Current Issues with Feeding Preweaned Heifers

摘要

Sometimes it seems as if we lose sight of the forest for the trees. We slip into habits or traditions with little consideration to what our original goals were for the subject at hand. It's important to remember some facts about the neonatal calf. This is a newborn animal that is immunoincompetent and dependent upon timely absorption of colostrum. It requires a nutrient dense diet and is highly susceptible to heat loss from cold environments. This animal requires highly digestible nutrients that arefrequently expensive. Consequences of mismanagement include diarrhea, respiratory disease, and death. Less research is available to suggest the impact of poor nutrition and management during the preweaning period on later productivity and longevity. Theaccepted paradigm for preweaned calf management during the previous 30 years has centered on limit feeding milk or milk replacer to encourage early weaning, accelerated rumen development, and consumption of less expensive dry feeds. Programs which reduced feed costs and encouraged labor efficiency were encouraged. These management strategies encouraged limited gains during the first month of life. More recently academics and industry workers have questioned this strategy, especially when one considers that no other species limit feeds their newborns to encourage early weaning. Rather a new paradigm is being suggested which recognizes that this is a newborn calf with nutrient requirements for growth that are not satisfied by limit feeding programs. Logic argues that some deposition of fat may be desirable in the neonate as body reserves for suboptimal environmental temperatures or as energy stores when intake is depressed and energy requirements increase during illness. New goals for growth are suggested which encourage the doubling of a calf's birth weight by 56 days. Calf management practices should be adopted which first address the biological needs of the calf and then seek to achieve reasonable feed cost and labor efficiency. This presentation will highlight current issues associated with feeding preweaned heifers that are receiving noteworthy attention from both academia and industry.