Effect of diet composition and fattening start weight on body growth and carcass compositions of Moghani male lambs

This experiment was conducted to investigate the effect of diet and fattening start weight on body growth in the different stages of the fattening periods and carcass compositions of Moghani male lambs. For this purpose, 36 heads of Moghani male lambs with three weights classes (Light, medium and heavy weight) were used with two diets (alfalfa to concentrate ratio of 70 to 30 (diet 1) and 30 to 70 (diet 2)) were fattening up to the time which their weights were 55 kg. The lambs were placed in individual cages for control the amount of feed daily intake and residual collected. The diets of high concentrate compared with diet of high forage were more favorable effect on body weight during the fattening at all stages and also daily weight gain (P<0.05). The significant difference was between heavy weight lambs (112 g/day) with light weight lambs (153 g/day) on daily weight gain (P<0.05). The diet had significant effect on carcass efficiency, hot and cold carcass weight, fat-tail weight and liver weight (P<0.05) and also percentage of fat-tail weight to carcass weight ratio (P<0.05). Negative correlation existed between fat-tail weight with different component of the carcass, especially with its valuable parts (leg, sirloin, breast and shoulder). Generally, high concentrate intake caused increase of fat-tail stores. Fattening with low weight increased daily weight gain, but in higher age was associated with fat stores in Moghani male lambs.