Incorporation of environment and feed quality into a net energy model for beef cattle

The California net energy system has gained wide acceptance as a method for predicting rates of gain in growing and finishing beef animals. Researchers at the University of Kentucky, in co-operation with agricultural scientists in two regional research projects, NC-114 and S-156, have developed an interactive model that enhances the usefulness of the net energy system by including skeletal size, feed quality, temperature and relative humidity to determine feed intake and utilisation. Basically, the intake based on feed availability, nutrient composition, potential skeletal size and heat loss potential. After the feed is consumed, it is utilised according to the productive status of the animal, i.e. growth, lactation, foetal development, etc., using a modified form of the net energy system to predict weight change.The model allows a researcher to easily modify environment, feed, breed characteristics and productive status so as to evaluate their influence on the performance of the animal.