Analysis of the growth of Corriedale lambs and their nutritional limitation in a traditional production system

Abstract

A study of the stage from birth to weaning of Corriedale lambs was carried out. The animals were running on natural pastures, with continuos grazing and with their mothers during 5 months, similarly to a traditional production system in Uruguay. In the experiment 20 male lambs were used, they were weighed monthly and one per week was slaughter to study carcass growth, stomach development, ruminal content and ruminal mucosa. Pasture availability and quality were determined monthly. Lamb birth weight and carcass birth weight were 3,98 and 1.07 kg.; at weaning (140 d) they were 30.75 and 12.35 kg respectively. Carcass growth stopped at 90 d. live weight continued due to an increase of rumen content. Ruminal digestion was similar to an adult from 40 d. Low digestibility of pasture (initial: 55,3%; final: 35.6 %) and the limited capacity of rumen were the main causes of the low growth rate. The decrease in protein content of pasture (6.7% at weanning) could contribute to the low growth rate. Through simulation procedures it was possible to determined that at weanning 93% of the energy intake was used 10 mantein body weight.