Protein levels in diets for European pigs in the tropics. 1. The effect of methionine supplementation on the protein requirement of growing pigs

Abstract

SUMMARYOne hundred and twenty-eight Landrace and Large White pigs were allocated on the basis of sex, litter origin and initial weight to one of 16 treatments, made up of four basal 16, 18, 20 and 22% protein diets, each supplemented with either 0·00, 0·10, 0·15 or 0·20% synthetic DL-methionine, at a common digestible energy level of 3740 kcal/kg. Pigs were reared between 8 and 50 kg live weight. Growth rate of pigs and efficiency of feed conversion were significantly improved as the protein levels were increased up to the 20% protein level, optimal performance being on the 20% protein diet, with added 0·15% methionine, giving a total methionine+cystine level of 0·65% and a lysine level of 1·07%. Addition of synthetic methionine to the diets resulted in significant improvement in the rate and efficiency of gain only at the 16 and 18% protein levels.Carcass leanness and fatness increased and decreased respectively over the whole range of protein levels. Graded addition of DL-methionine within each protein level did not influence carcass characteristics.Nitrogen retention showed optimal utilization of dietary nitrogen to be at the 18% protein level, with a total dietary methionine + cystine level of 0·61%, which was at variance with the levels indicated by both growth and feed efficiency.