2011 Alpharma Beef Cattle Nutrition Symposium:enhancing beef production efficiency with new knowledge and technologies: building the bridges for future collaboration.

The beef cattle industry relies on the utilization of high forage diets to maintain the cow herd, develop replacement females, and stocker operations. Forage quantity and quality fluctuate with season and environmental conditions. Depending on the class and physiological state of the animal, a grazed forage diet may not always meet nutritional requirements resulting in low ADG or weight loss if supplemental nutrients are not provided. It is important to understand the consequences of such weight loss and the economics of providing supplementation to the beef production system. Periods of nutrient restriction can actually result in compensatory gain once dietary conditions improve and may be of less impact in breeding animals where actual weight is not as important as animals destined for the feedlot provided reproductive efficiency is not compromised. A rapidly evolving body of literature is also demonstrating effects on subsequent offspring developing in a restricted environment in utero. Maternal stimuli or an insult during a critical period of fetal development having long-term implications for the offspring is the concept of fetal programming. In recent studies at the University of Nebraska, calf birth weights were unaffected while calf weaning weights were greater from cows gestated on dormant winter range receiving protein supplementation during late gestation compared with non-supplemented cows. Subsequent steer carcass weights and quality grades were also improved in calves born to supplemented dams and more heifers from supplemented dams were pubertal before breeding and had greater pregnancy rates. This body of research provides compelling evidence of a fetal programming response to maternal nutrition in beef cattle. Future competitiveness of the beef industry will continue to be dependent on the utilization of high forage diets to meet the majority of nutrient requirements. Consequences of nutrient restriction must be considered not only on individual animal performance but also the developing fetus.