This study was conducted to determine the optimal ratio between sulphur containing
amino acids and
lysine in diets for growing-finishing pigs. Therefore, 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 concentrations of
lysine (0.62, 0.70 and 0.78%) and various ratios between sulphur 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 was adjusted by individual supplementation of the diets with DL-
methionine. Increasing dietary levels of
lysine from 0.62 to 0.78% continuously increased daily
body weight gains and improved feed conversion efficiency as well as 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 various dietary
lysine concentrations. The optimum ratio between sulphur containing
amino acids to
lysine according to quadratic regression analysis was 0.60, for both, growth and feed conversion. Reducing the ratio between sulphur 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 ratio 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 percentage) were achieved already at a ratio of sulphur containing
amino acids to
lysine of 0.53.