Estimation of matabolizable energy requirements of Lori-Bakhtiari ram lambs

Fifty six Lori-Bakhtiari ram lambs (mean body weight (BW) 35. 43±0. 56 kg) were used in a completely randomized design to measure maintenance and growth requirements of metabolizable energy (ME). َIn duration of desing period (100 days) the lambs were divided into five equal groups (each group consist of 10 lambs) and fed different amounts of feed Including ad-libtum، 85، 70، 55 and 40 percent of the ad-libtum group. After 10 days adaptation period، six lambs of similar body weight and age were killed at the beginning of the experiment to compare final empty body weight (FEBW) with initial weight. Animals were individually fed on a pelted roughage- concentrate diet، and apparent digestibility energy were determined. At the end of experimental period all lambs were slaughtered and the right sides of all carcasses were cut according to Iranian method then dissected into muscle، fat and bone. Energy requirement for maintenance and growth was measured by regressing MEI on daily body weight gain (BWG)، and daily empty body weight gain (EBWG). The energy requirements، for growth calculated from equations derived were 0. 125، 0. 167، 0. 212، 0. 261 and 0. 318 McalKg-1BW0/75day-1 for the growth rate 4. 44، 7. 61، 10. 25، 13. 01 and 13. 55 (g EBWG Per Kg-1 BW0/75) respectively. The ME requirement for maintenance (Zero growth) that calculated from regressing equations was 0. 085 McalKg-1 BW0/75day-1. When the lambs were given 0. 318 Mcal (MEKg-1BW0/75day-1)، had a significantly higher (P<0. 001) carcass fat (35. 63 v 33. 63)، feed conversion ratio (9. 07 v 8. 15)، and same body weight gain than the lambs given 0. 261 Mcal (MEKg-1 BW0/75day-1). The results of this experiment showed that 0. 261 Mcal (MEKg-1 BW0/75day-1) improved feed conversion ratio and body weight gain than other groups.