Effects of sex and energy intake between 48 and 90 kg live weight on protein deposition in growing pigs

ABSTRACT Twenty four entire male and 24 female pigs growing from 48 to 90 kg live weight were used to investigate the effects of five rates of food intake supplying daily between 23 MJ digestible energy (DE) and 41·8 or 39·2 MJ DE for entire males and females respectively, on rate of protein deposition, and on growth and body composition. Entire males deposited protein faster than females, and for both sexes the rate of protein deposition increased linearly with increase in energy intake up to 33 MJ DE per day ( P < 0·001) but was not significantly affected by further increase in energy intake. Average daily gain increased quadratically ( P < 0·001) with increase in energy intake and at all levels was higher for entire males than for females. Food:gain ratio (g food per g growth) which was lower for entire males improved with increase in energy intake up to 33 MJ DE per day and deteriorated with further increase in energy intake. At 90 kg live weight entire males contained less fat and more protein and water in the empty body than females. For both sexes, body fat content increased at a decreasing rate with increase in energy intake up to 33 MJ DE per day, and at an increasing rate with further increase in energy intake. Total energy retained was linearly ( P < 0·001) related to energy intake and at all rates of energy intake was higher for females than for entire males. The estimates of DE required for maintenance were 15·9 MJ/day (0·664 MJ/kg M 0·75 per day) and 12·4 MJ/day (0·51 MJ/kg M 0·75 per day) for entire males and females, respectively.