The effects of short-term recombinant bovine somatotropin treatment on fattening performance, carcass composition and visceral organ weights in karayaka lambs in Turkey.

Recombinant bovine somatotropin (bST) was administered s.c. to lambs for 6 weeks to evaluate its effects on fattening performance, carcass composition and visceral organ weights. Twenty male Karayaka lambs were injected with 250 mg bST every two weeks. Body weight, live weight gain, feed intake and feed conversion rate were not affected by treatment. Head, feet, skin, liver, spleen, kidneys, filled and empty gastrointestinal tract, penis, testis, pelvic fat and internal fat weights were similar for the two groups. Lung weight increased by 17.4% (P<0.01) and weight of heart decreased 22.7% (P<0.05) in bST treated lambs. The only carcass characteristics that were affected by bST administration were limb muscle which increased from 1331 g to 1417 g (P<0.05), loin fat which decreased from 275 g to 174 g (P<0.01), shoulder fat which decreased from 26 g to 13 g (P<0.01) and total fat/final weight percentage which decreased from 9.8% to 7.6% (P<0.05). The results of this study show that prolonged release formulation of bST treatment reduces fat tissue, but does not significantly affect fattening performance or weights of visceral organs, muscle and bone.