Conversion of the energy of the food into edible energy by two types of table poultry

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Abstract
In 2 experiments with both Rhode Island Red (RIR) x Light Sussex (LS) and modern hybrid cockerels, groups of 12 were given various diets until they reached a mean live weight of about 3-1/2 lb., when they were killed. This was at 12 weeks for the RIR x LS birds and at 9 or 10 weeks for the hybrids. Half the birds in each group were dressed and then cooked in an autoclave for 20 min at 15 lb pressure of steam before separation of the edible material as flesh, skin and giblets, and subsequent analysis. The other half were analysed after removal of the contents of the alimentary tract to give an estimate of total body energy in each group. There was no significant difference between the 2 breeds in the dressed and ready-to-cook weights as a percentage of live weights. Although in the 1st experiment the weights of cooked edible matter as a percentage of the live or dressed weights was greater for the slower-growing RIR x LS cross than for the hybrid birds, it was not so in the 2nd experiment. The total weight of edible material after cooking was 30-33% of the live weight, divided into 20-23% from the flesh, 6-7% from the skin and 3-4% from giblets. Of the total body energy in the birds, some 36-38% was in the edible material after cooking, with 19-22% in the flesh, 12-15% in the skin and about 3% in the giblets. The overall efficiency in converting dietary metabolizable energy into edible energy was 7. 7 and 8. 6% for the Rhode Island Red x Light Sussex and 8. 6 and 11. 3% for the hybrid birds. The greater efficiency of the hybrid birds in converting dietary metabolizable energy into edible energy arises from their faster growth to the finishing weight and consequent reduction in the energy required for maintenance to that weight.