The effect of winter and summer nutritional levels on the reproductive performance of beef heifers bred at 2 years of age

1990 ◽  
Vol 51 (2) ◽  
pp. 255-262 ◽  
Author(s):  
A. van Niekerk ◽  
R. Kernick ◽  
A. W. Lishman
Keyword(s):  
Birth Weight ◽  
Breeding Season ◽  
Reproductive Performance ◽  
Pregnancy Rates ◽  
Minor Role ◽  
Beef Heifers ◽  
Original Hypothesis ◽  
Different Levels

ABSTRACTReproductive data of 139 Simmentaler heifers, previously subjected to different levels of winter and summer nutrition, over a 3-year period, were analysed. Pregnancy rates of 77% and 96% were achieved during the first and second seasons for the two groups of heifers, respectively. Winter and summer nutritional levels affected the number of heifers culled, but had little effect on conception. There were no significant differences in the weight at mating between the heifers that conceived and those that failed to conceive. Mean date of conception was within 30 days and 20 days of the commencement of the breeding season for the first and second season, respectively. Post-weaning nutrition played a relatively minor role in affecting the time of conception. Birth weights of the progeny were not affected by treatment. Calf birth weight was however, significantly (P < 0·05) correlated with the weight of the dam at mating. Sixty-three % of the heifers produced three calves in 3 years, 35% produced two calves in 3 years and only two heifers produced one calf in 3 years. The data supported the original hypothesis that the emphasis, when heifers are bred at 2 years of age, should be shifted away from a physiological base to one where management and grazing strategy are more important in rendering the enterprise economically viable.

scholarly journals Effects of management system on beef heifer growth and reproductive performance

2020 ◽  
Author(s):  
Parker A Henley ◽  
Frank A Ireland ◽  
Igor F Canisso ◽  
J Lannett Edwards ◽  
Daniel W Shike
Keyword(s):  
Development Strategy ◽  
Breeding Season ◽  
Reproductive Performance ◽  
Body Condition Score ◽  
Pregnancy Rates ◽  
Fescue Toxicosis ◽  
Soybean Hulls ◽  
Randomized Design ◽  
Condition Score ◽  
Calf Performance

Abstract This study evaluated the effect of heifer development system on body weight (BW), body condition score (BCS), fescue toxicosis symptoms, reproductive performance, and subsequent calf growth of fall-calving beef heifers. Angus × Simmental heifers [n = 399; 240 ± 20.0 kg initial BW; age = 252 ± 20 d] were stratified by BW and BCS and assigned to 1 of 12 groups in each of the 2 production years. The study utilized a stratified randomized design. Pens were randomly assigned to 4 treatments: drylot (DL) development (fed ad-libitum diet consisting of 90% hay and 10% DDGS on a dry matter basis), grazing endophyte-infected fescue supplemented daily (2.3 kg as-fed/heifer/d; 50:50 mix of soybean hulls and DDGS; E+/S), grazing endophyte-infected fescue and supplemented from the midpoint of treatment period until breeding (4.5 kg as-fed/heifer/d; 50:50 mix of soybean hulls and DDGS; E+/LS), and grazing novel endophyte-infected fescue with no supplement (NE+/NS). Treatments ceased on d 168 [time of artificial insemination (AI)] and heifers were commingled and managed as a group through second breeding season. Heifers in DL had greatest (P ≤ 0.05) BW and BCS from d 28 until d 254. Furthermore, E+/S heifers had greater (P ≤ 0.05) BW and BCS than both E+/LS and NE+/NS from d 28 until d 168. On d 56 and 84, E+/LS heifers had lower (P ≤ 0.05) BW and BCS compared to NE+/NS, but on d 148 treatments reranked and E+/LS remained at a greater (P ≤ 0.05) BW and BCS compared to NE+/NS through the first breeding season. Drylot heifers had greatest (P ≤ 0.05) percentage cycling and percentage of mature BW at AI (66.6%) and had greater (P ≤ 0.05) AI and overall pregnancy rates compared to E+/LS and NE+/NS. The E+/S (55%) and E+/LS (53.7%) heifers were developed to a greater (P &lt; 0.01) percentage of mature BW than NE+/NS (49.3%). A greater (P ≤ 0.02) percentage of DL and E+/S heifers were pregnant at the end of the first breeding season (89.3 and 85.1%; respectively) compared to NE+/NS (61.5%). In summary, DL heifers had the greatest BW and BCS at AI, percentage cycling, and AI pregnancy rate. However, this strategy did not result in differing overall pregnancy rates between DL, E+/S, and E+/LS and there were no differences in milk production, rebreeding reproductive performance, and calf performance between all treatments. Finally, the poorest AI and overall pregnancy rates of the NE+/NS heifers suggests this is not a viable development strategy for fall-born heifers.

scholarly journals Effects of Polyunsaturated Fatty Acids (PUFA) Supplementation on Reproductive Performance of Beef Heifers Submitted to Fixed-time Artificial Insemination (FTAI) Protocol

2019 ◽  
Vol 47 (1) ◽  
Author(s):  
João Batista Souza Gorges ◽  
Andressa Varella Gonsioroski ◽  
Eduardo Pradebon Da Silva
Keyword(s):  
Reproductive Performance ◽  
Reproductive Function ◽  
Pregnancy Rates ◽  
Beef Heifers ◽  
Pufa Supplementation ◽  
Group 2 ◽  
Ovulatory Follicles ◽  
Dietary Treatments ◽  
And Control ◽  
Group 1

Background: More recently, polyunsaturated fatty acids (PUFA) supplements have been used in grazing beef herds in attempt to influence specific metabolic pathways and hormones that directly modulate reproductive function. Supplementation of calcium salts of PUFA can positively influence ovarian follicular growth, luteal function, and improve reproductive performance in dairy and beef females. The aim of this experiment was to evaluate strategies of dietary treatments using PUFA supplementation for 30 days before or after FTAI protocol and its effects on of ovulatory follicle size, ovulation, pregnancy and gestational losses rates in beef heifers.Materials, Methods & Results: One hundred and ninety-nine Brangus heifers (24 ± 3 months-old; BW= 320 ± 15 kg; BCS= 2.85 ± 0.17) were randomly assigned in three different groups to receive dietary treatments. Group 1 (n = 70) was fed with 0.5 kg/day of a protein-mineral mixture supplement containing 0.2 kg/day PUFA (Mix A)during 30 days before FTAI, Group 2 (n = 68) received the same supplement 30 days after FTAI and Control (n = 61) only the supplement without PUFA (Mix B) during all period. Heifers were submitted to estrous synchronization treatment using progesterone (P4), estradiol benzoate (E2) and prostaglandin F2a  (PGF). Ultrasound exams were done to measure ovulatory follicle diameter and to determinate ovulation and pregnancy rates on Day 30 and 60 after FTAI. Daily gain (DG) was higher (P < 0.05) only when heifers received supplement containing PUFA (Group 1= 30 days prior FTAI) and (Group 2= 30 days after FTAI). PUFA supplementation before FTAI also resulted in larger ovulatory follicles diameter (P < 0.05) in Group 1 (11.2 ± 2.5 mm) compared to Group 2 (9.9 ± 2.3 mm) and Control (10.0 ± 2.07 mm). Ovulation rates were similar (P > 0.05) in Group 1 (90%), Group 2 (75%) and Control (67%). Pregnancy rates were higher (P < 0.05) in Group 1 (Day 30= 67.1% and Day 60= 64.2%) when compared with Group 2 (Day 30= 48.5% and Day 60= 44.1%) and Control (Day 30= 49.2% and Day 60= 45.9%). Gestation losses were similar (P > 0.05) among Groups 1 (6.6%), 2 (9%) and Control (6.6%).Discussion: Rumen-protected supplemental lipids have been used to increase energy density and to determine direct positive effects on reproduction in dairy and beef herds.  There is evidence that feeding moderate amounts of PUFA supplements can improve energy status and result in significant differences in DG as it was observed during experimental period. Thus, heifers that received 0.2 kg/day of PUFA supplement 30 days before FTAI protocol had also a positive effect on ovulatory follicles size, but ovulation rates were similar in groups. Beneficial effects of pre-breeding PUFA supplementation were observed on pregnancy rates on Days 30 and 60 after FTAI, but pregnancy loss was not different among dietary treatments in beef heifers. Based on this study, PUFA supplementation before FTAI protocol had a positive effect on reproductive performance of beef heifers by directly improving ovarian function, uterine environment and early embryonic development. Results indicate that pre-breeding PUFA supplementation to beef heifers is a suitable strategy to increase pregnancy rate in FTAI programs. Therefore, for a better understanding of interactions of nutritional strategies and utero-ovarian functions more evaluations are needed to understand the mechanisms by which feeding PUFA may improve reproductive function in beef heifers.

scholarly journals Duration of the breeding season on the reproductive performance of Anglo-Nubian goats during dry and rainy periods

2014 ◽  
Vol 4 (1) ◽  
Author(s):  
José Monteiro Almeida-Irmão ◽  
Leopoldo Mayer Freitas Neto ◽  
Marcelo Tigre Moura ◽  
Jairo Pereira Neves ◽  
Paulo Fernandes Lima ◽  
...  
Keyword(s):  
Breeding Season ◽  
Reproductive Performance ◽  
Pregnancy Rates

The study was aimed to evaluate the effect of breeding season (BS) duration on goat reproduction during dry (DS) and rainy (RS) periods. Females were kept 300 m apart from bucks for 60 days. Females were randomly distributed among BS groups of 25 (BS25), 35 (BS35), and 45 (BS45) days during DS and RS. All females cycled, except during BS45 in DS (95%). The duration of BS did not affect estrous incidence during DS and RS. The percentage of females with two estrous was similar in RS (BS25: 30%, BS35: 35%, BS45: 35%) and DS (BS25: 25%, BS35: 30%, BS45: 25%). Three estrous were observed in BS35 and BS45 during RS (5%). First estrous (FE) and second estrous (SE) were detected from days in BS25 (FE: 1-21, SE: 7-21), BS35 (FE: 1-23, SE: 6-27), and BS45 (FE:1-23, SE: 9-20) during RS. During DS, estrous were detected within days BS25 (FE: 1-17, SE: 6-23), BS35 (FE: 1-20, SE: 6-24), and BS45 (FE: 2-21, SE: 6-21). Pregnancy rates were similar in RS (BS25: 90%, BS35: 95%, BS45: 95%) and DS (BS25: 75%, BS35: 80%, BS45: 75%). In conclusion, goat BS can be shorten despite weather without any effect on reproduction.

scholarly journals THE EFFECT OF DIFFERENT LEVELS OF DRY SEASON SUPPLEMENTARY FEEDING ON THE REPRODUCTIVE PERFORMANCE OF YANKASA SHEEP IN A TWICE-YEARLY LAMBING PROGRAMME

2021 ◽  
Vol 14 ◽  
pp. 41-49
Author(s):  
O. A. Osinowo ◽  
M. S. Doma ◽  
N. Pathiraja ◽  
V. Buvanendran
Keyword(s):  
Birth Weight ◽  
Litter Size ◽  
Reproductive Performance ◽  
Post Partum ◽  
Dry Season ◽  
Supplementary Feeding ◽  
Northern Nigeria ◽  
Consistent Increase ◽  
Different Levels

Ninety-four pregnant Yankasa ewes were divided into 3 groups and fed;(1) 0, (2) 200 or (3) 400 g/head/day of a concentrate supplement in addition to 6 h grazing daily, from 35.9±2.0 days before, to 98. 122.0 days after lambing in the dry season between 2 Jan vary and 15 May 1984 in Zaria, Northern Nigeria. There were no significant differences (P>0.05) bet den groups in litter size and adjusted birth weight in the initial lambing 35.9±2.0 days into the experiment although the latter showed consistent increase with level of supplementation. Adjusted 90-day Weaning weights increased significantly (P<0.05) with each increase in level of supplementation: 5:5, 7.1 and 8.6kg for groups 1, 2 and 3 respectively. Correspondingly, the percentage of lambs weaned increased (48.6, 56.4 and 90.7%) while ewe mortality declined (12.9, 10.0 and 3.0%) with increasing level of supplementation, The percentage of ewes exhibiting oestrus within 98.1±2.0 days postpartum increased with level of supplementation: 77,8,91.3 and 96.8% for groups 1, 2 and 3 respectively. However, of the ewes showing oestrus, there were no significant differences between groups in post-partum intervals to oestrus and conception. Litter size from matings during the experiment showed non-significant increase with level of supplementation. It is concluded that dry season supplementary feeding is essential for optimum reproductive performance of Yankasa sheep in a twice-yearly lambing programme. 

EFFECTS OF EXPOSURE TO BULLS AND BODY WEIGHT ON REPRODUCTIVE PERFORMANCE IN BEEF HEIFERS

1985 ◽  
Vol 65 (1) ◽  
pp. 31-36 ◽  
Author(s):  
M. MAKARECHIAN ◽  
A. FARID ◽  
R. T. BERG
Keyword(s):  
Body Weight ◽  
Pregnancy Rate ◽  
Breeding Season ◽  
Reproductive Performance ◽  
Control Group ◽  
Group Effect ◽  
Beef Heifers ◽  
Heavy Body ◽  
Breed Group ◽  
Calving Season

Calving records of 174 2-yr-old heifers from four breed groups; Hereford (HE), Beef Synthetic (SY), Dairy Synthetic (SD) and Crossbred Hereford (HX) were used in this study. Half of the heifers were exposed to three epididymectomized bulls for 6 wk before the start of the breeding season. While exposure to bulls had little influence (P = 0.51) on pregnancy rate, it advanced the calving date by 5.5 days compared with the control group (P < 0.05). Calving season in the exposed heifers was 2 wk shorter than that in the control group. Effect of heifer body weight at the start of breeding season on pregnancy rate differed (P < 0.05) among the four breed groups. Low body weight at mating was associated with lowered fertility in SY, SD and HE while very heavy body weight resulted in lowered fertility in SY and SD breed groups. Increase in body weight advanced calving date in the HX breed group only. Key words: Beef cattle, heifer reproduction, bull exposure, body weight

scholarly journals PSIV-10 Effects of stair-step vs. constant supplementation amount on growth, reproduction, and intravaginal temperature in Bos indicus-influenced beef heifers

2020 ◽  
Vol 98 (Supplement_4) ◽  
pp. 288-288
Author(s):  
Elizabeth A Palmer ◽  
Rhaiza A Oliveira ◽  
Mario Binelli ◽  
Thiago Martins ◽  
João Vendramini ◽  
...  
Keyword(s):  
Breeding Season ◽  
Reproductive Performance ◽  
Fixed Effects ◽  
Reproductive Tract ◽  
Treatment Time ◽  
Bos Indicus ◽  
Beef Heifers ◽  
Estrous Synchronization

Abstract This study investigated growth and reproductive performance of Bos indicus-influenced beef heifers provided a concentrate supplement at either a constant or stair-step supplementation. Sixty-four Brangus heifers were stratified by initial BW and age (255 ± 20 kg; 270 ± 22 d) and assigned to 1 of 16 bahiagrass pastures (4 heifers/pasture). Treatments were randomly assigned to pastures (8 pastures/treatment) and consisted of concentrate DM supplementation at: (1) 1.50% of BW from d 0 to 100 (CON) and (2) 1.05% of BW from d 0 to 49 and 1.95% of BW from d 50 to 100 (STP). Supplementation started on d 0 and continued until start of estrous synchronization on d 100. Intravaginal temperatures (16 heifers/treatment) were collected every 30 minutes from d 25 to 31 (September) and d 85 to 91 (November). All heifers were provided supplement at 1.50% of BW from d 101 to 211. Heifers were bred by AI from d 113 to 115 and Brangus bulls were placed with heifers from d 121 to 211. Data were analyzed using the MIXED procedure of SAS with treatment, time, and interaction as fixed effects. From d 0 to 49, ADG did not differ (P = 0.87); however, STP heifers had greater (P = 0.01; 0.73 vs. 0.56 kg/d) ADG from d 50 to 100 compared to CON heifers. Percentage of pubertal heifers, percentage of heifers in estrus, or reproductive tract scores did not differ between treatments (P ≥ 0.40). Intravaginal temperatures were greater (P &lt; 0.0001) for CON vs. STP heifers from d 25 to 31 but did not differ (P = 0.74) from d 85 to 91. Using a stair-step vs. constant supplementation amount (1.05 to 1.95% vs. 1.50% of BW) before the breeding season reduced intravaginal temperatures and increased overall ADG in Bos indicus-influenced beef heifers.

scholarly journals Difference in Body Weight at Breeding Affects Reproductive Performance in Replacement Beef Heifers and Carries Consequences to Next Generation Heifers

Animals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2800
Author(s):  
Ramanathan K. Kasimanickam ◽  
Vanmathy R. Kasimanickam ◽  
Madison L. McCann
Keyword(s):  
Body Weight ◽  
Breeding Season ◽  
Reproductive Performance ◽  
Production Traits ◽  
Next Generation ◽  
Beef Heifers ◽  
Balanced Diet ◽  
Reproductive Indices

Nutrition imprinting carries consequences across generations. The effect of 55% vs. 65% of mature cow body weight (MBW; 545 kg) at breeding on the reproductive performance of heifers and their offspring was investigated. Angus-cross dam heifers were randomly fed to attain 55% (n = 1622) vs. 65% (n = 1578) of MBW, and offspring (F1) heifers born to dam heifers [55% (n = 1285) vs. 65% (n = 1324)] were fed to attain 65% of MBW. Bodyweight and reproductive indices were recorded throughout the study. In dam heifers, puberty (44% vs. 53%), breeding season pregnancy (86.4% vs. 90.6%) and 21-day calving rates (55.2% vs. 65.4%) did vary, but dystocia rate (8.7% vs. 9.0%) did not differ between 55% and 65% MBW groups. Puberty (49.2% vs. 58.2%), breeding season pregnancy (87.2% vs. 92.8%) and 21-day calving rates (53.8% vs. 64.1%) did differ (p < 0.05), but dystocia rate (8.4 vs. 9.2%) did not differ between F1 heifer groups. In conclusion, 55% of MBW at breeding negatively affected the reproductive performance of heifers and its offspring heifers. The recommendation is to feed heifers a balanced diet to reach 65% of MBW at breeding with consideration of production traits.

Genetic and environmental influences on beef cattle production in Zambia 4. Weaner production from purebred and reciprocally crossbred dams

1981 ◽  
Vol 33 (2) ◽  
pp. 165-177 ◽  
Author(s):  
W. Thorpe ◽  
D. K. R. Cruickshank ◽  
R. Thompson
Keyword(s):  
Birth Weight ◽  
Mortality Rate ◽  
Beef Cattle ◽  
Breeding Season ◽  
Reproductive Performance ◽  
Live Weight ◽  
Cattle Production ◽  
Weaning Weight ◽  
Beef Cattle Production ◽  
Calving Rate

ABSTRACTEstimates of dam reproductive performance are reported for purebred Africander, Angoni, Barotse and Boran dams, and the reciprocal crossbreds of the latter three breeds, under ranching conditions in Zambia.Mean performances based on a maximum of 1996 records collected over six parities were: calving rate, 65·6%; weaning rate, 62·8%; calf birth weight, 26·6kg; calf weaning weight, 163·6kg; and dam live weight at weaning, 363 0 kg.Purebred Africander and Barotse dams had significantly poorer calving rates, 542 and 57·6% respectively, than the purebred dams of the Angoni and Boran breeds, 69·1 and 66·0% respectively. Reciprocal crossbred dams of the latter two breeds had the highest calving rates, 71·2 and 74·4%. Heterosis estimates for calving rate were 0·8% for Angoni/Barotse crosses, 7·8% for Angoni/Boran crosses and 10·3% for Barotse/Boran crosses and, for weaning rate, 3·7, 6·7 and 11·5% respectively. There were no differences between reciprocal crossbred dams for calving and weaning percentages. The mortality rate of calves born to crossbred dams was 40% and that of the calves born to purebred dams of the same breeds 4·7%. Dam status at mating had an important effect on fertility with the calving rate of dams dry at mating, 89·1%, contrasting with a rate of 39·8% for those dams that were lactating at mating and that had calved late in the season.There were large differences between breeds for calf weights but heterosis estimates were small and nonsignificant. There were no differences between the progeny weights of reciprocal crossbred dams. Sex, date and period of birth, and dam status had significant effects on calf weights.Africander dams had the heaviest, and Angoni dams the lightest, live weights at weaning, 421·1 and 320·7 kg respectively. Heterosis estimates for dam live weights were small and non-significant, and reciprocal crossbred differences were unimportant. Dams which lost most live weight during the dry season, that had extremely light live weights at the beginning of the breeding season or that gained little weight during the breeding season had significantly poorer fertility than other dams.Overall estimates of heritability derived by dam/daughter regression were 0·20 for calving percentage, 0·76 for calf birth weight and 0·72 for calf weaning weight.

60 Reproductive Performance After Timed Artificial Insemination Followed by Timed Embryo Transfer of In Vitro-Produced Embryos in Beef Cattle

2018 ◽  
Vol 30 (1) ◽  
pp. 169
Author(s):  
G. Holguin-Sanabria ◽  
F. J. F. Collares ◽  
E. P. Silva ◽  
L. H. Aguiar ◽  
P. Rodriguez-Villamil ◽  
...  
Keyword(s):  
Beef Cattle ◽  
Embryo Transfer ◽  
Breeding Season ◽  
Reproductive Performance ◽  
Bos Taurus ◽  
Pregnancy Rates ◽  
Release Device ◽  
Chi Squared ◽  
Rectal Palpation

The combined use of timed AI (TAI) and embryo transfer (TET) has the potential to increase reproductive efficiency in beef cattle. This study evaluated reproductive performance in beef cattle after TAI followed by TET of in vitro-produced embryos at the onset of the breeding season. A total of 476 multiparous non-suckling Bos taurus females (body condition scores of 2.9 ± 0.4 on 1 to 5 scale) were oestrous synchronized with 2 mg of oestradiol benzoate (IM) and a 1.9-g intravaginal progesterone release device (Day –11), which was removed on Day –2, followed by 0.48 mg of sodium cloprostenol, 400 IU of eCG, and 0.5 mg of oestradiol cypionate (IM). In experiment I [no heat detection (HD), or no HD, n = 387], TAI was carried out 48 h later (Day 0), whereas in experiment II (after HD, n = 89), AI was performed 12 h after the onset of oestrus up to 48 h after intravaginal insert removal, when remaining females were inseminated (Day 0). Day-7 blastocysts produced by IVF from abattoir-derived oocytes were individually transferred (TET) 7 days after TAI (Day 7) to 186/387 and 44/89 females in experiments I and II, respectively, ipsilateral to the corpus luteum. Then, fertile mature Bos taurus bulls were introduced on Day 12 into the herds (1:25) up to Day 90. Determinations of pregnancy outcome after TAI, TAI+TET or natural mating, twinning rates, and pregnancy losses were done by ultrasonography and rectal palpation on Days 30, 60, and 125. Data were analysed by the Chi-squared test (P < 0.05). Pregnancy rates (Day 30) were lower after TAI (104/201, 51.7%) than after TAI+TET (126/186, 67.7%) with no HD (experiment I), but similar between TAI (32/45, 71.1%) and TAI+TET (30/44, 68.2%) after HD (experiment II). Twinning rates were lower in TAI groups with no HD (6/104, 5.8%) and after HD (2/32, 6.2%) than in TAI+TET groups with either no HD (42/126, 33.3%) or with HD (14/30, 46.7%). Overall pregnancy was similar between groups after the end of the breeding season: 90.0% (181/201) and 90.3% (168/186) for TAI and TAI+TET with no HD, and 84.4% (38/45) and 84.1% (37/44) for TAI and TAI+TET after HD. Pregnancy losses were higher after TAI+TET with no HD (27/126, 21.4%) than TAI+TET after HD (3/30, 10.0%), and TAI with (2/32, 6.3%) or without (9/104, 8.7%) HD. The TAI+TET with no HD resulted in fewer fetuses per served (0.69) and pregnant (1.30) female than TAI+TET after HD (0.89 and 1.44), whereas TAI with no HD had fewer fetuses than TAI after HD per served (0.50 v. 0.69) but not per pregnant female (1.05 v. 1.03), with both being lower than the TAI+TET groups. In summary, TET after TAI with no HD increased pregnancy and twinning rates. Also, heat detection increased pregnancy rates after TAI and twinning rates after TAI+TET. The TAI+TET combination may be advisable for reproductive schemes with no HD, whereas no benefit of TAI+TET was seen over TAI regarding pregnancy rate if TAI is coupled with HD, but HD may increase prolificacy after TAI+TET. The economics of the use of TAI+TET is under evaluation, by assessing calving, weaning, and postnatal weight gain rates between groups.

Effect of passive immunization against testosterone on the reproductive performance of Scottish Blackface ewes in different levels of body condition at mating

1985 ◽  
Vol 41 (1) ◽  
pp. 97-102 ◽  
Author(s):  
S. M. Rhind ◽  
R. G. Gunn ◽  
B. A. Morris ◽  
J. Clayton ◽  
I. D. Leslie ◽  
...  
Keyword(s):  
Birth Weight ◽  
Survival Rate ◽  
Mortality Rate ◽  
Body Condition ◽  
Reproductive Performance ◽  
Passive Immunization ◽  
Corpora Lutea ◽  
Wide Range ◽  
Different Levels ◽  
Category Score

ABSTRACTThe effect of passive immunization against testosterone on reproductive performance was investigated in 180 mature Scottish Blackface ewes in different levels of body condition at mating. Ewes were fed to achieve a wide range of condition (scores 1·5 to 3·0) by 2 weeks before a synchronized mating. During the week before mating, 90 ewes were each injected with 32 ml of a neat anti-testosterone antiserum (1: 96 000 initial titre) and 90 ewes were untreated. At about 55 days after mating, 50 immunized and 50 control ewes were slaughtered and the numbers of corpora lutea and embryos present were recorded. The proportion of immunized ewes that conceived during two periods of mating was in excess of 0·9 in all condition categories. By contrast, untreated ewes in the low condition category (score =£ 2·00) had significantly lower conception rates than ewes in higher condition categories. Immunized ewes with condition scores of 2·50 or less at mating had significantly higher ovulation rates, litter sizes and lambing rates compared with control ewes, while immunized ewes with scores of 2·75 or higher were not significantly different from control ewes in these measurements. There was no effect of immunization on embryo mortality rate, lamb sex ratio, lamb birth weight, or lamb survival rate in the 1st week after birth.

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