Orientador: José Luiz Moraes Vasconcelos / Banca: Roberto Sartori Filho / Banca: Guilherme de Paula Nogueira / Resumo: O objetivo desse estudo foi avaliar o efeito das concentrações de progesterona no desenvolvimento folicular e a influência do diâmetro folicular e duração do proestro na concepção de novilhas púberes inseminadas após detecção de cio ou submetidas à IATF. No exp.1, 723 novilhas foram sincronizadas com o protocolo: D0: benzoato de estradiol (BE, 2,0 mg, Estrogin®) + CIDR®; D7: dinoprost trometamina (PGF2a, 12,5 mg, Lutalyse ). As novilhas foram distribuídas aleatoriamente no dia 0 para inserção de CIDR® sem utilização prévia (CIDR1) ou utilizado previamente por 18 dias (CIDR3) e retirada no dia 7 ou dia 9 seguido de detecção de cio e inseminação 12h após o cio. No exp.2, 1083 novilhas foram sincronizadas de acordo com o exp1, entretanto todos dispositivos foram removidos no dia 9 e os animais foram inseminados 48 h (0,5 mg, i.m., ECP® no dia 9), 54 ou 72 h (100 μg, im., Fertagyl® no dia da IATF). No exp.3 474 novilhas foram distribuídas aleatoriamente para receberem: D-1: 2mg de BE no grupo 3; D0: 1 e 2 mg de BE respectivamente nos grupos 1 e 2. Todas novilhas foram sincronizadas com CIDR1, receberam 12,5 mg de PGF2a no dia 7 e 0,5 mg de ECP no dia 9. No grupo 2 foi aplicado 200 UI de eCG no dia 9. As novilhas foram inseminadas 48 horas após a remoção do dispositivo, perfazendo assim 3 grupos experimentais: grupo 1 (1 mg de BE no D0), grupo 2 (200 UI de eCG no D9) e grupo 3 (CIDR por 10 dias). Nos exp.1 e 2 o diâmetro do maior folículo (ØFD) e amostras de sangue (P4) foram obtidas em um subgrupo de animais no dia 7 e dia 9. No dia da IA e IATF foi feita avaliação do ØFD em um subgrupo de animais no exp.3 e em todos animais no exp1 e 2. Amostras de sangue para dosagem de P4 foram colhidas 7 dias após a IA ou IATF em um subgrupo de animais do exp.1 e em todos animais nos... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The aim of this trial was to evaluate the effect of progesterone concentration in follicular development and influence of follicular diameter and length of proestrus in the conception rate of pos pubertal heifers inseminated after detection of estrus or submitted to TAI. In exp.1, 723 heifers were synchronized with the protocol: D0: estradiol benzoate (EB, 2.0 mg, Estrogin®) + CIDR®; D7: dinoprost trometamina (PGF2a, 12.5 mg, Lutalyse ). The heifers were randomly assigned on D0 for inserting CIDR® without prior use (CIDR1) or previously used for 18 days (CIDR3) and were withdraw on day 7 or day 9 followed by heat detection and insemination 12 hours after estrus. In exp.2, 1083 heifers were synchronized according to exp1, however all devices were removed in day 9 and the animals were inseminated 48h (0.5 mg, i.m., ECP® on day 9), 54 ou 72 h (100 μg, im., Fertagyl® on day TAI). In exp.3, 474 heifers were randomly assigned to receive: D-1: 2 mg of EB in group 3; D0: 1 and 2 mg of EB respectively in groups 1 and 2. All heifers were synchronized with CIDR1, received 12.5 mg of PGF2a on day 7 and 0.5 mg of ECP on day 9. In the group 2 was administered 200 UI of eCG on day 9. The heifers were inseminated 48 hours after device removal, so three experimental groups were formed: group 1 (1 mg of EB on D0), group 2 (200 UI of eCG on D9) and group 3 (CIDR for 10 days). In the exp.1 and 2 the diameter of the largest follicle (ØFD) and sample of blood (P4) were obtained of subset of animals on day 7 and day 9. On days of AI and TAI the diameter of the largest follicle (ØFD) was measured in the subset of animals in the exp.3 and all animals in the exp.1 and exp.2. Blood samples for P4 assays were harvested seven days after AI or TAI in subset of animals the exp.1 and all heifers the exp.2 and exp.3. Pregnancy diagnosis was... (Complete abstract click electronic access below) / Mestre

A series of 4 observational studies was performed on a Bovelder herd at Johannesburg Water’s Northern Farm. The heifer and cow breeding seasons started on 15 October and 1 November every year, and consisted of 50 d and 60 d of oestrus observation respectively, with once daily artificial insemination (AI). Five to 7 days after the AI period bulls were added in multi-sire groups for a period of 42 d. Pregnancy diagnoses were performed between 23 March and 26 April every year. The farming system had been in place for >25 years, with few deviations. In the first study, reproductive tract scoring (RTS) by transrectal palpation on a 5- point scale was performed 1 day before the start of breeding on a group of heifers (n = 272) born in 2002. Heifers with RTS 1 or 2 were estimated to be pre-pubertal, those with RTS 3 pubertal and those with RTS 4 or 5 post-pubertal. Pre-breeding body weight (BW) and body condition score (BCS) were recorded, and Kleiber ratio (KR) was calculated (average daily gain/end weight0.75). Heifers were followed until they weaned their first calves. The objectives of this study were to determine if RTS is a valid tool to predict reproduction and production performance in limited bred beef heifers, and to compare its predictive value with that of BW, BCS, age and KR. After adjustment for BW and age, RTS was positively associated with pregnancy rate to the 50 day AI season (P < 0.01), calf weaning weight (P < 0.01) and pregnancy rate to the subsequent breeding season (P < 0.01), and negatively associated with days to calving (P < 0.01). RTS was a better predictor of fertility than was vi KR, and similar in its prediction of calf weaning weight. It was concluded that RTS is a predictor of heifer fertility and compares well with other traits used as a predictor of production outcomes. It was further hypothesised that RTS may predict long-term reproductive performance due to its association with pregnancy outcome and days to calving after first breeding, combined with reports that heifers calving early tend to calve early in subsequent seasons and have increased lifetime production. In study 2, a 7-year longitudinal study, 292 beef cows in two age cohorts were observed from 1-2 d before their first breeding season (day of RTS), until they had weaned up to 5 calves. Years to reproductive failure was defined as the number of years until a cow failed to become pregnant during the AI season. Animals with RTS 1 or 2 were at increased risk of early reproductive failure compared to those with RTS 4 or 5 (HR = 1.4, 95% CI 1.0, 1.9) despite the fact that RTS was not associated with calving rate or days to calving after the second calving season. The predictive value of RTS was lower in the age cohort with a higher prevalence of anoestrus. Most animals with RTS 1 or 2 that were subsequently detected in oestrus were in early to mid di-oestrus at the time of scoring. It was concluded that RTS is a valid culling tool to improve long-term reproductive success in a seasonal breeding system, by excluding poor performing animals. It was further concluded that the predictive value of RTS decreases with increasing prevalence of anoestrus and at certain stages of the oestrous cycle. Apart from failure to calve, dystocia as a result of foeto-maternal disproportion is the cause of significant production loss in beef heifers. Internal pelvis area (PA) can be calculated as the product of vertical and horizontal diameter of the pelvis measured transrectally using a calliper device. In study 3, the effects of five culling strategies using prebreeding PA data on calving and dystocia rates and on pre-breeding and calf birth weight (BWT) were compared in 484 heifers. Multiple regression analyses were used to determine independent predictors of PA, calf BWT and dystocia. Hypothetical culling of 10 or 20% of heifers was applied within age cohort after ranking by each of the following: unadjusted PA (PA); PA adjusted to 365 d of age (APA); PA:BW ratio (PA:BW); PA adjusted to the median BW of the group by the regression coefficient of PA on BW(BWPA) and PA similarly adjusted to the median lean BW (LBWPA). Dam parity, calf BWT and either BWPA or LBWPA were the only independent predictors of dystocia (P < 0.05), whereas the effect of PA tended to be significant only after adjusting for calf BWT (P = 0.08). After culling by PA or APA, retained heifers were heavier, had a higher calving rate and calves tended to be heavier at birth compared to culled heifers, but dystocia rates were not different. Although culling by PA:BW resulted in lower dystocia rate, it resulted in lower pre-breeding BW in retained than in culled heifers. Culling by BWPA and LBWPA had better sensitivity and specificity for dystocia than PA, and resulted in higher calving- and lower dystocia rates in the retained heifers, without affecting the pre-breeding BW or calf BWT. It was concluded that pelvimetry is a useful culling tool to aid in the management of dystocia in yearling heifers, and that adjustment of PA to median BW within age group improves its accuracy and avoids the undesirable side-effects of using unadjusted PA. The strong association of PA with calving rate resulted in the hypothesis for study 4, namely that PA can add prognostic value to RTS as a predictor of reproductive failure in beef heifers. Transrectal ultrasound (US) examination of the reproductive tract was also investigated in this study (n = 488) with the objective of identifying which ultrasonographic measures taken at a single point in time before the onset of breeding were independently associated with reproductive outcomes. In this study pregnancy failure was defined as the failure to become pregnant after the AI and bull breeding periods while anoestrus was defined as the failure to be detected in oestrus during the entire 50 d AI period. BCS, uterus horn diameter, absence of a CL, largest follicle of less than 13mm and PA were the pre-breeding examination variables that remained in prognostic models (P < 0.1). Combining either the model based on the three remaining US measures or RTS with PA provided more accurate prognostic models for pregnancy failure and anoestrus than using RTS alone (P < 0.05). It was concluded that US measures have prognostic value for pregnancy failure in restricted bred yearling heifers as a result of their association with anoestrus, and that smaller PA has additional value to identify poor performing heifers. In conclusion, pre-breeding examination is useful to identify beef cows with lower potential to reproduce successfully over the long term in a restricted breeding system. It is recommended that PA should always be included in such examination, either unadjusted or adjusted by BW, in herds with a low and high incidence of dystocia respectively, in combination with ultrasonography of the reproductive tract. When ultrasonography is not available, the accuracy of RTS by transrectal palpation can likely be improved by repeating it in low scoring animals after 7 days. / Thesis (PhD)--University of Pretoria, 2013. / gm2014 / Production Animal Studies / unrestricted

The purpose of these studies was to evaluate the effects of a dietary fat supplementation on growth, reproduction and performance characteristics of replacement beef heifers reared in different management systems (pasture and dry lot conditions). The objectives were (1) to quantify changes in body composition traits and growth performance of replacement beef heifers fed different levels of fat in the supplemented diet,(2) to determine the reproductive performance of heifers supplemented with dietary fat in either a ryegrass pasture system or a dry lot system, and (3) to determine the value of real-time ultrasound technology (RTU) as an alternative technology to assist producers in the decision making process within replacement beef heifer programs. Over the three year study, we observed that both high (3 - 5%) and low (1.5 ? 2.5%)levels of dietary fat supplementation of replacement heifers did not have a negative affect in reproductive performance and body composition traits significantly, compared to controls (pasture-base, no supplementation. However, a positive response with respect to some body composition traits was observed in animals fed the higher level of dietary fat in 2004 and 2005 studies. Overall, growth of animals grazing ryegrass outperformed animals supplemented with dietary fat in a dry lot system; yet when dietary fat supplementation was integrated with a ryegrass pasture system, besides the positive effects in body composition traits metabolic changes in relevant reproduction hormones were observed with the addition of dietary fat treatment. Finally, the use of information on body composition traits of replacement beef heifers through the use of real-time ultrasound technology in the decision-making process resulted in a small financial return in these studies. However, the use of this alternative technology in a replacement beef heifer program may have additional value beyond the limited feeding periods reported here. These may include, a greater ability to predict heifer fertility as linked to growth and developmental characteristics (e.g., body composition traits), yet this requires further study.

no abstract provided by author / Master of Science

Rapid rearing of dairy heifers during late prepuberty has been linked to impairments in mammary development and reductions in milk yield. Our objective was to determine how varying energy intakes between 2 and 14 wk of age affect mammary parenchymal development. At 2 wk of age, Holstein calves were assigned to 1 of 4 treatments (HH, HL, LH, and LL) with 2 levels of energy intake (High or Low) and 2 periods of growth (2 to 8 and 8 to 14 wk of age). At 14 wk, parenchyma at the stromal interface, mid-gland, and above the cistern were collected, fixed, and embedded in paraffin. Digital images of stained sections were used to determine tissue composition (% epithelium, lumen, and stroma). Immunochemistry revealed estrogen receptor (ER) and Ki67 (nuclear proliferation antigen) positive cells, type IV collagen, fibronectin (FN), and laminin. Images representing 4 increasing grades were used to quantify ECM protein deposition. Lumenal and stromal areas were 3.5 ± 1.4% higher (p<0.01) and 4.0 ± 1.7% lower (p<0.01), respectively, in HH and HL heifers. Ki67 labeling in terminal ductular units and subtending ducts was 2.1 ± 0.8% (p<0.01) and 1.4 ± 0.7% (p<0.05) lower for the same feeding level combination. FN deposition was also increased (p<0.05) in HH and HL heifers. High rates of gain between 2 and 14 wk of age resulted in greater lumenal area and reduced cell proliferation in mammary parenchyma at 14 wk of age. Changes in FN deposition could have mediated growth differences. / Master of Science

No description available.

The aim of this study was to evaluate the effects of M. elsdenii (Me) dosing on dairy heifer performance. A secondary set of data (feed intake, heifers birth weights, age and Weight at insemination, and first lactation milk performance) of heifers (dosed and not dosed with Me) was obtained from the dairy herd of the Agricultural Research Council – Animal Production. Data were arranged in a complete randomised design and analysed as repeated measures. Milk, pre-weaning starter and metabolised energy intake did not differ between the control and the Me groups. Post-weaning starter feed intake was higher (p=0.03) for Me fed heifers than control heifers. The post-weaning metabolisable energy intake was also higher (p=0.03) for heifer fed Me than control heifers. The average daily weight gain of heifers dosed with Me was higher during the pre-weaning period (0.66 kg/day; p=0.04) and after weaning (1.12 kg/day; p=0.03) compared to control (0.60 and 0.65 kg/day, respectively). At 42 and 70 days old, the BW of Me-heifers was greater (75.8 ± 2.6 and 91.2 ± 4.6 kg) than control heifers (61.9 ± 2.6 and 77.2 ± 4.6 kg) (p<0.05). There was no difference (P>0.05) in BW at insemination, number of insemination and milk yield between the two groups of cows (p>0.05). Early feeding of Me to heifers in the present study positively affect heifer growth during and early after milk feeding period, confirming previous report. Animal weight at puberty and the subsequent milk production were not influenced by feeding Me. It is possible that Me did not survive long after weaning to continue to express its influence on animal performance. / Agriculture and  Animal Health / M. Sc. (Agriculture)

Call number: LD2668 .T4 1984 S585 / Master of Science

This study was conducted to: i) determine the effect of residual feed intake (RFI) on first parity fertility and subsequent lifetime productivity of 820 females ranked as low, medium, and high RFI in western Canada and ii) investigate the relationship between RFI measured as a heifer and re-measured as a mature cow. No significant correlations were found between RFI and fertility/productivity traits. A negative trend (P < 0.10) was observed between RFI, RFIfat and MPPAbw, however, this trend was no longer apparent when RFI was adjusted for back fat and feeding event frequency (RFIfat&activity). No significant (P < 0.05) relationship was found between heifer RFI and cow RFI. These results suggest that selection for feed efficient, low RFI heifers i) has no impact on their fertility and productivity as cows, and ii) may not lead to superior feed efficiency as a mature cow as measured by RFI and Cow DMI. / February 2017

Graduation date: 1998