Effects of nutritional level and carcase weight on the different anatomical body parts and muscle weights of male broilers

1. The anatomical constituent of the carcase and the relative distribution of skeletal muscle in the different body parts were compared among male broiler groups reared with broiler foods with high nutritional levels for up to 80 d (H80d), and layer foods with low nutritional levels for up to 80 (L80d), 95 (L95d) and 108 d (L108d). 2. The carcase weight of the low nutrition birds increased from 2470 g in L80d to 3600 g in L108d through 2820 g in L95d, while H80d birds arrived at 2970 g after a 15 d shorter term of fattening compared to L95d. At that stage the carcase of H80d contained 49.2% whole skeletal muscle, similar to 50.9% in L108d, and these values were larger than the 45.8% in L80d and 44.8% in L95d. Conversely, the whole visceral organ was contained at a smaller percentage in H80d and L108d compared to L80d and L95d. The percentage weight of whole bone, intermuscular adipose tissue, skin and abdominal fat did not differ among the bird groups, except for the L108d carcase which contained the smallest percentage whole bone. 3. The forelimbs muscles comprised 25.2% of the carcase in H80d and L108d, which was larger than 22.5-22.7% in L80d and L95d. The muscle percentage of the hind limbs was largest in L108d (21.1%), medium in H80d (19.4%), and smallest in L80d (18.7%) and L95d (18.0%). The antebrachial muscle showed the largest percentage in H80d and the percentages of femoral and crural muscle were largest in L108d. The big shoulder muscle subpart was 20.2-20.3% in H80d and L108d, which was larger than 17.9-18.0% in L80d and L95d. 4. Age-related change of the percentage weight was observed markedly in the pectoralis, iliotibialis lateralis, flexor cruris lateralis and gastrocnemius muscles across the low nutrition bird groups with different ages. On the other hand, the H80d birds attained the largest percentage in the pectoralis, supracoracoideus, and femorotibiales muscles. 5. From these results, it was indicated that broiler foods with high nutritional levels do not only promote the growth rate of broiler, but also enhance the meat quality by stimulating the development of skeletal muscle within the valuable breast part.