EFFECT OF PROTEIN LEVEL AND LYSINE AND METHIONINE SUPPLEMENTATION ON THE PERFORMANCE OF GROWING PIGS: RESPONSE OF DIFFERENT SEXES AND STRAINS OF PIGS

Two factorial experiments have been conducted with corn–soybean diets. Four types of pigs and three "sexes": males, females and castrated males, were used. The first experiment showed that Lacombe and Yorkshire strains responded to an increase in dietary protein from 13 to 16% by growing faster, whereas Landrace and a crossbred strain did not. The males grew faster than the females. In the second experiment, the effects of adding lysine and/or methionine to diets containing either 12 or 14% protein were investigated. There was no significant improvement in gain or feed efficiency when either amino acid was added separately, but there was a substantial response when they were added together. Landrace, Yorkshire and Hampshire × Landrace pigs were used in this experiment and the Landrace gained more slowly than the other two types.