s i t y who were invo lved wi t h t h e c o l l e ct ion o f t he d a t a u s e d .. Thanks are due t o Mr R . P . Lewe r , Mr A . B . P l easan t s and Mr C . J . Dodd f o r the i r as s i s t ance dur i n g t he p e r i o d of comp u t er f ami l i a r i z a tion . They and o t he r c o l l e agu e s and fe l l ow s t uden t s h ave p rovided a sou r c e o f s t imu l a t ing d i s cuss ion o n many o c c a s i ons .. S incere t hanks are due t o Mr s A . F . Barton for ski l l f u l ly typ i n g t h e manus c r ip t .. I wish t o exp r e s s my utmo s t app r e c i a t ion and s p e c ia l t hanks to my w i f e , Re e t a f o r provid i ng t h e i n s p i r at ion .. Wi thout her r e s o l u t e. s up p o r t and encouragement t he t a sk may neve r have b e en comp le t ed . The a f f e c t ion r e c e ived f rom t he Chopra and Varma f ami l i e s encouraged me in the a c c omp l i shmen t of t h i s t a s k .. Th i s the s i s wa s made p o s s ib l e t h rough the awar d o f a C ommonwe a l t h S ch o larship .. The grant o f s t udy leave by the Ind i an Coun c i l o f. Agr i cu l t u r a l Re search i s g r a t e fu l ly acknowl edged ..

(7) v i.. T ABLE O F CONTENT S Chap t e r ii. AB STRACT AC KNOHLEDGEMENTS. V. L I ST OF T ABL ES. X. L I S T OF F I GURES. xii. ONE. INTRODUCTION. 1. TWO. REVIEW CF. 4. LITERATURE. CLAS S I F I C AT IONS OF GENOTY P E- EN V I RONMENT INTERACTIONS FALCONER ' S CONC EPT OF GENET I C CORRELAT I ONS BETWEEN P ERFORMAN C E IN DIFFERENT ENV I RONMENTS Exp e r ime n t a l ev i d e n c e f o r Fal coner ' s c o n c e p t GENOTYPE- ENVIRONMENT INTERAC T I ON S IN SHEEP. 12 13 20. Growth charac t e r is t i cs. 21. C ar c as s ch a r a c ter i s t ics. 29. F l e e ce chara c ter i s t i c s. 32. Re p roduc t ive t r a i t s i n O t hers GENET I C PARAMET ERS. THREE. 4. ewes. 41 45 46. He r itab i l it y. 4 fi. Gene t i c c o r r e latio n s. 60. GEN ERA L CONCLUSIONS. 78. SOURCE OF DATA. 79. THE D AT A. 81.

(8) v i i.. TAB LE. OF. CONTENTS. (continued). Chap t e r. FOUR. STATI STICAL HETHODS. 86. PRESENCE OF INTERACT I ON. 86. ANALY S I S OF VA RIAN C E. 88. Le ast s q u a r e s and computing methods. 88. F i t t i ng models t o the data. 90. Es t imat i on o f mean s quare s , variance and covarian c e components. 96. LEAS T SQUARES E S T IMATES. 98. POOL ING OF TH E S I RE GRO UP P E RIODS ANALY SES. 98. PART I T I ONING THE VARIAT ION. 99. VARIANCE CO NPONEN T ESTH1ATES. 99. GENET IC P A RANETERS. FIVE. 101. H e r i t ab i l it y. 10 1. Gene t i c c o r r e l a t io n s. 103. RESULTS AND. DISCUS SION. E S T I NATES OF NON- GENET I C FACTORS , I NTERACT I ON S AND VARIANCE C ONPONENTS. 1 05. 105. Ho gge t l i ve -we i gh t. 1 10. Greasy f l e e c e w e i g h t. 115. Clean w o o l we i g h t p e r un i t a r ea. 1 18. Clean s c o u r e d y i e l d. 1 20. S t ap l e l e n g t h. 12 1. Me an f ib r e diame t e r. 124. S t anda r d d e via t i on o f t h e f i b r e d i ame t e r. 125. Qua l i ty number. 127. C r imp s per c e n t ime t e r. 128. To t al c r imp numb e r. 1 30.

(9) vi i i .. TABL E O F CONTENTS ( c on t inued ) Chap t e r Charac t e r grade. 131. T i p p i ne s s grade. 1 34. Hand l e grade. 135. Lus t re grade. 1 37. Greasy c o lour grade. 138. Scoured colour gr ade. 140. D i s c o l o ured area g r ade. 14 1. Co t t in g grade. 143. Co t t e d a rea grade. 144. Soundne s s grade. 146. HER ITAB I L I TY ESTIMATE S , INTRA-TRAIT GENETI C CORRELAT IONS AND INTERAC TION VARIANC E COMPONENTS. 148. Ho g ge t l ive-we i gh t. 152. Greasy f l eece we i gh t. 155. C l e an woo l we i gh t p e r u n i t area. 1 56. C l e an s c oured y i e l d. 15 7. S t a p l e l en g t h. 158. Me an f i bre d i ame t e r. 159. S t andard dev i at ion o f the f i bre d i ame t e r. 161. Qual i t y number. 162. C r imp s p e r ce nt ime t e r. 163. To t a l c r imp numb e r. 1 64. Chara c t e r grade. 165. T i p p i ne s s grade. 1 67. Han d l e grade. 168. Lus t r e grade. 169. Greasy c o lour grade. 1 70. S c o u red c o lo u r g r ad e. 171. D i s c o l o u red area grade. 172. Cot t ing grade. 173. Co t t ed area grade. 1 74. S o undne s s grade. 1 76. INTER-T RA I T GENET I C C ORRELATION S. 177.

(10) ix.. TABLE. (continued). Cha p t e r SIX. OF CONTENTS. CONCLUDING DISCUSSION ON PRACTICAL U1PLICATIONS. BIBL10GRAPHY. 185. 1 94.

(11) x.. LIST OF TABLES Table 1. 2. 3. 4. 5. Some published estimates of heritability of live-weight, wool quantity and quality traits in s heep. 48. Some published estimates of genetic correlations between various characteristics for live-weight, wool quantity and quality in sheep. 64. Combined stocking rate analysis. Calculation of reductions in sums of squares and expectations of mean squares. 94. Within s tocking rate analysis. Calculation of reductions in sums of squares and expectations of mean squares. 95. Percentage of total variance attributable to each factor for each variable from the combined stocking rate analysis pooled from the different Sire group periods. 106. 6. Least squares estimates and standard errors of environmental effects for HLW and GFW. 111. 7. Least squares estimates and standard errors of environmental effects for WA and Y. 119. 8. Least squares estimates and standard errors of environmental effects for SL and MFD. 1 22. Least squares estimates and standard errors of environmental effects for SFD and QN. 126. Least squares estimates and standard errors of environmental effects for CPC and TCN. 1 29. Least squares estimates and standard errors of environmental effects for CHG and TG. 132. Least squares estimates and standard errors of environmental effects for HG and LG. 1 36. Least squares estimates and standard errors of environmental effects for GCG and SCG. 139. Least squares estimates and standard errors of environmental effects for DAG and CG. 142. Least squares estimates and standard errors of environmental effects for CAG and SG. 145. 9. 10. 11. 12. 13. 14. 15.

(12) xi.. OF TABLES ( continued ). LIST Table 16. Heritability estima t es o f v a r ious tra it s. analyses by diffe ren t. 17. Intr a-trait gene t ic erro r s o f t r ait s. 18. t raits. me t h o d s. 14 9. co r rela t ions a n d s t anda rd. in two s t o cking rates. Gene t ic c o r relatio n s various. and standard er ro r s. o b t a ined f r o m t he p o oled. and s t anda rd e r r o r s. from the pooled analysis. v a r iance and covariance. 151 among of. 178.

(13) xii.. LIST OF FIGURES. T i t le. Fig.. 1. 2. (A, B) x enviro nmen t (X, Y ) int er ac t ions as sugge s t ed by Haldane ( 19 4 6) (af t e r McBride, 1 9 5 8 ). Illu s t ra t io n of geno t yp e. Typ e s of heredit y x environment int erac t io n (af t er Dunlop,. 3. 5. 9. 19 62). A cla s s ific a t io n of geno t yp e x environment int e r a c t io n s. s pec ially de signed for. animals, s t udies. (af t e r Pani,. 19 71). use in farm. 11.

(14) 1.. CHAPTER ONE. INTRODUCT I ON. Geno ty pe-envi ronme n t i n t e r a c t ion ( GE l ) o c curs wheneve r a chan ge f rom one envi ronme n t to ano ther resul t s in d i f f e r en t e f f e c t s on the geno t y p e s i n the popula t ion .. Thus if changing f rom environment 1 to. environment 2 add s 10 un i t s t o one geno type and 15 un i t s t o ano the r , GEl w i l l be presen t .. GEl imp l i e s that genotypic and envi ronme n t a l. e f f e c t s a r e no t ad d i t ive , i . e . , i n s t ead o f being able to a s s ume that a t r a i t x i s t he sum o f a geno t y p i c component and an environmen t a l compon e n t , i t i s ne c e s s a ry to ad d an e f f e c t due to the j o int i n t e ra c t i o n The p r esence o f GEl could r e s u l t in a. o f gen o t yp e and envi ronmen t .. change o f ranking o f the anima l s or at le a s t in the ma gni tude o f t h e i r d i f fe r en c e s .. The l a t t e r t ype w i l l bri ng a chan ge o f he r i t abi l i t y and. so w i l l i n f luence e f f e c t ivene s s o f s e l e c t i o n .. Th i s leaves no doubt. that p l anning o f a b reeding p rogramme depe n d s o n the magn i t ude of GEl as we l l as the e s t ima ted val ues o f o t he r gen e t i c p arame t e r s .. A maj o r p rob lem o f p rac t i c a l imp o r t ance posed by the p o s s i b l e. p re s en c e o f GEl is the cho i ce o f envi ronme n t a l c ond i t ions un d e r wh i ch t o p r a c t i c e s e le c t ive b r e e d in g . b reeder has t o de c ide. In p l an n ing a s e le c t io n p r o gramme , a. the envi ronmental c i r cums t an c e s und e r wh ich. the p ro gramme is conduc t e d .. Th i s is a very imp o r t an t d e c i s ion wh ich. b e c ome s mo r e c r i t ical as the range o f envi ronments in wh ich the imp roved s to c k are used comme r c ial ly , in c r e a s e s .. Should t h e breeder subj e c t t h e an imals among wh i ch s e le c t i on i s t o b e made t o a ' good ' environme n t wh i ch give s maximal exp r e s s i o n t o t h e d e s i red cha r a c t e r o r shou l d he rat h e r sub j e c t them t o c o nd i t ions , whe ther.

(15) 2.. ' go o d ' o r ' b ad ' und e r wh ich the imp roved g enotype i s des t ined sub s e q uen t l y t o l ive and p e r f o rm?. Fa l c on e r ( 1 9 5 2 ) and F a l c oner and. Lat y s z ewski ( 1 9 5 2 ) have d i scussed s ome a s p e c t s o f the gene r a l p rob l em o f env i r onmen t and s e l e c t ion .. In p a r t i c u l a r they have c r i t i c i z e d views ,. e xp r e s s e d by Hammond ( 1 9 4 7 ) , that env i ronmen t a l condi t ions i f un f avourab l e , w i l l p r ove t o b e a fac t o r l imi t in g the r e s ponse t o se l e c t io n .. In t he New Ze aland Romney b r e e d , i t is common for r am- b r e e d ing f l o cks t o b e l o c a t ed in areas of favourable env i ronme n t a l cond i t ions whe re rams are s e l e c t ed and bred und e r adequate leve l s of nu t r i t ion and in above-ave r a ge husbandry and manageme n t t o a l l ow h i gh individual· pe r fo rmanc e t o b e achieved ( S t evens ,. 1946;. Rae , 1 9 6 4 ) .. The p ro geny. of t he r ams b re d in t he s e f l ocks , however , are exp e c t e d to p roduce s a t i s f a c t o r i l y over a wide range of environme n t al cond i t io n s , usually much l e s s f avourab l e than t ho s e o f t h e ram-breeding f locks .. In a farming. sys t em wh ich r e l i e s on pas ture f e e d i n g , chan g ing the s t o cking r a t e is the maj o r me thod b y wh ich the lev e l of n u t r i t ion supp l ied to the sheep can be var ied .. The r e fo r e , as long as the c u rrent sys t em o f s e l e c t ion o f. b reed ing r ams rema ins in p r a c t i c e , t here i s an obvious n e e d t o inve s t i ga t e the imp a c t o f geno t y p e o f s i r e s x s t o cking r a t e and o th e r imp o r t an t i n t e r a c t ions on the e f f e c t ivene s s o f selec t ion .. C le a r l y , i f n ut r i t iona l. l eve l s f lu c t ua t e v i o lent ly , as t h e y do , f rom low s to cking r a t e s t o h i gh s t ocking r a t e s and i f t he r e are imp o r t an t geno type o f s i r e s x s to cking r a t e i n t e r a c t ions , the e f f e c t ivene s s o f s e l e c t ion may be s eve r e l y p re j u d i ce d .. L i t t l e c r i t i c a l in f o rmat ion is ava i l ab l e on the impo r t ance. o f t he s e in t e r a c t ions in sheep and on woo l t r a i t s .. The p urpo s e o f t h i s s t ud y was to inves t ig a t e t he p o s s ib le in t e r a c t ions b e twe en the geno t y pe s o f s i res w i t h in t he New Zeal and Romney b re e d o f sheep and d i f f e re n t levels o f s tocking r a t e .. Thus, the wo rk.

(16) 3.. was p rimarily c o ncerned with detecting and evaluating the r o le played by the sire x stoc king rate inter a c tions with regard to the str u c tu r e of h er itability estimates i n hogget live-weight, clean wo o l weight per unit a rea, mean fibre diameter, number,. c r imps per. h andle,. lustre,. greasy fleece weight,. clean s c o u r ed yield,. staple length,. standa rd deviation o f the fibre diameter,. c entimeter,. greasy c o lour,. total c rimp number, sco ured c olour,. c otted area and so undness o f wo o l.. c h a r a c ter,. quality tippiness,. discolo ured a rea,. c o tting,. S ir e x year inter actio ns were also. c o nsidered.. In o rder to. o btain information and assess the p r a c ti c a l implications. of the observed inter a c tions under investigation,. the estimation of th e. genetic p ar ameters and some environmental effects was co nsidered to be necessary.. As an outline of the sc o p e of the thesis,. th ree major. top ics may be mentioned.. 1.. Estimation of no n-genetic f a c to rs and inte r a c tion effects on e a c h. char a c ter so th a t th e a p p r o p riate adjustment of. the. data fo r the differences in the known environmental fa c to r s a n d inter a c tions c a n be made p rio r t o the genetic studies of v a riation and cova riation.. 2.. Estimation o f herita bility estimates in different sto cking r a tes and of intratrait genetic. c o r relations to p r ovide. statistical evidenc e of sire x stoc king r a te inter a c tions in the flo c k under study.. 3.. Estimation of inter-trait genetic. c o r relations to describe. what other c h a r a cters a r e likely to change in futu r e gener ations i f o ne p a rtic ula r. c h a r a cter i s under selection..

(17) 4.. CHAPTER TWO. REV I E\.J OF LITERATURE. CLAS S IF ICAT IONS OF GENOTYPE- ENVIRONMENT INTERACTION S C l a s s i f i c a t ions o f GEl have b e en made b y Ha ldane ( 1 9 4 6 ) , Ma t h e r and Jones ( 1 9 5 8 ) , Mc B r ide ( 1 9 5 8 ) . Dun l o p ( 1 9 6 2 ) , Pan i ( 1 9 7 1 ) a n d o t hers . A t t e mp t s have been made by s eve ra l wo rke r s t o t ake into a c c oun t the e x t e n t of the change s i n rank ing o f the s a me genotypes in d i f f e r en t env i ro nmen t s and t h e s i ze o f the d i f f e r en c e s between the envi r onment s and b e tween the ge ne t i c e f f e c t s .. Hald ane ( 1 9 4 6 ) c l as s i fied the GEl wh i ch may o c c u r when gen o t y p e s d i f f e r ing a t. a. s in g le locus are exposed t o c o n t r a s t i n g environmen t s .. Con s i de r ing two geno t yp e s (A , B) a nd two envi ronme n t s ( X , Y ) a s an examp l e , he tabu l a t e d s ix d i f f e r e n t t y p e s of inte r a c t ions w i th the c r i t e r ion that gen o t y p e rank .. A. in a n envi ronment X has a lway s the h i ghes t. He gave no a t t e n t ion t c the types o f d i f f erences b e tween the. envi ronments and b e tween geno types . are p r e s e n ted graph i c a l ly in Fig .. The s i x types o f in t e ra c t i o n s. 1.. _Ma t he r and Jon e s ( 1 9 5 8 ) de s c r ibed t h e d i f ferenc e s a mo n g t h e f o u r phen o types g iven b y two genotypes i n each o f the two env i ronme n t s i n t e r ms o f t h r e e p a r ame t e r s , d a me a s u r ing the a ver age e f f e c t o f gen i c d i f f e rence s , e 1 me a s u r ing the ave r age e f f e c t o f d i f ferences in env i ro nmen t and g l me asuring the GEl .. The q uantity g 1 , the s t a t i s t i ca l. int e r a c t ion o f d a and e 1 i s e s t i ma t ed by (A : X + B : Y ) - (A : Y. +. B : X). wi th s ign ignored , i . e . , taken a s the a mount added by the i n t e r a c t i o n to the pheno types of A i n env i ronment X and B in envi ronmen t Y , a nd dedu c t ed from the pheno typ e s of A in Y and B in X..

(18) 5.. 1 (b). 1 (a) Ax. 1. Ax. ~. 2. A. 3 X. 4. �. By. By 2. 3. Ax. 1. Ax. Ay. 2. Bx. � z. �. 3. 4. Ay. /. By By. 4 (a). 4 (b ). Ax. 1. Ax. By. 2. 3. Ay. 4. X. A Fig .. Bx. 1:. B. Ay A. B. I l l us t r a t ion o f geno type (A , B ) X environment (X, Y ) i n t e r a c t ions as sugge s t ed by Haldane 0. 9 4 6) ( a f t e r McBride, 1958 ) ..

(19) \. 6.. McBride ( 1 9 5 8 ) p ropos ed t o c l as s i fy GE l on the f o l l owin g b as i s :. 1.. Gene t i c d i f f e r ences a s int ra-popul a t ion geno types and i n t e r-popu l a t ion ge no t ype s .. 2.. Env ironme n t a l d i f f e rences as micro-environme n t s and ma c ro-envir o nmen t s .. Type A ( in t ra-popul a t ion , mi cro-envi ronmen t a l ) :. Th i s wou ld i nvo lve. i n t e rac t ions be tween those envi ronmen t al f a c t o r s wh ich o c c ur whe n a l l an imals appear t o b e t r eated a l ike ( i . e . , are i n a s in g l e gene r a l e nvi ronmen t ) and are f rom a s ingle popul a t io n gene t i c a l ly s u c h a s a s ingle h e r d o r f lock .. Type B ( in t ra-pop u l a t ion , ma c ro-environme n t a l ) :. Th e s e are in t e rac t i on s. wh ich migh t o c cur i f the gene t i c d i f f e rence s o f anima l s f rom a r e l a t ive ly homo genous gene t i c group we re e xposed t o large environmen t a l d i f ference s . The pre s ence o f type B i n terac t i ons is o f imp o r t ance t o p l ant and animal b re e d e r s concerned w i t h s e l e c t ion wi t h i n b r e e d s or s t rains . o f type B in t e ra c t ion s has f o l l owed two l ine s ;. Th e s t u dy. the s t a t i c and dynami c .. The s t a t i c approach c o n cerns the behavi our o f d i f f e r e n t fami l ie s w i t h in the normal r ange o f geno types c omp ared in two o r mo r e c on t ras t i n g environme n t s .. Wh ile t h e i nve s t iga t i ons o f t y p e B i n t e ra c t ions in s t a t i c. popula t i ons may g ive s ome ind i c a t ion as t o wh e ther the enviro nmen t i s impor t a n t i n s e le c t ion p rob lems , the s e que s t i o n s can b e answe red conclus ive ly by sel e c t ing und e r d i f fe ren t envi ronmen t a l cond i t i on s ; i . e . , by the dynamic appro ach to the prob l em .. Fal c o ner ( 1 9 5 2 ) , Falconer and. La t y s z ewski ( 1 9 5 2 ) , Fa l c oner ( 1 9 6 0) , Korkman ( 1 9 6 1 ) , Fowler and Ensminger ( 1 9 6 0) , Da l t o n ( 1 9 6 7 ) and o t h e r s cond u c t e d s tud ies of t h i s type ..

(20) 7.. Typ e C ( int e r-popu l a t ion, mi c ro-environmen t al ) :. Such interac t ions c o u l d. b e illus t r a t e d by an inte r a c t ion o f se veral l i n e s , s t ra in s , bree d s o r c r o s s e s wi th env ironme n t al variab i l i t y wi t h i n f l o cks .. The ideas on. h e t e ro s is put f o rwa rd by Rob e r t s on and Reeve ( 1 9 5 2 ) sugge s t tha t the h e t erozygous geno types are comp e t ent t o h and le a wider r ange o f micro envi ronmen t s than the h omozygous geno t ypes and a r e thus l e s s subj e c t to environme n t a l var iat ion .. In t e rp re t i ng the re s u l t s in v i ew o f t h e above. sugge s t s that the mi c ro- envi ronmen tal f l uc tuat ions c ause some popula t i ons ( the pureb r e d s ) to vary , y e t they produ ce no e f f e c t on o ther popula t i o n s ( the h yb r i d s ) . in t e r a c t ions .. He t e ro s i s , in t h i s sense , is an examp le o f type C However, type C intera c t ions are no t generally th ough t t o. b e impo r t ant i n the f i e l d o f a p p l ied gen e t i c s .. Typ e D ( int e r-popu l a t i on. ma c ro-environmen t a l ) :. Ty p e D in t e ra c t i o n s are. f o und in gene t i c gro ups t h a t show large va r i ed responses t o the dif f e r e nt e nv i r onmen t s .. The p re s en ce o f type D i n t e r a c t ions wou l d i n f l u e n c e. i mpor t an t d e cis ions i n a nimal and plant breed ing .. Before the animal. b r eeder can locate the b re e d o r s t rain t h a t wi l l p e r f o rm b e s t in h i s environme n t , h e mus t t e s t for the pr e s ence o f type D i n t e rac t i ons . Having f o und the b e s t s t r a in for h i s p a r t i c u l a r cond i t ions , he mu s t t hen d e c id e whe ther the c ond i t ions und e r wh ich h i s se l ec t i on is to b e c a r r i e d o u t a re i mp o r t ant ;. i . e . , whe t h e r any type B i n t e ra c t ions are p r e s en t .. Ha ldane ( 1 9 4 6 ) c l a s s i f i ed the. GEl. wh i c h may occur wh en gen o typ e s. d i f fe r in g a t a single locus a r e exposed t o c o n t r a s t ing envi ronmen t s , and Dunlop ( 1 9 6 2 ) extended Hal dane ' s c l a s s i f i c a t ion t o c over the t y p e s o f in teract i on wh ich may o c cur wi t h groups o f anima l s d i f f e r ing at many l o c i . A simi lar approach was adop t ed by McBride ( 1 9 5 8 ) .. Dun lop ident i f i e d. f o ur types o f intera c t ion a c c o r d ing t o magn i t ud e o f d i f f erenc e s in.

(21) 8.. geno t y p e and envi ronment .. He arbi t r ar i ly c lass i f ie d gene t i c. d i f f e r e n c e s as e i t her large o r s ma l l , d e f in ing s ma l l gene t i c d i f ferenc e s a s tho s e occurring among in d iv iduals o f a s ingle pop u l a t ion s u ch as s i n g l e f l ock or the related f l ocks of a breed or s t r a i n and large gene t i c d i f f e r e n c e s as those be tween s t r a ins , b reed s , s p e c i e s o r even wider gene t i c d iv i s ion .. S i mi la r l y , h e de f i ned s ma l l env i r onmen t a l d i f fe rence s. as th o s e o c curring f r om ind ividual to individual in a s in g l e general env i ro nment whe re d i f ference s due to such d e f i nab le e l e me n t s in the envi ronme n t as f i e l d , age , sex, e t c . are ei ther non- e x i s t en t o r have been c o r r e c ted f o r , and large environme n t a l d i f f e ren c e s as tho se b e tween d i f fe re n t d i s t r i c t s or regions or widely hu s b andry or nut r i t ional regime s .. His me thod of c l a s s i f icat ion is i l lus t ra t e d in F i g . 2 .. In t e r a c t i on o f type. l:. s ma l l x small -. Th i s may o c cur in the us u a l. mod e l o f sources o f va r i a t ion in a pop u l a t i on where g e n o t y p e s and envi ronme n t s are uncorre l a t ed . e s t ima t e ;. The s e interact ions are d i f f i cu l t to. i f p r e s en t , a so u r c e o f va r i a t ion o f unknown s i z e co u l d l ead. to a f a l l in the h e r i t ab i l i ty and hen ce hind er p rogre s s by s e l e c t ion . Th i s t y p e o f inte rac ti on c o r r e s pond s to type A o f Mc B r i d e ' s ( 1 9 5 8 ) c l a s s i f i c at ion .. In t e ra c t i on o f type 2 :. la rge x sma l l -. The s e may o c c u r when there are. large d i f fe rence s b e tween geno types and sma l l d i f f e r en c e s b e tween env i r onme n t s , s u ch as several b r e eds in one are a .. The s e i n t e rac t ions. are s e l d o m imp o r t ant and are d i f f i c u l t t o e s t imat e .. In t e r ac t ion o f type 3 :. s mal l. x. large -. Th is c l as s o f i n t e r a c t i on. co r r e s ponds t o t ype B of McBr id e ' s c l a s s i f i c a t ion .. Large int e r a c t ions. o f th i s t ype are a h indran ce t o sele c t ion as the sma l l gene t i c.

(22) 9.. TYPE OF I NTERACT I ON ENV I RONMENTAL D I FFERENCES. Fig . 2 :. 1. G ENET I C DIFFERENCE S. Typ e s o f Hered i t y x Env ironmen t In t er a c t ion ( a f t er Dun lop , 1 9 6 2 ).

(23) 10.. d i f f e rences are s e p a r a t e d by large env i ronme n t a l d i f ferences .. In many. coun t r ie s , s ir e s a re produced in s t ud f l o c k s wh ich are usua l ly s i t u a t e d in good areas , t h e an imals b e ing t r ea t e d t o above- ave rage husbandry p ra c t i ce s ;. mal e s a r e then d i s t r ib u t e d fo r use over a wide r ange o f. envi ronmen t s .. Inve s t i gat ion of the magn i t udes o f type 3 intera c t ion i s If a common founda t i on s t o ck we re. the re fore o f cons i d e r able imp o r t an ce .. randomly d iv id e d i n t o two d i s t r i c t env i ronme n t s and then s e l e c t e d und e r the s e enviro nmen t s , t he d i f f e r ences in the geno types deve l oped und e r t he s e re g ime s wou l d s t em o r i gina l l y f rom t h i s type o f i n t e ra c t ion , b ut i t may we l l deve l o p into type 4 in t e ra c t ion by the end o f the exp e r imen t ; i . e . , gene t i c group s showing large d i f ferent ial response t o the d i f f e rent environmen t s .. Th i s has been reco rded by Fa l coner and La t y s z ewsk i ( 1 9 5 2 ). i n s e l e c t i on fo r b ody we igh t i n mice .. In t e ra c t ions o f type 4 :. large. x. la rge -. i n t e r a c t ions o f grea t e s t ma gni tude .. Mo s t l i kely to f i n d. Int e r a c t ions o f th i s type are o f. imp o r t ance in choo s i n g the c l a s s o f o r gan i sm suited t o a p a r t i c u l a r envi ronmen t .. Type 4 can b e desc r i bed a s s t rain. x. envi ronme n t .. the. s t ra in b e in g ex i s t in g or sp e c i f i ca l ly deve loped . Re cen t ly , Pan i ( c i te d by Pan i and La s l e y , 1 9 7 2 ) a t temp t e d t o c las s i fy t h e inte r a c t ion in the context o f b r e eding o f anima l s f o r d i f f e rent env ironme n t s .. He b a s e d the c l a s s i f i c at ion on whe the r the rank. of genotypes und e r c on s iderat ion change f rom one env i ronme n t to the o t he r and also i f the intera c t ion e f f ec t s a r e s t a t i s t i c a l ly s i gn i f i c an t . His c la s s i f i c a t ions ( t ype 1 - 4 ) are p r e s e nt ed in Fi g . 3 .. Type 3 in. this case r e f l e c t s t he kind of in t e r a c t ion whe re a d i f fe rence in h e r i t ab i l i ty ( d i f f e r ence in the ma gn i t u d e of genet i c width ) b u t no change in rank was n o t ed .. In type 4 , the e s t ima t e o f he r i t ab i l i ty ma y o r may. no t a ccompany the change in ranks ..

(24) 11.. Ay By. Ax Bx. Ax Bx. No. Type 1 change in ranks s i gn i f ic ant interaction. No. No. Type 2 Ch ange i n ranks sign i f i c a n t in t e r a c t i on. Ax. ------. By. Ay. A:v:.. Bx. Bx. Type 3 change in ranks S i gn i f i cant in t e r a c t ion No. Type 4 Ch ange in ranks Si gn i f i c ant in t e r a c t ion. ENVIRONMENTS. Fig . 3:. Ay. (X, Y). A c l a s s i f i c a t i on o f geno t yp e x environment i n t e ra c t ions spec i a l ly d e s i gned f o r use in f a rm an imal s t u d i e s ( a f t e r Pan i , 1 9 7 1 ).

(25) 12 .. FALCONER ' S CONCEPT OF GENETIC CORRELATIONS BETWEEN PERFORMANCE IN DIFFERENT ENVIRONHENTS. Gene t i cis t s and b reeders a re p r ima r i l y in t e r es t e d in the t r a nsmi t t i ng ab i l i t y of an ima l s and p l an t s .. Th i s i n t e r e s t is n o t. confine d to j us t o ne t r a i t but to seve r a l t ra i t s wh ich t o g e t h e r make up t o t a l p roduc t ion and not j u st fo r the expres s i on o f t h e s e t ra i t s in one environment but in a range of environmen t s .. Fa l c oner ( 1 9 5 2 ) made a con s i de rab l e con c e p t u a l �d vance i n h a nd l i n g o f th i s s ubj e c t when h e con s i d e red t h e p rob lem o f p e r f o rman c e un d e r two envi ronme n t s as a case o f two d i f f e rent cor r e la t e d char a c t e r s , thus extending the conc e p t o f gene t i c c o rre l a t ion (Ha ze l , s i tu a t ion .. 1 9 4 3 ) to t h i s. Th i s con cept a l l ows one t o e s t ima te the r e l a t ive progre s s. th a t can b e mad e f rom d i r e c t s e l e ct i o n fo r p e r fo rman c e i n a g i ve n enviro nment or from ind ire c t s e l e ct i o n p r a ct iced i n a d i f f e r e n t e nvi ronmen t .. He a r gued tha t s in re p e r f o rma n c e i n a f avou rab l e. envi ronme nt h as a dif ferent genetic bas i s f r om p e r f o rma nce i n an unfavourab le envi ronmen t , a supe r i o r genotype in one envi ronment c o u l d no t b e expe c t e d t o b e a su p e r io r i n. a. dif ferent envi ronment .. Th e. ma gn i t ud e of the c o r re l a t ion c o e ffi c i e n t ( r G) i s a me a s ure o f t h e prop o r t ion o f t h e genes wh i ch are common t o bo th cha r a ct e r s . t he n a l l o f the genes are c ommon t o b o t h and two ch a r a c t e r s c an b e regarded as one and n o GEl o c c u r r ing .. Fa lconer ( 1 9 5 2 ) de sc rib e d t h e ab ove conc e p t by an a p p li c a t ion o f t h e r u l e s o f path c oe f fi c i e n t s a s f o l l ows :. Let cha r a ct e r s. l. and 2. s t a nd f o r p e r f o rman ce ( e xp r e s s ed i n s t and a r d devi a t i o n s ) of s ome t r a i t un de r two envi ronmen ts.. D i re c t s e l e c t i on f or J will p roduce gain. p rop o r t ional t o h f ( s ince �G 1. =. ih 1 0 1 ) .. S e l e c t i o n for l on t h e b a si s.

(26) 13.. o f 2 w i l l be ( al l e l s e b e ing e q ua l ) p r o p o r t ional to h 2 r 1 when 6G 2 gen e t i c change , h deviat ion uni t s ,. 2 a. he r i t ab i l i t y , i. =. =. s e l e c t ion d i f f e r en t i a l in s t andard. gene t ic s t andard d eviat ion ,. r. =. gene t i c c o r r e l a t ion .. When t he quan t i ty h 2 r 1 2 excee d s h 1 i n d i r e c t s e l e c t io n i s mo r e e f f i c i ent t han d irect s e l e c t ion .. However , GEI reduces r 1 2 and may mak e s e l e c t ion. in o ne env i ronmen t for p e rforman ce in ano t her ine f f i c i en t .. Jame s ( 1 9 6 1 ). d eveloped the s t a t i s t ical a s p e ct o f the p rob l em by ext ending Falconer ' s ( 1 9 5 2 ) t reatmen t t o the case wh ere gene t i c gain in b o t h env i ro nmen t s is d e s ired , t hough the two environme n t s may d i f f e r .. Fal coner ( 1 9 5 2 ) p o in t ed out tha t i f con t ro l of the env ironment invo lved on ly a reduct ion in envi ronme n t al variance , the g ene t i c co rre l a t ion wou l d be un i t y .. I f h 21 and h 2 a !e r e s p e c t ive l y t h e 2. he r i t ab i l i t ie s o f p e r f o rmance in cont r o l l e d and uncon t ro l l e d e c onomi c environment and r G is the gene t i c c o r r e l a t ion b e tween t hem , then i f h 1 r G i s gre a t e r than h 2 , s e l e c t ion shou l d b e c a r r i ed o u t und e r the cont r o l led env i ronment .. Exp e r imental ev idence for Fa l c oner ' s con c e p t. T h e s t udy o f GEI based o n the t heory p r epo unded by Fal coner ( 1 952 ) and further d eve loped by D i ckerson ( 1 9 6 2 ) in gene ral , has f o l l owed two l in e s - t he dynam i c and the s t a t i c .. In the dynamic app roach to GEI , the p o s s ib l e accumu l a t ions o f d i f f e rent ial r e s ponses are me asured when s e l e c t ion i s p r a c t i s e d in d i f f e rent environmen t s .. I t i s po s s ib le t o con t ras t t h e d i f f e r e n t. b ehaviour o f t h e geno t yp e s in d i f f e r e n t envi ronments when t hey a r e 0. s e l e c t e d not only in their environment o f s e l e c t ion b u t a l s o in o t he r env ironmen t s .. The p ub l ished exp e r imen t s in mammal s are r e s t r i c t e d.

(27) 14 .. a lmo s t exclus ively t o growth r a t e on ad libitum and res t r i c ted f e e d i n g r e gi mens f o r ra t s and mice .. Es t ima t i on o f GEl , as und e r t aken by. Fal coner and Latys zewski ( 1 9 5 2 ) i s imprac t i cable in l ive s t o ck b e c a u s e o f the number o f genera t ions required and the n e ce s s i t y for avo id ing t e mpo ral var i a t ions in envi ronme n t .. S ince the e s t ima t ion of the pa rame t e r s w i t h. t h e requi red pre c i s ion ne c e s s i t a t e s t he me a s u r e ment o f a large numb e r o f ind ividua l s i n each o f t h e alt ernat ive envi ronmen t s , t h e cos t appe a r s t o b e prohib i t ive in farm an i mal s .. One such s t udy r epo r t ed so f a r by. Fo,v l er and Ensminger ( 1 9 6 0 ) in p i gs des erves men t ion .. An a l t ernat ive to the dynamic approach is the s t a t i c approach in wh i ch the relat ive pe r f o r mances o f d i f f e r e n t geno t ypes are me asured unde r d i f f e r en t environmen t s in fac t or i a lly d e s i gned expe r i me n t s and t h e in t e r a c t ion var iance e s t i mat ed .. Ideal ly , one would wish t o c o mpare. the p e r f o r man ce o f the s ame geno t ype ove r d i f f e re n t environmen t s . is usually not p o s s ib l e w i t h dome s t i c an i ma l s .. Th is. Hence groups o f r e la t e d. i n d i v idual s , i . e . , p a t e rnal ha l f - s ibs , b reeds , s t rains are c o mmonly cho sen f o r s t udy .. Con s id e rab ly less r e s ou r c e s are requi red f o r t h e. s t a t i c approach and a numb e r o f worke rs have appl ied i t t o the farm a n i mals .. Wh i l e the i nve s t i g a t ions of GEl in s t a t i c p opula t ions may give ind i c a t ions as t o whe th er t he envi ronmen t i s i mp o r t an t in s e l e c t ion p rob lems , t he s e q ues t ions c an , in f a c t , only be answe red conclus ive ly b y s e le c t ing unde r d i f f e r e n t envi ronme n t al cond i t ions .. Falcon e r and Lat ys z ewski ( 1 9 5 2 ) repo r t e d the r e s u l t o f a s e l e c t i on e x p e r i me n t in support of Fal cone r ' s ( 1 9 5 2 ) con t e n t ion .. The e f f e c t o f. t h e p lane o f nut r i t ion on improvemen t in body we ight a ch ieved b y s e le c t ion w a s s t ud ied in mic e .. Two s t ra in s d e r ived f rom a s ingle.

(28) 15.. fo unda t ion populat ion were s e l e c t e d in exac t ly t he s ame manner for we i gh t at 6 weeks o f age:. one s t rain was fed ad lib .. and the o th e r was. r e s t r ic t ed to ab out 75% of the no rma l food i n t ake b e tween t h e ages o f The. wea n i n g and we i gh ing - t h a t i s , b e tween t h e ages o f 3 t o 6 we eks . r e s ul t o f s e l e c t ion was however, d ifferent in each env i ronme n t . inc r e a s ed und e r s e l e c t ion i n b o th s t ra ins;. We i g h t. t h e ave rage increase per. gene r a t ion in t he full d i e t s t rain was 1 . 5 % o f the un s e l e c t e d we i gh t , and 1 . 3 % in t he,r es t r i c t e d s t rain .. The h e r i t ab i l i t y was h i gh e r in t h e. re s t r i c ted d i e t s t rain b e in g 0 . 2 9 o n res t r i c t ed d i e t a n d 0 . 2 0 on fu l l . Exchan g e s o f n u t r i t ional leve l we re made be tween the s t rains a f t e r 5 , 7 and 8 gene r a t ions o f s e l e c t ion .. When reared on the r e s t r i c t e d d i e t ,. t he re s t r i c t ed d ie t s t ra i n was sup e r i o r in 6 week we i gh t , t h e fu l l d i e t s t ra in showing n o improveme n t over t h e uns e l e c t e d leve l .. When reared. on f u l l die t , the full d ie t s t rain was supe r i o r but the r e s t r i c t e d d i e t s t r a in d id no t f a l l far s ho r t o f i t and showed a ma rked imp roveme n t over t he uns e l e c ted leve l f o r full d i e t .. It i s concluded t h a t t h e. r e s u l t s do no t support H arnrnond ' s t h e s i s .. Ano t he r e xp e r iment w i t h m i c e se l e c t e d on op t i mal a n d subo p t i ma l d ie t s wa s rep o r t e d b y Falconer ( 1 9 6 0 ) .. Two -way s e l e c t i on was app l i e d. t o one p a i r o f l in e s for grow t h rate when ind ividuals were r e ared o n. a. h i gh p l ane o f nu t r i t ion and t o ano ther pair o f l ines when ind ivi d u a l s we r e r e ared on a l ow p l ane o f nu t r i t ion .. The s e l e c t e d t r a i t s were high. and l ow b ody wei gh t gain from 2 1 t o 42 d ays of age . n o rmal and h i gh f ibre . o f age by 2 0 % .. The d i e t s were. Th e l a t t e r reduced grow t h f rom 2 1 t o 4 2 days. Re s ul t s o f t h i s exp e r ime n t showed t h a t 2 1 t o 4 2 days. body we i gh t whe n me asured on the op t imal d i e t , was increased almo s t as muc h b y s elec t ion on the s ub o p t i mal as on t h e op t imal d i e t b u t g rowth on the s ub o p t ima l d i e t wa s n o t incre a s ed at all by s e l e c t i on on t h e.

(29) 16.. In. op t imal d i e t .. this and t h e p rev ious exp e r ime n t by Falconer and. La t y s z ewski ( 1 9 5 2 ) s e l e c t ion on op t ima l d i e t s imp roved only growth on th e o p t imal d i e t s but s e l e c t ion on s ubo p t imal die t s imp roved growth on bo th d ie t s .. Re s u l t s o f t he two exp e r ime n t s ind i c a t e that i t may b e. be t t e r t o s e l e c t under t h e wo r s t cond i t i ons rather than the b e s t cond i t ions i f the s e l e c t ed p o pula t i on is e xp e c t ed to p e r form over a range o f envi ronmen t s .. It. i s al so o f i n t e r e s t that the mice s e l e c t e d. f o r in creased grDwth o n the s ubopt ima l die t were less f a t a n d we re be t t e r mo thers than tho se s e l e cted on the o p t imal d ie t s .. Falcon e r. s t a t ed tha t t h e resul ts i n h i s exper iment wh i ch r e f e r t o t h e final out c ome of th i r t e en gener a t i o n s o f s e l e c t i on , d o not a c cord we ll with the t h e ory o f s e l e c t ion f o r c o r r e l a t e d charac t e r s .. Over the f i r s t f ew. gene r a t ions the resul t s we r e in reasonably good agre ement wi th the theo ry .. The d is c repan c i e s p r obably arose from chan g e s o f the gene tic. p ar ame t e rs wh i ch took p l a c e duri ng the course of s e le c t io n .. Th e re are. o th e r s tudies o f GEl on mi c e , Drosophi la and Tribolium, s imilar to th a t o f F a l c oner and Latys zews ki ( 1 9 5 2 ) an d Fa l c one r ( 1 9 6 0 ) .. Mo s t o f the work on m i c e i s based on s e l e c t ion w i t h in d i f f e ren t d i e t s and on s i r e pro geny g r o u p s s t udied in re l a t ion t o the d i f f e re n c e s i n q u a l i t y and quan t i ty o f f e e d ( Youn g , 1 95 3 ; al.. 1966 ;. 1972 ) .. Da l t on , 1 9 6 7 ;. Ko rkman , 1 9 6 1 ;. B a t ernan 1 9 7 1 and 1 9 7 4;. Park e t. Kownacki and Geb l e r ,. Young ( 1 95 3 ) exam in e d the s t r a in x d i e t i n t e r a c t ions and. o b s e rved the s l ower growth o f C5 7 s t ra in o f mice on c rushed o a t s than the CBA s t rain .. The her i t ab i l i ty e s t imat e s o f body weigh t was l owe r. ( 0 . 0 6 6 ) in a s e l e c t ion on a l ow p lane and h i gher ( 0 . 2 1 8 ) in a s e l e c t i on on a h igher p l ane o f nut r i t i o n ( Korkrnan , 1 9 6 1 ) ..

(30) 17.. Park et a l .. ( 1 9 6 6 ) inve s t i g a t e d the inf luenc e o f f e e d i n g r e g ime on. t he e f f e c t s of s e l e c t ion for p o s t -wean ing gain in the rat and p o in t ed to the d e s irab i l i t y of s e l e c t ing under the c o nd i t ions in wh i ch it i s e xp e c t ed the d e s cendan t s are t o be kep t .. When compared in e a c h r e g ime ,. t h e s e le c t ion l ine devel op e d i n t hat r e g ime t ended t o give a l a r g e r r e s p o n s e than t h o s e devel oped i n o t her r e g ime s .. Dal t on ( 1 9 6 7 ). o b s e rved that t h e i nd i r e c t responses o n e i t her p l ane ( fu l l d i e t and d i lu t ed d i e t ) were equal to the d ir e c t r e spon s e s on the s ame p l an e . Howeve r , Dalton ' s f ind ings do not so much contradict Falconer ' s recommendat ions as remove the i r l imi t a t ions .. Other s t ud i e s c i t ed. by B a t eman ( 1 9 7 1 , 1 9 7 4 ) and Kownacki and Gebler ( 1 9 7 2 ) a l s o s up p o r t Falconer ' s gener al thes i s .. W i l s on et a l .. ( 1 9 7 2 ) ob s erved that there. wa s n o ind i cat i o n that s e le c t ion could b e increased b y subj e c t i n g m i c e t o t emperature s t re s s dur ing the s e l e c t ive p r o c e s s .. Ext ens i ve s t ud ies r e l a t in g t o the p ro b lem o f GE l have b e e n mad e w i t h the lab . i n se c t s .. In a s e r i e s o f s t ud i e s on the e c o l o g i c al. g e ne t i c s o f Drosop hi la Rob e r t s o n ( 1 9 59 ,. 1 9 63 ) reveal ed t h e i n t e r. dep endancy o f gene t i c and env i ronme n t a l f a c t o r s in d e t ermining t h e n a t u r e o f q uan t i t a t ive variat ion .. Lines s e l e c t e d f o r large and sma l l. b o dy s i z e i n Drosophi la showed r e l a t ive l y lar ger we ight reduc t i o n when g rown on subop t imal d ie t s than d i d ind ividuals f rom the uns e�e c t ed populat ion .. Druger ( 1 9 6 2 ) found the magn i tude o f corre l a t ed r e s ponse. for wing- length unde r the t emp e r a t u r e o th e r than that of s e l e c t i o n was i n f luenced b y b o th d i re c t i on of s e l e c t i o n and cul turing t empe r a t u r e . However , the he r i t ab i l i t y e s t ima t e s ob t a ined under two d ivergent cond i t ions ( l arval den s i t y ) were very c l o s e in an exp e r ime n t b y Frahm and Koj ima ( 1 9 6 6 ) .. Th e ' corr e l a t ed ' r e s ponse o f a l in e was u s u a l l y. a s l arge as t h e l in e ' s p r imary r e sp ons e ..

(31) 18 .. In s t ud i e s o f growth o f Tribo lium cul t ured in d i f ferent humid i t i e s , McNary and Be l l ( 1 9 6 2 ) and Bray et a l.. ( 1 9 6 2 ) f o und G E l s i gn i f i c an t ly. i n f l uen c ing the responses t o s e l ect ion .. B e l l and McNary ( 1 9 6 3 ) however ,. found that sele c t ion for growth in t he subop t imal environment gave a c o rr e l a t ed response in the o p t imum e qual in b o t h the r ep l i c a t ions t o t h e d i r e c t r e sponse o f s e l e c t i o n under o p t imum cond i t ion s .. Hard i n and B e l l. ( 1 9 6 7 ) r eported t h a t the max imum p e r f o rmance in a c e r t a in env i r onmen t r e s u l t e d from s e l e c t ion in t h a t envi ronmen t and the max imum average p er f o rmances resul t e d from s e l e c t ion in the poor envi ronmen t .. Yamada. and Be l l (1 9 6 9 ) ob s e rved in a s e l ect ion expe r imen t t h a t the d ir e c t s e le c t io n respon s e s exceeded c o r re l a t e d responses und e r b o t h leve l s o f nu t r i t i o n (Good and Poor ) and average p e r f o rmanc e o f l in e s s e l e c t e d f o r large l a rval s i z e und er ' Po o r ' e xceed ed ave rage p e r f o rman c e o f lines se l e c t e d for large size und e r ' Good ' .. An e xp e r iment comparab l e t o those o f Falcon e r on mice was cond u c t e d by Fowl er and En smi n g e r (1 9 6 0 ) wi t h swine and de serves men t i on . two l ine s .. They r andomly d iv i d e d a cros sbred populat i o n o f swine in t o One was selec t e d f o r increased aver a ge d a i l y ga i n for. wean i n g t o 6 9 kg und e r a full f e eding regime (H) .. The o t her l ine was. s e l e c t e d for the s ame t ra i t at a feeding leve l of 70% that of f u l l f e e d gr oup ( L ) .. The resul t s o b t a in e d were q u i t e s imi lar t o those o f. Fal coner i n tha t gain i n we i g h t o c curred i n l in e s s e l e c t ed wi t h in t h e h i gh ( H ) a n d t h e l ow (L) nu t r i t i onal p l an e s .. Al s o , whe n the s t o ck s. s e le c t e d on t he o n e p l ane we r e t r an s f erred t o t h e o t h e r t h e L was equiva l e n t in g a in t o H s t oc k in the H r e gime but the H s t o ck was inf e r i o r to the L s to c k on t he L regime but apparen t l y superior to t h e found a t ion s t oc k .. The L s t o c k had higher e f f i c iency i n t h e u t i l i s a t i o n. o f f e e d t h an t h e H s t o ck on bo t h regime s ..

(32) 19 .. The ap p roa ch o f Falconer ( 1 9 5 2 ) to the p r ob lem o f GEI and the r e s u l t s of the other exper imen t s reviewed above lead t o the f o l l owi n g main i n f erenc e s .. One general p r in c i p l e wh i ch seems t o emerge from the exp e r imen t s o n GEI i s that they are mo s t l ikely t o b e found whe re i n t e rpopul a t ion geno t yp e s and mac roenv i ronmen t s are invo lved .. The genera l i t y o f. i n f e renc e s p o s s ib le f rom the above exper imen t s are l im i t ed b y the f a c t t hat the magn i t ude o f d i f feren c e s b e tween t h e environme n t s and be twe en t he gene t i c e f fe c t s vary in d i f f eren t s i tuat ions .. Th i s leads us t o. the n e c e s s i t y o f exp lo r i n g the i n f luence o f a varie t y o f env i ronmen t s and gen o types on each o f the t r a i t s in wh i ch w e have in t e re s t .. The. f ind ings from the exp e r iment s reviewed above i n gen e r a l sup p o r t F a l coner ' s the s i s .. The resul t s are in agreement in sugge s t i n g that. p r o gr e s s f rom s e l e c t ion under un f avourab l e cond i t ions approaches or equals t h a t und e r f avourable cond i t ions when t h e obj e c t ive i s t o improve p er f o rmanc e in a favour ab l e envi ronment .. Howeve r , s e l e c t ion und e r the. unfavourab l e cond i t ions c on s i s t en t ly p roduced mo re response than d id s e le c t io n under favourab l e cond i t i ons when the obje c t ive i s improveme n t i n the unf avou rab le o r average envi ronmen t s .. I n gener a l , exper imen t a l. i n f orma t i o n doe s no t i nd i c a t e that one c an exp e c t t o enhance p r o g r e s s b y s e l e c t ing i n an env i r o nmen t d i f f e r en t f rom t h a t in which t h e p o p u la t i o n i s t o b e p ro duced .. And f inally , the c o n s e q uences o f GEl e x i s t in g f o r two env i ronme nt s c a n b e p r e d i c t e d f rom ( 1 ) the gene t i c correla t io n be twee n the two environmen t s f o r a t r a i t ; environrnen t s -; environment s .. ( 2 ) the her i t ab i l i ty e s t imat e s in t h e two. ( 3 ) the phenotyp i c var i an c e s o f a t r a i t i n two S ince the value o f the h e r i t ab i l i t y depends on the.

(33) 20 .. magn i t ude o f a l l t he componen t s o f varianc e , a change in any o f t h e s e w i l l a f f e c t it .. GENOTYPE- ENV IRONMENTA L INTERACT I ONS IN SHEEP. A remarkab l e d ive r s i t y i s obs e rved in sheep produc t ion s y s t ems throu ghout the wor l d .. Sheep are exp e c t ed t o l ive and p ro duce a. cons i d e rable var i e ty o f produc t s ;. meat , wo o l and milk e t c . , over a. wider range o f environmen t s than mo s t f a rm an imals .. The preva i l i n g. f armin g p r ac t i c e s d o n o t permit as r i gid a c o n t rol o f envi ronme n t s i n rais ing sheep as i s p o s s ib l e w i t h the dairy c a t t l e o r poul t ry .. S in ce. o p t imum produc t i o n i s c r i t ical o f any l ive s t o c k ent e rp r i se , the exi s t en c e of GEl and p a r t icularly of gen o t y p e x nut r i t ion i n t e ract i o n s and breed geno type x envi ronment f o r c omp onent s o f p roduct ion and rep roduc t ion in sheep are l ikely t o be impo r t a n t .. Re l at ively l i t t l e c r i t i ca l in f o rmat ion i s available on t h e imp o r t ance o f GEl i n sheep .. The s t at i c exp e r imental app roach , in. whi ch t he relat ive p e r f o rmance o f d i f f e ren t genotypes are me asured under d i f f e rent envi ro nment s in f a c t o r ially d e s i gned e xp e r ime n t s and the i n t e r a c t ion v a r i a n c e e s t imat ed , has b e e n a pp l ied i n mo s t o f the s t ud i e s c ondu c t e d in sheep . f o r t h i s approach .. Cons iderab ly l e s s resou r c e s a r e r e q u i r e d. The cho i c e o f the geno t y p e s and t rea tmen t s , h a s ,. i n gener a l , been arb i t r a ry c r e a t ing a body o f l i terature w i t h a wide r ange o f gen o t yp e s and t reatment s comb ina t io n s .. Int e r a c t ions i nvo lving. d if ferences in nut r i t ional s t a t u s or l ev e l s have rece ived mor e a t t en t ion t han r e search on any o t her env i ronme n t a l e f f e c t s.. A r ev i ew o f t h e. repo r t s on var ious t ra i t s o f e conomic imp o r t an c e i n s h e e p i s p r e s e n t e d b e low ..

(34) 21.. Growth charac t e r is t i c s. Gen o type x nut r i t ion King and Young ( 1 9 5 5 ) condu c t ed an exper iment showing the r e sp on s e s in b o dy we igh t a n d body me asuremen t s e xh i b i t e d b y young ewes o f the Blackface , Che v i o t and. Wi l t shire breeds und er two nut r i t ional and two. temp e r ature t r e a tment s .. The d i lu t ion o f o a t s by cha f f was adop t ed a s. a c onvenient me thod o f r e s t r i c t ing the d i e t .. The warm e nvironment. ° cons i s t ed of p e n s in a hea ted a n ima l-house kep t at 6 0- 6 5 F .. The c o l d. env ironment cons i s t e d o f p ens e r e c t e d i n a very windy a l l e y exp o s e d t o r i g o r s o f a c o l d winter .. Neither b r e ed x env i ronmen t nor b r e e d x p lane of nut r i t ion was s i gn i f i cant in y e ar l ing we ight . of h ind- c annon and t ib ia ;. Ske le t a l me asurement s s u ch a s l e ngth. width of h ind- c annon and heart - g i r t h sh owed. the p r e s en c e of marked s i gn i f i c an t i n t e r a c t ions due to mor e rap i d growth of B l ackface sheep on the h i gh p l an e of n u t r i t ion .. The n e g a t ive resul t s. for c ha r a c t e r s wh i c h gave i n s i gn i f i cant i n t e r a c t ions were l e s s i n f o rmat ive , s in c e they may b e a r e f l e c t ion only o f the sma l l s cale o f the e xp e r imen t . Th i s e xp e r iment c o r r e sponds t o Type 4 o f Dunlop ' s c l a s s i f i c a t i o n ; i . e . , when gene t i c and envi ronme n t a l d i f f er e n c e s are b o t h l a r ge .. Four breeds (Linco ln , Corriedal e , Polwa r t h and Fine Me r ino ) were ma int a ined on two nut r i t ional r e g ime s by D a l y and Car t e r ( 1 955 ) . Though the int era c t ions we r e not spe c i f i c a l l y s t ud i e d , they con c lu d e d t ha t : "With f ew excep t i ons t he a b s o l u t e or r e l a t ive values o f the char a c t e rs measured form a s mo o t h s e r i e s f r om the Fine Mer ino through the P o lwarth and C o r r iedale t o the Linc o l n - e i th e r in t h e a s c end ing o r the d e s cend in g order o r s how l i t t le o r no d i f f e rence b e tween t h e b r e e d s ( e . g . b o d y length and he i gh t , f o o d int ake p e r uni t ne t t l ive we i gh t ;.

(35) 22 .. t o t al s kin produ c t s p e r un i t food i n t ake ) .. The re l a t ive p o s i t i on s o f. the breeds were gene r a l l y ma in t a ined a s f o o d was progres s ive l y reduced " . However , t here was an ind icat i on o f the GEl whe n examining the ra t i o o f body we i ght at unr e s t r i c t e d int ake t o body we i ght a t 2 0 % o f t h i s i n t ak e , t he Me r i no showin g the gre a t e s t percen t age r e s p onse t o changes in nut r it ional level .. Mars t on , P i e r c e and Car ter ( c i t ed by Turner and Young , e xamined s t rain x env i ronment i n t e r a ct ions i n Austral i a .. 1969) Two Me r in o. s t r a in s ( s t rong wo o l and fine woo l ) were f e d a t two nut r i t ional l eve l s . The s t rong wo o l s t rain s howed a grea t e r body we i ght r e s ponse to good n u t r i t ion .. King et a l .. ( 1 9 5 9 ) s t udied the d i f fer ent i a l response o f l amb s o f The l amb s. var i ous b reeds and cros s e s t o d i f f e r e n t p l an e s o f nu t r i t i on .. o f two b r e e d s and f ive c r o s s e s of she ep we r e wint ered i n h i gh -h i gh , h i gh- low , l ow-h i gh and l ow-low nut r i t ional env i ronment s and s ub s e q u en t ly b r ought t o the same we i gh t for s l augh t er .. I n b o dy we i ght , the ma i n. f e at ure o f the expe r ime n t was t h e simi l a r i t y o f t he res ponse t o d i f f erent environmen t s .. Body me asureme n t s a l s o showed con f o rmi ty. b e tween b reeds in response to envi ronmen t s .. Morley ( 1 9 5 6 ) in an exper iment invo l v i n g the progeny o f d i f f e r e n t Me r ino rams kep t on a h i gh and a l ow p l ane o f n u t r i t ion found no i n t e r a c t ions in body we i gh t at 6 mon t h s but h i ghly sign i f i c an t i n t e r a c t ions were evident a t 1 2 and 1 7 mon t h s b o dy we i gh t .. At the colle c t ive f arm in Al t a i , U . S . S . R . S t akan et a l .. ( 1963). found that t he heri t ab i l i t ie s were lower under p o o r than good environme n t a l cond i t ions .. S t u d i e s were condu c t e d invo lving two group s.

(36) 23.. o f l amb s reared on two p l anes o f nu t r i t ion , h i gh and l ow ;. her i t ab i l i t y. e s t ima t e s o f 0 . 1 5 and 0 . 0 5 r e s p e c t ive l y were found f o r we i gh t . Var i a t i o n of t h i s charac t e r was l e s s i n high p l ane t han in low p l an e .. E f f e c t iven e s s o f s e l ec t i on o f sheep o f Ku chugury b r e e d group und e r d i f f e r en t feed ing r e g imes w a s inves t i gated by An f ino genova ( 1 9 7 0 ) i n the U. S . S .R. ade q ua t e .. Ewes were fed on an adequat e d i e t o r a d i e t 2 3 % l e s s t h an The g ene t ic var iance amoun t ed t o . 1 2 and . 3 0 r e s p e c t ively ;. t he p e r ce n t age o f lamb s c l a s s e d grade 1 rose f rom 42 t o 5 1 % f o r p ro geny o f grade 1 or grade 2 dams and f r om 7 to 4 3 . 2 % for p ro geny or grade 4 dams when dams on inadequate d i e t we re p l aced on ade q u a t e d i e t .. E r c anbrack and P r i ce ( 1 9 6 9 ) s t ud i e d whe t h e r the e f f e c t s o f e arly weaning on grow t h rate was the s ame in Rambo u i l l e t , Targhee and Columb i a l amb s .. A l l lamb s we r e reared in the s ame f l o ck t o an ave rage. age of 75 days and hal f f rom e ach b reed were weaned and p l aced in a dry l o t , the r ema in in g ha l f s t ayed w i t h t h e i r dams .. Amon g i nb r ed lamb s. ( 3 3 % inbred ) , no s i gn i f i c an t i n t e r a c t ion b e tween breed and wean ing respons e was ob s e rved t hough i n the non- inbred group t h e r e was a s igni f i c an t in t e r a c t ion b e tween b r e ed and respons e .. I n t he non- inb r ed. gr oup T arghees we r e superior in d a i ly gain among lamb s n o t we ane d . Targh e e s a l s o we r e sup e r io r among c e r t i f i ed lamb s b u t Co lumb i a s we re s up e r i or among l amb s having a c ce s s t o p a s t ure .. In an inter im r e p o r t o f a long t e rm exper ime n t t o s tu dy the GEl i n the c omp onent s o f l amb product i o n , J o y c e e t a l .. ( 1 9 7 6 ) reported the. e f f e c t s o f mature b o d y s iz e a n d f er t i l i t y on t h e level and e f f i c i ency o f animal pr oduc t ion .. Four geno t y p e s o f sheep ( Coopwor t h , Perendale. and two Romney s t rains ) were ma i n t a ined o n three d i f f e r e n t s t o cking rates ( 2 6 ewe s / ha , 2 1 ewes / ha and 1 6 ewe s / ha ) .. There was no change i n.

(37) 24 .. t h e r e l a t ive ranking o f geno types in t e rms o f ewe l ive we i gh t s .. Ewe. mor t a l i t y was s imilar f o r a l l geno types and a l l s t o cking r a t e s . Increas ing s t ocking r a t e reduced lamb b i r t h we i ght by 5 % , the e f fe c t b e in g mo re marked f o r mu l t ip l e born lambs t han f o r s in g l e born . Geno t y p e x env i ronment i n t eract ions have n o t b e en analy sed as ye t .. The he r i t ab i l i ty e s t ima t e s o f b i r t h weight in two f l ocks we r e 0 . 5 8 t o 0 . 7 6 and 0 . 5 2 to 0 . 7 6 r e s p e c t ively on t he h i gher p lane o f nu t r i t ion . Fo r sheep on the lower p l ane o f nut r i t ion the co rresponding h e r i t ab i l i t y (Burd ukovskaya and T imashev , 1 9 7 1 ) .. e s t imat e s were 0 . 34 and 0 . 2 3. The s e ob s e rvat i ons were made in an exp e r ime n t t o d e t e rmine the e f f e c t o f type o f s e l e ct ion and level o f nu t r i t ion o n t h e her i t ab i l i ty o f b i r t h we i gh t i n Sovie t Me r ino sheep .. Breed x r a t ion concen t ra t e level on r a t e and e f f i c ieny o f l amb growth was inve s t iga t ed by Gl imp ( 1 9 7 1 ) . i n t e r a c t ion was observe d .. A s i gn i f icant ( P < 0 . 0 1 ). Su f f o l k and Hamp s h i r e lamb s showed. d i f f e r en t i a l response to e ne rgy l ev e l f o r l amb growth .. The t r i a l was. d iv ided int o t hree p e r i o d s and s ix t re a tme n t s r e p r e s en t i ng s ix f e e d i n g s chedul e s .. Lambs f rom e ig h t breeds were randomly d ivided i n t o two l o t s. p er t re atme n t group .. S u f f o lk and Hamp s h i r e l amb s gained f a s t e r when. t h e r a t ion energy level was increased above the l eve l p rovided in t h e f ir s t two t reatment s wh i l e n o d i f f e r en t i a l r e s p o n s e t o energy l e v e l wa s o b s e rved among o t her b r e e d s .. T e s t ing and evalu a t i o n o f p ro geny o f s ir e s und e r d i f f erent envi r onmen t s was carried out by Go l ' t sb la t and Budan s t ev ( 1 9 7 3 ) i n U . S . S . R.. Three s ire groups t o t al l ing 7 0 young P r e c o c e r ams were e a ch. r e a r e d under d i f f erent s e t s o f management c o nd i t i o n s ;. group 1 on. p a s ture , group 2 and 3 a t t e s t ing s t a t ions on g r o up and i n d ividual f e e d.

(38) 25.. r e s pe c t ively .. The r e were no s i gn i f ic ant GEl for growth o r food. conve rs ion and sires ranked i n t he s ame order on t hr e e s e t s o f t e s t cond i t ions f o r their pro geny .. Hohenboken et a l .. ( 1 9 76b) fo und no s i gn i f i c an t b r e e d x env i ronment. i n t e r ac t i o n s f o r b ir t h we ight .. Fo r weaning we igh t , s i r e x management. sys t em was h ighly s ign i f ican t .. Th ere were no sign i f i c an t d am b re ed x. management i n t eract ions . �. The s e r e su l t s were obta ined f rom an exp e r imen t. invo lving d i a l l e le c ro s s among three b r e ed s r ep l i c a t ed over three years and two graz ing management sys t ems .. Breeds were the S u f f o l k , Hamp s h i r e. a n d W i l lame t t e and managemen t sys t ems we re h i l l p as tu r e s v s i r r i ga t ed p a s t ur e s .. The b as i c mathema t i c a l mo d e l included env i r o nmen t al e f f e c t s. (management sy s t ems , years , managemen t. x. year int erac t ions , a g e o f dam ,. sex and b i r t h and rearing typ e ) , breed and b r eed x environmen t i n t e r a c t ion e f f e c t s .. In add i t i on , s ir e s ne s t ed wi t h i n b r eed ,. management sy s t ems and year we re inc l uded .. Genotype x l o c a t i o n The Canada Depar tment o f Agr i c u l t ur e and the Vir g i n i a Ag r i cu l t u r a l S t a t i on co-o p e r a t ively s t ud i ed G E l i n s h e e p ( Ca r t e r et a l . , 1973 ) .. 1 9 7 1 a , 1 9 71b ,. The e xp e r iment invo lved ewe s o f two breed cro s s e s , Nor th. Count ry Chev i o t (NC ) rams x Cana d i an Le i c e s t e r ( L ) ewes and Hamp shire x (Hamp shire x Ramb ou i l le t ) b ackcro s s e s comp a red t hr ough f ive lamb c r o p s ( 1 9 6 1- 6 5 ) at two l o c a t ions ; Virgin i a , U . S . A .. O t t a,va , On t a r i o , Canada and G l ade S p r ing ,. The d i f f e rence in la t i tude r e su l t ed in a cons i d e r ab l e. d i f f e rence in t h e r e l a t ive summe r-win t e r d a y length and l'onger c o l d e r wint e r s a t O t t awa .. The s ame Su f fo l k r ams were u s ed each s ea s o n a t b o t h. s t a t ions a n d t he r ams w e r e rep laced annual ly .. Car t e r e t a l .. ( 197 1a). ob s e rved s igni f ic an t lo c a t i o n x b re e d c r o s s i n t e r a c t ions f o r we i g h t o f.

(39) 26 .. lambs '"'eaned per ewe ma t ed .. The i n t e r a c t ion ap p ro a ch e d s i gn i f i c an c e. ( 0 . 0 5 < P < O . lO) f o r body we ight o f t he ewe a t bree d i n g t ime .. The. s i gni f i c an t b reed x loc a t io n i n t e r a c t ion f o r we ight of l amb s weaned p e r ewe mat ed may b e p o s s ibly d u e t o t he d i f f e r en t ial f er t i l i ty o f two kinds of ewe s a t d i f ferent locat ions .. The magn i t ude o f t h e i n t e ra c t ion. component i n body we ight of the ewes was sma l l and p ro b ab l y not o f e c onomic s i gn i f ic ance .. S ign i f i c ant ewe breed c ro s s x l o c a t ion intera c t ions were ev i de n t for b ir t h we i ght and adj us t ed 1 2 0 d ay we igh t b ut not f o r aver age d a i l y g a i n from b i r t h to wean ing ( Ca r t e r e t a l . , 1 9 7 1 b ) . lamb s f r om N C x L ewe s. >N<�. B ir th we ight o f. :.eavi e r a t both l o c a t ions b u t t h e d i f ference. was much larger in O t t awa t han i n V i r g inia r e s u l t ing i n a s i gn i f i cant breed x l o c a t ion interact ion ( P < O . O S ) . resp e c t t o 1 2 0 d a y we i ght .. The s i tua t ion was s imilar w i t h. A l a r g e and highly s ign i f i c an t i n t er a c t ion. was ob served b e tween ewe breed c ro s s an d type of b i r t h f o r b ir t h we igh t . Wh i l e s i gn i f i ca n t ewe breed c r o s s x l o c a t i on i n t e r ac t i o n s were pre sen t f or b ir t h and 1 2 0 d ay we igh t , the d i f f e r ences invo lved were r e l a t ive ly sma l l .. S train x l o c a t ion inter a c t ions in b ody t r a i t s we r e inve s t i ga t e d b y Dunl op ( 1 9 6 3 ) .. In this exp e r ime n t f ive s t r a ins o f Aus t r a l i an Me r ino. were comp a r e d at three locat ions w i t h cont ras t in g environmen t s in New S o u t h Wales and Queen s l an d .. Rams were r o t at e d b e tween t h e l o c a t ions. to ens ure s im il ar i ty i n the three s e t s of geno t ypes . d a t a were anal y s e d by separate year-age o f ewe group s .. The r e s u l t ing Ob s erva t ions. were made on body w e i gh t , body lengt h , w i d t h of h ip s , w i d t h of shoulde r s , d e p t h o f che s t and length of l e g .. No s i gn i f i c a n t s t rain x y e a r and. s t r a in x lo c a t ion int e r a c t ions were ob s e rved f o r adult we i gh t s .. With.

(40) 27 .. one excep t ion i n t e r a c t ions among the ma in c l as s e s were not imp o r t an t s o u r c e s o f var i a t ion in b o d y s i z e .. The excep t io n was year x l o c a t ion. int e r a c t ion wh i ch was s i gn i f i c ant in over 60% o f t e s t s .. The s e. i n t e r a c t ions b e tween year and locat ion were brought about by var i ab i l i t y i n p a s t u re cond i t ion f rom one year t o the next i n any g iven l o c a t ion . H i s f in a l co n c l u s ion was t h a t the s p e c i f i c a d ap t at ions are no t imp o r t an t when c ho o s ing a n exi s t in g s t r a in , at l e a s t f o r the range o f envi ronmen t s , s t r a i n s and produ c t i on me a s u r e s s t u d i e d .. G E l and the e f f e c t s o f envi ronment s on pheno typ i c and gene t i c var i a t i on was s tud ied by Osman and Bradford ( 1 9 6 5 ) i n a n exper ime n t condu c t ed at two l o c a t ions w i t h Targhee- t ype sheep .. The d i s t an c e. between l o cat ions was no t g r e a t and t he main d i f ference a p p e a r e d t o b e in n u t r i t ion with sheep a t Hop l and F i e l d s t a t ion hav i n g a l ower p l ane o f nut r i t i on than at Dav i s .. E i gh t Targhee-type rams were used on a l l. ewes in b o t h loc a t ions i n order to ensure that t he d i f f e ren t grou p s in the expe r iment we re gene t i c a l ly as s imi l ar as p o s s ib l e i n i t i a l ly . Dav i s l amb s rece ived creep f e ed whe reas Hop l and l ambs d i d not .. The. chara c t e r s s tud i e d were b i r t h and 1 2 0 d ay weigh t , gain f rom we aning t o f a l l and f r om f a l l t o shearing , 4 5 0 d ay we i gh t and con f o rma t ion s core . For many t r a i t s me an level o f p e r f o rmanc e was muc h h igher a t Davis . The pheno t y p i c vari ance was h i ghe r in t h e ' good '. (Dav i s ) t h an t h e ' po o r '. (Hop land ) environmen t wi t h t he r e s u l t t h a t the s e le c t ion d i f f eren t i a l was a l s o h igher f o r t h e ' go o d ' env ironment .. Her i t ab i l i t y e s t ima t e s. ob t a ined f rom pat ernal h a l f - s i b f o r 1 20 d ay we i gh t and year l in g t r a i t s were h i gh e r i n b e t t e r environmen t .. S i re x loca t ion int e ra c t io n was. ne g l i g ib l e in birth we i gh t t hough it was s i gni f i cant i n one of the year s .. S ire x l o c a t ion e f f e c t s were f ound t o b e h i gh ly s i gn i f i c ant. ( f rom p o o l e d mean square s ) for 450 days weight b u t were n o t.

(41) 28 .. s i gn i f i cant f o r 1 2 0 day we igh t . group geno t yp e s and l o c a t i o n s. by. S t ud ies o f intera c t ion i nvo lving u lo o d S t an s f i e l d e t a l .. ( 1 9 6 4 ) also i nd i c a t e d. t he ab s ence o f i n t e r a c t ion e f f e c t s on b i r t h we i g h t and wean ing we igh t in s heep .. Radomska ( 1 9 6 5 ) inve s t i ga t ed s i re x f l ock ( con founded wi t h. l o cat ion ) i n t h e p ro g e ny o f Me r ino ra ms .. B i r t h we i g ht , we ight at l O O. d ays (weaning ) , d a i ly g a i n t o l O O days and body we i g h t a t s ix and 12 months were s t ud i ed .. In t e r a c t ions we r e f o und t o b e n e g l i gible f o r. b ir t h we i g h t b u t t h e p r e s e n c e o f s i re x s t a t i o n ( t e s t i n g s t a t ion v s f l ock ) wa s no t ed f o r wean i ng we i gh t .. Genotype x sex Vesely and Rob i s on ( 1 9 7 0 ) s t udied s i re x s e x i n t e r a c t ions. in. g rowt h. t ra i t s s u ch as body we i gh t , wean ing we igh t , ave r a ge d a i l y gain , f i n al w e i gh t , t o t a l g a in and f e ed e f f i ciency in Romn e l e t and Rambo u i l l e t . G E l were no t s i gni f i c an t f o r any o f t h e t ra i t s .. The he r i t ab i l i t i e s. t h e t r a i t s d id n o t d i f f e r s i gn i f icantly b e tween t h e two s e xes .. of. They. c on c l uded f rom the r e s u l t s t h a t no s i gn i f i cant d i f f e r en c e s in the r ank ing o f s i re groups e xi s ted .. Gen e t i c c o r r e l a t ions b e tween t h e two s exes were. c a l c u lated t o ve r i fy the c on c l u s ions . \vere o b t a i ned .. Very h i gh gene t i c corre lat ions. Only t h e c o r r e l a t ion f o r b i r t h we i g h t in Ramb o u i l l e t and. f e e d e f f i c iency i n Romn e l e t appeared to dev i a t e marked ly f r om uni t y . Ab s e n c e o f s i gn i f i c ant s i r e - s ex in t e r a c t ions , s imilar i t y o f h e r i t ab i l i t i e s i n two sexe s and very h i gh gene t i c c o r r e l a t ions s u gges ted t h a t t he geno t ype s e x i n t er a c t ions we re not imp o r t an t in the t wo p o p u l a t ions o f t h e s t udy .. Brown e t a l .. ( 1 9 6 1 ) in t h e s tudy o f eva l ua t i o n o f f a c t o r s a f f e c t i n g. t he g rowt h o f s p r i n g lamb s f ou nd n o s i gn i f i ca n t l ine x sex i n t er a c t i on in b i r t h we ight and 1 2 0 d ay we i ght and wean i n g we i gh t . s igni f i c an t d i f f e r ences d ue t o s ex and l in e .. Ther e wer e n o.

(42) 29.. Geno type x year and o t he r s Rae ( 1 9 5 8 ) i n a s t udy o f gene t i c var i at ion and covar i a t ion in p roduct ive chara c t e r s o f New Zealand Rornney sheep f ound the in t e r a c t ion of s i res and years for body type o f sheep was no t s i gn i f i c a n t .. No s i gni f i c an t int e r a c t ion for body w e i g h t b e tween gene t ic o r i g in and age we r e f ound by D i e z. et. al .. ( 1 9 7 4 ) in C o r r i e d a l e s o f three. d i f f erent o r i g ins kep t in Peru a t a l t i t ude s o f 4 2 60- 5 0 0 0rn .. P e t e r s and Heaney ( 1 9 7 4 ) s t ud ied the int e r a c t ions i n fac t o r s i n f luenc ing t he growth o f l ambs reared ar t i f i c ia l l y o r w i t h t h e i r darns . I n c l uded in the exp e r iment we re the l amb s o f S u f f o l k and Sh ropsh i r e b re e d s and the i r re c ipro c a l c r o s s e s and O t t awa synthe t i c o r i g i n .. The re. were s i gni f i c ant int e r a c t ions o f rearing sys t em wi th b r e e d s of l amb ( P < 0 . 0 1 ) , s e x ( P < 0 . 0 5 ) , t yp e of b ir t h up t o 7 0 d ay s and rearin g s y s t em wit h year ( P < 0 . 0 1 ) in grow t h rate up to 1 4 0 d ay s of age .. C a r c a s s Charac t e r i s t i c s. Geno t ype x nu t r i t ion No s igni f i cant i n t e r a c t ions we r e ob s e rved b e tween s i re x ra t ion for c arcass t r a i t s ( c a r c a s s weigh t , d re s s in g p e r c ent , c a r c a s s grade , l o in e ye area and percent o f fat in carcas s ) by O srnan and Bradford ( 1 9 6 7 ) i n an exper imen t compa r in g g r ade Targhee l amb s a t two leve l s o f n u t r i t ion .. King e t a l .. ( 1 9 5 9 ) o b s e rved no s igni f i cant in t e r a c t ions for c a r c a s s. we i gh t , che s t c i r c umf eren c e , eye mus c l e (wi d t h x d e p t h ) and dep t h o f f a t ove r the eye muscle i n an exper iment t o s t udy d i f f e r en t i a l r e s p on s e o f l amb s o f var i o u s breeds an d cro s s e s t o d i f f e r e n t p lanes o f nu t r i t ion ..

(43) 30 ·. S i gni f i cant geno t y p e x nu t r i t ion and geno type x environment in t er a c t ions we re repo r t ed for growth , s laugh t e r we i gh t , d re s s i n g percent age , car c a s s c omp o s i t ion and meat cha r a c t er i s t i c s b y Budans t ev ( 1 9 7 3 ) i n an exper ime n t of me a t p rod u c t ion o f l amb s s ired by d i f f e r e n t. rams a n d fat t ened unde r d i f f erent cond i t ion s , i . e . , indoors vs p a s t u r e .. G E l e f fe c t s on l amb growth and c a r c a s s me r i t were repo r t ed b y Hohenb oken e t a l .. ( 1976b). ( s e e a l s o p 2 5 ) f ro m a dial l e l e c ro s s among. t hree b r e ed s rep l i c a t e d over three years and two graz ing management sys t ems .. In this s tudy both geno type x env i ro nment and ma t in g s ys t em x. env i ro nment interac t ions for g rowth and c a r c a s s qual i t y wer e s t ud ie d . For c a r c a s s wei gh t p e r d ay o f age , b reed of s ir e x management sys t em was h i ghly s i gn i f i cant .. B r e ed o f s ire x management sy s t em were a l s o. s igni f i cant f o r f in i sh s core and USDA qua l i t y gr ade .. S i r e b reed x y e ar. i n t e ra c t ions were s i gn i f i can t for f in i sh s c o r e (P< O . O l ) , percent kidney f at and fat thi ckne s s ( P < O . OS ) .. Imp o r t an t b re e d rank chan ges d id not. o ccur f o r any of t h e s e i n t e ra c t ions .. The only s i gn i f i cant d am b re e d x. year e f f e c t was percent k idney f a t (P<O . O l ) i n wh i ch b r eed o f dam e f f e c t s were more var iable i n some years than i n o t he r s . changes o c curred .. No imp o r t an t r ank. B r e e d o f s i re x b reed o f d am int e r a c t ions we r e. a b s e n t f o r a l l me asures o f c a r c a s s me r i t wh i l e b o th breed e f f e c t s and s ire e f f e c t s w i thin b r e e d we r e s i gni f i can t .. No three f a c t o r int er a c t ion. of s ir e b reed x d am b r e e d with management sy s t ems or with year was s i gn i f i c an t .. Geno type x l o c a t ion Car t e r e t a l .. ( 1973). ( s e e also p 2 5 ) examined the genotype-lo c a t i o n. i n t e r a c t ions i n t h e lamb c arcass t r a i t s and f o un d that t h e int er a c t ion was h i gh l y s i gn i f i c an t (P< O . O l) f o r c a r c a s s we i gh t and carcass grade ,.

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