POST-WEANING EVOLUTION OF MUSCLE ENERGY-METABOLISM AND RELATED PHYSICOCHEMICAL TRAITS IN THE RABBIT

Metabolic differentiation in muscles was analysed in 50 rabbits of New Zealand White breed (strain INRA 1077) slaughtered at 28, 42, 56, 70 or 84 days. The activity of enzymes representing the glycolytic (fructose 1,6-diP aldolase) and the oxidative (NADP-isocitrate dehydrogenase) (ICDH) energy metabolism pathways, and two related physico-chemical traits, haem pigment content and ultimate pH, were estimated in semimembranosus proprius + soleus, psoas major and longissimus lumborum muscles. Aldolase activity was lowest in semimbranosus proprius + soleus, which are pure betaR and the most precociously developed muscles, whereas haem pigment content and ultimate pH were highest; however, physico-chemical traits changed moderately during growth. In the psoas major (pure alphaW) and in the longissimus lumborum (mixed muscle), which develop later, aldolase activity increased until the 56th and 70th day respectively. The decrease in ICDH activity lasted longer, especially in the longissimus lumborum muscle. A significant negative relationship between aldolase activity and ultimate pH may explain why the ultimate pH decreased during fattening.