Effect of protein level on growth performance, non-carcass components and carcass characteristics of young sheep from three breeds

The objective of this study was to evaluate the effect of crude protein (CP) level and breed type on growth, non-carcass components and carcass characteristics of young sheep during the fattening period. Forty-two 1-year-old sheep of the Barbarine (BB), Queue Fine de l'Ouest (QFO) and Noire de Thibar (NT) breeds, with an average weight of 32 kg, were fed diets with two CP levels: 160 and 110 g CP/kg of DM [high protein (HP) and low protein (LP) diet, respectively]. Each breed was divided into two groups and received a daily ration composed of 1 kg of a concentrate (204 and 132 g CP/kg of DM for HP and LP, respectively), and 0.5 kg of oat hay/sheep. day. The trial lasted 120 days after which all of the animals were slaughtered. It was found that protein level had not affected the growth rate, although the slaughter weight was 48.75 and 51.56 kg for groups receiving the LP and HP diets, respectively. Overall, carcass yields, non-carcass components and carcass composition were similar for both CP levels (50%, 18% and 32% of muscle, bone and fat, respectively). However, the HP diet promoted fat depots and the development of third grade fat meat whereas the LP diet enhanced first grade leg and lean meat. The BB breed had a higher dressing percentage and a lower offal percentage than QFO and NT breeds. The QFO breed recorded the heaviest internal fat whereas the NT registered the heaviest internal organs and the highest percentage of leg and shoulder. From the findings it can be concluded that CP requirements for young sheep could be limited to 110 g CP/kg of DM.