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The objective of the current study was to evaluate the effect of lactation on oocyte quality and in vitro embryo production in Gyr (Bos indicus) cows. A total of 187 multiparous cows (92 lactating and 95 non-lactating) were subjected to a single session of follicular aspiration. Follicle puncture was performed on a random day of the estrous cycle, without prior application of hormonal drugs. The recovered oocytes were subjected to maturation, fertilisation, and in vitro culture. The results indicated that in lactating Gyr cows had the following values of studied variables: number of follicles visualised (22.1±11.38), number of recovered oocytes (17.4±10.21), number of grade III oocytes (7.0±5.86), rate of viable oocytes (72.1±13.11%), number of blastocysts D7 (2.5±2.26) and blastocyst rate (18.3±15.61%), in relation to non-lactating cows (27.7±11.53; 21.1±10.06; 9.8±6.08, 77.4±10.08%; 4.9±3.34; 30.2±15.41%, respectively). In conclusion, the lactation period in Gyr cows affects the performance of in vitro embryo production programmes. [ABSTRACT FROM AUTHOR]

The luteal vasculature plays a critical role in corpus luteum (CL) function and provides important information on the physiology and pathophysiology of this structure. To quantify the blood flow of the luteal tissue, Doppler ultrasound is used to detect the flow of red blood cells through the blood vessels. The objective of the present study was to determine the degree of irrigation of the CL evaluated by Doppler ultrasound on the day (D0) of embryo transfer (ET) and 25 days post-transfer and its relationship with the percentage of early gestation in Holstein recipient cows. Thirty multiparous, non-lactating Holstein cows were used as in vitro embryo recipients. The blood supply rate of the CL and the percentage of gestation were evaluated. The corpora lutea were categorized into 1 (high), 2 (medium) and 3 (low) according to the degree of blood supply. The percentage of cows with these degrees of CL irrigation on the day of transfer were 50% (15/30), 23.3% (7/30) and 27.7% (8/30). On day 25 post-transfer they were 33.3% (10/30), 43.3% (13/30) and 23.3% (7/30), respectively. Additionally, the percentage of early gestation (25 days post-transfer) was evaluated for grades 1, 2 and 3 of CL blood supply, whose results were: 20% (6/30), 6.6% (2/30) and 0%, respectively. It was possible to conclude that the Holstein breed recipients classified in high degree of CL blood irrigation, presented better (P < 0.05) percentage of gestation of embryos of in vitro origin. [ABSTRACT FROM AUTHOR]

The objective of this work was to evaluate the effect of pre-exposure of progesterone (P4) in Nelore breed cows in the postpartum period, undergoing a fixed-time artificial insemination program (FTAI). 74 multiparous cows with 2,5 body condition, acyclic, were used. For the determination of the state of anestrus, ultrasound scans were performed evaluating the absence of the corpus luteum and taking blood samples in order to verify endogenous P4 levels < 1 ng / mL. The cows were submitted to three experimental groups, being an untreated group and two groups with previous P4 exposure for 3 and 6 days before the start of the estrus synchronization protocol. Animals underwent synchronization protocol based on progesterone, estradiol benzoate, prostaglandin and equine chorionic gonadotropin. 45 days after the IA, the pregnancy diagnosis was made. No differences (P > 0.05) were observed between the gestation rates of the experimental groups. In conclusion, pre-synchronization with P4 in Nelore cows in the postpartum anestrus period did not improve pregnancy rates after artificial insemination. [ABSTRACT FROM AUTHOR]

The objective was to characterize the follicular dynamics and the measurement of estradiol during the estrous cycle of cows of the Blanco Orejinegro creole. They were selected 10 cows of the Blanco Orejinegro creole and subjected to estrus synchronization protocol with the implementation of an intravaginal device more 2 mg Progesterone estradiol benzoate via I.M. Eight days later, the device of progesterone was removed and applied 150 μg of cloprostenol. 24 hours later, was administered 1 mg estradiol benzoate. After ovulation, ultrasounds were performed at intervals of 24 hours, throughout the estrous cycle. The length of the estrous cycle was 21 ±0,4 days, the dominant follicle diameter was 7,0± 0,2 mm and 6.7 ± 0,3 mm for the second largest follicle, diameter of the ovulatory follicle 14,3 ± 0,5, growth rate of the dominant follicle during the last 96 hours prior to ovulation was 1,05 ± 0,4 mm per day. In conclusion, the follicular dynamics and hormonal creole cows of the race Blanco Orejinegro (Bos taurus adapted) presented patterns similar to those observed in the races Bos taurus (not adapted) and Bos indicus. [ABSTRACT FROM AUTHOR]