Progesterone release profile and follicular development in Nelore cows receiving intravaginal progesterone devices.

This study aimed to evaluate the progesterone (P4) release profile provided by four commercially available intravaginal P4 devices, as well as the effect of circulating P4 concentrations exclusively from these devices on the development of the dominant follicle (DF) in Nelore (Bos indicus) cows. Therefore, non-lactating multiparous Nelore cows were enrolled in an experimental design, over three replicates, starting on Day -9 with the insertion of a reused P4 device (2 g - original P4 load) for 7 d, followed by two treatments of cloprostenol sodium (PGF; 0.482 mg), 24 h apart, on Days -3 and -2. Just before device removal, on Day -2, a norgestomet ear implant was inserted and, 2 d later (Day 0), at the time of norgestomet withdrawal, cows were randomly assigned to receive one of the intravaginal devices: Primer (0.5 g); Prociclar (0.75 g); Sincrogest (1 g); or CIDR (1.9 g), and 2 mg of estradiol benzoate (EB) im. Blood samples were collected immediately before P4 device insertion, 12 h later and daily over 15 d (1 d after P4 device removal). Ultrasound examinations were performed on Days 0, 7, 8, 9, 10, 12, and 14 to evaluate ovarian dynamics. Results are presented as mean ± SEM and differences were considered when P ≤ 0.05. Overall, the devices resulted in distinct circulating P4 concentrations over 10 d, varying according to their initial P4 load and P4 impregnated surface area. Primer provided the lowest circulating P4 concentrations over time, whereas, CIDR had the greatest concentration. Sincrogest and Prociclar were similar, producing intermediary circulating P4. There was no effect of treatment on the DF diameter on any specific day, nor on follicular growth rate from Day 7-10. However, the Primer device resulted in a greater mean DF diameter over time. Additionally, greater circulating P4 concentrations, mainly during the first 3 d of device insertion, were associated with smaller DF diameters regardless of the treatment. In conclusion, results from this study provided a better understanding of the P4 profile of intravaginal P4 devices, as well as, their effect on DF development in Bos indicus cows. These data contribute to optimize the use of P4 devices in the reproductive management of beef cattle.

Effects of experimental exposure to zearalenone on reproductive system morphometry, plasma oestrogen levels, and oocyte quality of beef heifer.

The aim of the present study was to evaluate the effects of zearalenone (ZEA) on the reproductive system morphometry, oestrogen (E2) levels and oocyte quality of beef heifers. Twenty non-pregnant purebred Nellore (Bos indicus) heifers [age, ≥18 months; initial body weight, 348 ± 30 kg (mean ± standard deviation)] were used. The animals were randomly divided into experimental group and a control group of 10 animals each. Group experimental was administered 300 ppb ZEA per os for 98 days, and the control group was administered placebo per os for 98 days. The administration of ZEA was carried out daily by adding mycotoxin to the diet. All heifers were evaluated weekly via rectal ultrasound examinations (12 weeks). Diameters of the right and left uterine horns, right and left ovaries, largest antral follicle and corpus luteum were measured. Vulva size was also measured. Blood samples were collected to estimate E2 levels. At the end of 12 weeks, the heifers were slaughtered, and the ovaries were sent to the laboratory for in vitro embryo production. A completely randomized design was adopted, and repeated measures analysis of variance (p < .05) was performed (except for oocyte quality). Vulva size (p = .0985); diameters of uterine horns (p = .0522), ovaries (p = .6955), antral follicles (p = .6355) and corpus luteum (p = .3808); and E2 levels (p = .3379) were not affected by the treatments. ZEA-contaminated diet significantly reduced (p = .05) the proportion of viable oocytes (49.4%, n = 207) compared with the control diet (59.9%, n = 222); however, the blastocyst rate did not differ between the groups (p = .9418). The results indicate that contamination of beef heifer's diet with 300 ppb ZEA affected neither morphometric parameters nor plasma oestrogen levels; however, ZEA contamination was detrimental to oocyte quality.

Genetic market in cattle (Bull, AI, FTAI, MOET and IVP): financial payback based on reproductive efficiency in beef and dairy herds in Brazil.

A number of reproductive biotechnologies are currently available to multiply offspring from high genetic merit animals to enhance reproductive efficiency and profitability both in dairy and beef herds. Some of these technologies such as fixed time artificial insemination (FTAI), when correctly implemented, generally allow greater reproductive performance than natural breeding. Besides the use of frozen-thawed semen during artificial insemination, cattle recipients can also be synchronized to receive embryos (produced in vivo or in vitro) at set dates with fertility results that usually outperforms natural breeding as well as artificial insemination (AI), particularly during warm seasons and in repeat breeders cows. Altogether, the use of hormonal programs to synchronize ovulation time simplify field routine, can easily fix physiological limitations related to postpartum anestrus (beef cows), poor estrus detection efficiency due to less evident estrus signs (dairy cows), making AI and ET viable to commercial herds both in terms of results and economical returns.