Anti-Müllerian hormone (AMH) concentration and number of recovered oocytes (ROOC) are phenotypic parameters associated with in vitro embryo production. More recently, anogenital distance (AGD) has been proposed as a proxy for fertility in dairy cattle that is easy to collect at a low cost. The aim of the present study was to characterize the AGD and its phenotypic and genetic associations with AMH and in vitro embryo production in Bos indicus Gyr dairy cattle. Hypothesis was that the number of ROOC, in vitro produced embryos, and AMH concentration would increase as the AGD decreases. From July to December 2021, a single morphometrical measurement of AGD was collected in 552 donors from 6 herds in Brazil. A subset of donors had AMH assayed on the same day. Only OPU events that occurred up to 12 mo preceding, and 7 mo succeeding the AGD measurement were used to assess the association between AGD, AMH, and in vitro embryo production. Thus, 472 donors (1,551 ovum pick-up events, and 140 donors with AMH) were considered in the analysis. A raw average was calculated for each individual donor's ROOC, viable oocytes, total produced embryos, viability rate, and embryo rate (defined as total produced embryos/viable oocytes). Comparisons were conducted within age categories: 3 to < 6 years or 6 to < 10 years. Phenotypic associations were performed in SAS software. Genetic correlations were estimated using BLUPF90 family programs. The AGD (128.7 mm ± 14; Mean ± SD) had a normal distribution and was highly variable (83 to 172 mm) among the Gyr population. Our experimental hypothesis was partially supported by a phenotypic association of a greater number of total produced embryos (R² = 0.023; P = 0.03) as AGD decreased. Our results failed to support an increase in AMH concentration along with a decrease in AGD. In addition, positive and low genetic correlations were observed between AGD and viable oocytes (r = 0.08), and embryo rate (r = 0.20). Greater (P < 0.001) number of viable oocytes and embryos were observed in donors in the High compared with Intermediate and Low recovered oocytes categories within both ages categories. The age interval of 3 to <6 years showed a greater number of recovered and viable oocytes for the High AMH compared with the Low category, but no differences were observed among the AGD categories. In summary, for the Gyr breed, AGD was phenotypically inversely associated with a quantity-related parameter, such as the total number of produced embryos. In contrast, AGD showed a low genetic correlation with qualitative-related outcomes such as viable oocytes and embryo rate. Further studies should be performed to validate these retrospective analyses and to better understand the association between anogenital distance and in vitro embryo production.

The aim of this cross-sectional observational study was to assess whether nulliparous Holstein heifer fertility is associated with (1) energy reserve-related traits, such as body condition score (BCS) and body weight (BW); (2) ovarian reserve-related traits, such as Anti-Müllerian hormone (AMH) and antral follicle count (AFC); and (3) development-related traits, such as anogenital distance (AGD) and vulval length (VUL). From August 2022 through July 2023, we used a prospective approach in which the phenotypic traits (BCS, AMH, AFC, AGD, BW, and VUL) of 698 Holstein heifers were measured once at approximately 12 mo of age (at the beginning of the breeding program). All heifers were submitted to the herd reproductive management from 367 ± 3 d of age and 297 kg of BW until 570 d of age, or 5 breedings. Fertility outcomes (age at first service, pregnancy per AI (P/AI) at first service, age at conception, and number of services per conception) were retrieved from software records. Pearson correlations were performed among phenotypic traits collected. The strongest correlations (r >0.5) observed were for AGD with VUL and AMH with AFC. Associations of phenotypic traits with fertility outcomes were determined using generalized linear models. Body condition score was the phenotypic trait most associated with fertility outcomes. Associations of AMH, AFC, AGD, BW, and VUL with fertility were not observed or very weak. Further, we divided the data into BCS tertiles and performed association analyses by category. The top BCS tertile was associated with greater BW (365.7 ± 1.8 vs 356.0 ± 1.5 kg), greater P/AI at first service (65.0 ± 4.0 vs 52.0 ± 4.0%), and fewer number of services per conception (1.5 ± 0.10 vs 1.8 ± 0.09) compared with the bottom tertile. Moreover, AGD was greater in the top and bottom tertiles compared with the middle tertile. Finally, BCS was associated with time to conception based on the Cox proportional hazards survival analysis, indicating that heifers with greater BCS became pregnant earlier. Based on the results observed in the current study, we would expect benefits for fertility by improving management practices that result in heifers with greater BCS at first service, but ovarian reserve-related traits (AMH, AFC) and developmental traits (AGD, VUL) were not associated with fertility outcomes in our study.

O objetivo deste estudo foi verificar a associação entre o tamanho do perímetro escrotal e as características físicas e morfológicas dos ejaculados em 191 touros da raça guzerá. Os touros foram divididos por faixas etárias dos 12 aos 36 meses de idade. As mensurações de perímetro escrotal e medidas testiculares foram obtidas com ajuda de paquímetro e fita métrica de acordo à metodologia do Colégio Brasileiro de Reprodução Animal. Os animais que apresentaram perímetro escrotal ≥ 19 cm foram submetidos à coleta de sêmen utilizando-se estímulo eletro-ejaculatório. Foram avaliadas as características espermáticas dos ejaculados como motilidade, vigor e também realizadas avaliações de concentração espermática e a presença de células arredondadas. A correlação do perímetro escrotal com a motilidade espermática por faixa etária foi positiva r=0.94; (P<0, 005). Neste estudo foi observado que a presenças de espermatozoides com gota citoplasmática proximal, células arredondadas no ejaculado e defeitos de cabeça dos espermatozoides são as características de avaliação objetiva que mais poderiam ser utilizados para seleção de precocidade da produção espermática em machos bovinos. Pode ser concluído que a normalidade da produção espermática na raça Guzerá considerando conjuntamente todos os parâmetros representativos de maturidade do processo da produção espermática foi atingida com idade acima de 28 meses e perímetro escrotal acima de 30 cm.

Bovine twin birth is associated with detriments including increased embryo/fetal losses, malpresentation and dystocia. Incidence of these is lessened in bilateral versus unilateral twin pregnancy. This study was undertaken to assess use of follicular ablation by aspiration to create bilateral twin pregnancies in females with genetic potential for ~3.5 ovulations per cycle (Trio allele carriers). In Experiment 1, carriers (n = 30) and non-carriers (n = 10) were synchronized for ovulation and timed artificial insemination (TAI). Follicles (> 5 mm) in excess of one per ovary were aspirated ~16h preceding TAI. Follicle count for females with follicles on only one ovary was reduced to two. Blood was sampled 2 weeks post-TAI to assess progesterone (P4) concentrations; fetal count was determined by ultrasound 6 weeks post-TAI. P4 concentration post-TAI was significantly (P < 0.001) associated with both genotype and subsequent pregnancy status (pregnant non-carriers, 7.06 ± 0.68 ng/mL; pregnant carriers, 5.54 ± 0.55 ng/mL; non-pregnant non-carriers, 5.22 ± 1.05 ng/mL; non-pregnant carriers, 3.13 ± 0.42 ng/mL). Experiment 2 was undertaken to offset negative effects of follicular aspiration on subsequent P4 concentration observed in Experiment 1. Carriers (n = 38) and non-carriers (n = 32) were submitted to fixed-TAI and follicle ablation as described. Additionally, accessory corpora lutea were induced by administration of hCG (carriers) at d6 post-TAI. Consequently, P4 concentration post-TAI was significantly (P < 0.05) associated with subsequent pregnancy status (pregnant, 8.48 ± 0.61 ng/mL; non-pregnant, 6.70 ± 0.63 ng/mL) but not with genotype (carrier, 8.01 ± 0.59 ng/mL; non-carrier, 7.17 ± 0.64 ng/mL). Fetus number was greater in carriers (Exp1, 1.64 ± 0.81; Exp2, 1.45 ± 0.09) versus non-carriers (1.00 ± 0.00, both Experiments). Singles, twins, and triplets occurred in carriers in Experiment 1, whereas multiples in Experiment 2 were limited to twins. Genotype effects on pregnancy rate were not significant (P > 0.10) in either experiment. Results suggest follicular ablation to create bilateral twin pregnancies in Trio carriers is feasible but requires induction of accessory corpora lutea to offset the negative effects of follicular aspiration on subsequent P4 concentration.

Summary: Needle-free system delivery of cloprostenol in cattle was validated by luteolysis based on corpus luteum (CL) volume, progesterone concentrations, and CL blood flow. i.m. = intramuscularly.