Body composition studies on the growing pig.

The present study on the body composition of the growing pig has been undertaken in order to clarify some of the aspects of early growth in meat producing animals. The pig was chosen as an experimental animal because it is physiologically young at birth and so grows rapidly, passing through a wide range of physiological events in a short time. The deuterium oxide dilution method for determining body water in-vivo was thoroughly tested, and was found to give results which agreed closely with those obtained in-vitro by carcass dessication. The method was then used to determine the body water in thirty-three piglets from four litters at frequent intervals when the animals were between one and sixty-five days of age. One piglet from each litter was killed weekly for the in-vitro determination of total body composition by classical methods. Prediction equations relating total body protein, ash, and fat to total body water were calculated and using these relationships and the results of the above in-vivo body water determinations, the total body composition of the piglets was estimated serially as they grew. Good agreement between the results of the in-vivo and in-vitro determinations was obtained in the case of pigs which had been analysed for body water in-vivo prior to being sacrificed for in-vitro body composition analysis. The serial body composition data obtained indicated that the growth of the pigs consisted of a series of distinct phases which were intimately related to the process of physiological aging. In each growth phase, the relative rates of gain of protein and of body weight slowly increased to a maximum which was followed by an abrupt decrease in both rates of gain. The relative rate of fat gain, however, followed an inverse pattern to that above, with fat being gained rapidly at the beginning of each growth phase, and with body fat energy being used at the end of each phase to support the accelerated rate of protein gain.Land and Food Systems, Faculty ofGraduat