Impacts of beef cow nutrition on conceptus development

Two experiments were conducted to determine the effect of maternal nutrient restriction followed by realimentation during early to mid-gestation on uterine blood flow (BF), maternal performance, and conceptus development in pregnant beef cows. In Experiment 1, effects of maternal nutrient restriction followed by realimentation during mid-gestation on uterine BF of lactating, multiparous cows were evaluated. Nutrient restriction from d 30 until 140 of gestation did not alter total uterine BF. However, upon realimentation (from d 140 to 198 of gestation), there was enhanced ipsilateral uterine BF. In Experiment 2, effects of maternal nutrient restriction followed by realimentation during early to mid-gestation on late gestation uterine BF, maternal performance, and conceptus development was evaluated using non-lactating, multiparous cows. Slaughters were performed at d 85, 140, and 254 of gestation. During late gestation when all cows were receiving similar nutrition (100% of the NRC requirements), ipsilateral uterine BF and total BF were increased in cows that were previously nutrient restricted from d 30 until d 85 of gestation and realimented until d 254 of gestation. Therefore, results from both experiments suggest that the bovine placenta may be programmed to function differently after a period of nutrient restriction. Duration of restriction or realimentation impacted maternal performance and organ weights. The dam might become more efficient in the utilization of nutrients after being realimented as gestation advances. Nutrient restriction during early pregnancy tended to increase fetal and placental size by d 85. However, when cows were restricted longer or when realimented, there were no observable differences in placental or fetal growth. The maternal system may adapt to allow for fetal catch up growth during later gestation by enhancing uteroplacental nutrient transport capacity or placental function.;From the results obtained in these 2 experiments we can conclude that maternal nutrient restriction during early gestation enhances conceptus growth and uterine BF later in pregnancy. Perhaps, timely management strategies might result in enhanced conceptus development. Even though more research is necessary, opportunities to intervene appear to be available during times of poor nutrition in beef cow/calf systems.