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.

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

The aim of this study was to evaluate the progesterone (P4) release profile provided by eight commercial intravaginal P4 devices, as well as the effect of circulating P4 concentrations produced exclusively by these devices on the development of the dominant follicle (DF) in non-lactating multiparous Holstein cows. All cows were submitted to the same experimental design starting 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, 6 and 7 d after device insertion. Just before device removal, a Norgestomet ear implant was inserted and, 2 d later (Day 0), simultaneously to Norgestomet withdrawal, cows received one of the tested intravaginal devices and 2 mg of estradiol benzoate (EB) im. In Exp.1 (n = 22; three replicates), cows were randomized to receive: CIDR (1.38 g); PRID-Delta (1.55 g); Prociclar (0.75 g); or Repro sync (2 g). In Exp. 2 (n = 29; four replicates), cows were randomized to receive: Cue-Mate (1.56 g); DIB 0.5 (0.5 g); DIB (1 g); PRID-Delta (1.55 g); or Sincrogest (1 g). Blood samples were collected before P4 device insertion (Day 0), 12 h later and daily over 15 d (1 d after P4 device removal). Ultrasound examinations were performed to evaluate growth of the DF on Days 0, 7, 8, 9, and 10. Results are presented as mean ± SEM and differences were considered when P ≤ 0.05. Overall, the circulating P4 profile and mean circulating P4 over 10 d differed among treatments. However, no effects were observed on the DF diameter and follicular growth rate from Day 7-10 after P4 device insertion. In Exp. 2, devices that provided higher circulating P4 concentrations were associated to a slower DF growth during the treatment period. Finally, this study provided a better understanding of the P4 release profile produced by intravaginal P4 devices as well as their effect on circulating P4 concentrations and DF development in non-lactating Holstein cows.

Effect of cyclic heat stress on thyroidal hormones, thyroid histology, and performance of two broiler strains.

This study determined thyroid hormone (T3 and T4) serum levels and investigated thyroid gland histology, as well as two broiler strains performance kept at different periods of heat stress. Broilers (560 Cobb Slow™ and 560 Hubbard Flex™) were distributed in control environment (0) reared following the thermal recommendations, and environments 1, 2, and 3 exposed to high temperatures for 1 h, 2 h, and 3 h a day, respectively, from 14 to 42 days old. At 21, 28, 35, and 42 days old, blood samples were collected to determine T3 and T4 serum levels. At 42 days old, thyroid glands were removed for histological analyses. The performance was calculated weekly. T3 levels decreased with age advance, while T4 serum concentration was higher at 42 days old (23.27 nmol L-1) and lower at 28 days old (15.69 nmol L-1). The histological sections revealed that thyroid morphology was well preserved. Live weight was higher in Cobb Slow™ (2.97 kg) than Hubbard Flex™ (2.93 kg) broilers at 42 days old. It is possible to conclude that cyclic heat stress exposure for a 3-h period from 14 to 42 days old did not affect performance, thyroid histology, or T3 and T4 serum levels. Cobb Slow™ broilers had the best live weight values at slaughtering. With increasing age, T3 levels decreased and T4 levels increased for both strains.