Different modes of food restriction and compensatory growth in double-muscled Belgian Blue bulls: animal performance, carcass and meat characteristics

Fifty double-muscled Belgian Blue bulls were divided improve groups. The fi rst group (control, CG) was given, on an ad libitum basis, a fattening diet based or? sugar-beet pulp. In G2 and G3, fattening was interrupted 103 and 187 days, respectively after the beginning of the experiment, by approxima tely a 2-month period of food restriction during which the animals received a maintenance ration. The last two groups, namely G4 and G5, received for about 4 months a limited amount of the restriction diet to support growth o f 0.5 and 0 kg/day, respectively, before being fattened as CG. The average daily gain was 1.48 kg/day in CG v. 1.33, 1.30, 1.43 and 1.61 kg/day during the period of ad libitum feeding in G2, G3, G4 and G5. Higher nitrogen (N) balance during compensatory growth in G2, G4 and G5 (78.8, 82.0 and 74.6 v . 53.3 g N per day in CG, P < 0.001) resulted mainly from a higher efficien cy of N retention. In G3, however, compensatory growth was characterized by lower N digestibility and efficiency of N retention. Muscle proportion in the carcass was higher in G3 while fat plus connective tissue proportion wa s lower (P < 0.05). Muscle pH values in CG were lower than in the other gro ups (P < 0.01) but ether extract values were higher. The intramuscular fat of G2 and G3 was characterized by higher proportions of polyunsaturated fat ty acids.