Date of this Version
Restricted energy intake can suppress the overall productivity of cattle. Restricted energy intake can decrease overall productivity of beef cows through, among other traits, decreased milk production, calf performance, and reproduction. However, failure of a cow to conceive is the major component affecting the overall production efficiency of the cow herd. In a companion report included in this publication ("Postpartum Interval Is Influenced by Nutritional Environment and Biological Type"), we demonstrated that the postpartum intervals for breeds of cattle with different genetic potentials for growth and milk production were differentially affected by restricted energy availability. This report, along with numerous other studies, confirms the fact that limited availability of energy can increase the time it takes cows to resume estrous cycle activity after calving. However, the mechanism(s) by which limited energy intake influences resumption of estrous activity after calving is not known. The objective of this study was to identify how changes in metabolic hormones correspond to the time from calving to resumption of cyclicity. In addition, results from this study may explain why diverse biological types of cattle respond differently to restricted energy availability.