METABOLIZABLE ENERGY-REQUIREMENTS FOR MAINTENANCE AND GROWTH OF AWASSI LAMBS

Twenty four Awassi lambs (mean BW 24.4 kg) were used in a two periods experiment to measure maintenance (zero growth) and growth requirement s of metabolizable energy (ME). During the pre-treatment period (perio d 1, 3 weeks) all lambs were maintained at a constant level of feed in take (2% RW). During the treatment period (period 2, 10 weeks) the lam bs were divided into four equal groups and fed different amounts (2, 3 , 4 and 5% of BW). Six additional lambs of similar BW and age were kil led at the beginning of the experiment to compare final empty body wei ght (FEBW) with initial body weight (IBW). Twelve lambs, divided into four equal groups were fed the experimental diet in the same amounts a s in the growth experiment (period 2) to determine the digestibility o f energy. Energy requirement for maintenance (EM) was measured by both constant weight technique, using data collected during period 1, and regression technique by regressing ME intake on body weight gain (BWG) and empty body weight gain (EBWG). EM measured during the constant we ight period (pre-treatment) and overall experimental period (pre-treat ment plus treatment periods) were 0.482 and 0.466 MJ of ME per kg M(0. 75) per day. Predicted energy requirements for growth (Eg) calculated from equations derived during the treatment period were 0.433, 0.623, 0.782, 0.910 and 1.007 (MJ per kg M(0.75) per day) for the growth rate s 50, 100, 150, 200, and 250 (g per day) respectively. It is concluded to be more appropriate to use the values derived during the overall e xperimental period for maintenance and the overall treatment period fo r growth as they are most applicable to production situations.