ABSTRACT The objective of this study was to evaluate the effect of timed artificial insemination (TAI) on pregnancy rates, reproductive efficiency, and mean weaning weight of calves at the end of breeding season in Nellore females. In this work, 744 Nellore females were divided into two groups: in group I (n = 396), the females were subjected to natural service during the breeding season, which lasts for 180 days. In group II (n = 348), a hormonal protocol was performed for synchronization of ovulation, and the females were subjected to TAI. Afterwards, these latter females were then serviced by a cleanup bull until the end of the breeding season. The group II obtained a higher pregnancy rate as well as higher reproductive efficiency compared with group I. The weaning weight of group II calves was greater than that of group I. The use of TAI combined with cleanup bulls enables higher pregnancy rates and a better reproductive efficiency in relation to the use of only natural service. In addition, weaning calves born from TAI are heavier than calves born from natural service.

Resumo: O objetivo deste trabalho foi avaliar os efeitos da doadora, estação do ano, do touro e do tipo de sêmen, na produção in vitro de embriões da raça Sindi (Bos indicus). Para isso, avaliaram-se 434 sessões de aspiração folicular in vivo (OPU), realizadas em 152 doadoras, com a utilização de sêmen sexado e não sexado de 22 touros. Analisaram-se as seguintes variáveis: doadora; idade da doadora; estação do ano; touro; tipo de sêmen; oócitos recuperados; viáveis e degenerados; e as taxas de clivagem e de blastocistos. Observaram-se efeitos da doadora e do touro sobre os oócitos recuperados, viáveis e degenerados e sobre a taxa de blastocisto. O ano foi dividido em estações chuvosa, de outubro a março, e seca, de abril a setembro. Na estação chuvosa, a proporção de oócitos viáveis aumentou, enquanto a de degenerados diminuiu. As doadoras com menos de seis anos tiveram maior proporção de oócitos viáveis e menor, de degenerados. O sêmen não sexado obteve as melhores taxas de clivagem e de blastocistos. Doadoras de até seis anos apresentam a maior proporção de oócitos viáveis, e o maior número de oócitos viáveis é produzido na estação chuvosa. O sêmen não sexado resulta em melhores taxas de clivagem e de blastocistos.

Abstract: The objective of this work was to evaluate the effects of donor, season of the year, sire, and type of semen on in vitro embryo production of the Sindhi breed (Bos indicus). To this end, 434 in vivo ovum pick up (OPU) sessions, performed in 152 oocyte donors, were evaluated using sex-sorted or unsorted semen from 22 sires. The following variables were analyzed: donor; age of the donor; season of the year; sire; type of semen; recovered, viable, and degenerated oocytes; and cleavage and blastocyst rates. The effects of the donor and sire were observed on recovered, viable, and degenerated oocytes, and on blastocyst rates. The year was split into rainy season, from October to March, and dry season, from April to September. In the rainy season, the proportion of viable oocytes increased, while the proportion of the degenerated ones reduced. Donors with less than six years of age had a higher proportion of viable oocytes and a lower proportion of degenerated ones. Unsorted semen obtained the best cleavage and blastocyst rates. Donors with up to six years of age show the greatest proportion of viable oocytes, and the greatest number of viable oocytes is produced during the rainy season. Unsorted semen shows the best rates for cleavage and blastocysts.

The objective of this study was to evaluate the effect of the follicular wave synchronization method on the superovulatory response of Girolando embryo donors. Seven cows and five heifers were divided into three treatments according to the method of the follicular wave synchronization prior to superovulation. The donors were superovulated with eight FSH decreasing doses, adding 133 mg per animal. The superovulatory response was evaluated using an ultrasound device to quantify the number of corpora lutea. The number and quality of recovered structures were also evaluated. Animal category (cow or heifer) and genetic group influenced the superovulatory response, in which heifers showed a greater response (100% in all treatments) compared with cows, which showed 85.7%, 57.1% and 57.1% superovulatory response for standing estrus, GnRH and P4 + BE groups, respectively. The genetic group also showed influence on superovulatory response, in which the 3/8 animals had an average of 10.3 corpora lutea per donor compared with the 3/4 animals, which showed 4.9. The follicular wave synchronization treatments did not show differences in superovulatory response, recovered structures and viable structures. The treatment of follicular wave synchronization with GnRH or with P4 + BE can be used in Girolando donors with the same efficiency as the standing estrus group, and 3/8 Girolando heifers respond better to the superovulatory treatment.

The objective of this study was to evaluate the reproductive parameters of Sindhi cows aiming to improve the efficiency of fixed-time artificial insemination protocols in this breed. For this purpose, sixteen Sindhi cows were divided into two groups: in group I (EB, n = 8) animals received an intravaginal P4 implant and an application of 2 mg of estradiol benzoate on day 0. On day 8 the implant was removed and 10 mg of Dinoprost were applied; on day 9, 1 mg of estradiol benzoate was applied, and animals were fixed-time artificially inseminated 36 hours later; in group II (EB + eCG, n = 8) animals were subjected to same treatment, and on day eight 400 IU of eCG were applied. From day 0 animals were examined daily by a trans-rectal ultrasound device, where in each assessment the largest follicles of each day were measured. The reproductive parameters observed for groups I and II were: emergence of follicular wave, 4.5±1.4 and 3.8±0.3 days; interval between wave emergence and ovulation, 5.8±1.4 and 7.1±0.3 days; interval between wave emergence and implant removal, 3.5±1.4 and 4.1±0.3 days; interval between implant removal and ovulation, 74.0±11.8 and 82.5±4.2 hours; diameter of the dominant follicle (DF) at the time of implant removal, 7.5±2.5 and 6.6±1.5 mm; maximum diameter of DF, 10.47±8.85 and 3.7±1.2 mm; growth rate of DF, 0.90±0.83 and 0.7±0.6 mm/day; ovulation rate, 75% and 100%; and pregnancy rate, 0% and 50%, respectively. There was no significant difference between the groups. We observed that eCG was not efficient in improving the reproductive parameters analyzed in this breed.