Productivity and body composition of Black-headed Mutton sheep x Polish Merino crossbred rams fed complete pelleted mixtures with different energy concentrations

Thirty-two Black-headed Mutton sheep x Polish Merino crossbred lambs weighi ng about 22 kg were divided into two groups and fed two isonitrogenous comp lete pelleted diets containing low (group L) or high (group H) metabolisabl e energy (ME) levels. The animals were fattened to a final liveweight of ab out 36 kg. Average daily gains in groups L and H were 228 and 250 g; intake per kg gain was: ME, 56.6 and 54.8 MJ; crude protein, 718 and 649 g, respe ctively. Mean daily clean wool fibre production was similar in both groups (3.66 vs 3.75 g). The concentration of ME in diets did not significantly in fluence dressing percentage or morphological composition of the carcass. Th e protein content in 1 kg of empty body weight (EBW) ranged from 18.6 to 18 .8%, fat from 17.6 to 18.1%, while energy value from 11.25 to 11.55 MJ in g roups L and H, respectively. The utilisation of ME available for growth (k( f)) by lambs from groups L and H was similar (0.38 vs 0.40). Animals from g roup H deposited a little more protein in EBW gain (39.1 g/d) than lambs fr om group L (36.8 g/d).