Effect of concentrate supplementation on herbage consumption, milk production and composition, and on liveweight and condition score change in early lactation : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agric

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(1)Copyright is owned by the Author of the thesis. Permission is given for a copy to be downloaded by an individual for the purpose of research and private study only. The thesis may not be reproduced elsewhere without the permission of the Author..

(2) EFFECT OF CONCENTRATE SUPPLEMENTATION ON HERBAGE CONSUMPTION ,. MILK PRODUCTION AND COMPOSITION ,. AND ON LIVEVEIGHT AND CONDITION SCORE CHANGE IN EARLY LACTATION. A thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science Animal Science Department Massey University,. Palmerston North. NE� ZEALAND. �ISITIPORN SUKSOMBAT. 1988.

(3) ii. ABSTRACT. Each o f 1 5 s e t s o f i d en t i cal twins was graz i ng t r ea t me n t s ,. the. pas ture. concen t ra t e f e d t r ea tmen t ( CF ) . pas t u r e o n ly. and. those. fed. a l l oc a t ed. t reat me n t. to. ( PF ). Cows i n P F t r e a t m en t. two. and t h e were. fed. cows i n CF t re a tmen t wer e s u p pl emen t ed of. w i t h c o n c e n t ra t e s .. The. p e r enn i al rye g r ass .. The ex per imen t was c a r r i e d ou t f o r 1 4 weeks. ( 1 4 t h S e p t em b e r-2 1 s t. swards. used. were. p r ed om i n an t ly. December 1 987 ) o f the ear ly g r a z i ng s e a s o n. o f 1 987 .. T h e expe r i men t was carried ou t in two w i t h an. a l l owance. 1 9 87 a n d Pe r i od 21s t to. 30th. II. pe r i o d s ,. P e r i od. I. o f 20 kgDM/ cow/day f rom 1 3 t h t o 27 t h Oc t o b e r wi th a n allowance. November. 1 98 7 .. of. M i lk. 25. kgDM/c ow/day. yield ,. f ro m. m i lk c o mpos i t i on ,. an i ma l l i vewe i g h t and cond i t i on s core were meas u r e d .. H e r bage i n t ake was es t ima t e d by and was. 10 . 0. and. 9.0. sward. cu t t i n g. t e chni q u e. kgDM/ cow/day f o r supplemen t ed c ows , and. 1 1 . 8 and 1 2.2 kgDM/cow/day for. unsupplemen t e d cows i n Pe r i od s and. II. r e s p e c t ively .. Suppleme n t e d. cows. c o n s umed. I 6.7. kgDM/c ow / day concen t ra t e s i n b o t h p e r i od s .. T h e r e was a s i gni f i cant increase concen t r a t e s u p p lemen t a t i on .. The. in. mi lk. Yields. of. f a t i n P e r i o d II .. milk. due. to. average res p o n s e was 0 . 40 kg. m i l k/kg c onc en t r a t e OM ea t en or 0.68 kg m i lk/kg e a t en .. yield. e x t ra. feed. DM. cons t i tuen t s were i n c r e as e d ex ce p t f o r.

(4) iii. Concen t ra t e f e e ding had no e f f ec t o n lac t o s e. c oncen t ra t i ons. increased .. Sup p lemen t ed. bu t. m i lk. cows. m i lk. pro t e i n. and. milk. concen t r a t i on. was. l i vewe i g h t. and. more. gai ned. fat. cond i t i on s core t han unsupplemen t ed cows .. Concen t r a t e supp leme n t i n c reased kgDM/kgDM ea t en .. concen t ra t e. H e r bage. kgDM/kgDM. i n t ake. concen t ra t e. e a t en was. and. t o tal. 0 . 69. d e c reased. ea t e n .. MJME/MJME by. Res i dual. i n c r e a s e d by concen t r a t e s u p p l emen t a t i on .. i n t ak es. an. by. concen t r a t e. ave rage. herbage. 0 . 65. mass. 0 . 34 was.

(5) iv. ACKNO'ilLEDGEHENTS. I w i sh. to. t hank. Dr . c . v .. guidance ,. i nvaluea b l e. my. Holmes ,. as s i s t ance ,. adv i c e. s u p e rv i s o r , and. for. en cour agemen t. t hroughou t my s t ud i e s .. I a l s o w i s h t o t hank the following people :. Pro fessor B . R .. Vatki n f o r encouraging me t o s t udy i n. New. Zealand .. The s t af f s of Da i ry Research. Uni t. for. the i r. a s s i s t ance. during the expe r i me n t done. J.M.. Ren d e l and. V.. S e r e e p rasert for helpful. s ugges t i ons. and guidance wi t h s t a t i s t i cal p r o cedures .. M . F�. Sco t t and R . A .. Vatson f o r t h e i r help w i t h. che m i cal. analys e s .. V.. Cha tupo te f o r h i s as s i s t an ce i n d rawing g raphs .. The New. Zealand. Government. for. the. scholar s h i p. that. allowed m e t o c a r ry o u t my s t ud i e s .. The Dai ry Farming Promo t i on Organ i s a t ion o f. allowing m e to s t udy in New Zealand .. Thai land. for.

(6) V. F i na l ly , t o my w i f e , Piyarat , their. p a t i ence ,. comprehens i on ,. and support. my. son , and. t hroughou t a l l t h e period o f my Mas t e ra t e s t udy .. Sukr i t ,. for. encouragemen t.

(7) vi. TABLE OF CONTENTS. TITLE PAGE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i. ABSTRACT. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ii. ACKNOVLEDGEMENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i v. LI ST OF TABLE S .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. x. LI ST O F F I GURES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x i i. L I ST OF P LATE S . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . x i i i. 1 INTRODUCTI ON. .. .. .. .. .. .. .. .. .. .. 2 REVI E\1 O F L ITERATURE . .. .... .. .. .. .. .. .. .. . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. ... .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. 2 . 1 EFFECTS OF SU PPLEMENTARY FEED G IVEN TO GRA ZING COVS 2 . 1 . 1 E f f e c ts on Feed I n t ake and Subs t i t u t i on Ra t e 2 . 1 . 1 . 1 Ty pe of supplements . .. 2 . 1 . 1 . 2 Leve l of f e e d i ng . .. 2 . 1 . 1 . 3 Qual i t y o f feeds . .. .. .. 2 . 1 . 1 . 4 Phys i o l og i cal s t a t e. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 2 . 1 . 2 E f f e c t on Residual Herbage Mass. ... . .. 2 . 1 . 3 E f fe c t on M i lk Y i e ld and Compos i t i on . . .. 2 . 1 . 3 . 1 Type o f suppleme n ts 2 . 1 . 3 . 2 Level o f f eed i ng . . . 2 . 1 . 3 . 3 Qual i t y o f f eeds. .. .. .. .. .. .. .. .. .. .. .. ..... .... ... .. .. .. .. .. .. .. .. .. .. ... .. .. . .. . . . .. .. .. .. 2 . 1 . 3 . 4 S tage o f l ac t a t i on and level o f. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. •. .. .. •. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . 1. .. .. .. .. .. .. · .. .. .. .. . .. .. .. .. .. .. .. .. 2 . 1 . 4 E f f e c ts o n Li vewe i gh t and Body Cond i t i on Score. 3 3 3 3 4 6 6 7 7. .8. . .9 11 13 14.

(8) vii. 2 . 2 E FFECTS O F LEVEL O F FEEDING I N EARLY LACTATION . . .. .. .. . . . 16. 2 . 2 . 1 E f f e c ts on M i lk Y i e l d and Compos i t i on . . . . . . . . . . . 1 7 2 . 2 . 1 . 1 Immed i a t e e f fe c t . . . . . . . . . . . . . . . . . . . . . . . . . 1 7 .. 2 . 2 . 1 . 2 Car ryove r e f f e c t . . . . .. .. ......... .. ... .. . . .. .. .. . . . 18. 2 . 2 . 2 E f f e c t s on Livewe i gh t and/ o r Body Cond i t i o n . . . . 2 0 .. 2 . 2 . 2 . 1 Imme d i a t e e f fe c t .. .. .. .. .. ....... .... .. 2 . 2 . 2 . 2 Car ryover e f f e c t . . . . . . .. .. .. . . . . . . . 20 .. ............. .. .... 2 . 3 FACTORS CONTROLLING HERBAGE INTAKE B Y GRAZING DAIRY. .. .. . 21 . 22. 2 . 3 . 1 Volun t ary Food I n t ake . . . . . . . . . . . . . . . . . . . . . . . . . 2 2 .. .. 2 . 3 . 1 . 1 Me tab o l i c f ac t o rs . . . . . . .. .. ......... .. 2 . 3 . 1 . 2 Phys i cal fac t o rs . . . . . . . . . . . . . . . . . .. 2 . 3 . 1 . 3 Behav i o u r a l fac t ors . . . . . . . . . . . . . . .. 2 . 3 . 2 Pas t ure Fac t o rs .. .. ... .. ... .. .. .. .. ................... 2 . 3 . 2 . 1 Herbage mass . . . . . . . . . . . . . . . . . .. .. .. .. . . . . 23 .. ..... . . .. .. .. .. ... .. .. . 24 . 27. . . . . 28. . . . . . . . . . . . 28. 2 . 3 . 2 . 2 Herbage a l l owance . . . . . . . . . . . . . . . . . . . . . . 3 0 .. �. .. .. 2 . 3 . 2 . 3 Herbage d i g e s t i b i l i ty . . . . . . . . . . . . . . . . . . . . 3 1 .. 2 . 3 . 3 An i mal Fac t o rs .. .. .............. .. ........... .. .. .. .. . . . .32. 2.3 . 3 . 1 S i z e , l ivewe igh t , body cond i t i on , age . . . . 3 2 .. 2 . 3 . 3 . 2 E f f e c t o f p r egnancy . . .. 2 . 3 . 3 . 3 E f f e c t o f lac t a t i on . . .. .. .. .. .. . . . . . . . . . . . . . . . . 33 .. . ... .......... .. .. 2 . 3 . 4 E f f e c t of Suppl emen t ary F e e d i ng . . . . . . . . . . . . . 2 . 4 OBJECTIVE OF THE STUDY . . . . . . . . . . . . . . . . . . . . . .. .. .. .. . . 34. . . . 35. . . . . . . . . . 36.

(9) vi i i. 3 MATERIALS AND METHODS. .. .. .. .. .. .. .. .. .. .. .. .. 3 . 1 PRE-EXPERIMENTAL CONDITIONS 3 . 1 . 1 Cl i ma t ological Da t a .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 3 . 1 . 2 An i mals and T r e a tmen t s. . .. .. . . .. .. .. .. 3 . 1 . 3 An i ma l , Sward and Feed Manageme n t s 3 . 1 . 4 Pas t ures and Concen t ra t e s 3 . 2 MEASUREMENTS .. .. .. . . .. .. .. .. .. .. .. .. .. .. .. 3 . 2 . 1 F e e d Measu remen t s . . . . .. 3 . 2 . 2 An i ma l Measuremen t s 3 . 2 . 2 . 1 I n t ake. .. .. .. .. 3 . 2. 2 . 2 Li vewe igh t. .. .. .. .. .. .. .. .. .. . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. ..... 3 . 2 . 2 . 3 Body cond i t i on. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ... .. .. .. .. .. .. .. .. .. . .. . .. .. .. .. .. .. .. .. .. .. .. .. . .. 3 . 2 . 2 . 4 M i lk produc t i on and compos i t i on . .. 3 . 3 STATI STI CAL ANALYSI S . .. 4 RE SULT S. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ..... .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. ... .. .. .. .. .. .. .. .. .. . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 4:2 . 1 Pregraz ing Cond i t i o ns 4 . 2 . 2 Her bage In take. .. .. .. .. .. .. .. 4 . 2 . 3 Res i dual Herbage Mas s 4 . 3 ANI MAL PERFORMANCE S 4 . 3 . 1 Gene ral. .. .. .. .. .. .. .. .. .. .. ... .. .. .. .. . .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .... ... .. .. .. .. .. .. .. . .. . .. .. . .. .. .. .. .. . . . .. ... . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. ... .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ... .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . . .. .. ... .. .. . .. .. .. .. ... .. .. .. .. .. .. .. .. .. .. .. . .. .. 37. 39 41 42 42 42. . 44. .. .. 37. . 38 .. .. .. .. .. 4 . 1 CHEMICAL ANALYSI S AND GRO S S ENERGY DETERMINATI ON OF 4 . 2 SWARD CHARACTERI STICS. .. .. ... .. . . 35. .. 44 45 45 46. 49. . 49. . 50 .. . 50. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . 53 57 59. . 59 .. 4 . 3 . 2 Yi e l d s o f M i l k , M i lk Fat , M i lk Pro t e i n a n d . . . . . . 6 0 4 . 3 . 3 Mi lk Compos i t i ons. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 4 . 3 . 4 L i v eweigh t and Body Cond i t i o n Score. .. .. .. .. .. .. . .. .. .. .. .. . . .. .. .. .. .. .. . .. .. .. .. .. 62 64.

(10) ix. 5 DISCUSSION. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 5 . 1 EFFECT OF CONCENTRATE SUPPLEMENTATI ON O N HERBAGE. .. .. .. .. .. .. .. .. •. .. 80 80. 5 . 1 . 1 Measureme n t o f He rbage In t ake . . . . . . . . . . . . . . . . . . . B O 5 . 1 . 2 Herbage In t ake and Subs t i t u t i o n Ra t e. .. 5 . 1 . 3 Explan a t ion o f Reduced Herbage I n t ake 5 . 1 . 4 E f f e c t o n Res i d u a l Herbage Mass. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 5 . 2 EFFECT OF CONCENTRATE SUPPLEMENTATION ON MILK. .. . 82. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 84 90 93. 5 . 2 . 1 M i lk Y i e ld . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3 5 . 2 . 2 Y i e lds o f M i l k Cons t i t uen t s . . . . . . . . . . . . . . . . . . . . 1 1 1 5 . 2 . 3 Re s i dual E f f e c t on Y i elds o f M i lk and I t s . . . . . . 1 1 1 5 . 2 . 4 Compos i t i on o f M i lk. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 5 . 3 EFFECT OF CONCENTRATE SUPPLEMENTATI ON ON LIVEWEIGHT. 6 CONCLUSI ON. .. .. 7 B I B LI OGRAPHY. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . ... . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .... .. .. .. .. .. .. .. .. .. ... .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 113 116. . . 1 18 .. .. .. .. 120.

(11) X. LIST OF TABLES. Table. 3 . 1 Common Abbrev i a t i ons . . . . . . . . . . . . . . . . . . . . . . . . . . . .. Table. 3 . 2 C l i ma t ol ogi cal data t hrougho u t the expe r i me n t . . . . . . 3 9. Table. 3 . 3 Da t a f o r cows a t t he s t a r t o f t h e expe r i m en t . . . . . . . 40. Ta ble. 3 . 4 Summary o f the expe r i men t al des c r i p t ion . . .. Tab le. 4 . 1 Da t a f o r the analyses of feeds used i n t h e expe r i men t . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1 .. .. . . . . .. .. .. .. . . 38. . . 41. .. Table. 4 . 2 Mean values and resul t s o f ANOVA f o r t he amoun t s o f p r egra z i ng pas t u r e mas s ( kgDM / ha ) f o r t h e two t reatmen t s in P e r i o d s I and II . . . . . . . . . . . . . . . . . . . . . 52. Table. 4 . 3 M ean values and resul t s o f ANOVA for t he amoun t s o f he rbage , concen t ra t e and t o tal DM a l l owan c e ( kgDM/ cow/day ) f o r t he t w o t re a t men t s i n P e r i od s I and I I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3 .. Table. .. 4 . 4 Mean values and resul t s o f ANOVA f o r t h e amoun t s o f ME o f f ered f rom herbage , concen t ra t e and t o t a l ME allowance ( MJ / cow/day) for t he t w o t rea t men t s i n P e r i ods I and I I . . . .. . . . . . . . . . . . . . . . . 54 .. Table. .. .. .. .. .. .. .. .. .. 4 . 5 Mean values and resul t s o f ANOVA for t he amoun t s o f DM consumed from t he pas t ure, concen t ra t e and t o t al apparen t DM i n t ake ( kg/ cow/ day ) for t h e two t r ea tmen t s in P e r i ods I and I I . . . . . . . . . . . . . . . . . . 56 .. Table. .. .. .. .. .. .. .. 4 . 8 M ean values and resul t s o f ANOVA f o r t h e amoun t s o f res i dual he rbage mass ( RHM, kgDM /ha ) f o r t h e two t reat me n t s in P e r i ods I and I I . . . . . . . . . . . . . . . 60 .. Ta ble. .. 4 . 7 I n c rease in t o t al DM and M E i n t akes cau s e d b y t h e consum p t i on o f 1 kgDM o r 1 M J M E a s con cen t ra t e s i n Per i ods I and I I . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 8 .. Table. .. 4 . 6 M ean values and resul t s o f ANOVA for t he amoun t s o f ME cons umed from t he he rbage , concen t ra t e and t o t al ME cons umed ( MJ / cow/day ) f o r the two t re a t men t s in P e r i ods I and II . . . . . . . . . . . . . . . . . 57 .. Table. .. .. 4 . 9 Y i elds o f mi lk, mi lk f a t, mi lk p r o t e i n a n d m i lk l a c t o s e ( kg/ cow/day ) f o r the two t re a t men t g r o u p s i n P e r i ods I and I I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Table 4 . 10 Concen t ra t i on o f f a t , p r o t e i n and l ac t os e ( % ) f o r t h e t w o t reatmen t groups i n P e r i od s I and I I . . . . . . . 6 5.

(12) xi. Table 4 . 1 1 Mean values and resu l t s o f ANOVA f o r t he i n i t i al and f i na l l i vewe i gh t ( kg/ cow ) , t h e ini t i a l and f i nal body cond i t i on s c o r e ( un i t s ) , li vewe i gh t c hange ( grm /day ) and cond i t i on s co r e change ( uni t s / mon t h ) for t he two t rea t me n t groups i n P e r i o d s I and I I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .·. .. . 67. Table. 5 . 1 Changes i n i n t ake o f pas t u re and r e s idual h e rbage ' mass per un i t of add i t i onal Hay, S i lage o r Concen t ra t e expres s ed as kgDM/kg s u pplemen t DM, MJME/MJME supplemen t or kgDM/ha by gra z i ng cows . . . . 8 6. Tab l e. 5 . 2 Change i n y i e lds o f m i lk ( kg/ kgDM supplemen t ) and i t s cons t i tuen t s ( grm/ kgDM s u p p lemen t ) p e r un i t o f add i t i onal Hay, S i lage o r Concen t ra t e t o graz i ng cows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 5. Table. 5 . 3 Change in concen t ra t i ons o f m i lk cons t i t uen t s (%) , l i vewe igh t ( grm/kgDM supp lemen t ) , and body cond i t i on s c ore ( un i t s / mo n t h ) per uni t o f add i t i onal Hay, S i lage o r Concen t ra t e t o g ra z i ng d a i ry cows . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 9 .. .. Tab l e. 5 . 4 Changes in animal p e r f o rmance p e r kg ex t ra f eed D M ea t en by graz i ng d a i ry cows . . . . . . . � . . . . . . . . 104. Table. 5 . 5 Calcu l a t e d ene rgy balance f o r t he two t re a t men t s i n P e r i o d s I and I I . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 0.

(13) xii. LIST OF FIGURES. F igure. 4 . 1 E f f e c t of concen t ra t e s u pp l emen t a t ion on m i lk produc t i on over t he e x p e r i men t a l per i od . . .. F igu re. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 4 . 6 E f f e c t o f concen t r a t e s u pplemen t a t ion on concen t ra t i on o f m i lk p r o t e i n . . . . . . . . . . . . .. .. 4 . 7 E f f e c t o f concen t ra t e supplemen t a t ion on concen t r a t i on o f m i l k l a c t o s e . . . . . . . . ... .. . 68. . 69 .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 71. .. .. 73. . . . 74. 4 . 9 Trend in l i vewe i gh t change over the exp e r i men t a l pe r i od . . . . . .. . . . . . .... . . ... .. .. .. .... .. .. . . 72. 4 . 8 Rela t i on s h i p be tween changes i n l i vewe i g h t and changes in body cond i t i on s c ore over 14 weeks of expe r i men t . . . . . . . . . . . . ... .. F i gure. .. .. .. F i gure. .. 4 . 5 E f f e c t o f concen t ra t e s u pplemen t a t ion on concen t ra t i on o f m i l k f a t . . . . . ........ .. F igu re. .. .. .. F i gu r e. .. 4 . 4 E f f e c t o f concen t ra t e supplemen t a t ion o n m i lk . . . . . . .... ..... . . lac t os e y i eld . . . . . . .. F i gu r e. .. 4 . 3 E f f e c t o f concen t ra t e s u pplemen t a t i on o n m i lk pro t e i n y i e ld . . . . . .. .... . . . . . . . . . 70 .. F i gu r e. .. 4 . 2 E f f e c t o f concen t r a t e s u p p lemen t a t i on on m i lk f a t y i e ld . . . . . . . .. ... .. . .... . . . . .. F igure. .. .. .. .. .. 75. 76. F i gu r e 4 . 10 Trend i n body cond i t i on score change over t he exp e r i men t a l per i od . . .. .. . . . . . . . 77 .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ..

(14) xii i. LIST OF PLATES. P l a t e 4 . 1 E f f e c t o f concen t ra t e supplemen t a t i on on r e s i dual herbage mass ( a ) unsu p p lemen t e d group ( b ) s u p p l emen t e d group . . . . . . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. P l a t e 4 . 2 E f f e c t o f concen t ra t e s u p p l emen t a t i on on r e s i dual herbage mass ( a ) u n s u p p lemen t ed group ( b ) s u p p l emen t e d group ( Cl o s e d u p ) . . . . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 78. 79.

(15) CHAPTER 1 : INTRODU CTI ON.

(16) 1. INTRODUCTION. In New Zeal and d a i ry farmers rely on grazed pas t u r e as t he mai n s o u r c e o f f eed for t he i r da i ry manageme n t a t t emp t. to. stock,. and. t h r ough. t he i r. ma t ch annual demand w i th pas t u re su pply .. Howeve r , i n some years , sign i f i can t pas t u r e d e fi c i ts. can. occur. due t o excep t i onally cold or we t w i n t ers reduc ing pas t u r e grow t h r a t e s par t i cularly. on. those farms wi t h early cal v i ng .. s i t ua t i ons farmers are forced to u s e su ppl emen ts. such. I n such as. hay ,. si lage and meal concen t r a t e i n o rd e r t o f i l l the t em p o ra ry ' gap ' i n p as t u r e su p p ly .. The p rese n t s t udy was des i gned and the e f f e c t. i n i t i a t ed. to. exami n e. o f concen t ra t e sup pl emen t on an i ma l p e r f o rmance when. pas t u re a l l owance was res t r i c t ed , as i n the above examp l e s ,. and. when a l l owance was adequa t e .. Al t hough several expe r i men ts A r r i ga-Jo r d an. and. Ho lmes , 1 98 6 ;. ( Je nn i ngs. and. Gra i nge r , 1 987 ). H o l me s , 1 9 8 4 ; have. shown. r e l a t i v e ly poor and une conomi c res ponses t o concen t ra t e feed i ng , t h e s e have. generally. been. r e l a t i vely. shor t - t erm. s t ud i es .. Because many fac t o rs , such as leve l o f feed i ng , feed qual i ty and the an i ma l. i ts el f ,. c an. a f f ec t t h e response of graz i n g c ows t o. s u p pl e men t s , i t i s pos s i ble t ha t l onger- t e r m concen t ra t e f eed ing may show d i f f er en t and even more f avourable e f fec t s ..

(17) 2. The presen t. s t udy. f a c t o r s concerned f ee d i ng and also. wi t h the. graz i ng d a i ry cows .. also the. fac t o rs. a t t emp t s res ponse. to. de t ai l. the. maj o r. o f cows t o s u pp le men t ary. i n fluenc i ng. herbage. i n t ake. by.

(18) CHAPTER 2 : REVI E�. OF. LITERATURE.

(19) 3. 2 REVIEV OF LITERATURE. 2 . 1 EFFECT S OF SUPPLEMENTARY FEED GIVEN TO GRAZING CO�S .. 2 . 1 . 1 E f fe c t s on Feed In t ake and Subs ti t u tion .. There i s general agreemen t t ha t when su pplemen t s wi t h unres t r i c t ed. pas t u re. of. g ood. Bryan t , 1 9 7 8 ;. o f t en. S t ockdale and. Trigg , 1 9 85 ;. G r ainge r , 1 987;. �i lls , 1 988 ) .. The. term. supp lement is consumed .. King and. ' s ubs ti t u t i on r a t e ' i s pas t ur e. DM. qua l i t y o f. feed ing. he rbage. and. i n t ake. The subs t i t u t i on r a t e and. the amoun t o f t o t a l DM i n t ake can be i n f luenced by t he s u pp lemen t s , t h e. and. S t akelum , 1 9 8 6a , b , c ;. u s ed t o d e s cr i be t he amoun t o f reduc t i on i n kgDM. ( Hu t t on. Meij s. Trigg , 1 9 8 2 ;. Hoeks t r a , 1 984 ;. when 1. inc r e a s e d. S t ockdale e t a l . , 1 9 8 1 ;. and. Bryan t. S t o ckdale , 1 981 ;. fed. quali ty , cows c onsume l e s s. pas t u r e a l t hough t o t a l feed i n t ake i s and Parker , 1 9 6 6 ;. are. type. of. level o f her bage and s u p p lemen t s , t he su pplemen t s ,. physiolog i c a l. s tate. of. an i ma l s arid probably t he i n t erac t i on b e t ween t he s e f a c t o rs .. 2 . 1 . 1 . 1 Type o f supp lemen t s. Suppleme n t ary feeds a r e usually u s e d t o suppl emen t gra z i ng pa r ticularly when herbage i s i n s ho r t supply . t y p e of. supplemen t. H o lmes , 1 9 7 4 ;. effects. of. on subs t i t u t ion r a t e a r e var i a b l e ( Umoh and. B ryan t and. c o n founding e f fe c t. The. of. T rigg , 1 982 ) ,. p r o ba bly. o w i ng. to. the. feeding l evel , rela tions hi p wi t h pas t u r e. quali t y o r balance o f the w h o l e d i e t .. Howeve r ,. s u p p lemen t a tion.

(20) 4. wi t h a. p a r t i cular. nu t r i e n t. i nc re a s e the i n t ake o f. pas t u re. Pro t e i n. s u b s t i t u t ion r a t e .. w hi ch i s d ef i c i en t i n t h e d i e t can resu l t i ng. The. range. those. repor t e d. Demarqui l ly ( 19 7 9 ) ,. B i nes. reduc t i on. of. def i ci e n t. subs t i t u t i on. f e e d s a t vari ous phys i olog i cal s t a t e can s i m i la r t o. a. in. su pplemen t a t i on , f o r i ns t an c e , can. i n c re a s e pas t u r e i n t ake when t he d i e t is ( Kemp t on , 1 983 ) .. in. ra t e. be. in. pro t e i n. f o r var i ou s. cons i d ered. to. be. by Leaver e t al . ( 19 68 ) , J ou rne t and ( 197 9 ) ,. Meij s. ( 198 1 ). and. Leaver. ( 1 9 85 ) .. T o t al OM in t ake i s usually i n cre a s ed w i th t o g ra z i ng. c ows .. At. r e s t r i c t ed. h e rbage. su pplemen t a t i on. allowan ce , o f fe r i ng. g r a s s s i l age as a buffer feed leads t o a large i n c r eas e i n t o t a l D M i n t ake. ( Roge rs , 1 97 9 ;. Ph i ll i p s. B ryan t , 1 9 7 8 ;. and. Leaver ,. 1 9 8 5b ) .. 2 . 1 . 1 . 2 Level o f feed ing. The ex t e n t t o response t o. wh i ch. herbage. DM. suppl emen t a ry. feed i ng. under. largely d epend e n t o n H o e ks t r a , 1 98 4 ) .. level. of. herbage. Regard l e s s. of. the. i n t ake. type. reduced. in. graz i ng cond i t ion i s a l lowanc e of. s u b s t i t u t ion ra t e i s inc reased w i t h i nc r eas i ng Hoeks t ra ( 19 8 4 ). is. ( Me i j s. and. su pp l emen t s , t h e HA .. Meij s. and. wi th conc en t ra t e su pp lemen t i ng t o graz i ng cows ,. f o un d t h a t t h e subs t i t u t i on r a t e was s hown t o decrease f rom 0 . 50 a t a h igh HA t o 0 . 1 1 a t a low HA .. S i m i lar relat i onsh i p was also. o b s e rved w i t h hay suppleme n t ( El d r i dge and Ka t , 1 9 8 0 ; H o lmes , 1 988 ) and. � i l ls. and. s i lage s u pp l emen t ( Ph i l l i p s and Leaver , 1 985b ) ..

(21) 5. The r ela t i onsh i p be tween t he amoun t o f s uppl e me n t consumed and subs t i t u t ion rate has been s hown re v i ewing 1 1. z e ro. to. be. incons i s t en t .. graz ing exper i men t s cove r i ng t h e r ange 0-5 . 2. kg concen t ra t e DM , M e i j s ( 1 9 8 1 ) s howed a mean sub s t i t u t i on o f 0 . 45 .. ra t e. For a f ur t h er i n c remen t o f concen t ra t es o v e r t h e r ange. 2 . 7 - 6 . 9 kg. concen t r a t e. s u bs t i tu t i on r a t e was. DM. in. 0 . 60 .. re l a t i on s h i p, however ,. this. the Th i s. has. s ame exp e r i me n t s , t h e mean i nd i c a t ed. t he. curv i l i near. no t been con f i rmed in graz i ng. t r i al s w i t h lac t a t ing cows ( Me i j s and Hoeks t ra , 1 9 8 4 ) , w i t h ca t t l e ( Umoh Davey , 1 9 7 0 ;. and. Ho lmes , 1 9 7 4 ). Tayler. ( 1 9 7 4 ) , Combe l l a s. and et. and. by. graz ing. bee f. i n door t r i a l s ( Tapar i a and. � i lkins on, 1 9 7 2 ) .. Sarker. and. Ho lmes. al . ( 1 9 7 9 ) , and S t o ckd ale and T r i gg ( 1 985 ). even f ound a d e c r eas ing subs t i tu t i on r a t e a t h i gher i n t akes. In. dry. cows ,. he i fe r s. and. concen t ra t e. l ac t a t i ng. cows. res pe c t i v e ly .. I t i s s i mp ly tha t a t h i gh level o f feed i ng, e i t he r h i gh HA or h i gh suppleme n t in t ake , subs t i t u t i on r a t es are i n c reased. bu t. HA i s more l i ke ly to play a maj o r d e t e rm i nan t in i n f luen c i ng t he magn i t ud e o f subs t i t u t ion r a t e s ..

(22) 6. 2 . 1 . 1 . 3 Qual i t y o f feeds. The subs t i t u t i on ra t e can b e a f fe c t ed by s u p p lemen t .. Meij s. ( 19 8 6 ). f i b r e s up p lemen t ( 1 2 . 4. compared. and. 11. 7. a. the. q ua l i t y. of. h i gh s t arch w i t h a h i gh. MJME/ kgDM. respec t i ve l y ). for. g r a z i ng d a i ry cows and concluded tha t t h e h i gh s t ar c h s u p p lemen t caus ed h i gher. redu c t i on. in. the. consump t i on. o f pas t u r e ( 0 . 45. kgDM /kgDM as concen t ra t e ) t han t he low s t arch kgD M / kgDM. as. supplemen t ) .. He. s ugge s t ed. s u b s t i t u t ion r a t e was rela t ed t o the rumen t h e h i gh. s tarch. concen t ra t e. t ended. supplemen t change. t ha t. fe rmen t a t i on ,. celluloly t i c. ac t i vi ty. of. m i c robes .. resul t s. obse rved. J enn i ngs. and. Holmes. by. c on ce n t r a tes o f high or low qual i ty r e s p e c t ively ) .. Vi th. fo rage. i n f o rma t i on rela t ed t o a l . ( 1 9 8 1 ) and. K i ng. the. and. of. the. u nd e r feed ing , a l t hough. (13 . 6. d i f f e ren t. S t ockdale. suppleme n t t hey. whe r e. and. S i mi lar. ( 1 98 4 ). 12 . 0. with. MJME/kgDM. s u p p lemen t a t i on , t h e r e i s no t much. r e l a t i v e qual i ty o f hay compared abi l i ty. in. t o de c rease t he rumen pH ,. a f f e c t i ng t he were. (0 . 21. to did. ( 198 1 ). wi t h. sugge s t ed. pas t u r e. coun t e rac t no t. S t o ckdale. qual i ty .. compare. t ha t t he. d e t erm i n ed the. et. e f fe c t s. s u p p lemen t s. t he of of. d i f fe ren t d i ges t i b i l i ty .. 2 . 1 . 1 . 4 Phys i o logi cal s t a t e. I n f orma t i on about t h e e f f e c t o f s t age o f lac t a t i on s u b s t i t u t ion r a t e. is. c on t rad i c t ory. P h i l l i ps and Leaver , 1 98 5 a , b ) .. on. OM. ( J enni ngs and Ho lmes , 19 8 4;.

(23) 7. 2 . 1 . 2 E f fe c t on Res i dua l H e rbage Mas s. Supplemen t a t i on can B ryan t and. reduce. t he. gra z ing .. cows. res i dual. herbage. mas s. is. Cons i d e r i ng t h a t when su pplemen t s. i n creased b y 1 00-200 kgDM / ha .. e a t less pas t ure , an increase i n res i dual h e rbage. mass is presumably due to the su bs t i t u t i on r a t e f o r h e rbage. of. T r i gg ( 1 982 ) concluded from many exper i men t t h a t f o r. e ach 1 kgDM o f suppleme n t consumed ,. a r e fed. severi ty. ( � i l l s , l 988 ) .. of. su pplemen t s. The extent o f var i a t i on i n i n c r e a s e d. re s i dual he rbage m a s s i s p r obably. due. to. the. d i f f erences. in. h e r b age mas s , herbage a l l owance , level o f supplemen t feed i ng and the s u b s t i t u t i on ra t e .. 2 . 1 . 3 E f f e c t on M i lk Yield and Compos i t i on .. The e f fe c t o f su p p lemen t a ry feed i ng on m i lk y i e ld and m i l k compo s i t i on was. revi ewed. by. Bryan t. and. T r i gg. ( 1 982 ). who. t h e ave rage res ponse was a n ex t ra 0 . 5 k g o f m i l k. concluded t h a t. o r 2 1 g r m o f m i lk f a t f or each addi t i onal 1 kgDM consume d , w i t h. a. range. of. of. 0 . 32. supp lemen t. -0 . 2 t o 1 . 4 kg and - 6 t o 63 g rm o f. m i lk and m i lk f a t respec t i vely . average response. of. kg. Leave r. et. al . ( 1968 ). revi ewed. mi lk/kg supple men t e a t en whereas. J ourne t and Dermarq u i l ly ( 1 9 7 9 ) conclud ed an average r e s po n s e o f 0 . 4 kg m i lk / kg sup p lemen t cons umed . r e s p o n s e can. be. a t t r i bu t able. to. The. var i a t i ons. d i f f e rences. in. in. t he type o f. s u p p lemen t s , i n M E concen t ra t i o n per kgDM o f su pplemen t , i n amou n t and. s u ch. the. qual i t y o f bo t h pas t ure and supplemen t s consume d , i n. s t age o f l ac t a t i on , in level. of. produc t i on. and. p ro b ably. the.

(24) 8. combi na t i on o f t hese f a c t o r s a f fe c t i ng t he respon s e .. 2 . 1 . 3 . 1 Typ e o f supplemen t. Mos t ev i dence has shown tha t when rega rdl ess. of. the. type. of. d i e t,. cons t i tuen t s generally i n c r eas ed . rev i ewed by. Bryan t. and. T r i gg. su pplemen t s. y i elds. Based. on. ( 1 98 2 ) ,. of the. Those. fac t o r s. includ i ng. s u pp lemen t , frequency o f feed i ng and. m i lk. fed,. and. i ts. l i m i ted. data. t h e r e i s n o conv i n c i ng. e v i denc e t ha t produc t i on r esponse was a f fe c t ed by supp lemen t s .. were. the. type. of. qual i ty and q uan t i ty o f. i n t erac t i on s. among. t he s e. fac t o r s i n ass o c i a t i on wi t h pas ture fac t o r s ra t h e r t han t h e type of s u p p lemen t. i tself. affect. an i mal. produc t i on. r e s pons e .. I re land, Wa lsh ( 1 9 6 9 ) , for example, fed graz i ng d a i ry cows. In wi th. concen t ra t e or hay ad l i b i t um and observed d i f feren t r e s p on s e t o bo t h s uppl emen t s. type, o f. He sugge s t ed t ha t t h e d ige s t i b i l i ty , no t t he. su ppleme n t s. s u pp lemen t .. Th i s. a f f e c t ed. d i f feren t. respon se. per. kgDM. i mp l i ed t h a t as t he two supplemen t s con t a ined. d i f fe r en t ME concen t ra t i on, the ME i n t ake o f t h e cows were. also. d i f fe r en t and. When. hence. comp a r i sons have concen t ra t e s ,. t he. been. Rogers. cows showed d i f f e r e n t r e s p o ns e . made. et. b e t ween. al . ( 1 983 ). ene rgy. s hown. that. and. pro tein. s ign i f i c an t ly. grea t e r res ponses t o p ro t e i n t han ene rgy suppleme n t s o c cu rred i n only 4 o u t o f 8 i n c rease i n. the. 5% r e s pec t i vely .. expe r i men t s .. One. of. t he. exp e r i me n t. showed. y i e l d of m i lk, fat and pro t e i n by 1 6 %, 1 9% and Concen t ra t i on o f. pro t e i n concen t ra t i on was d e p ressed .. fat. was. i n c r e as e d. whe reas.

(25) 9. Al t hough t h e type o f su pplemen t s was p r o d u c t i on. r es pons e ,. c o n s t i tuen t s .. it. did. fat. M i lk. s u p p lemen t a t i on ( J enn i ngs Ph i l l i p s. H o l me s , 1 9 8 6; un l i ke ly to. but and. and. a f f e c t ed. The. was. by. Howeve r , fat hay. redu c t i on. in. milk. by. by. s i l ag e and. Arr i ga-Jordan. and. concen t r a t i on. was. a l . , 1 9 8 1;. milk. of. S t o ckdale. s u p pl emen t a t i on et. affect. d e p re s s ed. i n c reas e d. Leave r , 1 9 8 5 b;. t en d e d t o b e i nc reased ( S t ockdale Leave r , 1 9 8 5 a ) .. was. Holmes , 1 984;. S t akelum , 1 9 8 6 a ) . be. it. to. concen t ra t i on. concen t r a t i on. c o ncen t r a t e s u p p l emen t a t i on. T r i gg , l985;. affect. unl ikely. fat. a l though i t Phi l l i ps. and. conc en t ra t i on. co n cen t ra t e supplemen t a t ion has been sugges t ed t o be. due. by. to. a. h i gh p roduc t i on o f pro p i on i c a c i d and a low p r oduc t i on o f ace t i c and bu tyr i c a c i d s i n t h e rumen , depres s i ng t he secr e t i on o f m i l k f a t ( Rook. and. Thomas , 1 98 3 ) .. i n creased. by. concen t ra t e. T r i gg , 1985 ;. M i lk. s u p p l emen t a t i on. S t akelum , l 986a , b ). m i lk p r o t e i n. concen t ra t i on. protein. con c en t ra t i on was and. ( S t ockdale. Hay s u p p l emen t s had no e f f e c t on. but. s i l age. t ended. to. reduce. c on cen t ra t i on o f m i lk p r o t e i n ( Ph i l l i ps and Leaver , 1 9 8 5b ) .. M i lk. l a c t os e co ncen t ra t i on was un l i kely t o be a f f e c t ed by t h e type o f s u p p lemen t s .. 2 . 1 . 3 . 2 Level o f feed i ng. The e f f e c t. of. sup p lemen t a t i on. ( kgFCM/kgDM supp l emen t ) i n creased ( Leaver. et. a l . , l 9 8 1;. and. B ryan t. d e c reased al . , 1 9 6 8; T r i gg , 1 982;. P h i l l i p s and Leave r , 1 9 8 5 a , b;. on. an i ma l. p e r fo rmance. as t he overall feed i ng l e v e l B ryan t , 1 9 7 8; S t o ckda l e. S t akelum , 1 9 8 6 a;. S t oc kd a l e. et. and T r i gg , 1 9 8 5; G r a i nger , 19 8 7 ) .. \.

(26) 10. V i t h concen t ra t e supplemen t , S t o ckdale and T r i gg ( 19 8 5 ) obs e rved t h a t i n c reases. in. t o t a l DM i n t ake from 8 . 0 to 1 4 . 9 kg r e s u l t ed. i n d e cr eases i n m i l k r es ponse f rom 1 . 6 t o 0 . 55 kg/ kg. su pp l emen t. ea t en b u t i ncreases i n l i vewe i g h t gain .. A t comparable sup p lemen t i n t ake, response was low a l l owance. than. herbage. T r i gg, 1 98 5 ;. at. a t h i gh al lowance and t h i s usually o c curred. i n ass o c i a t ion wi t h t h e lower subs t i t u t ion for. grea t er. ( Ph i l l i p s. and. rate. Leaver, 1 9 8 5 a;. S t akelum, 1 98 6 a ;. of. s u p p lemen t. S t ockd a l e. G r a i nge r, 1 98 7 ) .. G o rdon. and ( 1979),. and Le Du and Newberry ( 1 9 8 2 ) even repor t e d overal l r e s p o n s e s o f 1 . 2, and. 2 . 9-3 . 5. kg. mi lk/kg. concen t r a t e. consumed, t o severe. re s t r i c t i on .. The e f f e c t o f level o f supp lemen t i n t ake on y i eld res ponse was v e ry small .. Such e f f e c t t ended t o. overal l feed ing. l ev el. and. sup plemen t. s hown a. of. i t s cons t i tuen t s. w i th. consumed ( Bryan t. and. largely. on. t he. t he amoun t o f pas t u re i n t ake r a t h e r. t han t he level o f tendency. d e p end. i t sel f .. Many. experi men t s. have. d e c reas ing res ponse in y i e ld s of m i lk and i ncreas ing T r i gg, 1 9 8 2 ;. the. level. Phi l l i ps. s u p p l emen t. of. and Leav e r, l 9 85b;. S t o ckda le and T r igg, 1 9 8 5 ) .. M i lk compos i t i ons were a f f e c t ed no t only by s up p l emen t. bu t. also. Expe r i men t s i n wh i ch r oughage t o. by t he. t he effect s. level of. of a l t e r i ng. t he. type. of. s u p p l emen t a t i on . t he. ra t i o. of. concen t ra t es had been s tu d i ed ( B ros t e r e t a l . , 1 9 7 9;. S u t t o n e t al . , 1 9 80 ) .. Vhen the ra t i o o f roughage t o concen t ra t es.

(27) 11. was reduced , m i lk f at concen t ra t ion f e l l The f a l l. in. milk. fat. concentra t i o n. e f fe c t s o f an inc r ease in m i lk s e c re t i o n .. There. was. also. bo t h. was. y i e ld some. in. exp e r i men t s .. due t o t h e com b in e d. and. a. e v i dence. d e c r eas e that. a. in. fat. d i f ferent. r e s pons e o c cu r red when d i f fe ren t typ e s o f concen t r a t e s w e r e u s ed ( Su t t on , 1 98 1 ) . s t arch such. as. concen t ra t i on .. a. Concen t ra t es con t a i n i ng c ereal. grains. led. to. those. cer eal. p r o po r t i on. of. depres s i on i n m i lk f a t. Mai ze and so rghum p roduced. concen t ra t i on than. h igh. a. h igher. m i lk. fat. g r a i ns �on t a i n i ng h i gh s t ar c h. ( Su t t on , 1 98 1 ) .. 2 . 1 . 3 . 3 Qua l i ty o f feeds. The e f f e c t of supplemen t a t i on on the d iges t i b i l i ty of whole d i e t. is. A. unclear .. d e p r e s s ion i n d iges t i b i l i ty i n t he. d i e t o f g ra z i ng cows su p p l emen t ed wi t h concen t ra t e ) has. t he. concen t r a t e. ( -0 . 4%/kgDM. been shown by Arriga-Jordan and Holmes ( 1 9 8 6 ) .. T h i s was probably due t o a. reduc t i on. in. gas t ro- i n t e s t i na l. pH. whi ch r esu l t ed in a r educ t i on i n t he d iges t i b i l i ty of s t a rch and cell wall. carbohy d r a t e. (Reid. et. al . , 1980) .. ( 1 9 8 0 ) d i d , howev e r , no t f i nd t h a t d e p res s i o n c ows suppleme n t ed. wi th. hay .. E l d r i dg e and Ka t in. non- la c t a t i ng. The a b s ence o f t h e e f f e c t o f hay. supplemen t on the d iges t i b i l i ty of t h e d i e t observed by t h e m can be a t t r i bu t ed tha t such e f fec t would depend on t h e d ig e s t i b i l i ty o f th e hay and o f the pas ture r a t h e r t han t h e t h e hay alone .. d iges t i b i l i ty. of.

(28) 12. M i lk y i eld was unli ke ly t o b e a f fe c t ed by t h e t he s u p p lemen t s. i t sel f .. in. qual i ty. sup plemen t .. Me i j s. s t arch wi t h a high f i b r e supp lemen t r e s pe c t i vely ) f or. graz ing. m i lk p roduc t i on f r om h igh s uppl emen t was t rea t m en t .. due. of. I t r e f l e c t ed t he d i f f erence i n herbage. i n take caused by d i f f e rence concen t r a t i o n ) o f. qua l i ty. to. ( 1986 ). ( 12 . 4. compared. and. 11 . 7. or. ME. a high. MJME/kgDM. da i ry cows and conc luded t h a t a h i gh f i bre. a. ( d i g es t i b i l i ty. supplemen t. h i gher. t han. h i gh. s ta r c h. herbage in t ake i n h i gh f i b r e. T h e fa t concen t ra t i on o f t he m i lk. was. a lso. h i gher. w i th t he f i brous con cen t ra t es due t o dec reased molar propo r t ion s of p r o p i on i c. ac i d. in. t he. rumen .. Ano t h e r gra z i ng compa r i s o n. be tween h i gh qual i ty and low qua l i ty concen t ra t e supp lemen t a t i on ( 1 3 . 6 and 1 2 . 0 MJME/kgOM resp e c t i vely) has been made by J enn ings and H o lmes ( 1 984 ) . cows fed. No s i gni f i can t d i f ference i n m i lk. y i e ld. of. e i ther h i gh or low qua l i ty concen t ra t e supplemen t s was. obse rved bu t m i lk fat concen t ra t i on was d e p re s s e d when cows we re fed t h e h i gh qual i ty concen t ra t e .. A l t hough Hu t t on S t o ckdale et. al .. and. ( 1 98 1 ). Parke r all. ( 1 9 65 ) ,. Parke r. ( 1966 ). and. have s hown pas t u re-hay d i e t s t o. have lower nu t r i t i v e value when compared wi t h pas t u re on ly , K i ng and S t ockdale ( 1 9 8 1 ) found the rela t i ve nu t r i t i ve value hay , i n. t e rms. t h a t o f pas t ure .. of. t he. o f p r oduc t i on and body cond i t i on , was s i m i lar t o The fo rmer au t h o r s. u sed. hay. hav i ng. t he. OM. d iges t i b i l i ty of 5 3 , 60 and 6 3% res p e c t i ve ly , whereas the la t t e r au t h o r s repor t e d. the. OM. d iges t i b i l i ty. add i t i on , t h e O M d iges t i b i l i t i es o f s t ud i es was. h igher. than. hay. of. pas t ure. hay. of. o f fe red. 7 0%. in. In these. ex cep t i n t h e t r i al s o f King and.

(29) 13. S to ckd a l e ( 1 98 1 ) t h a t. hay. pas t u r e ( 7 0. r espe c t i v e ly ) .. and. 6 3%. was. h i gher. in. d iges t i b i l i ty. These s e emed to i nd i ca t e. tha t t h e response t o a supp leme n t i s unl i kely t o depend rela t iv e diges t i b i l i ty. of. t he. p ropo r t i on o f t h e s e componen t s i n s i lage qual i ty. wh i ch. is. s u p pleme n t t he. t he. The. effect. of. supplemen t e d t o s t a l l feed ing c ows on ( Rogers , 1 985 ) .. aver age d iges t i b i l i ty of h i gh ( ea r ly c lo s u r e ;. The. Sep t ember , 2 3 ) and. O c t ober , 10 ) qual i ty s i l ages we re 7 2 . 5 and The. 6 7 . 6% r espe c t ive ly .. on. an d pas t u r e and t h e. diets .. m i lk p r oduc t i on has been recen t ly exam i n ed. of low ( la t e c l o s u re ;. t han. cows fed h i gh qual i ty s i lage p roduced. 1 . 1 5 kg FCM o f m i l k grea t e r t han. those. cows. fed. low. qual i ty. s i lage , bu t the l i vewe i g h t changes were s i m i l a r .. 2 . 1 . 3 . 4 S t age o f la c t a t i on and level o f p roduc t i on. Res ponse i n m i lk o u t p u t to i n c reased s u p p lemen t i n p u t been s ugges t ed. to. d e c l ine. as. lac t a t i on. has. advance ( Bros t e r and. Thomas , 1 98 1 ) s i nc e more energy i n t ake i s par t i t i oned t owards t he l i vewe i g h t a nd l e s s t o m i lk w i t h works by. advanc i ng. lac t a t i o n .. Recen t. Ph i l l i ps and Leave r ( 1 9 8 5 a ) and S t o ckdale e t a l . ( 1 98 5 ). also r epo r t ed a d e c reas e in m i l k y i e ld per kgDM supplemen t e a t en as lac t a t ion advan c e . J enn i ng s and. Ho lmes. H oweve r , t h i s e f f e c t was no t o b s e rved ( 1984 ). and. Ph i l l i p s. and. by. Leave r ( 1 9 8 5 b ). s u ppl emen t ing wi t h concen t r a t e and s i lage r e s p e c t i ve ly ..

(30) 14. Marg i na l res ponse i nc r eased. by. the. milk. ( kg. FCM / kgDM. po t en t i a l. of. s u p plement ) the. cows .. a l . ( 1 98 7 ) r e po r t ed a margi na l response o f 0 . 6 , 1 . 2 and cows o f. be. C o u l on 1.6. et for. a po t en t i a l o f m i lk y i e ld o f 2 6 kg , 2 6-29 kg and > 2 9 kg. re s pe c t i v e ly . only. can. in. H i gh y i e l d i ng cows s howed a g r e a t e r r e s p o n s e. milk. s u pp lemen t a t i on. produc t i on low. t han. but. also. y i e l d i ng. in. l i vewe i gh t. gain. ( Ph i l l i p s. cows. no t to and. Leave r , 1 9 8 5a ) .. 2 . 1 . 4 E f f e c t s on Li vewe igh t and Body Cond i t i on Score .. Many t r i al s have shown tha t on mos t occas i ons , s u p p l emen t s reduced l i vewe igh t depend ing on. those. ( 2 . 1 . 1 and 2 . 1 . 3 ) . t e rm t r i als. loss. and. or. f a c t ors. even. i n c reased. ou t l i ned. in. li vewe igh t. the. p r ev i ou s t o p i c s. B ryan t and T r i gg ( 1 9 8 2 ) revi ewed many showed. gain. sho r t. the ben e f i t f o r 1 . 0 kgDM o f s u p p lemen t. cons umed o f 1 50 grm/ kgDM reduc t i on i n l i vewe i g h t l o s s. in. e a r ly. lac t a t i on .. The e f f e c t of supp lemen t a t i on on l i vewe i gh t changes i s n o t a lways r e p o r t e d .. However , Hu t t on and Parker. S t o ckda le ( 1 9 8 1 ). and. B ryan t. and. ( 19 6 6 ) ,. King. and. T r i gg ( 1 9 8 2 ) have obs e rved a. c o r respond i ng t endency for grea t e r i nc reases i n l i vewe i gh t ga i n s d u e t o s u p plemen t s , when t he ove r a l l l e v e l o f feed i ng i n creased ..

(31) 15. T y p e of s u pp lemen t i s u n l i ke ly t o a f f e c t the l i vewe igh t change . type d o a f f e c t abs e n c e. of. I ts. l i vewe igh t. pos i t i ve. and. qual i ty and. effec t. s c o re. l i vewei gh t. consumed as hay a t very h i gh HA i n t he t r i al s a l . ( l 9 8 1 ) was. in. quan t i t y ra t he r t han i t s. cond i t i on on. response. c hange .. change of. The. per. un i t. S t o ckdale. et. mai nly due t o t he r e l a t i vely low d i ge s t ib i l i t y o f. hay c o mpared wi t h pas ture o f f e red and t o v e ry h igh. s ubs t i t u t i on. r a t e a s wel l .. Any e f fe c t o f sup plemen t a t i on on m i lk response to. be. adverse ly. a f f e c t ed. by. l i vewe i gh t. gai n. is. because. pa r t i t i on o f energy con sumed be tween m i lk a n d l i vewe i gh t In. nega t i ve r e l a t ionsh i p . ene rgy i n take l i vewe igh t gain effec t .. is. early. pa r t i t i oned bu t. as. to. lac t a t i on. l i ke ly. has. the a. la c t a t i on , for examp l e , mo re produce advan ce. m i lk. and. less. to. t h i s shows reverse.

(32) 16. 2 . 2 E F FECT S O F LEVEL OF FEEDING I N EARLY LACTATION.. A t a g i ven level o f feed i ng in early lac t a t i on , c ows l ower i n l i vewe i gh t or body cond i t i on s co r e at m i lk t han. c ows. r a t her. t han. T h e l i vewe i gh t the. rate. of. or. a f f e c t i ng f u t u re. level o f. p r oduc t i on. King e t al . , 198 5 ) . feeding. precalvimg. ( Roger s. at. s i m i lar. in. more. less. cond i t i on. at. l ivewe i gh t. or. impor t an t. e t al . , 1979 ;. fac t o r. G r a i nge r e t. Ne i t her t h e type o f d i e t n or had. a. measurable. subs equen t m i lk y i e ld , m i lk compos i t i on cows calve. body. change. cond i t i on score p r i o r t o calv i ng i s the. al . , 1 98 2 ;. p roduce. calv i ng a t h i gh e r l ivewe igh t or cond i t i on s co r e. ( Gr a i ng er e t al . , 1 9 8 2 ) . calving. calvi ng. or. i n f luence. l i vewe i g h t. if. the on the. we igh t or cond i t i on s c ore ( Hu t t on , 1 9 7 2 ;. Rogers e t al . , 1 98 1 ) .. Changes in level o f feed i ng are ou t p u t o f. t he. r e f l e c ted. in. cow and in changes i n body we i gh t .. bo t h. milk. Unde r f eed i ng. in e a r ly la c t a t i on , for examp le , resul t e d i n a redu c t i on i n m i lk y i e ld , l i vewe igh t and cond i t i on s cor e , and i n an m i lk compos i t i on ,. no t. only. but. ( carryover e f fec t ). ( B ros t e r , 1 9 7 1 , 1 9 7 2 ;. a l . , 1 9 87 ) .. later. t he. ( i mmed i a t e e f fec t ). Bros t e r and Bros t er , 1984 ;. the. du ri n g. Bros t e r e t. s t age. t i me. al t era t i on. o f und e r f e e d i ng. a f t er G r a i nger. a l . , 1 984 ;. of. und e r f ee d i ng e t a l . , 1 98 2 ; S t o c kd a l e. et.

(33) 17. 2 . 2 . 1 E f f e c t s on M i lk Y i eld and Compos i t io n .. 2 . 2 . 1 . 1 I mmed i a t e e f fec t. Under feed i ng i n early lac t a t i o n r e d u c e d y i e l d and the c ompos i t i on. of. mi l k .. B ryan t. a l tered. a n d T r i gg ( 1 98 2 ) s umma r i s ed. seve ral t r ials f rom Aus t ral i a and New Zea land and concluded t h a t o n ave rage a 38% res t r i c t i on o f D M. i n t ake. reduc t i on. Th i s. in. m i lk. fat. yield .. resul t ed can. be. in. a. 24%. express ed. in. quan t i t a� iv e t e rm s t h a t a decreas e i n D M i n t ake 1 . 0 kg cause d decrease in. 39. grm. m i lk. propo r t i onal t o. the. dura t i on. and. ( B ryan t. T r i gg , 1 9 7 9 ;. fat .. a. The e x t en t o f t h i s d e c r e a s e i s and. s e ve r i t y. G ra inger. and. add i t i on , t he res ponse t o change i n level. of. und e r f eed i ng. Wi lhelms , 1 9 7 9 ) . of. feed i ng. in. In milk. y i e l d i s grea t e r a t low levels o f feed i ng t han at h i gher leve l s , i s g r e a t e r in h i gh er than in lower y i e l d i ng cows and i s lower i n mi d - l a t e lac t a t i o n t han in e arly lac t a t i on ( Bros t e r e t al . , 1 9 8 1 ; Bros t e r and. Bros t e r , 1 9 8 4 ) .. feed i ng a f t e r calv ing w i ll. Of no t. in teres t en t i re ly. i s however t h a t good compens a t e. for. poor. feed i ng p r i o r t o c a l v i ng i f the cows calve i n low body cond i t i on score. ( Bryan t , 1 9 80 ;. al . , 1 9 8 6 ) . cond i t i on at. Al t h ough. a. pos i t i ve. et. al . , 1982 ; interac t i on. Treacher. et body. be tween. calv i ng and f eed i ng level in week 1 -5 for m i l k and. m i lk fat y i eld ( 2 0 ( 1 98 2 ) .. G ra i nger. weeks ). was. observed. by. Graing er. et. al ..

(34) 18. I mme d i a t e e f f e c t s o f f ee d i ng level on m i lk compos i t i on are smal l , however , cons i d e ring t h a t t h o s e s umma r i s ed by B ryan t T r i gg ( 1 9 8 2 ) i n t ake .. are. the. resul t. of. abou t. and. a 40% redu c t i o n i n DM. These au t h o r s also concluded tha t unde rfeed i ng in early. lac t a t i on had an unpred i c t able e f f ec t on f a t , bu t. generally. reduced. the. the. concen t ra t i on. concen t r a t i on. of. o f p r o t e i n and. s o l i d-no t - fa t in m i l k .. 2 . 2 . 1 . 2 Carryover e f fe c t. of. The e f f e c t m il k. s ubs equen t. ( B ros t e r , 1 9 7 2 ;. under feed i n g. y i eld. and. Bryan t. compo s i t i on. and. l a c t a t i on. early. in. been. have. on. revi ewed and. Bros ter. T r i gg , 1 9 8 2 ;. Bros t e r , 1 9 8 4 ) .. Recen t wo rks in New Zealand ,. Bu t t on. and. T r igg ( 1 9 7 9 ) and G l a s s ey � al .. B ryan t and. Parker. ( 1 980 ) a l l found no. s igni f i can t res i dual e f fe c t on y i e l d s of unde r f eed i ng lac t a t i o n .. Howeve r ,. f r om. Bryan t and T r i gg ( 1 9 8 2 ) whi ch. was. 0.5. t i mes ,. New. Zealand. repo r t ed. an. or. les s ,. und e r f e ed i ng i n early lac t a t i on . th e. UK. a nd. Hodgs o n , 1 9 7 9 ;. S c ot l and ,. no. mode r a t e c a r ryover e f fe c t , up to effect. ( �ood. and. Newcomb , 1 9 7 6 ;. a l . , 1 9 7 9 ) were obs e rved .. in. e a rly. and Aus t ra l i an t r i a ls ,. ave rage the. res i dual. i mmmedi a t e. e f f ec t. effect. of. Compared w i t h recen t works. in. res i dual. Bla i r et al . , 1 98 1 ;. ( 19 7 3 ) ,. effect. ( Combel l a s. and. Baker e t al . , 1 9 8 2 ) , sm all and 0 . 5-0 . 7. t i mes. Johnson , 1 9 7 7 ;. the. i mmed i a t e Le. Du. et.

(35) 19. These resul t s con t ras t ed t o t he early i n forma t i on f rom New Zealand ( Va l lace , 1 9 5 7 ;. Pa t ch e l l , 1 9 5 7 ) and the UK ( Br o s t e r , 1 9 7 2 ). wh i ch c a r ryover e f f e c t was t hree o r e f fe c t .. The. con t ras t ing. resu l t s. more may. t i mes. be. t he. i mmed i a t e. a t t r ibu t ed. to. gene t i c. v ar i a t i on i n t h e dura t i on and seve r i t y o f under feed i ng , mer i t , cow. t he. cond i t i on and mo re i m po r t an t t he s ubs equen t level o f. feed i ng .. Da t a on su bs equen t e f fec t s on mi lk c ompos i t i on s hown to. be. inconclus ive .. been. Flux and Pat c h e l l ( 1 9 5 7 ) rep o r t ed a. r e s i dual fall in m i lk fat concen t ra t i on i n early. have. f o l lowing. unde r fe ed i ng. lac t a t i on whereas G r a i ng er and V i lhelms ( 1 9 7 9 ) d i d n o t. f i nd t hi s , d e s p i t e an B ros t e r ( 1 9 7 2 ). apparen t. summa r i sed. e f fec t. from. curren t. feed i ng .. some early evi dence showing res i dual. e f fe c t on p r o t ein and lac t ose concen t ra t i on s i n t he m i l k . re cen t wor k s. ( S teen. and. Gordon , 1 9 8 0a , b ;. More. Glassey e t al . , 1 9 8 0 ). i nd i ca t e n o res idual e f fec t o n m i lk compos i t i on ..

(36) 20. 2 . 2 . 2 E f f e c t s o n Liv ewe i gh t and / o r B o d y Cond i t i on Score .. 2 . 2 . 2 . 1 I mmed i a t e e f fe c t. Und e r f ee d i ng i n early. lac t a t i on. generally. reduced. body. we i gh t and. cond i t i on s core ( B ryan t and T r i gg, 1 97 9 ;. al . , 1 9 8 2 ) .. An a verage o f 1 7 4 grm ex t ra l i vewe i gh t , w i t h a range. o f 2 7 - 5 7 0 grm , was a s s oc i a t ed wi t h an ex t ra. 1. G r a in g er e t. kgDM. i n t ake. in. Aus t ra l i an and New Zealand t r i als su mma r i s ed by B ryan t and T r i gg ( 1 982 ) .. The. var i ab i l i ty. of. res pons e. may. be. a t t r ibu t ed. d i f f e rences i n t h e ex t en t o f par t i t i on i ng o f f eed and body ga i n . w i l l us e. a. m i lk. Cows calv i ng in low body cond i t i on, f o r exampl e ,. grea t er. propo r t i on o f t h e f eed f o r l i vewe i gh t ga i n. bu t a smal l p r opo r t ion h i gher body. be tween. for. mi lk. produ c t ion. cond i t i on at calving .. than. those. wi th. A l s o as a cow approaches i t s. po ten t i a l m i l k p r oduc t i on t here f o r e an i n c r eas i ng propor t i on th e ex t ra. feed. to. of. cons umed w i l l be pa r t i t i oned t owards l i vewe i gh t. ga i n and t hus more f eed w i l l be requ i r ed. to. p roduce. an. e x t ra. m i lk produc t i on .. I t s hould a l s o no t e t h a t a t a g i ven level. of. i n t ake. t he. grea t e r t h e y i e l d po t en t i a l of t he cow t he smaller t he body g ai n and i n. c o n f o rm i t y. with. t h i s,. the. g r ea t e r. the. add i t i onal nu t r i e n t s to m i lk t han t o body by t he cow ( Bros t e r e t al . , 1 9 7 5 ) .. par t i t i o n o f h igh. y i e l d i ng.

(37) 21. 2 . 2 . 2 . 2 Carryover e f f e c t. The p r e v i ous less generous ly fed cows i n gai ned more. we igh t. be t t e r f e d. lac t a t i on. mid. ( B ryan t. cows. � i lhelms , 1 9 7 9 ;. in. an d. S t ockdale. lac t a t i o n. t han d i d t h e p revi ou sly. T r i gg , 1 97 9 ;. al . , 1 9 8 1 ) .. et. e a r ly. Th i s. G r a i ng er. and. o c cu rred. wi t h. equal d i e t s i n m i d lac t a t i o n a s we l l a s w i t h res t r i c t ed g ra z i ng . G ra i nger e t al . 1-5. of. ( 1 982 ) re p o r t e d t h a t i mp roved feed i ng. la c t a t i o n. conserved. body. t i s s ues ,. bu t. cond i t i on at calv i ng was a s s o c i a t ed w i t h grea t e r t h i s per i od .. In. weeks. 6-20. in. week. be t t e r. body. body. and. the. cows. con t i nued t o lose more ( 1 98 1 ) revi ewed. 46. gene rously f e d cows. in. in. on equal feed i n g , change i n body. cond i t i on s c o re was inversely propo r t i onal t o feed i ng weeks 1-5. loss. be tter. cond i t i on. level. in. body condi t i on at c a l v i ng. s c or e .. Bros t e r. and. Thomas. t r ials and conc lud ed tha t the prev i ou s l e s s gained. 0 . 15. kg/ d ay. lac t a t i on t han those we ll f e d th roughou t .. more. we igh t. in. mid.

(38) 22. 2 . 3 FACTORS CONTROLLING HERBAGE I NTAKE B Y GRAZING DAIRY COV S .. 2 . 3 . 1 Volun t a ry Food I n t ake .. Food i n t ake and i t s var i a t i on i s one o f t he maj o r d e t er m i n i ng level pas t u r e. and. e f f i c i ency. ( B i n e s, 1 9 7 9 ;. of. an i ma l. Hodgson, 1 9 8 2 ;. fac t o r s. produ c t i on. from. Leaver , 1 98 5 ) .. The. p r i nc i p l es of food i n t ake con t rol w hi ch have been s t ud i e d m ai nly unde r i n d o o r. feed ing. cond i t i o n. are. ass umed. to be a p p l i ed t o. graz i ng an imals wi t h c e r t a i n l i mi t a t i ons ( Arnold,1 9 70 ) , a l t hough food i n t ake by graz i ng an imals w i l l be a f f e c t ed. by. many. o t he r. fac t o r s by wh i ch s ta l l - fed animals are no t a f fec ted .. Volun t a ry food i n t ake o f ani mals i s i n f luenced by two ma i n fac t o r s , me t abol i c fac t or s - fac t o r s wh i ch i n fluen ce t h e requ i remen t s. for. nut r i e n t s. abs orbed nu t r i en t s , i n f luence ac commo d a t e. t he and. ( B aumgard t , 1 9 7 0 ; regula t i on. of. and. and. phys i cal. ani mal ' s. ab i l i t y. d i ge s t. it. B i nes , 1 9 7 1 ) . food. i n t ake. i n t e r - r ela t i o nsh i p be tween fac t o r s ( Hodgson, 1 9 7 7 ) .. these. i ts. ab i l i ty. to. me t abo l i s e. fac t o r s. fac t o r s. to. t he. in. cons ume the. For is t wo. feed,. to. an i ma l s. the. by. t he. d e t e rmined fac t ors. wh i ch. t ra c t. d ige s t i ve. graz i ng. an i mal. an d behav i o u r a l.

(39) 23. 2 . 3 . 1 . 1 M e t abo l i c fac t o rs .. The c on t ro l componen t. of. of. the. food. i n t ake. homeos t a t i c. c an. animal a t t emp t s. Baile to. and. con s i d e red. regu la t i on. be tween t h e an i ma l and i t s env i ronmen t and Forbe s , 1 9 7 4 ;. be. of. ene rgy. a. cons t a n t. a. balance Baile. ( Baumgard t , 1 9 7 0 ;. M cLaughl i n , 1 9 8 7 ) .. ma i n t a i n. as. I n gen e r a l t he. energy. balance. by. chang ing food i n t ake in propo r t i on t o i t s energy requi remen t and i t s al t er ed phys i olog i cal and envi ronmen t al c i rcums t ances ( Ba i l e and Forbes , 1 9 74 ) .. Phys i o l ogi cal con t rol i nvolve t h e. po t en t i al. feedback. of. t he end p r oduc t s o f d i ges t i on and me t abo l i sm t o neural r e c e p t o r s i n t he. bra i n .. The. recep t o r. s i tes. for. t h e feedback con t ro l. sys t em wh i ch i n f o rm t he bra i n abou t t h e nu t r i t i onal s t a t e o f t h e body apparen t ly. or i g i na t e. hepa t i c- p o r t al sys tem ,. in. ad i pose. t i ssue. cerebros p i na l flu i d ( Baumgard t , 1 9 7 0 ;. Vola t i le fa t ty a c i d s r a t h e r prod u c t s o f. energy. d i ges t i on. componen t s o f. food. i n t ake. Mayer , 1 9 7 0 ;. B i nes , 1 9 7 1 ;. in. and / o r. p e r i pheral. t han. glucose. rum i n an t s. are. and. ( Ba i l e. sys t em. S o es t , 1 98 2 ) .. impo r t an t .. ( Ba i le The. role. and of. the. main. are p o s s ible. P r o p i ona t e. a ce t a t e are recogni sed as pos s ib l e · feedback s ignal s i n ruminan t s. and. Fo rbes , 1 980 ) .. regula t i on Van. t rac t ,. gas t ro i n t es t i nal. t he. of. and and. s a t i e ty. Mayer , 1 9 7 0 ). whereas bu t y ra t e i s l e s s. lac t a t e. c o n t rovers i a l ,. is. depres s i ng the mo t i l i ty of the s t omach ( Fo rbes , 1 980 ) .. p r obably.

(40) 24. I t has been involved i n. sugges t ed. t ha t. the. fall. in. rumen. pH. is. t h e c es s a t i on o f feed ing ( Kaufman n , 1 9 7 6 ) , a l t h ough ,. as f o r t he f ree f a t ty a c i ds ( Ba i l e and Forbe s , 1 974 ) i n t h e s ho r t t e r m , there i s l i t t le i n forma t i on t o show i f t h ey. are. a. cause. Food i n t ake o f rumi nan t s i s res t r i c t ed p r ima r i ly by. rumen. rather than an e f f e c t of changes i n fee d i ng .. 2 . 3 . 1 . 2 Phys i ca l fac t or s .. capac i t y s i nce f i b rous feeds. it may. is. gene t i c. B i ne s , 1 9 7 1 ;. t ha t. rumi nan t s. bul ky and. have. consumed. e a t i ng. be fore. to. obtain. t he d i e t ary ene rgy r equ i red by. M e i j s , 1 98 1 ) .. p roduc t i on. for. po t e n t ial. t h ey. fed. s top. s u f f i c i en t nu t r i e n t s the i r. ev i d en t. ( Camp l i ng , 1 97 0 ;. The phys i cal l i m i t a t ion i s r e l a t ed t o. t he d i s t en t ion o f t h e r e t i culo rumen and ra t e o f d i sappearance o f d iges t a f rom t h e re t i cu lorumen .. D i s t en t i on o f t h e r e t i culo rumen. Rumi nan t s f ed a large propo r t i o n of roughage consum e to cons t a n t rumen. fill. ( Camp l i ng , 1 9 7 0 ) .. a. The s i ze o f t he rumen i s. par t ly d e t e rm i ned by t h e s i ze o f abdomi nal cav i ty , wh i ch appears to be. l i m i t ed. ( Bines , 197 1 ) .. in. wh i ch. ex t en t. However ,. foe t a l enlargemen t cav i ty. the. and. s ugge s t ed. to. wh i ch. t he. rumen. fa t. depos i t i o n. that. There. s t re t ch. can. c a pa c i t y can be a f f e c t ed by. reduced. wi t h in the. re t i culorumen a n d t h i s i s a s s o c i a t ed w i t h a an i ma l s ( Forbes , 1 9 80 ) .. it. the. abdominal. ext ens i on reduced. of. i n t ake. the by. are s t re t ch r e c e p t o rs in t h e rumen.

(41) 25. wall b u t t h e unknown .. exac t. The. mechani s m. p robable. s t imula t i on of the. of. t ransmi s s i o n. mechan i s m. humoral. can. i n t ake. be. by. regula t i ng. s till. rema i ns. d i s comfo r t ,. by. fac t or s. by. or. mechan i s m of rum i na t i on ( Van Soes t , 1 9 8 2 ) .. The phys i cal l imi t a t i on o f s pace i n t h e t rac t i mp l i es. that. ( Raymond , 1 9 6 9 ; rela t ed t o. volume. �ald o , 1 98 6 ) .. r a t he r. than. Phys i cal. gas t ro - i n t es t i n a l. m a s s i s o f i m po r t an c e. con t ro l s. are. p r i m a r i ly. t he capa c i ty o f t he d i ge s t i v e t ra c t ( F reer , 1 9 8 1 ) , t o. the f i b r e con t en t o f the feeds and t o t he and passage ,. therefore. the. rate. of. degrad a t i o n. i n d i ge s t i ble f r a c t i on o f t h e DM i s. th e maj o r phy s i cal fac t or l i m i t i ng i n t ake ( Chase , 1 9 8 5 ) .. In a d d i t i on phys i cal proper t i es quan t i t i e s ea ten. at. meals. and. of. feed. will. of. ea t i ng .. pa t t e rns. i n f luence H i gh e r. dens i ty g r a i n s , f o r example , a r e l i kely t o be consumed i n amoun t s in. meals. wi th. low. l arge. f r equency , whi l e low dens i ty s t raw. d i e t s are l i kely t o be e a t en i n more. f r eque n t. meals. of. small. amoun t s ( Ba i le , 1 9 7 5 ) .. Howeve r , the r o l e o f gu t f i l l as con t r o l mechani sm o f f o o d i n t ake i s s t i l l con t rovers i a l , a n d i t has b e e n th e type. of di e t .. as s o c i a t ed. wi th. Some au t h o r s ( B i ne s and Davey , 1 9 7 0 ) r e po r t ed. a l i m i t a t i on t o food i n t ake by gu t capa c i t y i n. cows. fed. m i xed. d i e t , whereas o t he r s ( �aldo , 1 9 8 6 ) cons i dered t h a t h e rbage i n t ake is no t l i m i t ed by s mall or large i n t es t i nes ..

(42) 26. Ra t e o f d i sapp earance of d i ges t a. The ra t e o f d i ges t a pas s ing from the re t i culo rumen depends on the chem i cal compos i t i on o f the feed , t he rate a t feed is. w h i ch. the. b roken down phys i cally ( mas t i ca t i on and rumina t i on ) and. ch e mi c a l ly ( m i c r o b i al and enzyma t i c d i ge s t i on ) ,. the capac i ty. mus c u l a r. size. con t ra c t i on. of. t he. gu t. re t i cul o-omasal o r i f i ce. ( Me i j s , 1 9 8 1 ;. Re t en t i on. the. of. feed. in. m i c r ob i a l fermen t a t i on to d i ges t i on occu r r i ng. and. t he. Ulya t t. re t i culo rumen. t ake. place ,. wi t h. of. of t he. et. a l . , 1 985 ) .. al lows. s ubs t an t i a l. ove r. 60%. of. OM. t h e re t i culo rumen ( Ulya t t � al . , 1 9 85 ) .. in. Re t en t i on t i me i s in fluenced by a number o f d i e tary fac t o r s such as t he. amoun t. of. feed. f o r age : gr a i n r a t i os , f i b r e ( Freer , 1 9 8 1 ;. consumed ,. f i bre. co n t en t. fo rage. Shaver e t al . , 1986 ) .. re t i culo rumen. in clude. s i ze. of. movemen t par t i cles ,. of. par t i c l e s dens i ty. par t i c les; ra t e o f par t i cle reduc t i on , cell wall con t e n t o f feed , hyd ra t i on f r e q uency of a l . , 1 9 86 ) .. form ,. and phys i cal n a t u r e o f t h e. F a c t ors wh i ch a r e involved i n the from. phys i ca l. t i me ,. rumi nal. pH and. and. osmo t i c. abomasal. of t he. pres sure , s t r eng t h and. con t rac t i on. ( Shaver. et.

(43) 27. Und i ges t ed. re t i culo-omasal o r i f i ce. a f ter. be i ng. ( <2 . 0 mm) .. T h e s i z e o f p ar t i cl e i s. changes i n. d i ges t i b i l i t y ,. the. reduced t o f i ne par t i c l e s rela t i ve ly f o rm. phys i ca l. t y p e o f pas t ur e or l i vewe i gh t o f. t hrough. pass. merely. can. ma t e r i al. to. of the feed , i n t ake ,. an i ma l .. t he. i nsens i t i ve. The. amoun t. of. ma t e r i al passed per c on t ra c t i on o f the re t i culum ra ther t han t he p a r t i cl e s i z e. h a s been sugges ted t o b e probably more i mpo r t an t .. 2 . 3 . 1 . 3 Behav i oural f ac t o r s .. Da i ly herbage i n t ake i n f luenced by. (I). behav i oural f a c t ors .. i n t ake by a graz ing ani mal gra z i ng per. of. day. ( GT ,. is. a. graz i ng. an i mal. can. be. T h e amou n t of dai ly h e rbage. d e t erm i ned. by. the. t i me. s pe n t. m i nu t es ) , t he amoun t o f herbage consumed. per b i t e ( I B , gDM or gOM / b i t e ) and t he ra t e of b i t i ng per m i nu t e o f graz i ng t i me ( RB , b i t e / m i nu t e ) ( Allden. and. Vhi t t ake r , 1 9 7 0 ) .. Thus : I. =. x. GT. RB. x. IB .. The var i a t i on in I B i s u s u ally gre a t e r than var i a t i ons i n e i t h e r R B or GT ( S tobbs , 1 9 7 3 ; s e ns i t i ve componen t. to. d en s i ty , sward h eigh t , S i nce any. Hodgson , 1 9 8 1 ) and appears t o be t h e mos t var i a t i ons l e a f / s t em. in. sward. s t reng t h ,. cond i t i on s ( bulk sward. s t ru c t u re ) .. compens a t i ng changes i n RB o r GT a r e usually l i mi t e d ,. I B i s l i kely t o be a maj o r d e t erminan t o f d a i ly ( Leaver , 19 8 5 , Hodgson , 1 98 5 ) .. herbage. i n take.

(44) 28. T h e GT. for. rarely. et. exceeds. al . , 1 9 8 7 ) ,. ruminati on. w i th. t i me. 10. otherwi s e and. other. 12. h ou r s / d ay. graz ing. would. behav i ou r a l. In the short term , the rate o f herbage intake p e r. requi r ements . minute o f. cow. Pop p i. ( Leaver , 1 9 8 5 ; int e r f e r e. a. g r a z ing t i me ( RB x I B ) f a l l s stead i ly w i th increas ing. prox i m i t y o f. the. grazed. ho r i z on. to. the. ground. level. The e f f e c t o f supplemen t at i on has been repo r t ed t o. reduce. ( Hodgson , 1 9 7 7 ) .. G T between. 9 - 3 8 minu t es /kgDM for graz ing cows supplemen t ed w i t h. concen t rates. ( Sa rke r. Demarq u i l l y , 1 9 7 9 ;. and. Holmes , 1 9 7 4 ;. Arriga-Jordan. and. Journe t. Holmes , 1 9 8 6 ) ,. and s i lage. ( Ph i l l i ps and Leaver , 1 985 b ) , or hay ( P h i l l i ps and Leaver , 1 9 8 5a ) .. 2 . 3 . 2 Pasture Fac t o rs .. 2 . 3 . 2 . 1 H e rbage mass .. Her bage mass i s i mpo r t an t for because. it. e f f e c t i vely. con t ro l s. con t inuously t he. quan t i ty. grazed. stock he rbage. of. ava i l able for graz ing each d ay whereas he rbage allowan ce i s mo re i mportan t f o r rota t i onally grazed cows .. Inc reas e s in he rbage mas s per un i t area have been r e p o rted to cause. increases. in. dai ly. J am i e s on and. Hodgson , 1 9 7 9 ;. Holmes , 1 9 8 3 ;. Fo rbes and. o ther s t u d i es. have. h e rbage. intake. ( Hodgson , 1 97 5 ;. S t o ckdale and King , 1 9 8 3 ;. Hodgs on , 1 9 8 5 ,. Zoby and. S t ockdale , 1 9 85 ) ,. wh i le. repor t e d dec reases o r no change ( Hodgson et.

(45) 29. Hodgson , 1 9 7 7 ;. et. Bar t h olomew. Reardon , 1 9 7 7 ;. a l . , 1 97 7 ;. However ,. M e i j s , 1 98 2 ) .. al . , 1 9 8 1 ;. many examples have s h own. th e rela t i onsh i p be t ween he rbage mas s and herbage i n t ake asymp t o t i c ( Hodgson , 1 9 7 7 ; and Jami eson , 1 9 8 1 ; cons t a n t increase. Combellas and Hodgson , 1 9 7 9 ;. M eij s , 1 9 8 2 ) . in. i n t ake ,. the. po i n t. i nc r ease in i n t ake . lack o f. any. re la t ed t o. Hodgson. if. a. t he res pons e i s l i near , o r a cu rv i l i n ea r ,. asym t o t e - beyond wh i ch t here i s no fur t h e r Th i s d e c l i ne i n herbage. fur t h e r the. be. Such relations h i p i nd i c a t e s. d e c l i n i ng i n c reme n t a l inc reas e , i f t he res ponse i s to a. to. i n t ake ,. or. t o tal. i ncrease beyond t he asym t o t e i s gen e r a l l y. d e c reas e. in. herbage. qual i ty. ( Me ij s , 1 9 8 1 ;. S t ockdale , 1 9 8 5 ) a s s o c i a t ed w i t h pas t u re aging .. Howeve r , a t a g i ven level o f i n t ake is. un l i kely. to. he rbage. allowan ce ,. h e rbage. be a f fec ted by the va r i a t i on of he rbage. mass o f f e red to l a c t a t ing c ows ( Holmes , 1 9 8 7 ) or dry cows ( Ho lmes et a l . , 1 9 7 9 ) .. Combe l las and Hodgson ( 1 9 7 9 ) wi t h lac t a t i ng cows ,. c o n f i rmed t h e early f i nd ing o f Reardon ( 1 9 7 7 ) wi th. s t eers. that. he rbage i n t ake w a s no t a f f e c t e d by herbage mass wi t h i n t h e r ange o f 2 , 000-4 , 000 p rogress i vely .. kgDM/ha. bu t. above. this. range i n t ake d e c l i ne d.

(46) 30. 2 . 3 . 2 . 2 H erbage a l l owance .. F o r r o t a t i onally grazed s t ock herbage a l l owance been s hown. per f o rmance. ( Combel la s and. Le Du e t a l . , 1 9 7 9 ;. Hodgson , 1 9 7 9 ;. Glass ey e t a l . , 1 980 ; S t o ckdale , 1 98 5 ) ,. King and. or. M cLenaghan , 1980 ;. be tween HA. of. lac t a t i ng. S t o ckd ale , 1 984 ;. non-lac t a t i ng. cows. cows. B ry an t , l 9 80 ; M i t ch e l l , 1 985 ;. ( Holmes. and. Nga rms ak , 198 2 ) .. The r e l a t i onsh i p and. be tween. a n i mal. HA. and. perfo rman ce. a p p roaches amoun t. max i mum. a c t ually. at. herbage. have. asymp t o t i c ( Combel l as and Hodgs on , 1 9 7 9 ;. t han t he. has. t o be an impor tan t d e t e rm i nan t o f t he herbage i n t ake. and cons equen t ly of t he an i mal. OM i n t ake. ( HA ). i n t ake ,. and. been sugge s t ed to be H e r bage. B ryan t , 19 80 ) .. an allowance 4 t i me s g r e a t e r. cons umed. ( Hodgs on , 1 9 7 6 ) ,. bu t. only. s t a r t s t o d e c l ine markedly when HA i s less t han twi ce i n t ake f o r lac t a t i ng c ows. ( Le Du � al . , 1 9 7 9 ) .. In con t ras t t o t h e f o r me r ,. Combe l l as and Hodgson ( 1 9 7 9 ) repo r t ed gra z i ng c ows. was. t ha t. he rbage. i n t ake. of. near maxi ma l when g raz i ng e f f i c i ency , d e f i ned. as h e rbage i n t ake expressed. as. a. propor t i on. of. the. h e r bage. a l l owan c e , was 50% or less .. Ass o c i a t ed w i t h i nc reas e i n HA i s an i n crease i n h erbage mas s. ( RHM ) ,. and. HA. or. RHM. h erbage i n t ake ( Le Du e t al . , 1 9 7 9 ;. can. be used to i nd i ca t e. Ho lmes , 1 9 8 7 ) .. The e f f e c t o f. H A can be a f f e c t ed by pas ture s pe c i es ( S t o ckda le , l 985 ) , mass ( Combel las. and. Hodgson , l 9 7 9 ) ,. qual i t y ( Hoogendoorn , 1987 ) .. season. To avo i d par t of. res i dual. h e rbage. ( Holmes , l 9 8 7 ) tha t. and. v a r i ab i l i t y.

(47) 31. B u tler e t. al . ( 1987 ). s ugges t ed. t ha t. HA should b e expressed i n. t erms o f green lea f a l l owance .. 2 . 3 . 2 . 3 H e rbage d i ges t i b i l i ty .. As a gener a l p r i n c i ple , d iges t i b i l i ty. is. a. s a t i s fa c t o ry. way o f exami n i ng nu t r i t i ve value and i t s i n f luence on t he amoun t of. f o od. i n t ake. by. an. an i mal. ( Hodgson , 1 9 7 7 ) .. It. d e t e r mined by the pas t ur e s pe c ies presen t , s t age o f managemen t i mposed. upon i t ( Bake r , 1 9 7 6 ) .. d i ges t i b i l i t y have been ( Raymond , 1 9 6 9 ;. revi ewed. in. Re i d e t al . , 1 980 ;. can. a f fe c t. g row t h. be and. Fac t o rs a f f e c t i ng t he. detail. by. many. au t ho r s. M i nson , 1 98 2 ) .. Diges t i b i l i t y i s a maj o r d e t ermi nan t o f Conse quen t ly i t. will. an i mal. pas t ur e. qual i ty .. per f ormance ( Ho lmes , 1 9 8 7 ) .. Hodgson ( 1 9 7 7 ) showed a l i near and cons t a n t r a t e o f i ncrease. in. h erbage. OM. i n t ake. over. a. range. of. d i ges t i b i l i t i e s. d i ge s t i b i l i t i es of 80-83% f o r graz ing animals . exp e r i men t s quo t ed c o n founded by. by. changes. t h e phys i o log i cal t h e r e fore i mprec i s e. Hodgson in. up. to. Howev e r , i n mo s t. d i ges t i b i l i ty. ( 19 7 7 ) ,. was. s eason and t i me of year , and a l s o by. s ta t e. of. the. and. it. is. cow . no t. The a. rela t i onsh i p. good. pred i c t o r .. is The. d i f fe rences in an i mal r es ponse are rela t ed to t he d i f ferences i n t h e s i te. of. ( Po p p i , 1 98 3 ) .. d i ges t i on It. s e e ms. of. the. t ha t. pro t e i n t he. effect. and. organ i c. ma t t e r. o f d i ges t i b i l i ty o n. h e rb age i n t ake i s re la t ed t o r a t e o f passage o f feed t h r o ugh t h e d i g e s t i v e t rac t ..

(48) 32. 2 . 3 . 3 A n i mal Fac t o rs .. 2 . 3 . 3 . 1 S i ze , l i vewe igh t , body cond i t i on , age and geno t y p e .. The s i z e o f the an i ma l v o lume o f. the. abdominal. c a p a c i ty ( B i nes , 1 97 9 ; l i vewe i gh t o f. is. c r i t i ca l. cav i ty. wh i ch. M e ij s , 1 9 8 1 ) .. in is. de t e r m i n i ng rela t ed. to. In ad d i t i on , the. the rumen. s i ze. and. graz i ng ani mals are h ighly correla t ed .. Vo lun t ary. i n t ake i s there fore pos i t i vely rela t ed t o l i vewe igh t .. Howeve r ,. f o r adu l t. an i mals. l i vewe i gh t could be an i m p re c i s e s ca l e r w i t h. re s p e c t t o body s i z e because o f g u t f i l l o r f a t con t en t a l t hough i t i s generally reported ( B i ne s , 1 9 7 6 , 1 9 7 9 ;. that. t he. heav i e r. an imal. eats. m ore. Meij s , 1 9 8 1 ) .. The rela t i onsh i p be tween feed i n t ake and l i vewe i gh t may b e a f f e c t ed by t he con f ound i ng e f fec t o f t he f rame. size. cond i t i on .. for an i mals the. For. example ,. at. any. g i ven. s i ze. and. body. f a t t e r t hey are the heav i e r t hey are , t here fore , i n t ake i s o f t en I t i s also. i nv e r s e ly correla ted wi th body we i gh t ( Fo r bes , 1 98 6 ) . e v i d e n t that , a t a comparable l i vewe i gh t ,. thin. cow. at. calving. a t e more than fat cows .. The age o f t he cow i n fluences i t s feed i n t ake i n t o any. cons equent. effect. i n c re a s e s as an i mal grows , l iv ew ei gh t ( For bes , 1 986 ) .. of bu t. age on body w e i gh t . no t. in. d i re c t. add i t i on. Feed i n t ake. p r op o r t i on. to.

(49) 33. The v a r i a t i o n i n f eed i n t ake asso c i a t ed w i th geno t y p e be explained. by d i f f e rences i n body we i gh t and in level of m i lk. produ c t i on ( Owen , 1 98 8 ) . ( HBI ) cows. ate. For graz i ng cows , h i gh. bree d i ng. i ndex. more f eed ( 6- 2 0% ) dur i ng par t of lac t a t i on t han. d i d low b reed ing i ndex ( LBI ) cows O f i n t eres t. can. ( Holmes. and. McM i l l an , 1 9 8 2 ) .. i s t o no t e tha t F r i es i ans HBI were ligh t e r t han LBI. bu t a t e more feed p e r cow or per kg 0 · 7 5 wher e as Jers eys HBI w ere heavi e r t han L B I bu t a t e m ore feed per cow o r p e r kg 0 · 7 5 ( Ho lm es et a l . , 1 9 8 5 ;. B ryan t , l 98 5 ) .. 2 . 3 . 3 . 2 E f f e c t o f p regnancy .. Dur i ng pregnancy t he volume and con cep t us p r ogr es s i ve ly. nu t r i en t. demand. of. the. increase and t h e dam ' s end o c r i ne s t a t u s. changes ( Fo r bes , 1 9 70 , 1 9 7 1 ) .. Increases i n i n t ak e. mid pr egnancy ( For bes , 1 9 7 1 ;. B i nes , 1 97 1 , 1 9 7 6 ) m i gh t b e caused by. i n c reases in. me t abol i c. of. early. and. r a t e , by t he g row t h of the h e i fer , by a. po s s i ble i n c reas e i n t h e ra t e o f pas sage o f ene rgy requi remen t. in. the. deve l o p i ng. proge s t e rone levels i n t he blood .. t he. foetus. feed , or. by. the. by eleva t e d.

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