New approaches to superovulation in goats and sheep / Novos enfoques sobre superovulação em caprinos e ovinos

A superovulação é a principal tecnologia reprodutiva utilizada para a produção de embriões em ovinos e caprinos, mas a imprevisibilidade dos resultados continua sendo sua maior desvantagem. Vários fatores intrínsecos e extrínsecos são responsáveis por respostas superovulatórias variáveis em pequenos ruminantes e, portanto, esta questão é o foco principal de muitos estudos que visam melhorar a produção de embriões in vivo. A raça da doadora de embriões é uma fonte importante de variação nos resultados superovulatórios, e essa variabilidade pode ser observada não apenas entre genótipos prolíficos e não prolíficos. A suplementação com progesterona usada em conjunto com protocolos superovulatórios tem efeitos benéficos no desenvolvimento folicular e na produção de embriões; no entanto, a duração ideal da exposição à progesterona também parece variar entre as raças. Alguns estudos recentes dos tratamentos superovulatórios com hormônio folículo-estimulante (FSH) abordaram o tempo para iniciar um regime, a dose total do hormônio exógeno e o número de administrações. Além disso, embora a atividade ovariana seja fortemente afetada pela estação do ano, as flutuações anuais nas respostas superovulatórias ainda são controversas e mal compreendidas. Por último, vários estudos demonstraram que a eficácia dos tratamentos superovulatórios recorrentes pode diminuir, permanecer constante ou mesmo aumentar. Esta revisão tem como objetivo discutir os principais achados em torno da superovulação em pequenos ruminantes publicados nos últimos cinco anos.

Superovulation is the main reproductive technology used for embryo production in sheep and goats, but the unpredictability of results remains its greatest disadvantage. Several intrinsic and extrinsic factors are responsible for variable superovulatory responses in small ruminants and so this issue is the primary focus of many studies aimed to ameliorate in vivo embryo production. The breed of the embryo donor is an important source of variation in superovulatory outcomes, and such a variability can be seen not only between prolific and non-prolific genotypes. Progesterone priming used in conjunction with superovulatory protocols has beneficial effects on follicular development and embryo production; however, the optimal duration of progesterone exposure also seems to vary between breeds. Some recent studies of the superovulatory treatments using follicle-stimulating hormone (FSH) have addressed the time to start a regimen, total dose of the exogenous hormone, and the number of injections. Moreover, even though the ovarian activity is strongly affected by the season, annual fluctuations in superovulatory responses are still controversial and incompletely understood. Lastly, several studies have shown that the efficacy of recurrent superovulatory treatments can either decline, remain constant or even increase. This review aims to discuss the main findings surrounding superovulation in small ruminants and published in recent five years.

Effects of flushing with rehydrated corn grain silage on follicular development in tropical Santa Inês ewes

The objective of this study was to evaluate the effect of replacing ground corn (402 g kg−1 of dry matter) with rehydrated corn grain silage (RCGS; 425 g kg−1 of dry matter) in a flushing diet on follicular development in tropical Santa Inês ewes. Fifteen ewes were randomly assigned to one of two treatment groups: a diet with ground corn (control, n = 7) or a diet with RCGS (n = 8). The first day of the diets was designated d0, and the diets were fed for 30 days, up to two days after the end of the estrus synchronization protocol. The estrus synchronization protocol (intravaginal progestogen sponge for 11 days plus 300 IU eCG and 37.5 µg d-cloprostenol IM two days before sponge removal) started on d17 of the diets. The number and diameters of ovarian follicles ≥3 mm were assessed by ultrasound on the day before the diets were provided (d−1), on d14, and then daily from two days before sponge removal until ovulation or up to the eighth day after sponge removal. Blood samples were collected on days −1, 0, 6, 12, 18, 24, and 30 for glucose and urea analyses. There was no effect of the treatments on dry matter intake, plasma glucose, and urea nitrogen concentrations, or on the percentage of ewes that ovulated and on the number of ovulations. The number of follicles ≥3 mm did not differ between treatment groups; the number increased between d−1 and d14 and did not differ between d14 and d28. The diameter of ovulatory follicles at sponge removal, the interval from sponge removal to estrus, and the growth rate of the ovulatory follicles were greater in the RCGS group than in the control group, resulting in larger follicles at ovulation. Replacement of ground corn by RCGS in the flushing diet does not increase the number of ovulations but results in delayed onset of estrus and ovulation of larger follicles.(AU)