Objective: To describe some reproductive management programs that allow increasing the productive efficiency of ewes. Design/methodology/approach: Description main hormones and their application in sheep protocols. The subjects are reviewed based on academic references as well use protocols at Sheep Goat Reproduction Laboratory Colegio de Postgraduados, Mexico. Results: Hormones, socio-sexual s...

To establish sustainability in the dairy industry, it is important that cows become pregnant at a biologically optimal time and at an economically profitable interval after calving. In this review, the results obtained from Holstein cattle in an experimental herd for dairy research are summarized. First, the effect of age at first calving of heifers on productive and reproductive performance wa...

We tested whether a concentration of unleaded gasoline (UG) vapor that was selectively hepatocarcinogenic in female mice in a chronic bioassay is antiestrogenic and whether liver tumor promotion by UG is secondary to antiestrogenicity. Twelve-day-old female C57BL/6 x C3H F1 mice (hereafter called B6C3F1) received i.p. injections of N-nitrosodiethylamine (5 mg/kg) or vehicle. Beginning at 5-7 we...

The working hypotheses in this experiment were: that ovarian estradiol would inhibit luteinizing hormone (LH) secretion in heifers that were anestrus as a result of restricted dietary energy intake and the responsiveness of LH secretion to estradiol negative feedback would decrease during the period when restoration of estrous cycles occurred following feeding of diets adequate in energy. Fifte...

Achieving a consistently successful A.I.-breeding program in a cow-calf operation requires attention to those heifers and cows not having normal estrous cycles (cycling) at the beginning of the breeding season. Because so many factors contribute to whether breeding females are cycling, including weather patterns, nutrition (availability of native forages or stored feeds), age or days since calv...

UNLABELLED Castration, as well as the menopause, represents endocrine suppression that prevails the hypoestrogenism and their larger consequence on the skeletal muscle is to provoke sarcopenia. OBJECTIVE To study the morphometric alteration of striated muscle of castrated female rats. METHODS Twenty six female rats Wistar , distributed in two sub-groups, A and B, submitted initially to weig...