The allometric relationships between the body protein weight and the physical parts of five breeds of commercial broilers found in South Africa were determined in two serial slaughter experiments.
In the first experiment 144 birds, of two breeds were killed from one through ten weeks of age. In the second experiment 12 birds, from each of the four breeds, were killed at each weight of 125, 250, 500, 1000, 2000 and approximately 4000 grams. The carcasses were portioned into the commercially important physical parts. The weights of the skin, bone and meat components for each part were recorded. Chemical analyses were carried out for moisture, protein, lipid and ash in the first experiment, while abdominal fat pad weights were used to, indirectly; determine the body protein weights in the second experiment. Gompertz growth curves were determined for the second experiment. The chemical and physical data was used to calculate allometric equations relating body protein content to the other components and portions.
The rate parameters for the allometric relationships between body protein weight and the weights of the other chemical components were very similar to those determined previously by other researchers. No significant differences between breeds or sexes were found in the first experiment, but the breast portion and the breast meat component of the breast portion for the PXA breed were significantly larger than in the other breeds in the second experiment. There were no other breed or sex differences among the allometric relationships for the other commercially important parts in the second experiment, although the heads of the male broiler were significantly larger than those for the females.
The third experiment was designed to determine the effect on the allometric relationships of different nutritional regimes. Four dietary treatments differing in protein-to-energy ratio were used to bring about differing degrees of fatness in the carcasses of the broilers. Twelve birds from each treatment were killed at each weight of 125, 250, 500, 1000 and 2000 grams, and the carcasses portioned into physical parts. The weights of the skin, bone and meat components for each part were recorded and the body protein content was calculated using the abdominal fat pad weights. The data was analyzed to determine the allometric relationships for this experiment.
The dietary treatments and therefore, the fatness of the broilers had significant effects on most of the allometric relationships between the body protein weights and the weights of the physical parts. The birds fed the lowest protein-to-energy diet, generally had heavier portions than the birds fed the higher protein-to-energy diets. The parts which were not affected by the dietary treatments were: breast skin, thigh bone, wing bone and wing meat.
|Degree Type||Masters degree|