Development of a model of voluntary food intake and energy balance in lactating cows

SUMMARY Voluntary intake of a range of feeds by cows is predicted on the assumption that the cows will satisfy their energy requirements unless physical limitations intervene. Predicted patterns of intake throughout lactation agree generally with observed changes, including an eventual plateau in body weight due to a predicted physical equilibrium between abdominal fat and gut contents. An attempt to incorporate a depression in milk yield when physical limitations prevented energy requirements being met by food intake was successful only with good quality feeds.