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University of Wyoming

Initial Studies and Ongoing Efforts

    Climates with extreme variations in precipitation, such as Wyoming, routinely experience significant fluctuations on both quantity and quality of forage.  In fact, prolonged bouts during early gestation, where >50% of the National Research Council's (NRC) requirements for gestation are not met, are common.  Cattle and sheep on rangeland and not supplemented may lose a significant amount of weight from early to mid gestation, and even after supplementation later in gestation, the health and growth potential of their calves and lambs may have been compromised.  Growth and carcass characteristics of ruminants are known to vary considerably even when genetics and nutritional management are constant.  These differences in animal performance and composition have been attributed to variations in hormonal or metabolic status, as well as to the general health and immune status of the animal.  

Cattle
Newborn Lamb

        In sheep, as well as humans, the first half of gestation is critical for proper fetal organ and tissue growth, cell differentiation and development.  In our initial studies we reduced nutrient intake to 50% NRC requirements from days 28 through 78 of gestation in the ewe, which resulted in a 7.5% loss in maternal body weight and a fetus which was 30% lighter than in control fed (100% NRC requirements) ewes whose weight increased 7.5% body weight over the same period.  Of significant interest was the observation that the lighter fetuses of nutrient restricted ewes, exhibited markedly enlarged hearts, and altered skeletal muscle mass when compared to fetuses from control fed ewes.  Evidence suggests that these changes may lead to suboptimal cardiovascular function and altered carcass composition, respectively, of these offspring.  We are now producing lambs from ewes nutrient deprived from day 28-78 of gestation, and are evaluating their health, growth efficiency and carcass quality.

     Studies so far have demonstrated that offspring born to under-nourished mothers exhibit reduced kidney glomerular numbers, in association with the development of hypertension, by 8 months of age.  These lambs also exhibit reduced pancreatic insulin secretion and glucose tolerance.  Further, these lambs were hyperleptinemic and had increased body fat when compared to lambs from control-fed mothers.  We plan further studies on these lambs as they age to evaluate the impacts of in-utero under-nutrition on their health, cardiovascular and neuro-endocrine function, reproductive efficiency and behavior.  Based on results of these sheep studies, we have also initiated a study to evaluate the impacts of early gestational (days 30 - 120) under-nutrition in beef cattle on the health, growth efficiency and carcass quality of their offspring.
Cells