Studies on the reproductive performance of dairy cows in New Zealand and some factors which may influence reproductive efficiency : a thesis presented in partial fulfilment of the requirements for the degree of Master of Philosophy at Massey University

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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) STUDIES ON THE REPRODUCTIVE PERFORMANCE OF DAIRY COWS IN NEW ZEALAND AND SOME FACTORS WHICH MAY INFLUENCE REPRODUCTIVE EFFICIENCY. A THESIS PRESENTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF PHILOSOPHY AT MASSEY UNIVERSITY. CHOCKCHAI CHAIMONGKOL DECEMBER, 1 990.

(3) G EN ERAL A BSTRACT. This thesis is comprised of a series o f studies on aspects o f t h e reproductive performance of dairy cows in New Zealan d . The studies of ovarian a ctivity in post-part u m dairy c o w s b y u ltrasou n d exa m i nations were conducted in a spring- and an autumn-calving h e rd . T h i s study showed that there is seasonal variation in the initiation of p ost-partu m ovarian function in dairy co ws in New Zealan d , and this influences some a spects of reproduction. The interval from calvi n g t o the first post-partu m ovulation in t h e a u t u mn-calving herd was significantly shorter than that in t h e s p r i n g calving h erd . Oth e r reproductive indices were shorter in the spring-calving herd . The mean m i l k progesterone concentration d u r i n g the d i oest rous phase( Day 7- 1 6) of t h e normal first cycle for cows in the spring-calving herd was significantly higher than in animals i n t h e a utumn-calving herd . In addition , t h e mean number o f follicles in e a ch of the foll icle-size categories from 1 1 days before the first ovulation in spring-calving cows w a s significantly higher than in a u t u mn-ca lving cows. There were three wave-like patterns in the mean size of the larg e st follicle during the first n ormal cycle. The patterns of the mean nu mber of each follicle category and the mean size of the largest fo l l i cle in cows which had a short e n e d first cycle were similar t o t hose seen in t h e first t w o stages o f a normal first cycle. The follicular patterns in c o w s which had a short first cycle were a lso the same as those in the first stage of a normal first cycle. The use of gonadotrophin releasing h ormone (GnRH) in post-part u m anoestrous d airy cows in a spring-calving h e rd showed that the GnRH injection could i n d u ce luteinising hormone(LH) release a n d ovulations. The study of ovarian activity post injection showed that the G n RH-induced LH release was associated with an increase in average number of medium fol l i cles( M F's) and a decrease in large follicles(LF's) in the ovaries of treated cows. Treated cows ovulated 4. 7 ± 2 . 6 d a ys post-injection, while only one control cow ovulated o n t h e equival e nt of Day 5 post-injection. The reproduct ive indices in treated cows were improved, compared with untreated controls. Oestrous behavi ou r w a s studied in a group of sixteen Taurindicus h e ifers(Sahiwal x Holstein Friesian crossbreds) after oestrus synchronisation treatm ent b y using a C I D R (Control Intravag inal Drug Release) device. lt was found that t hese a n imals preferred to be m o u nted rather than to mount when i n oestrus. The m ean i n terval from CIDR removal t o the onset of oestrus was 3 1 . 5 ± 2 .3 h, with t h e mean d u ration of oestrus(8.3 ± 1 . 9 h). T h e use of visual observation i n combination with t a i l p ai nt scoring could detect all oestrous animals. The DairyMAN programme w a s used to analyse breeding records from t w o i nt ensively managed research d a i ry h e rds. Results from analyses produced by the programme were used to m o nitor and compare against standard or target values. The results showed that repro d u ctive p e rformance in the two herds was above target values. The i n crease i n the use o f h ormonal treatment such as p rostaglandin F2 .. to sync � ronise oestrus and/o r to i ncrease fertility of a herd, concomitantly with i m prov e ment in oestrus d e tection e fficien cy, resulted in an increase in submission rates and conception rates i n these herds..

(4) ii Nutritional supply before and a fter calving can redu c e reprodu ctive perform a n ce of a h e rd . Relatively low reprodu ctive performan ces were obtained in both h erds during the 1 985 season in which pasture growth was badly affected by climatic conditions. This was reflected in the lower occurrence of + PM H (behavioural oestrus events recorded before the mating period commences) in the No2 herd in 1 98 5 ( 6 1 %) , com pared with a target value of 8 5 % , whereas the average of all 7 years was 80 % . The conception rates of the herd were also affected as t h e first service pregnancy rate(PR) was only 43 % , compared with a target value of 5 9 % . The average o f a l l 7 years was 56 % . Relatively high reproductive performance was o btained in 1 98 6 . The submission rates(SR) at 3 and 4 weeks aft e r Planned Start of Mating ( PS M) were 94 and 1 00 % , respectively, compared with t a rg et values of 90 In additio n , the occurrence of + PM H was high in and 1 00 % , respectively. 1 9 86(90 % ) , compared with a target value of 8 5 % and an average of all 7 years(80 % ) . The first service PR was also high in 1 986(7 1 % ) . T h e proportional in cidences o f short return t o service intervals( 1 - 1 7 days) were h i g h ( 3 2 to 57 % ) in the No 1 herd which used natural mating, compared with 6 to 22 % in the No2 herd which used artificial insemination..

(5) iii. ACKNOWLEDGEMENTS. I would like to express my g ratitude to m y supervisor, Professor Roger Morris, for his. support, guidance and enthusiasm to this research work. Without his support, this thesis would not have been completed . Many thanks are to Dr Jock Macmillan, my eo-supervisor for his invaluable guida nce in the reproductive aspects, and corrections and approval of this thesis. Professor E . D. , Feilden, m y forme r supervisor before his retirement, for his guidance a n d preparation of the course of Certifi cate of Profi ciency, is really appreciated . I am very g rateful to Professor B . R . Watkins, who supporte d a n d e n couraged me t o study in New Zealand. His enthusiasm during my staying i n New Zealand is also a ppreciated . I am also grateful to Mr Chalermchai lekchom , the director of Dairy Farming Promotion of Thailand( DPO), for his support and encouragement . Many thanks go to my colleages in the Veterinary Section for their patience and hard work while I have been studying in New Zealand . Appreciation is also expressed to Dirk Pfeiffer for his h e l p i n parts of the statistical analysis and computer problems, to Barry Butler for his help in t ransferrin g dat a , to Fiona Di ckinson f o r her help i n solving computer problems, to Mr Wisitiporn Su ksombat for his help with statistical analysis, to Debbie Lovelock and Eugene Lanada for their assistance at some stages of the ultrasound exa m i nations, to Andrew Hardie, t h e manager of Massey Herds No 1 and No4, and farm sta ffs for their help while the u ltrasound examinations were done in the herds, to Murray Pearce and farm sta ffs in the No3 herd, Ruakura Agricultural Centre, Hamilton for their help i n the stu d y of oestrous behaviour i n Taurindicus heifers, to Dr Keith Lapwood and Jane Candy for their help in the preparation of milk progesterone radio i m m u noassay. Alberta Dick for his help i n t h e ultra sound examinations a n d his suggestions in some parts of this thesis were appreciated. Many thanks are d u e to Mrs Gay E ustace for her support and opening her home to me while I wrote this thesis. Also to Miss Jackie Eustace for h e r correction o f parts of this thesis. Special thanks are d u e t o Dr Kovit Nithich a i . He helped me with words of a dvice when I was discourage d , and M rs Ratchanee Nithichai for her willingness in m anaging and organising everyt h i n g for me during my study i n New Zealand. I thank the Thai students a n d Thai families i n New Zealand for their friendship and support, which made my stay i n New Zealand a very happy one.. The financial support from t h e New Zealand Government for m y study for a period of 3 years is also acknowledged..

(6) iv. Lastly, I a m g rateful to my parents for their encouragement during the long period I stayed in New Zealand ..

(7) V. TABLE OF CONTENTS. Pag e No. G E N E RA L ABSTRACT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i AC K N O W L E D G E M ENTS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ii . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii. TABLE O F CONTENTS LIST O F F I G U R E S . LIST O F TABLES. .. .. .. . . . .. . . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xix. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . xxiii. G ENERAL INTRODUCTI ON. . . . . . . .. .. . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . 1. CHAPTE R 1 : U lTRASONOGRAPHY IN THE STUDY O F OVARIAN ACTIVITY IN POST-PARTUM DAIRY COWS . . . . . . . . . . . . . . . . . . . . . . . 2 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Objectives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Literature Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 N euroendocrine Regulation of Post-partum Pituitary and Ovarian Function . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7. Pituitary Contents of luteinis i ng Hormone. . . . . . . . . . . . . . . . . . . . . . . 8. Recovery of Anterior Pituitary Gland after Parturition . . . . . . . . . . . . . . . 8 A Model of Endocrine Activity in the Post-partum Cow . . . . . . . . . . . . . . 9. Endocrine Regulation of Post-partum Ovarian Activity. . . . . . . . . . . . . . . 9. Patterns of Plasma luteinisi n g Hormone and Fol l i cle Stimulating Hormone in Post-partum Cow. . . . . . . . . . . . . . . 10. Post-partum Uterine a n d O v a rian Function . . . . . . . . . . . . . . . . . . . . . 1 0 Post a g landin F2• and Uterine Involution . . . . . . . . . . . . . . . . . . . . . . . 1 0 Influence of the Uterus o n Ovarian Function in Post-part u m Cow . . . . . . 1 1.

(8) vi Ovarian Steroids . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2. Oestradiol- 1 7p . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 2 Prog e sterone. . . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12. Short Oestrous Cycles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 3 Factors Influencing the Resumption of Ovarian Cycle Post-partum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 1 . Post-partum uterine infections . . . . . . . . . .. .. 2 . Su ckling . . . . . . . . . . . . . . . . . . . . . . . . . . 3 . Season and Climat i c e ffects 4 . M i l k yield . . . . . . 5 . Nutritional Status. .. .. . . . .. . . . . . . . .. .. .. . .. .. .. . .. .. .. . . .. .. .. .. . . 14. . . . . . . . . . . . . . . 16. . . . . . . . . . . . . . . . . . . . . .. .. .. . . . . . . . . . . . . . . 15. .. 5 . 1 . Nutrient intake . . . . . . . . . . . . . . . . . . . . .. . . . .. . . . . . . . . . . . . . . . 14. . . . . . . . . . . . . . . . . . . . .. 5 . 1 1 . Underfeeding. .. .. .. . 16. . . . . . . . . . . . . . 17 .. .. . . .. .. . . . . . . . 17. . . . . . . . . . . . . . . . . . . . . . . 17. 5 . 1 2 . Overfeeding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 7 5 . 1 3 . Weight and Body Condition Loss . . . . . . . . . . . . . . . . . 1 7 5 . 2 . Energy Balance. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18. 5 . 3 . Protein . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 8 5 .4. Vitamins a m d Minerals . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 8 6 . Ovarian Cysts . . . . .. .. .. .. .. .. .. .. . . . . . . . . . . . . . . . . . . . . . .. 7 . Age Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 . Breed Effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. .. .. .. . . 19 . . 20. . . . . . . . 20. Detection of Oestrus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 Ovarian Follicular Development . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22. Fol licular Development d u ring Post-pa rt u m Period . . . . . . . . . . . . . . . 22 Fol li cular Development d uring the Oestrous Cycle. .. .. . . . . . . . . . . . . . 24. Fol l i cular Population during the Oestrous Cycle . . . . . . . . . . . . . . . . . 24 Ultrasonography . . .. .. . .. .. . . . . . . . . . . . .. .. . . . . . . . . . . . . . . . . . . . 25.

(9) vii. Ultrasound Scanner Ultrasound Waves. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 . . .. .. .. .. . . .. .. .. .. . . .. .. . . . . . . . . . . . . . . . . . . .. . . . . . .. lntrumental components of a n u ltrasound scanner Production of Ultrasound Waves. . . . . . . . . . . . .. .. .. . . . . . . . 26. .. .. . . . . . . . . . . . . . .. .. .. .. .. . . . . . . . . . 26. . . . . . . . . . 26. 1 . Reflection . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. 2 . Refraction 3 . Scatter. .. .. .. .. .. .. .. . . .. .. . . . . . . . . .. .. . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . .. 4. Absorption. .. . . . . . . . . . . .. Resolution . . . . . . .. . .. .. . .. 1 . Axial Resolution. .. .. . . . . .. .. .. .. .. . . . . . . . . . . . . . .. . . . . . .. 2 . Lateral Resolution . . . . .. .. .. . . .. .. .. .. .. .. .. .. . . . .. .. .. .. . . . . . . . . . .. . . .. .. . .. .. . .. .. 1 . Specular Reflections. . . . .. .. . .. .. .. .. .. 27 27. . . . . . . . . . . . . 27 . . . . . . .. .. . . . . 27. .. .. . . . . . . .. . . . . . . . . . . . . . . . .. .. .. .. .. .. .. Interpretation of I mages on t h e Ultrasound Screen . . . . . . . . . . . . Artifacts :. .. . . . . . . . . . . . . . . . . . . . . .. .. 25. . . . . . . . . . . . . . 26. Ultrasound Image on the Screen . . . . . . . . . . . . . . . Attenuation . . . . . . . . . . . . . . .. .. .. .. .. 27 27. . 27 . 27. . . . . . . . . . . . . . . . . . . . . . . . 27. . . . . . . . . . . . . . . . . .. .. . . . . . . . . . . . . . 27. 2 . Non-specular Reflections . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 8 3 . Acoust i c Shadow Arti facts . . . . . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. 4 . Enhancement or Through-transmission Artifacts . . . . . 5 . Reverberation Artifacts. .. .. . . . . . 28. . . . . . . 28. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28. U ltrasonic Morphology o f the Ovary . . . . . . . . . . . . . . . . . . . . . . . . 2 8 Follicles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. .. . . . . . . 28. Corpus Luteu m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 9 Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30. Experimental Farms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Ani mal Samples. . . . .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30. Procedures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.

(10) viii. Milk Sample Collection. .. Ultrasound Examinations. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . . . .. .. .. .. .. .. .. . .. .. .. .. .. . .. .. .. . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. Validation of U ltrasonic Measurements of Follicular Diameters. .. 31. . 31. . . . . . . . 32. .. Criteria for Estimating the Day o f Ovulation . . . . . . . . . . . . . . . . . . . . 32 M i l k Prog esterone Radioim m unoassays. . . . . . . . . . . . . . . . . . . . . . . . 35. Procedures for Milk Progesterone Radioimm unoassays .. .. .. . . . . . 35. .. Milk Progesterone Assay Determinati on . . . . . . . . . . . . . . . . . . . . 3 6 Data Analysis . . . . .. .. . .. .. .. .. .. . . .. .. .. .. .. .. .. .. .. .. . .. .. .. .. . . .. .. .. .. .. .. .. . . . 36. Definitions o f some Terms Used in the Text . . . . . . . . . . . . . . . . . . . . 3 7 Results. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 39. Massey University Dairy H e rd N o 1 (Autumn-calving Herd ) . . . . . . . . . . . 3 9 Post-partum Reproductive Indices . . . . . . . . . . . . . . . . . . . . . . . . . . 39. 1 . Interval from Calving to Estimated Fi rst Post-partu m Ovulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 9 . . . . . . . . . . 40. 2 . Interval from Calving to First Post-partum Oestrus 3 . Submission Rate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40. 4. Interval from Calving t o First Service Post-partum . . . . . . . . . . . 40 5 . Interval from PSM t o First Service. . . . . . . . . . . . . . . . . . . . . . 40. 6 . Interval from PSM t o C onception . . . . . . . . . . . . . . . . . . . . . . 40 7 . Interval from First Service to Conception . . . . . . . . . . . . . . . . . 40 8 . Inte rval from Calving t o Conception . . . . . . . . . . . . . . . . . . . . 40 . . . . . . . . . . . . . . . . . . . . . . . . 41. 9 . First Service Conception Rate. 1 0 . Services p e r Conception . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1 Massey University Dairy Herd No4(Spring-Calving Herd ) . . . . . . . . . . . . 48 Post-partum Reproductive Indices .. .. . . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . 48. 1 . Interval from Calving to Estimated First Post-partum Ovulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48 2 . Interval from Calving to Estimated First.

(11) ix. Post-pa rtum Oestrus . . . . . . 3 . Submission Rate. .. . . .. .. . . . . . . . . . . . .. .. . . . . . . .. . . . .. .. .. 8. I nterval from Calving t o Conception . . .. .. .. .. . . . . . . . .. .. . . . .. Post-part u m Reproductive Indices between Autumn- and Spring-calving Cows .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . . . . .. . . . .. .. .. .. .. . .. . . . . .. .. . . .. . .. .. . . . . . . . . 49. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. Ovarian Follicular Distribution Post-partum . . . . . .. . .. .. .. . .. .. .. .. .. .. .. .. .. Massey Dairy No 1 . . . . Massey Daiey No4. .. .. .. .. . . . . .. .. . .. .. .. .. . .. .. .. .. .. . .. .. .. .. .. .. .. . .. .. .. 2 . Ovarian Follicular D i stribution before the First Ovulation Post-partum . . . . . . .. .. .. .. .. .. .. .. . . . .. . .. .. .. .. .. .. 2 . 1 . Ovarian Fol l i c u l a r Patterns before the First Ovu l ation i n C o w s which Ovulated within 30 days Post-partum . . . . . . . . . . . . . . . .. .. .. 2 . 2 . Follicular Patterns before the First Ovulation in both Aut umn-and Spring-calving Cows which Ovulated within 30 days Post-partum . . . . .. .. .. 2.3. Follicular Patterns before the First Ovulation in Cows which Ovulated 3 1 -60 days Post-part u m . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. .. 2 .4. Average Foll i cular Numbers before the First Ovulation . . . . . . . . . . . .. .. .. .. .. .. .. .. .. .. 3. Follicular Distrib u t i o n After the First Ovulation Post-partum . . . . . . . . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 3. 1 . Follicul a r Patterns After the First Ovulation in Cows w h i ch had a Short First Cycle . . .. .. .. . . . 50 . . 50. .. . . . 50. .. .. .. .. .. . . . . . . . .. . . . .. . . . . . .. .. .. . .. .. .. .. . .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. 50. .. 55. .. .. .. .. .. .. .. .. .. .. 57 57 57. . . . . . . 62. . . .. .. 49. .. . . . . . . 57. .. .. .. .. 49. .. . . . . .. 1 . Follicular Numbe rs i n Cycling and Non-cycling cows Post-partum . . . . . . . . . . . . . . . . .. . . 49. .. .. . . . . . . .. . .. .. .. .. .. .. . .. .. . . . . . . . . . . . .. .. .. . . . . . . . . . 49. .. . . . . . . . .. 7 . Interval from First Service to Conception . . . .. 1 0 . Services per Con ception. .. . . . . . . . . . .. 6 . Interval from PSM to Con ception . . . . .. 9 . First Service Conce ption Rate. .. . . . . . . . .. 4. Interval from Calving to First Service 5 . Interval from PSM to First Service. .. .. . . . . 62. . . . .. .. .. .. .. .. .. . . .. .. . .. .. .. .. .. .. 66. 66. . . . 66. .. .. .. .. . 69. .. 69.

(12) X. 3 . 2 . Follicular Patterns After the First Ovulation i n Cows which had a Shortened First cycle Length of 1 3- 1 8 d ays . .. .. .. .. .. .. .. .. .. .. .. .. .. .. 3 . 3 . Follicular Patterns After the First Ovulation i n Cows which had a First Cycle Length of 1 9-24 days . . . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 4. Follicular Patterns in Autu mn- and S pring -calving Cows which had a Normal First Cycle Post-partum before the Second Ovu lation .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 5. Follicular Distribution during a Normal First Cycle Post-partum . . . . . .. .. .. .. Milk Prog esterone Levels Ultrasound Images Discussion. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. 1. Post-partum Reproductive Indices. .. .. . .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. . .. .. .. .. .. .. .. .. 2 . 2 . Follicular Distribution after the First Ovulation. .. .. .. .. .. . . .. .. .. .. 73 74 74 89. . 89. .. . . . . . . . . . . . . 89. .. .. .. .. 73. 73. .. .. .. .. .. .. . . .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. 2. 1 1 . Seasonal Difference in the M e a n Number of Each Follicle Category before the First Ovulation . .. .. .. 2 . 1 . Follicular Distribution before the First Ovulation. .. .. .. 2 . Ovarian Follicular Distribution Post-partum. .. .. .. .. 1 . 3 . Interval from PSM t o First Service a n d Conception. .. .. .. .. 1 . 2 . I nterval from Calving to First Detected Oestrus .. .. .. 69. .. .. 1 . 1 . Interval from Calving t o First Ovulation. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 91. .. .. .. . .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. 91 92 92. .. 93. . . 93. .. 2 . 2 1 . Fol licular Patterns during the Normal First Cycle . . . . . . . . . . . . . . . . . . . . . . . . . . . 93 2 . 2 2 . Fol licular Distribution d uring t h e Shortened First Cycle . . . . . . . .. .. .. .. .. .. .. .. .. .. .. .. .. 2 . 2 3 . Follicular Distribution during t h e Short First Cycle . . . . . . .. .. .. .. .. .. .. .. .. .. 2 . 24. Follicular Distribution i n Cycl i n g a n d Non-cycling Cows . . 3. First Post-partum Cycles. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ... .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. . . . .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. 94. 94. 94 95.

(13) xi 4. Milk Progesterone Levels 5 . C ystic Ovaries Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 95. . . . . . . . . . . . . . . . . . . . . . . . . .. . . .. . . . . . . . 9 6. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 97. References. .. .. •. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. CHAPTER 2 : G O NADOTROPHIN RELEASING HORMON E IN POST-PARTUM ANOESTROUS DAIRY COWS . . . . . . . .. . . . . . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. 98. 1 17. .. Abst ract . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . 1 1 8 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1 9 O b je ct iv es . . . . . . . . . . . . . . . . . . . . . .. . .. . . . . . . . . . . . . . . . . . .. 1 1 9. Literature Review . . . . . . . . . . . . . . . . . . . . . . . . . . . .. . . .. . . . . . . . 1 20 Gonadotrophin Releasing Hormone(GnRH). .. .. .. Uses of GnRH during the Post-partum Period. .. .. .. .. .. .. .. .. .. .. . . . 1 20. .. . . . . . . . . . . . . . . . . 1 20. .. I nduction of Ovulation Post-partum . . . . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . . . 1 20. .. I nduction of Early Ovulation Post-partum to I m p rove Reproductive Performance . . . . . . . . . . . . . . . . . . . .. . . . . 1 2 1 .. Redu ction of Abnormal Ovarian Activity Post-partum Follicular Changes Afte r G n R H Injection. . . . . . . . . . 1 22. .. . . . . . . . . . . . . . . . . . . . . 1 22. .. Materials amd Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 23. Experim e ntal Farm Animal Samples Proced u res. .. .. .. .. . .. .. .. .. . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . 1 23 . . .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. Radioimmunoassays for Luteinising Hormone Milk Progesterone Radioi m m unoassays Data Analysis . Results. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. Before GnRH I njection After A GnRH Injection. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. 1 23 1 23. . . . . . . . . . . . . . . . . . 1 23. . . . . . . . . . . . . . . . . . . . . . 1 24. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. . . . .. .. .. . .. .. .. .. Follicular and Milk Progesterone Patterns Before and. .. . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. . . . .. .. .. .. .. .. .. .. .. .. .. . . 1 24 .. . . .. .. .. .. .. 1 26 1 26 1 27.

(14) xii. Afte r GnRH Injection. .. .. .. .. .. . .. .. .. .. . .. .. Fol licular Changes After the G n R H I njection. .. Reprod u ctive Indices After G n R H i njection . . Discussions. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. 1 28 1 28 1 37. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 41. G n R H-indu ced LH Release. .. .. .. .. .. .. .. .. .. .. Follicular Changes After G n R H I njection. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 141. .. . 1 42. Reprodu ctive Indices After G n R H Injection . . . . . . . . . . . . . . . . . . . 1 43 Conclusion. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 45. Referrences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 46 C HAPTER 3 : O ESTROUS BEHAVIO U R I N SYNCHRONISED TAU R I NDICUS HEIFERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 50 Abstract. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 51. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 53 O bjectives. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 1 53. Literature Review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 54 1 Oestrous Behaviour .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. 1 54. 1 . 1 . Behaviour of Oestrous Cows . . . . . . . . . . . . . . . . . . . . . . . . 1 54 1 . 2. Signs of Oestrus. .. .. .. 1 . 3 . The Onset of Oestrus. .. .. .. .. 1 .4. The Duration of Oest r u s 1 . 5 . Sexually Active G ro u p. .. .. .. .. .. .. .. .. .. .. .. . . .. .. .. .. . .. .. .. .. .. . .. .. .. . .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. . .. . .. .. .. . . . .. .. 3 . Factors Affecting the Expression of Oestrus. .. .. .. . . . . . . . . .. .. .. .. .. .. .. . .. .. .. .. .. .. 3 . 3 . Numbers of Animals i n Oestrus 3 . 4 . Breed Effects. .. .. .. .. .. .. .. .. .. . .. .. .. . .. .. .. 1 55 1 56. .. .. .. .. .. .. .. .. .. .. . . .. .. .. .. . . .. .. .. .. .. .. . . . . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. 1 56 1 57. . . . . . . . . . . . . . . . 1 57. .. 3 . 1 . Management and M a nagement Activity in the Herd . .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . 1 56. 2 . Oestrous Behaviour in Zebu Cattle. 3 . 2 . Season and Climate. .. . .. .. .. .. .. .. . .. .. .. .. .. .. .. .. . .. .. .. .. . . . . . . .. . . .. .. .. .. .. .. . 1 57. .. .. .. .. .. .. .. .. .. 1 58 1 58. . 1 58.

(15) xiii 3 . 5 . The Presence of a Bull in t h e Herd 4. Oestrus Detection 4. 1 . Visual Aids. .. .. .. .. . .. .. .. .. .. .. 4 . 2 . Non-visual Methods. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . . . .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . . . .. .. .. 1 58. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 1 59 1 59 1 59. Materials and Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 6 1. Animal Samples Methods. . . . .. . . .. .. .. .. .. .. .. .. .. Oestrous Observation. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. Data Analysis. .. .. 1. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. Oestrus M a nifestation. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 4. Oestrus Detection Techniques. 1. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 1 63 1 63 1 63 1 64. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. 1 65. . 1 66 . 1 66. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . 1 7 1. Oestrus Manifestation. 2 . Sexual Active G roup. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 71. . . .. .. .. .. .. .. 3 . Mounting and Mounted Frequency 4 . Oestrus Detection Conclusion. .. .. 3 . Mounting and Mounted Frequency in a Sexual Active G r o u p. .. 161. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 64. 2 . Sexual Active Group(SAG ). Discussion. 161. . . . . . . . . . . . . . . . . . . . 1 62. .. .. .. .. . . .. .. Some Terms Used in the Text R e sults. .. .. . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . 1 62. Deterination and Confirmation of Oestrus Tai l paint Scoring. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. . .. .. .. . .. . . . .. .. .. .. .. .. .. .. .. .. .. .. . . . .. .. .. .. .. . . .. . .. .. .. .. .. .. .. .. .. .. .. 1 72 1 73. . . . . 1 73. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 74. Referrences . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 75 C HAPTER 4: EVALUATING T H E R EPRODUCTIVE PERFORMA N C E OF TWO INTENSIVELY MANAG ED RESEARCH DAIRY HERDS USING T H E DAIRYMAN PROGRAMME . . . . . . . . . . . . . . . . . . . . . . . 1 78 .. Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 79.

(16) xiv Introduction O b jectives. .. .. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 181 .. .. Literature Review. .. .. .. .. .. .. .. · .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 1 81 1 82. Issues Known to Influence Reproductive Performance . . . . . . . . . . . 1 82 1 Conception Pattern . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 82 .. 2 . Submission Rate. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. . . . .. .. .. .. .. .. .. .. . . 1 82. Factors Affecting Submission Rate . . . . . . . . . . . . . . . . . . . . . . 1 82 2 . 1 . Previous Calving Pattern. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. . . .. .. . . . 1 82. .. 2 . 2 Nutritional Defi ciencies. 1 82. 2 . 3 Periparturient Diseases. 1 82. 2 . 4 Accurate and thorough Oestrus Detection . . . . . . . . . . . . 1 83 3 . Conception Rate. .. .. 3 . 1 . Fa male Factors. .. .. .. .. .. .. . .. .. .. .. .. .. .. 3 . 1 . 1 Post-part u m I nterval. .. .. . . .. .. .. .. .. .. .. .. .. .. .. .. .. 3 . 1 .4 Breeding Effe ct. .. .. . .. .. .. .. .. .. .. .. .. .. .. . . .. .. .. 3 . 1 . 7 Milk Produ ction 3 . 2 . Male Fa ctors. .. .. .. .. .. .. 3 . 3 . Management Factors. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 3 . 3 . 2 Nutritional S u pply. Oestrus Detection Rate. .. .. .. 3 . 3 . 1 Oestrus Detection . .. .. .. .. .. .. .. .. .. .. .. .. .. . . .. .. 3 . 1 . 5 The Effect of Parturient Diseases 3 . 1 . 6 Environmental Effect .. .. .. 3 . 1 . 2 Cow Condition at Calving 3 . 1 . 3 Age Effects. .. .. . . . .. . . . .. . .. .. .. .. .. .. .. . . . .. . .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . . . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. . .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . 1 83. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . 1 83 . 1 83. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . . .. . . .. .. .. .. .. . . .. . .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . . .. .. . . . . .. .. .. .. . . .. .. . .. .. .. .. .. .. .. .. .. 1 84 1 84 1 84 1 84 1 85. . . . 1 85. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. 1 85. . 1 86 1 86 1 87 1 87. Me�surement of Reprodu ctive Performance i n Seasonal Dairy Herds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 88 ..

(17) XV. 1 . Calving Patterns i n Dairy Cow . . . . . . . . . . . . . . . . . . . . . . . 1 88 2 . Calving Patterns i n Heifers . . . . . . . . . . . . .. .. . . . . . . . . . .. .. . 1 89. · 3 . Con ception Patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 89. Breeding Management Statistics . . . . . . . . . . . . . . . . . . . .. .. .. .. . . . 1 89. Increasing Fertility with Hormo n a l Treatment . . . . . . . . . . . . . . . . . . 1 90 M aterials and Methods . . . . . . . . . . . . .. . . . . . . . . . .. .. .. .. . . . . . . . . . 1 92. Ruaku ra Dairy H e rd No 1 . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . 1 92 Ruakura Dairy Herd No2 . . . . . . . . . . . . . . . . . . . . . . Data Analysis .. . .. . . .. .. .. .. .. . . . . . .. . . . . . . .. . . . . . . . . . . . . .. .. .. .. .. .. 1 92 .. 1 9 3. Definitions of Some Terms Used in the Text . . . . . . . . . . . . . . . . . . 1 94 D escription of Records Analysis Programme Used . . . . . . . . . . . . . . . . . . 1 95. DairyMAN Data Handling . . . . . . . . .. . . . . . . . . .. . . . . . . . . . . 1 9 5 .. Farm Data. 1 95. Herd Data. 1 95. Cow Data . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 96 DairyMAN Performance Reports . . . ... . . . . . . . . . . . . . . . . . 1 . Performance Indicators . .. .. . . . . . . .. .. .. . . 1 96. . . . . . . . . . . . . . . . . . .. .. 1 96. 1 . 1 Reprodu ctive Perfor m ance Indicators . . . . . . . . . . . . . . . . . . 1 96 1 . 1 . 1 Calving Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 96 1 . 1 . 2 Predicted Calvin g Spread Next Season . . . . . . . . . . . . . 1 97 1 . 1 . 3 H e rd in-calf Rate . . . . . . . . 1 . 1 .4 Premating Heat. .. .. . . . . . . . . . . . . . . . . . . . 1 97. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 97. 1 . 1 . 5 Submission Rate. 1 97. 1 . 1 . 6 Conception Rate. 1 98. Pregnancy Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 98 Non-return Rate. .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 98. 1 . 2 Health Performance I n d i cators . . . . . . . . . . . .. .. . . . .. .. . . . . 1 98.

(18) xvi 1 .3 Demographics. .. .. .. .. 1 . 4 Production Summary 2 .Diagnostic Indicators. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. The Cohort Groups for the Diagn ostic Reports 1 . Age. .. .. .. .. .. .. 2 .Calving Date. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 3 .Health Problem G ro u p . 4. Si res Used for Service .. .. .. . .. . .... .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. ... . .. . .. .. .. .. 5 .Te chnicians Used for Artificial lnseminations. 3 .Management Aids. .. .. The Cow Histories. .. .. .. .. .. .. .. .. .. .. The M anagement Guides. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. Ru akura Dairy Farm No 1. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. The Veterinary Visit Lists R esults. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .... .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 1 . Reproductive Performance Summary. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. 1 98. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 1 99 1 99 1 99 1 99 1 99. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 2 .Comparison of Herd S ub-Groups for Reproductive I n d i ces .. .. .. . 1 99 . 1 99 .. 200. . 200 .. .. .. 200 201. ......... .. . ................ ... 20 1. DairyMAN Performance Analysis. 2 .1 Calving Rate. .. .. .. .. . . .. . . 1 98. .. 6 .Time of Mating in the Breeding Programme relative to PS M .... . . . . . .. .. 1 98. .. . . . . . . . . . . . . . 1 99. .. .. . .. .. .. .. 2 . 2 Premating Heat 2 .3 Submission Rate. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. . .. .. .. .. .. .. .. .. .. .. .. .. .. 2.4 First and Second Service Pregnancy Rate 2 .5 Retu rn Interval Analysis 2 .6 Herd in-calf Rate. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 2 . 7 Predicted Calving S p read Next Season. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 201 20 1 203. .. . .. .. 203 203. . 206. .. .. .. .. .. .. .. .. 206 210 210. . . . . . .... . .... 2 1 0.

(19) xvii. Measurement of Reproductive Efficiency (The No 1 Herd) . . . . . . . . . 2 1 3 1. Interval from Calving to Fi rst Oestrus . . . . . . . . . . . . . . . . . 2 1 3. 2 . Inte rval from Planned Start of Mati ng(PSM) to First Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 3 3 . I nterval from Plan ned Start of Mating(PSM) to Conception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 4 . 4 . I nterval from First Service to Conception . . . . . . . . . . . . . . . 2 1 4 5 . Tota l Return to Service I n terval. . . . . . . . . . . . . . . . . . . . . . 214. 6 . Mi lkfat Production at PSM . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 5 The Ruakura Dairy Farm No2. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 222. D a i ryMAN Performance Analysis . . . . . . . . . . . . . . . . . . . . . . . . . 222 1 . Reproductive Performance Summary . . . . . . . . . . . . . . . . . . . 222 2. Comparision of Herd Sub-Groups for Reprod uctive I n d i ces . . . . 224 2. 1 Calving Rate. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224. 2 . 2 Premating Heat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 224. 2 . 3 Submission Rate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2 7 2 . 4 Return Interval Analysis . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2 7 2 . 5 First a n d Second Service Pregnancy Rate. . . . . . . . . . . . . . 227. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 228. 2 . 6 Herd in-calf Rate. 2 . 7 Pred i cted Calving Spread Next Season. . . . . . . . . . . . . . . . 228. Measu rement of Repro d u ctive Efficiency(The No2 Herd) . . . . . . . . . 234 1 . I nterval from Calving to First Oestrus . . . . . . . . . . . . . . . . . 234 2. Interval from Plan n ed Start of Mating (PSM) to First Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 3. Interval from Plan n ed Start of Matin g(PSM) to Conception . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 236 4. Interval from First Service to Conception . . . . . . . . . . . . . . . 239 5. Total Return to S e rv i ce Interval Discussions . . . .. .. . . . . . . .. .. .. .. . . . . . . . . . . . . . . . . . . . . . 239. . . . . . . . . . .. .. . . . . . . .. .. .. .. . . . . . . . . 243.

(20) xviii. Calving Rate. .. .. .. Submissio n Rate Pregnancy Rate. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. I nterval from Calving to First Oest rus. .. .. .. .. .. .. .. .. .. .. .. .. Planned Start of Mating to First Service and to Conception Tota l Retu rn to Service Interval Conclusion R e ferrences. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 243 243 244 245 246. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. .. 246 248 249.

(21) xix. LIST OF FIGURES Page No. Figure 1 .0. The estimated pasture p roduction(Kg DM/ha/day) in the autumn-( No 1 ) a n d spring-calvi n g ( No4) herds i n 1 989 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38. Fig u re 1 . 1. The percentage of the a utumn-calvin g cows(No 1 ) which ovulated with a n d without oestrus at first ovulation post-partum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47. Fig u re 1 2. The percentage of the a utumn-calvin g cows(No 1 ) which had normal, shortened and short first cycles post-partum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 7. Figure 1 . 3. The percentage of the spring-calving cows(No4) which ovulated with and without oestrus at first ovulation post-part um . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54. Fi g u re 1 . 4. T h e percentage of t h e spring-calving cows( No4) w h i ch had norma l , shortened a n d short first cycles post-partum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54. Fig u re 1 5. The percentage of cows from both herds w h i ch ovulated with and without oestrus at first ovulation post-partum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56. Fig u re 1 . 6. The percentage of cows from both herds which had norma l , shortened a n d short first cycles post-pa rtum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56. Fig u re 1 . 7. The mean numbers of e a ch follicle category i n the autumn-calving cows(cycling and non-cycling) d uring days post-partu m . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58. Figure 1 . 8. T h e mean numbers of each fol licle category i n the spring-calving cows(cycling a n d n o n-cycling) d u ring days post-pa rt u m . . . . . . . . . . . . . . . . . . . . . . . . . . . . 58. Figure 1 . 9. Follicular patterns Pre-OV 1 in 1 0 autu mn-calving cows which ovulated within 30 days post-p a rt u m . . . . . . . . . . . . . . . 67. Figure 1 . 1 0. Follicular patterns Pre-OV 1 in 1 0 spring-calving cows which ovulated within 30 days post-part u m . . . . . . . . . . . . . . . 68. Fig ure 1 . 1 1. Follicular patterns Pre-OV1 in 20 cows from both herds which ovulated within 30 days post-part u m . . . . . . . . . . . . . . . 70. .. .. Figu re 1 . 1 2. Follicular patterns Pre-OV 1 in 1 0 cow s from both herds.

(22) XX. which ovulated 3 1 -6 0 d ays post-partum. . . . . . . . . . . . . . . . . . 71. Figure 1 . 1 3. Follicular patterns a ft e r first ovulation (Post-OV1 ) i n 36 cows from both herds . . . . . . . . . . . . . . . . . . . . . . . . . . 7 5. Fig u re 1 . 1 4. Follicular patterns Post-OV 1 i n 1 0 cows which had a short first cycle cycle post-partum . . . . . . . . . . . . . . . . . . . . . . 76. Figure 1 . 1 5. Follicular patterns a ft e r first ovulation(Post-OV1 ) i n 8 cows which h a d a shortened first cycle post-partum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7 7. Fig u re 1 . 1 6. Follicular patterns a ft e r first ovulation(Post-OV1 ) i n 1 6 cows which h a d a normal first cycle post-partum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 78. Figure 1 . 1 7. Follicular patterns before second ovulation(Pre-OV2) i n 1 6 cows from both herds which had a normal first cycle post-part u m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 79. Fig u re 1 . 1 8. Follicular patterns i n 1 6 cows during a normal first cycle post-part u m ( O = Day of first ovulation) . . . . . . . . . . . . . . 80. Figure 1 . 1 9. Mean milk progesterone(P4) i n 1 1 a utumn(A) and 5 spring(S) cows d u ri n g a first normal cycle post-partum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 1. Figure 1 . 20. Mean milk progesterone levels(P4) a fter first ovulation in cows w h i ch had a short first cycle post-part u m . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82. Figu re 1 . 2 1. Mean milk progesterone levels(P4) a fter first ovulation in cows w h i ch had a shortened first cycle post-pa rtum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 82. Figure 1 . 22. Mean numbers of largest fol l i cles(LF) per cow in cycling and non-cycling animals during the post-part u m period a mong cows i n the No 1 herd . . . . . . . . . . . . 83. Figu re 1 .2 3. Mean numbers o f l a rg est follicles(LF) per cow i n cycling and non-cycling a n i m a l s d u r i n g the post-partum period a mong cows in t h e No4 herd . . . . . . . . . . . . 83. Figure 1 . 24. Mean numbers of m e d i um-sized follicle(MF) per cow in cycling and non-cycling animals d u ring the post-partum period a mong cows in the No 1 herd . . . . . . . . . . . . 84. Figure 1 . 2 5. Mean numbers of m e d i um-sized follicl e (MF) per c o w i n cycling and non-cy cl i ng a n i m a l s d uring the post-partum period a mong cows i n the No4 herd . . . . . . . . . . . . 84. Figure 1 . 26. Mean numbe rs of small-sized follicle(SF) per cow i n cycling and non-cycli n g a n i m a l s d u ring the.

(23) xxi. post-partum period a m o ng cows in t h e No 1 herd . . . . . . . . . . . . 85 Fig ure 1 . 2 7. Mean numbers of s m a ll-sized follicle(SF) p e r cow i n cycling a n d non-cycling a n i m a l s during the post-partum p eriod among cows in the No4 herd . . . . . . . . . . . . 85. Fig ure 1 . 28. Mean nu mbers of total follicles(TF) per cow in cycling and non-cycling animals during the post-partum period among cows in the No 1 herd . . . . . . . . . . . . 86. Fig ure 1 . 29. M ean numbers of total follicles(TF) per cow in cycling and non-cycling animals during the post-partum period a m ong cows in t h e No4 herd . . . . . . . . . . . . 86. Fig ure 1 . 30. An ultrasoun d sca n n e r used for ovarian examinations . . . . . . . . 87. Fig ure 1 . 3 1. Ultrasound images of the ovaries . . . . . . . . . . . . . . . . . . . . . . 88. Fig ure 2 . 1. Follicular patterns a n d progesterone levels(P4) of Cow T 1 74 after G n R H injection (0 = Day of GnRH injection) . . . . . . . . . . . . . . . . . . . . . . . . . 1 29. Fig ure 2 . 2. Follicular patterns a n d progesterone l evels(P4) of Cow T3 1 4 after G n RH injection (0 = Day of GnRH injection) . . . . . . . . . . . . . . . . . . . . . . . . . 1 30. Figure 2 . 3. Follicular patterns a n d progesterone l evels(P4) of Cow T369 after G n RH injection (0 = Day of GnRH i nj e ction) . . . . . . . . . . . . . . . . . . . . . . . . . 1 3 1. Fig ure 2 .4. Follicular patterns a n d progesteron e levels( P4) of Cow T42 7 after G n RH injection (0 = Day of GnRH injection) . . . . . . . . . . . . . . . . . . . . . . . . . 1 32. Figure 2 . 5. Follicular patterns a n d progesterone levels( P4) of Cow C55 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 33. Figure 2 . 6. Follicular patterns a n d progesterone levels(P4) of Cow C349 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 34. Figure 2 . 7. Follicular patterns a n d progesteron e levels(P4) of Cow C382 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 3 5. Figure 2 . 8. Follicular patterns a n d progesterone levels( P4) of Cow C43 5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 36. Figure 3 . 1. The distribution of t h e o nset of o estrus after C I D R i n 1 0 Taurindicus h e ifers. . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 68. Figure 3 . 2. The distribution o f t h e d uration o f oestrus i n 1 0 Taurindicus h e ifers. . . . . . . . . . . . .. Figure 4. 1. .. .. .. .. . . . . . . . . . . . 1 68. ·. The distribution of a l l return to service i ntervals of cows.

(24) xxii. in the No 1 herd from 1 984 to 1 988. . . . . . . . . . . . . . . . . . . . 242 Fig u re 4 . 2. T h e distribution of a l l return to service intervals o f cows in the No2 herd from 1 982 to 1 988. . . . . . .. . . . . . . . . . . . . 242.

(25) xxiii. LISTS OF TABLES Pag e No Pag e No. Table 1 . 1. Schedule of ultrasou n d examinations of autumn-calving cows from the Massey No 1 herd . . . . . . . . . . . . . . . . . . . . . . . 33. Ta ble 1 . 2. Schedule of ultraso u n d examinations o f spri ng-calving cows from the Massey No4 herd . . . . . . . . . . . . . . . . . . . . . . . 34. Table 1 . 3. The aliquots of milk progesterone radioimm unoassays . . . . . . . . . 3 6. Table 1 .4. Mean intervals of post-partum repro d u ctive indices for examined cows a n d for cows in the m a i n herds at the Massey No 1 (autumn cows) and No4(spring cows) herds. 42. Ta ble 1 . 5. Mean days from calving to first post-partum ovulation of the exam i ned cows from the autumn-( No 1 ) and spring-calving herds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43. Table 1 . 6. The m e a n interva l from calving to estimated first ovulation and oestrus post-part u m of the exa m in ed cows of differi ng ages in autumn(No 1 ) a n d spri n g ( No4) calving herds . . . . . . . . . . 44. Table 1 . 7. Numbers of monitored of autumn-(No 1 ) a n d spring-calving ( No4) cows which ovulated < 30 days or > 30 days post-partum that had short , shortened o r normal cycles post-partum . . . . . . . . . . . 45. Table 1 . 8. Interval from PSM to 1 -' service and conception, compared in each age g roup of both examined g ro u ps and the main herd of the Massey No 1 herd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46. Table 1 . 9. Interval from PSM to 1 -' service a n d conce ption, compared in each age group of both examined g ro u ps and the main herd of the M a ssey No4 herd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 1. Table 1 . 1 0. N u mber of autumn-( No 1 ) a n d spring-(No4) calving cows between each age group at first post-partum ovulation . . . . . . . . . . . . . . 52. Table 1 . 1 1. Numbe r of cows by a g e g roups from autumn- and spring-calving herds that had a short , shortened or normal cycle post-partum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3. Table 1 . 1 2. The mean number of each follicle category(SF,MF, LF and TF) and the mean size of t h e l argest foll i cle(LF size) from Week 2 to Week 7 post-part u m in cycling (CC) and non-cycling(NC) cows in the autumn-calving herd (No 1 ) . . . . . . . . 59. Table 1 . 1 3. Fol licular numbers between cycli n g ( C C ) a n d non-cycling(NC) cows in t h e autumn-calving h e rd ( No 1 ) . . . . . . . . . . . . . . . . . . . 60.

(26) xxiv. Table 1 . 1 4. Mean n u m bers of each follicle category between weeks post-part u m in cycling (CC) and non-cycli n g ( NC) cows in the autumn-calving herd(No 1 ) . . . . . . . . . . . . . . . . . . . . . . . 6 1. Table 1 . 1 5. The mean n um ber of each follicle category(SF,MF, LF and TF) and the mean size of the larg est follicle(LF size) from Week 2 to Wee k 7 post-partum in cycling (CC) and non-cycling(NC) cows in the spring-calving herd ( No4) . . . . . . . . . 63. Table 1 . 1 6. Follicular n u mbers between cycling(CC) a n d non-cycl i n g ( N C ) in the spring-calving herd (No4) . . . . . . . . . . . . . . . . . . . . . . . . . 64. Ta ble 1 . 1 7. Mean n u m ber of fol l i cles in each category b etween weeks post-part u m i n the spring-calving(No4) from both cycling (CC) and non-cycling (NC) cows . . . . . . . . . . . . . . . . . . . 65. Table 1 . 1 8. Mean n um bers of follicles in each category from 1 1 days Pre-OV 1 to first ovulation post-partum i n t h e autumn -(A) and spring-calving(S) cows . . . . . . . . . . . . . . . . . . . . . . . . 72. Table 2 . 1. Mean p a ra meters describing the characteristics of cows included in the trial inwh ich half of them injected with GnRH from 1 8 to 2 3 days post-partum . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 26. Table 2 . 2. Concentrations o f L H (ng/ml) before and after GnRH injection of treated and control cows . . . . . . . . . . . . . . . . . . . . . . . . . . 1 27. Table 2 . 3. Mean n um ber of follicles i n each category, the size o f the largest follicl e ( LF size) and m i l k progesterone level s ( P4, ng/ml) in treated and control cows before a GnRH injection (Day 0) and the mean 9 days later(from Day 2 to Day 9 ) . . . . . . . . . . . . . . . 1 38. Table 2.4. Mean n u m be r of folli cles in each category ( S F = small folli cle, MF = medium follicl e, LF = largest follicle and TF = total follicles) and the size of the l argest(LF size) i n treated and control cows before (Day 0) and aft e r the GnRH i njection from Day 0 to Day 9 (D 0 to D 9 ) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 39. Ta ble 2 . 5. Reprodu ctive indices o f treated and control cows after a G n R H i njection( 1 0 pg buserilin) . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 40. Table 3 . 1. The mean interval from CIDR removal to t h e onset of oestrus a n d t h e duration of oestrus in 1 0 Taurindicus heife rs. . . . . . . . . . . . . . . 1 6 5. Table 3 . 2. Positive ( + ) , negative(-) o r equivoca l ( ? ) occurrence o f oestrus a s determined b y visual observation , tailpaint scoring o r rect a l palpation of the ovaries t o det e ct the presence of a corpus luteum i n a g ro u p of 1 6 Taurindicus heifers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 67. Table 4. 1. Summary of reprodu ctive performance of cows in the No 1 herd from 1 984 to 1 98 8 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 202. Table 4.2. Summary of the 4 a n d 8 week calving rates of cows i n.

(27) XXV. each age group in the No 1 herd .. . . . . . . . . . . . . . . . . . . . . . . 204. Ta ble 4 . 3. Summary o f the occurrence of Premating H e a t a n d the first service PR of + PMH and -PM H cows in each age g roup and i n relation to t h e post-partum intervals( ± 40 days at PSM) . . . . . . . . . . . . . . . . . . . . . . . . . . 205. Tab l e 4 . 4. Summary o f 3 and 4 week submission rate of cows in the No 1 herd in each age g ro u p, a n d i n relation to the post-pa rtum intervals from 1 984 to 1 988 . . . . . . . . . . . . 207. Table 4 . 5. Summary o f t h e first a n d second service Pregnancy rate of cows in the No 1 herd in e a ch age group and in relation to the post-partum intervals. . . . . . . . . . . . . . . . . . . . 208. Table 4 . 6. Summary of t h e percentage o f t h e total return to service intervals which were short , normal a nd long cycles of cows in the No 1 herd in each age g roup, and in relation to the post-partum i ntervals from 1 984 to 1 988. . . . . . . . . . . . 209. Ta b l e 4 . 7. Summary of t h e percentages of 4 a n d 8 week herd in-calf rates of cows in each age group, and in relation to t h e post-partum intervals i n t h e No 1 herd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 1. Table 4 . 8. Summary o f the percentages o f 4 a n d 8 week predicted calving spread next season of cows i n each age g roup, and in relation to the post-partum interval s in t h e N o 1 h e r d from 1 984 to 1 98 8 . . . . . . . . . . . . . . . . . . . . 2 1 2. Ta ble 4.9. The mean interval from calving to first oestrus in each age group from 1 984 to 1 988 in t h e Ruakura dairy herd No 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 6. Tab l e 4. 1 0. The mean interval from Planned Start of M ating to first oestrus in each age g ro u p from 1 982 t o 1 988 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 7. Table 4. 1 1. The mean interval from Pla n n e d Start of Mating to conception of cows in each age g roup i n the No 1 herd from 1 984 t o 1 988. . . . . . . . . . . . . . . . . . . . . . 2 1 8. Table 4. 1 2. The interval from first service to conception in each age g roup of cows from the N o 1 h erd from 1 984 to 1 988 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 1 9. Table 4. 1 3. The p ercentage of cows in e a ch a g e g roup in the No 1 and No2 herds which had total short return to service intervals of 1 - 1 7 d ays. . . . . . . . . . . . . . . . . . . . . . . . . 220. Tab l e 4. 1 4. The number of cows in e a ch a g e g roup i n the No 1 herd which had various length of retu rn t o service intervals. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2 1.

(28) xxvi Ta ble 4. 1 5. Summary of the reproductive performance of cows in the No2 herd reproted by the DairyMAN p rogramme from 1 982 to 1 988 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 2 3. Table 4. 1 6. Summary of the calving rates at 4 a n d 8 weeks after Planned Start of Mating in e a ch age g ro u p of cows in the No2 herd from 1 982 to 1 988. . . . . . . . . . . . . . . . . . . . 2 2 5. Ta ble 4. 1 7. Summary of the occurre n ce of Premating H e at and the fi rst service pregnancy rate of cows with and without P M H i n each age g roup, and i n relation to the post-partum intervals from 1 98 2 to 1 988. . . . . . . . . . . . 226. Table 4. 1 8. Summary of 3 and 4 week submission rates of co ws in each age group in the No2 herd from 1 98 2 to 1 988. . . . . . . . 229. Table 4. 1 9. Summary of the percentage of the retu rn i n tervals which were short , normal a n d long in cows which had the post-partum intervals( ± 40 d ays at PSM) in the No2 herd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 230. Table 4.20. Summary of thefirst and second service pregnancy rates of cows in each age group, and in relation t o the post-partum intervals( ± 40 d ays at PS M ) in the No2 herd . . . . . . 2 3 1. Table 4 . 2 1. Summary o f 4 a n d 8 week H e rd in-ca l f rates o f cows i n each age group and i n relation to t h e post -partum intervals i n the No2 herd . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 3 2. Table 4 . 2 2. Summary of the 4 and 8 w e e k predicted calving spread next season of cows i n the No2 herd i n each age group and i n relation to the post-pa rt u m intervals. . . . . . . . . . . . . . . . 233. Table 4.23. The mean intervals from calving to first oestrus in each a g e g r o u p of c o w s from the No2 herd f r o m 1 98 2 to 1 988 . . . . . . . . 2 3 5. Table 4 . 24. The mean intervals from Pla n ned Start of Mating to first service i n each age group i n the No2 h e rd from 1 982 t o 1 988 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 3 7. Table 4 . 2 5. T h e m e a n intervals from Planned Start of Mating t o con ception i n each age gro u p of cows i n t h e No2 herd from 1 982 to 1 988. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 3 8. Table 4 . 2 6. T h e mean i ntervals from first service t o conception in each a g e group of cows in t h e No2 herd from 1 982 t o 1 988 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 240. Table 4.27. The number of cows i n each a g e g ro u p i n the No2 herd which had various length of return t o service intervals of less than 49 days. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 4 1.

(29) 1. GEN ERAL INTRODUCTION. This thesis is presented as a series of projects i n which some aspe cts of repro d u ctive performance of cows in New Zealand d a i ry herds have been studied and d escribed . lt comprises four projects, a n d ea ch proje cts represents one chapter . The first chapter specifically describes post-partum ovarian a ctivity i n autumn and spring-calving cows. Ultrasonic examinations were performed i n these animals to study ovarian follicular a ctivity after calvi n g , before and after first ovu l a t i o n , a n d d u ring the first cycle post-part u m . Ovarian follicular patterns d u ring these pe riods were also obtai n e d . The second chapter studies the u s e o f gonadotrophin releasing hormone ( G n R H ) to induce ovulations post-partum in a noestrous cows in a spring-calving herd . Follicular patterns before a n d after G n R H injection were monitored and reproductive performance after treatment was compared with untreated controls. Taurindicus a nimals(Sahiwai-Friesian crossbred) are produ ce d in N e w Zealand specifically for tropical countries in South East Asia and South America . These animals have resista nce to diseases, parasites and high temperature , and a cceptable milk production . Previous reports showed that Taurindicus animals p referred being mounted by other cows than mounting other cows when they were i n oestrus. Oestrous behaviour was studied i n the taurindicus heifers by usi ng visual observation and tail paint scoring . This study is presented i n Chapter 3. The l ast Chapter concerns the use of t h e DairyMAN Programme w h i ch has been designed and developed i n t h e Department of Veterinary Clinical S ciences, Massey University, New Zea l a n d . The programme was used to analyse breeding records collected in the No 1 and No2 herds a t the Ruakura Agricultural C entre , Hamilton, New Zea land . Results from reprodu ct ive analysis reports produced by t h e DairyMAN Programme f r o m these t w o herds were assessed . I m portant factors such as submission rate and oestrus detection which a re known to influence fertility in terms of herd breeding m anagement were a lso assessed ..

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