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O desenvolvimento da produção de gametas femininos (gametogênese) ocorre de forma interessante, pois seu processo depende de diversos fatores combinados. Esta revisão abordará esses mecanismos morfofuncionais do ovário e a foliculogênese, correlacionando a função dos fatores de crescimento ligados à Insulina (IGFs) que irão influenciar na produção de hormônios esteroides, na manutenção da maturação folicular, e ainda elucidar como a dieta alimentar auxilia melhor nessas fases. Além disso, com as novas pesquisas em reprodução animal, é importante enfatizar o papel e auxiliar os Fatores de Crescimento Insulínicos durante este processo fisiológico, mostrando todo o seu potencial para uma dinâmica folicular mais eficiente em qualquer espécie.

RESUMO Três experimentos foram realizados para adaptar um protocolo de sincronização de estro e da ovulação para ser utilizado em programas de inseminação artificial em tempo fixo (IATF) em vacas taurinas tropicalmente adaptadas. No Exp. 1 (crossover), vacas pluríparas Curraleiro Pé-Duro (n= 12) receberam um dispositivo intravaginal contendo 1g de P4 por oito dias e 2mg de BE intramuscular (IM) no momento da inserção do dispositivo (dia 0). No dia da remoção do dispositivo (dia 8), as fêmeas receberam 150μg de D-cloprostenol sódico e 300UI de gonadotrofina coriônica equina (eCG) IM, sendo, então, divididas aleatoriamente para receber 1mg de BE no dia 8 (BE8) ou 1mg de BE no dia 9 (BE9). A aplicação de BE no D9 atrasou a ovulação em aproximadamente 15 horas (P0,05). No Experimento 3, os protocolos hormonais de IATF BE8 e P4D9 foram testados para a taxa de prenhez, alcançando 23% (10/43) e 20% (9/45), respectivamente (P>0,05). Embora o grupo P4D9 tenha mostrado avanço na proporção de animais que responderam ao protocolo quando comparado ao protocolo BE8, este não se refletiu em melhora na taxa de prenhez. ABSTRACT Three experiments were performed to adapt a synchronization protocol of estrus synchronization and ovulation to be used in fixed time artificial insemination programs (FTAI) in tropically adapted Bos taurus cows. In Exp. 1 (crossover) multiparous Curraleiro Pé-Duro cows (n= 12) received an intravaginal device containing 1g of P4 for 8 days and 2mg of EB at the time of device insertion (Day 0). On the P4 device removal (Day 8) females received 150g of D-cloprostenol Sodic and 300IU of equine chorionic gonadotropin (eCG). Then, they were randomly divided to receive 1mg of EB on Day 8 (EB8) or on Day 9 (EB9). EB9 delayed ovulation approximately 15 hours (P0.05). In Exp. 3, EB8 and P4D9 protocols were used to evaluate the pregnancy rate, reaching 23% (10/43) and 20% (9/45), respectively (P>0.05). Although P4D9 protocol has shown improvement in proportion of animals that responded to the protocol when compared to EB8 protocol, it was not able to improve pregnancy rate.

The objective of this study was to evaluate the influence of a commercial milk-based extender compared with a self-made egg yolk extender in the quality of canine semen, stored with two different temperatures (5°C or 15°C) for short-term cooling. The ejaculate obtained was divided into two aliquots of equal volume, that was diluted with Milk extender or Egg Yolk extender, presenting a final concentration of 100 x 106 spermatozoa/mL. Diluted semen was placed into transport containers, maintaining final storage temperatures of 5°C and 15°C. Quality of chilled semen was assessed after 12, 24 and 36h of storage. Semen diluted with Milk extender resulted in higher motility, vigor and plasma membrane integrity (P

The objective of this study was to evaluate hormone and energy profiles in the postpartum period and to correlate these profiles with the resumption of ovarian cyclicity, as well as characterizing the postpartum short estrous cycle of Curraleiro Pé-Duro cows. Twelve Curraleiro Pé-Duro cows were examined via rectal palpation and ultrasound at 10 days postpartum, and subsequently examined daily to evaluate the resumption of ovarian cyclicity as well as every five days in order to evaluate uterine involution. Upon analysis of the data, it was possible to observe the formation of two distinct groups, one of which was comprised of those animals which returned to cyclicity within 60 days postpartum and another comprised of those animals which returned to cyclicity more than 105 days postpartum. Therefore, animals were divided into two groups; precocious, designated Ov Group, and delayed, designated NOv Group, wherein the cut-off time for all tests was 60 days postpartum. Statistically significant differences (P 0.01) between the groups occurred only regarding the day of 1st ovulation, which in the Ov Group averaged 51.4 ± 9.3 days and in the NOv Group averaged 138.3 ± 19.8 days postpartum. The other postpartum short estrous cycle variables assessed did not show statistically significant differences (P 0.05) between the groups. NEFA, BHBA and thyroxine concentration levels did not differ (P 0.05) between the groups in any of the statistical analyses. However, in the analysis comparing growth curves, triglycerides levels were higher for the Ov Group (P = 0.04) and cholesterol levels were higher for the NOv Group (P = 0.02). In this experiment, a small influence of a negative energy balance between the groups was observed, suggesting that these animals can present significant genetic variability due to natural selection, as evidenced by the formation of groups of animals with precocious and delayed reproductive characteristics.

Studies were conducted to characterize the effect of season of the year on testicular morphology, fresh and frozen/thawed semen quality from Curraleiro (Pé-duro) bulls in the Brazilian Central west region. Five adult, healthy bulls underwent an andrological examination and semen collection using an electroejaculator, once a month for a year. Fresh and thawed semen were evaluated for progressive sperm motility and sperm vigor, sperm morphology and acrosomal integrity. Testicular length and volume were less (P0.05) in April than in the other months of the year. For fresh semen, the ejaculate in April had less volume and sperm concentration (P0.05), while sperm vigor was less (P0.05) in June, increasing in January and February. With the frozen/thawed semen, the proportion of sperm was greater (P0.05) in April to July, decreasing from October to December. Semen collected in December had the greatest (P0.05) proportion of major defects while that collected in February/March had the highest proportion of minor defects. The proportion of live intact sperm reduced progressively from December to April/May. The marginal influence of the time of the year on testicular biometry and fresh semen in Curraleiro bulls shows the adaptation of this breed to the environmental conditions in the region. Thus, reproduction with natural mating should be successful at any time of year. For frozen semen collection for conservation programs, the best time of year is from June to September.