Effect of feed restriction during post-weaning growth on fiber characteristics of Biceps femoris muscle in the rabbit

At weaning (five weeks of age), 50 hybrid rabbits were at random divided into five groups (labelled blocks). Block 1, which were fed ad libitum with a commercial diet during weaning period, were slaughtered. The remaining rabbits were placed in individual cages and fed the same amount of food until slaughter, but differently rationed. From 5 to 8 wk of age, the rabbits coming from blocks 2 and 4 received 70% of ad libitum, meanwhile those belonging to blocks 3 and 5 received 90% of ad libitum. Animals of blocks 2 and 3 were slaughtered at 8 wk of age, while those of blocks 4 and 5 received the reverse restriction level and were slaughtered at 11 wk of age. All the animals were weighed before slaughter and the Biceps femoris muscle was immediately dissected and thereafter its fibers were typed (βR, αR and αW) and mean cross-sectional area was determined for each muscle. As expected, at eight-weeks slaughter age, rabbits given for 3 weeks the strictest feed restriction (70% of the ad libitum) showed the lowest body weight but presented significantly higher (P<0.01) body weights after successive 3 weeks of rationing at 90% of the ad libitum, if compared with the rabbits that followed the inverse feeding treatment. The 70-90% rationing mode reduced the proportion of oxidative fibers. No relationship was found between the enlargement of muscle fibers and body weight. At the light of actual knowledge further investigations are needed to better understand the relationship between feed restriction and fiber characteristics.