Phenotypic and genetic relationships among anogenital distance, anti-Müllerian hormone, and in vitro embryo production in Gyr dairy cattle.

Anti-Müllerian hormone (AMH) concentration and number of recovered oocytes (ROOC) are phenotypic parameters associated with in vitro embryo production (IVEP). 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 this study was to characterize the AGD and its phenotypic and genetic associations with AMH and IVEP in Bos indicus Gyr dairy cattle. The 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 ovum pick-up 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 IVEP. 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 the age categories of 3 to <6 yr or 6 to <10 yr. Phenotypic associations were performed in SAS software (SAS Institute Inc., Cary, NC). Genetic correlations were estimated using the BLUPF90 family of programs. The AGD (128.7 mm ± 14; mean ± standard deviation) 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) 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). A greater number of viable oocytes and embryos were observed in donors in the high compared with intermediate and low ROOC categories within both age categories. The age interval of 3 to <6 yr 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 AGD and IVEP.

Metabolic responses and performance of Holstein × Gyr heifers grazing Brachiaria decumbens supplemented with varied crude protein levels.

We aimed to evaluate the effect of supplemental CP on the nutritional characteristics and performance of Holstein × Gyr crossbreed heifers grazing intensively-managed Brachiaria decumbens throughout the year. Thirty-eight heifers with average initial body weight of 172.5 ± 11.15 kg (mean ± SE) and 8.2 ± 0.54 mo of age were randomly assigned to four treatments: three protein supplements (SUP) composed of soybean meal and ground corn fed at 5g/kg of BW, plus a control group (CON). The supplements had 12, 24 and 36% of CP for treatments S12 (n = 9), S24 (n = 10), and S36 (n = 9), respectively. The experiment latest one year, subdivided into four seasons: rainy, dry, rainy-dry transition (RDT), and dry-rainy transition (DRT). Feces and pasture samples were collected for 4 days in each season, using chromium oxide, titanium dioxide, and indigestible neutral detergent fiber (NDF) to estimate fecal excretion, supplement, and pasture intake, respectively. The data were analyzed using PROC GLIMMIXED of the SAS with repeated measures. No effects of supplementation were detected on pasture and NDF intake. However, SUP animals had a greater intake of DM, metabolizable energy, and metabolizable protein. A positive linear response on metabolizable protein intake was observed among SUP animals. We observed an interaction between treatment and season for all digestibility variables, with a positive linear response in CP digestibility among SUP animals during all seasons. For neutral detergent fiber (NDF) digestibility, we observed a positive linear response in RDT and rainy seasons and a quadratic response during the dry season. Furthermore, SUP animals had greater average daily gain (ADG) than non-supplemented animals, and among SUP animals, there was a quadratic response to ADG, with the greatest gain observed in S24. We observed greater nitrogen retention coefficient in SUP animals than in non-supplemented animals and a positive linear effect among SUP animals. Supplemental CP did not affect microbial protein production and efficiency. We observed an interaction between treatment and season for blood glucose, with SUP animals having greater glucose concentration in all seasons than non-supplemented animals. Additionally, we observed a quadratic response among SUP animals only during RDT and dry season, with the greatest glucose concentration in S24. SUP animals had greater blood concentrations of urea and IGF-1. In conclusion, SUP animals had greater intake, digestibility, and performance than non-supplemented animals, with the 24% CP supplement demonstrating the best metabolic responses and performance.

The effect of age and FSH stimulation on the ovarian follicular response, nuclear maturation, and gene expression of cumulus-oocyte complexes in prepubertal gilts.

This study investigated the effects of age and FSH treatment on the ovarian response, follicular fluid (FF) biochemical composition, nuclear maturation, and molecular profile of cumulus-oocytes complexes (COCs) recovered from prepubertal gilts. Thirty-five prepubertal gilts were separated according to age [140 (n = 20) or 160 (n = 15) days], and within each age, the gilts were allotted to receive either 100 mg of FSH [treated; G140+FSH (n = 10) and G160+FSH (n = 7)] or saline solution [control; G140+control (n = 10) and G160+control (n = 8)]. Thus, four experimental groups were included in this study. In the FSH-treated gilts, the percentage of medium follicles increased (P < 0.0001) in the same proportion with which the percentage of small follicles decreased (P < 0.0001). In addition, the glucose concentration in the FF obtained from medium follicles increased (P < 0.05), while that of triglycerides decreased (P < 0.05) in the FSH-treated gilts. The FSH stimulation also improved (P < 0.05) the number of grade I COCs obtained from medium follicles and the meiotic maturation and BCB + rates. FSH treatment only upregulated (P < 0.05) HMGCR expression in immature COCs from prepubertal gilts. The metaphase II and BCB + rates, FF glucose and plasma IGF-1 levels were greater (P < 0.05) in prepubertal gilts at 160 than at 140 days of age. Age had no effect (P > 0.05) on the transcript abundance of the target genes in immature COCs. Hence, oocytes obtained from 140-day-old prepubertal gilts appeared less meiotically competent than those of 160-day-old prepubertal gilts. Our study suggests a possible strategy of using FSH treatment to improve oocyte quantity, quality, and nuclear maturation in 140 and 160-day-old prepubertal gilts.

Effect of protein supplement level on the productive and reproductive parameters of replacement heifers managed in intensive grazing systems.

Evaluations of replacement heifers in intensively managed grazing systems in tropical conditions are warranted. Thus, we aimed to evaluate performance, muscle and mammary gland development, oocyte quality, and in vitro production of embryos of crossbred heifers grazing an intensively managed pasture and supplemented with high or low protein concentrates. Eighteen pubertal crossbred heifers (Holstein x Gyr) with an initial weight of 350 ± 8.0 kg were used in a 60-day trial. Two supplement types, 12% crude protein (CP) (S12CP) or 24% CP (S24CP), and a control treatment (mineral mixture, CON) were randomly distributed to the heifers. Throughout the experiment, four digestibility trials were performed over four consecutive days. Four ovarium pick-ups were performed to evaluate oocyte quality and in vitro embryo production. Lastly, ultrasounds of carcasses and mammary glands were performed. The intakes of dry matter (DM), digestible energy (DE), and CP were greater for supplemented (SUP) compared with CON heifers. The SUP heifers had a greater average daily gain (ADG) (645 versus 390 g/d) and rib eye area (58.78 versus 53.32 cm2) than the CON heifers. Oocyte recovery, quality, and follicle features were not affected by supplementation strategy. However, the cleavage rate (47.17% versus 30.31%) and blastocyst rate (27.91% versus 10.12%) were negatively affected by supplementation. The S12CP presented a blastocyst rate much lower than the S24CP (3.02% versus 17.23%). Carcass ultrasonography indicated a trend for greater rib eye area for S24CP and mammary ultrasonography indicated no effects of supplementation on mammary gland development. In summary, supplementation seems to be an appropriate strategy for satisfactory performance, with greater muscle deposition and no negative impacts on mammary gland development. However, in vitro embryo production was impaired when the animals received the supplementation with 12% CP.