The effect of lysine digestible energy ratio on growth performance and nitrogen deposition of hybrid boars, gilts and castrated male pigs

An experiment was conducted to examine the effects of dietary lysine/digestible energy (DE) ratio (g/MJ) on growth performance and body composition of boars, gilts and castrated males from 25 to 90 kg live weight. Twelve pigs (four of each sex) were assigned to each dietary treatment consisting of lysine/DE ratios from 0.4 to 1.4, in 0.2 g/MJ increments. Food was provided at proportionately 0.90 ad libitum and at 90 kg all pigs were slaughtered and the body composition of two pigs per sex per treatment was determined. Responses to lysine/DE ratios were similar for all sexes up to the optimum level after which daily live-weight gain (DLWG) and nitrogen deposition rate (NDR) deteriorated in gilts and castrated males. This deterioration may have been due to energy used for deamination of excess protein not being available for growth processes. Lipid deposition rate (LDR) remained constant from the 0.4 to 0.8g/MJ lysine/DE ratios and then decreased sharply to a lower plateau from the 1.0 to 1.4 g/MJ lysine/DE ratios suggesting that DE levels were adequate to meet NDR requirements up to the 1.0g/MJ lysine/DE ratio when it became limiting. The optimum lysine/DE ratio for the genotype tested from 25 to 90 kg live weight was of the order of 0.95 to 1.0 g/MJ. The maximum NDR of the genotype tested appears to be of the order of 28 to 30 g/day (175 to 187 g/day protein deposition rate).