Pre-breeding beef heifer management and season affect mid to late gestation uteroplacental hemodynamics

Abstract

In a well-managed beef herd, heifers should represent the most valuable genetics in the herd and be an improvement on the previous generation of females. Recent economic conditions have brought forth a trend in which heifers are developed in “low input” management scenarios where they typically achieve 50-55% of projected mature body weight at breeding as opposed to the more traditional 65-70%. Seasonal differences in calf performance and heifer reproductive efficiency have also been observed. The uterine environment during gestation is known to have lifelong epigenetic effects on offspring. This is often achieved by imposing suboptimal conditions or nutrition prior to breeding or during gestation, and the effects may be translated to the developing calf by altered patterns of uteroplacental blood flow. Thus, it was hypothesized that low input heifer development protocols resulting in light weight heifers at breeding may cause decreased uteroplacental blood flow during pregnancy compared to traditionally developed females even when nutrition during gestation is equivalent. Furthermore, it was posited that calving season may also alter uteroplacental hemodynamics. Therefore, the objective of the present study was to evaluate the effects of heifer development practices and season on uteroplacental hemodynamics during mid to late gestation of nulliparous beef females.