Anti-Müllerian hormone (AMH) is used as a marker of follicle population numbers and potential fertility in several species including horses but limited data exist across the lifespan. No one has decreased ovarian reserve experimentally to investigate whether a corresponding, quantitative decrease in AMH results. Concentrations of AMH across the lifespan were compiled from 1101 equine females sampled from birth to >33 years of age. Young and old mares (averaging 6 and 19 years) were hemi-ovariectomized and circulating AMH was assessed before and daily thereafter for 15 days. The remaining ovary was removed later and blood was drawn again before and after this second surgery for AMH determination. Polynomial regression analysis and analysis of mares grouped by 5-year intervals of age demonstrated AMH concentrations to be higher in mares aged 5–10 and 10–15 years than 0–5 years of age and lower in mares after 20 years of age. There was high variability in AMH concentrations among neonatal fillies, some of which had concentrations typical of males. Hemi-ovariectomy was followed by a decrease of AMH, almost exactly halving concentrations in intact mares. Concentrations of AMH had returned to intact levels in old mares before complete ovariectomy, as if exhibiting ovarian compensatory hypertrophy, but recovery of AMH was not evident in young mares. AMH may reflect ovarian senescence in mares after 20 years of age but is too variable to do so in the first two decades of life. The ovarian endocrine response to hemi-ovariectomy in mares appears to change with age.

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-The objective of this study was to examine the effects of suckling schemes (continued, controlled, and total separation) and the type of pregnancy on performance and serum cortisol concentration in lambs. A total of 29 Santa Inês ewes and 40 lambs were used, and the randomized block design was applied in a split-plot scheme with a 3 × 2 factorial arrangement in the plot and time in the subplot. For controlled suckling, the diet was supplied twice daily during one hour, starting on their 10th day of life. Total and average daily intakes of concentrate dry matter of lambs that underwent total separation was higher than those of lambs under continued suckling. Lambs subjected to total separation demonstrated higher concentrate dry matter intake/weight gain ratio, lower total weight gain, lower average daily weight gain, and lower weaning weight than those subjected to continued and controlled suckling. Lambs from single pregnancy demonstrated higher weight gain and obtained higher weight at weaning. Lambs subjected to total separation have a developmental delay. However, the lower performance of lambs subject to total separation cannot be attributed to stress because there is a decrease in the serum cortisol concentration over time.

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The aim of this study was to investigate possible relationships between morphometric characteristics of the bovine reproductive tract and measures of fertility, such as antral follicle counts (AFCs) and the number and quality of recovered cumulus oophorus complexes (COCs). First, the genital tracts of 360 abattoir Zebu/Holstein crossbred cows were studied. Rima vulvae length (RL), vulvar width (VW), ovarian size, pelvic fat, number of aspirated COCs, and AFCs were recorded. An index of COC quality (CQI) was established, which weighed overall gamete quality based on the IETS classification. Second, the same external measurements and AFCs (by ultrasound) were analyzed in live Tabapuã (Zebu) cows (n = 48). Relative RL and vulvar width were defined as the original measurements divided by the body weight of each cow for statistical analyses. In abattoir tracts, the AFC was smaller (P < 0.05) in animals with large VW (34.88 ± 3.50) than in animals with small (45.71 ± 2.57) and intermediate (42.25 ± 2.45) VW. The CQI was higher (P < 0.05) when the pelvic fat score was intermediate (3.22 ± 0.06) than that in lean (2.99 ± 0.08) and obese (2.90 ± 0.12) animals. The CQI was higher (P < 0.05) in the intermediate ovary group (3.19 ± 0.08) than in the small (2.96 ± 0.08) and large (2.95 ± 0.09) ovary groups. In live cows, the AFC was higher (P = 0.035) in females with large relative rima length than in those with small relative rima length (18.96 ± 1.97 and 14.76 ± 1.51, respectively). Similarly, AFC was greater (P = 0.0001) in females with large relative VW than in those with small relative VW (20.08 ± 1.36 and 11.16 ± 1.60, respectively). In conclusion, larger external genitalia relative to body size were good predictors of the ovarian follicular reserve in live animals.

Administration of progesterone (P4) after estradiol is usually performed to prepare non-cyclic mares as embryo recipients. However, there are successful pregnancy reports after embryo transfer in non-cyclic mares treated only with progestins. The objective of this study was to evaluate endometrial gene expression and immunostaining for estrogen receptor alpha (ERα), beta (ERβ) and progesterone receptor (PR) in seasonal anestrous mares treated with long acting P4 (LA P4). Endometrial tissue from eight seasonal anestrous mares was collected immediately before administration of 1.5 g of LA P4 and five days after. The receptors protein expression was evaluated by immunohistochemistry and the percentage of the immunostained area was determined by ImageJ software. Transcripts abundance for ERα, ERβ and PR were determined by RT-qPCR. Blood samples were collected daily to measure plasma P4 concentrations. Protein expression for ERα was greater (p < 0.05) after LA P4 administration, although gene expression was not affected by treatment (p > 0.05). There was no difference for ERβ protein expression (p = 0.07) and ERβ gene expression was reduced (p < 0.05) after treatment. Gene and protein expression for PR was not altered (p > 0.05). In conclusion, endometrial PR and ERα expression patterns after LA P4 administration were similar to those previously found in protocols using estradiol prior to LA P4 to prepare non-cyclic mares as embryo recipients.

The aim of this study was to evaluate the effect of different suckling regimens on body condition and interval from lambing to onset of the cyclic ovarian activity in Santa Inês ewes. Thirty-two ewes were allocated to blocks according to parity, number of lambs, and body weight and submitted to 3 treatments: continuous suckling (n = 11 ewes, 13 lambs), controlled suckling (n = 10 ewes, 14 lambs) with 2 suckling periods per day for 1 h from Day 10 postpartum (pp), or early weaning (n = 11 ewes, 14 lambs) with total separation of the lambs from Day 10 pp. The animals were evaluated in the interval from Day 12 pp to first estrus or to Day 60 pp. Dry matter intake was evaluated daily. The body weight of ewes and lambs and body condition score (scale 1 = thin and 5 = fat) of ewes were evaluated at lambing and at every 6 days after. Lambs were weighed at weaning. Estrus was monitored twice daily with a teaser ram. Blood samples for progesterone measurement were collected and ovarian ultrasonography was done at intervals of 3 days from Day 12 pp to first estrus or to Day 60 pp. Dry matter intake was analyzed over time, considering 9 periods, with PROC MIXED of SAS (2008; SAS Institute Inc., Cary, NC, USA). Body weight, body condition score, interval from lambing to first ovulation, and weaning weight were analyzed using the GLM procedure, ANOVA, and an F-test. The intervals from lambing to first estrus and to follicles with a diameter ≥5 mm were analyzed considering a Poisson distribution and the percentage of estrus manifestation was analyzed considering a Bernoulli distribution, by generalized linear models, using PROC GENMOD. The dry matter intake did not differ (P > 0.05) among treatments (2.3 ± 0.1, 2.2 ± 0.0, and 1.6 ± 0.0 kg day–1), but it differed over time (P < 0.05). The body weight gain (3.3 ± 1.0, 3.0 ± 0.9, and 2.1 ± 1.4 kg), body condition score gain (0.2 ± 0.1, 0.2 ± 0.1, and 0.2 ± 0.1), percentage of estrus manifestation (63.6, 50.0, and 54.5%), interval from lambing to first estrus (45.0 ± 3.9, 44.0 ± 7.2, and 32.3 ± 5.4 days), follicle with a diameter ≥5 mm (31.0 ± 3.3, 33.9 ± 3.0, and 34.9 ± 4.5 days), and ovulation (38.0 ± 3.6, 35.6 ± 3.9, and 26.5 ± 3.2 days) did not differ among treatments (P > 0.05). The dry matter intake was correlated with body weight in ewes that were submitted to continuous suckling (r = 0.7; P < 0.01) and controlled suckling (r = 0.6; P < 0.01), but not in those submitted to early weaning (r = 0.2; P > 0.05). The body condition score was correlated with body weight in ewes submitted to continuous suckling (r = 0.8; P < 0.01), controlled suckling (r = 0.4; P < 0.01), and early weaning (r = 0.5; P < 0.01), and with dry matter intake in those submitted to continuous suckling (r = 0.4; P < 0.01). Weaning weight was lower (P < 0.05) in lambs subjected to early weaning (19.0 ± 1.0, 18.3 ± 1.0, and 15.2 ± 0.6 kg), but their health was not compromised. Continuous suckling did not delay the return to postpartum cyclic ovarian activity and did not influence the postpartum body condition of Santa Inês ewes and should be used by producers. The financial support of Fundação de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) and Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) is acknowledged.

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