ESTIMATING THE METABOLIZABLE ENERGY REQUIREMENT FOR PREGNANCY IN SHEEP

A model is developed in which the metabolizable energy (ME) requiremen t for growth and maintenance of the foetus, uterus and udder are descr ibed explicitly for sheep. The efficiency of the use of ME for the gro wth of the products of conception (k(p)) is assumed to be the same as that for growth in non-pregnant animals. Using the results from the mo del to calculate the efficiency of the use of ME for conceptus growth (k(c)) in the conventional manner yields values with a similar magnitu de and similar variation with food quality as those estimated experime ntally. It is concluded that separately accounting for the growth and maintenance of the foetus, uterus and udder is preferable in models bu t It unnecessary in feeding standards.