Effect of clenbuterol on productive performance, body composition and muscle biochemistry in the rabbit

Twenty New Zealand White rabbits (INRA 1077 strain) were given a complete and balanced diet including a clenbuterol additive (100 μg per day) between 70 and 98 days. They were compared with 20 control rabbits. The treatment improved the growth performance (29.90 vs 26.07 g/day), the feed conversion (5.45 vs 6.46 g feed per g gain) and the carcass yield (64.37 vs 61.11%), by decreasing the relative weights of the skin and the digestive tract. Moreover, all organs in which development is precocious, were found to be relatively lighter. The muscle/bone ratio of the carcass was improved (7.56 vs 6.38), resulting in a greater relative development of muscle tissue, without any change in bone tissue weight. Perirenal and interscapular fat percentages in the carcass were reduced (3.23 vs 3.83 and 0.68 vs 0.86, respectively). Clenbuterol, a repartitioning agent, had therefore modified the growth allometry of the organs and tissues. In the hindleg region (Biceps femoris, Tensor fasciae latae, Semimembranosus accessorius), the ultimate muscular pH was increased, (+0.31 pH units on average), while the cooking loss was reduced (24.23 vs 24.88%). In the m. longissimus lumborum, the increase of ultimate pH (+0.31 units of pH), under the effect of clenbuterol, was explained by a relative increase in the oxidative metabolic pathway represented by aldolase/ICDH ratio (246 vs 284) and by a decrease in glucidic content (total glycosyl residues) of muscle (16.6 vs 26.2 μ mol g ). Due to its effects on muscular biology, clenbuterol is thus likely to cause a change in meat quality.