PERFORMANCE OF LAMBS GRAZING IN A BUFFELGRASS (CENCHRUS-CILIARIS) PASTURE AND ESTIMATION OF THEIR MAINTENANCE AND ENERGY-REQUIREMENTS FOR GROWTH

During a period of 15 weeks (July through November 1989), 40 lambs (Ra mbouillet X Pelibuey; 25 castrated males and 15 females) were randomly grouped among five energy treatment levels (five males and three fema les per treatment level), The energy supplement ranged from 0.8% to 2. 0% of body weight (BW), adjusted weekly. After the morning supplement feeding, lambs were allowed to graze freely for 7-9 h in a buffelgrass (Cenchrus ciliaris) pasture. Male lambs were harnessed for total coll ection of feces, during the last 10 days of the study. Total organic m atter and crude protein intakes increased (P < 0.05) with an increase in energy supplementation. Average daily gain of lambs also increased (P < 0.05) with an increase in the level of energy in the diet. The re gression of metalizable energy (ME) intake (kcal per kg(0.75) per day) on BW gain resulted in an estimated daily ME requirement for maintena nce of 85.9 kcal per kg(0.75), and for gain was 0.54 kcal ME per g gai n per kg(0.75). Maximum growth of lambs was 147 g per day with a level of energy supplementation of 2.0% of BW. Even though there was a line ar response in BW gain of lambs due to energy supplementation, the eco nomics of supplementation response were worthy for the level of supple mentation of 0.8% BW, with the type of supplement used in this study, Thus, to reduce the cost of supplementation of grazing lambs in a buff elgrass pasture it is recommended to include sources of high energy in the supplements such as fats or oil.