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Submitted to: University of Missouri Agricultural Experiment Station Publication
Publication Type: Other Publication Acceptance Date: 2/15/2000 Publication Date: 2/15/2000 Citation: BELLOWS, R.A. REPRODUCTION RESEARCH AFFECTING BEEF COW PRODUCTIVITY. UNIVERSITY OF MISSOURI AGRICULTURAL EXPERIMENT STATION PUBLICATION. p. 1-18. 2000. Interpretive Summary: This is a review of research results of genetic and environmental factors resulting in dystocia. Selection for rapid-growth breeds results in increased dystocia. If heifers are to be saved for replacement females, their sires must be evaluated carefully for direct and maternal calving ease. Acceptable percentages of dystocia, maximum neonatal survival, and optimum reproductive performance of the dam are dependent on adequate nutrition. Maternal-fetal disproportion at parturition is a major causative factor affecting dystocia. Recent research shows clearly there is an endocrine/metabolite aspect to dystocia with detectable circulating endocrine and metabolic concentration differences in dystocial dams 10 days prior to the actual event. Synchrony and patterns of the prepartum endocrine and metabolic cascade are important for normal parturition. Exercise during gestation had no effect on dystocia, but increased feed requirements. Early obstetrical assistance increased neonatal survival and calf weight gain from birth to weaning and improved subsequent reproductive performance of the dam. Fat supplementation of the dam during the last trimester of gestation resulted in improved cold tolerance in newborn calves and also resulted in a positive effect on rebreeding of the dam and increased weaning weights of the calf. Results in lactating first-calf heifers have been more consistent and of greater magnitude than in mature cows. Technical Abstract: This is a review of research results of genetic and environmental factors resulting in dystocia. Selection for rapid-growth breeds results in increased dystocia. If heifers are to be saved for replacement females, their sires must be evaluated carefully for direct and maternal calving ease. Acceptable percentages of dystocia, maximum neonatal survival, and optimum reproductive performance of the dam are dependent on adequate nutrition. Maternal-fetal disproportion at parturition is a major causative factor affecting dystocia. Recent research shows clearly there is an endocrine/metabolite aspect to dystocia with detectable circulating endocrine and metabolic concentration differences in dystocial dams 10 days prior to the actual event. Synchrony and patterns of the prepartum endocrine and metabolic cascade are important for normal parturition. Exercise during gestation had no effect on dystocia, but increased feed requirements. Early obstetrical assistance increased neonatal survival and calf weight gain from birth to weaning and improved subsequent reproductive performance of the dam. Fat supplementation of the dam during the last trimester of gestation resulted in improved cold tolerance in newborn calves and also resulted in a positive effect on rebreeding of the dam and increased weaning weights of the calf. Results in lactating first-calf heifers have been more consistent and of greater magnitude than in mature cows. |
