The effect of rate of gain during the growing and finishing periods on the feed efficiency and carcass composition of the pig: I. Rate of gain during the growing period from 18 to 57 kg live weight

Abstract

SUMMARYTwo experiments were carried out in which pigs were grown at controlled high, moderate or low growth rates from 18 kg to slaughter at 57 kg live weight. Linear measurements and density determinations were carried out on the carcasses. In the second experiment the right-hand side of each carcass was divided into four joints and each joint was physically dissected into three components, bone, subcutaneous fat plus skin and ‘lean’ meat. The boneless tissue of each joint was analysed for moisture, ether extractable fat and nitrogen.It was found that an increase in the rate of live-weight gain tended to improve the efficiency with which feed was converted into live weight.The percentage of fat in the side was significantly increased by more rapid growth rates.The conformation of the side was altered by treatment, the proportion by weight of the middle region increased with increasing rate of live-weight gain and was accompanied by corresponding reductions in the proportions of the gammon and shoulder regions. These changes were largely due to an effect on the distribution of fat throughout the side, but there were also minor changes in the distributions of bone and fat-free lean.The high rate of gain was associated with a greater proportion of belly in the side. This was due to an increase in the proportion of lean meat in this region, presumably a functional effect caused by an increased intestinal volume.There was no treatment effect on the chemical composition of the fat-free boneless meat which was found to differ significantly between joints.