Influence of the dietary ratio between sulphur containing amino acids and lysine on performance of growing-finishing pigs fed diets with various lysine concentrations

This study was conducted to determine the optimal ratio between sulphur con taining amino acids and lysine in diets for growing-finishing pigs. Therefo re, a total of five trials was carried out in which growing-finishing pigs (live weight range between 53 and 105 kg) were fed diets with various conce ntrations of lysine (0.62, 0.70 and 0.78%) and various ratios between sulph ur containing amino acids to lysine. The diets contained 12.9 MJ ME per kg and 13.5% CP; the ratio between sulphur containing amino acids to lysine wa s adjusted by individual supplementation of the diets with DL-methionine. I ncreasing dietary levels of lysine from 0.62 to 0.78% continuously increase d daily body weight gains and improved feed conversion efficiency as well a s carcass characteristics. There was no significant interaction between the dietary lysine supply and the ratio between sulphur containing amino acids to lysine on animal performance parameters. This means that the effect of the ratio of sulphur containing amino acids to lysine was similar for vario us dietary lysine concentrations. The optimum ratio between sulphur contain ing amino acids to lysine according to quadratic regression analysis was 0. 60, for both, growth and feed conversion. Reducing the ratio between sulphu r containing amino acids to lysine from 0.59 to 0.53 and 0.47 reduced body weight by 3 and 12%, resp., and elevated the feed conversion raiio by 2 and 12%, resp. An increase of the ratio between sulphur containing amino acids to lysine from 0.59 to 0.65 failed to increase the animal performance. In contrast to animal performance parameters, optimum carcass characteristics (eye muscle area, fat area above eye muscle, meat-fat ratio and lean percen tage) were achieved already at a ratio of sulphur containing amino acids to lysine of 0.53.