The effect of bypass protein supplementation on the reproductive performance of Merino sheep grazing mixed karoo veld

Ewe productivity is one of the most important factors that determine the profitability of small stock farming. The most important components of ewe productivity are the total weight of lamb produced, body weight at culling and, in the case of wool producing sheep, the amount and quality (mainly fibre diameter) of the wool. From 65 to 88% of the total income from wool sheep is derived from mutton, while it is even higher in the case of mutton sheep. This emphasises the importance of increasing the kilograms of meat produced per hectare in order to increase ewe productivity and thus profitability. Probably the easiest way to do it is by increasing the weaning percentage of the ewes and the growth rate of the lambs. Although weaning percentage can be enhanced by increasing the conception rate of ewes and number of multiple births, the best option is probably to decrease the lamb mortality rate. Most lamb mortalities (± 80%) occur in the period just before birth until seven days after birth and research has shown that nearly 80% of these mortalities are related to the nutrition of the ewe during the last weeks before lambing and the first weeks after lambing (Seymour, 1998). The amount of colostrum available at lambing and the milk production of the ewe after lambing are important factors influencing lamb survival and growth rate of lambs. The supply of sufficient protein during late pregnancy and lactation influences the quantity as well as quality of milk produced. Research results suggested that the supply of a high level of bypass protein (rumen undegradable protein) is essential to increase the colostrum and milk production of ewes (Hinch et al., 1996). The high cost associated with supplementation of reproducing ewes, especially with bypass protein sources, necessitate further investigations into this matter. This study investigated the effect of bypass protein supplementation on the reproductive performance of Merino sheep on Mixed Karoo veld