EFFECT OF METHIONINE SUPPLY AT HIGH AND LOW DIETARY METHIONINE TO CYSTINE RATIOS ON THE PERFORMANCE OF GROWING PIGS

In a growth trial using 8 x 12 pigs, the requirement for methionine an d sulfur amino acids in the 20-60 kg and 60-95 kg growth periods was d etermined at two different methionine:cystine ratios in thebasal diet (A and B). During the first growth period, the high-cystine basal diet contained 0.26% cystine and 0.18% methionine, whereas the low-cystine diet contained 0.18% cystine and 0.26% methionine. During the second period, the cystine/methionine percentages were 0.21/0.18% and 0.17/0. 24%, respectively. In both growth periods, diets A and B were suppleme nted with 0%, 0.04%, 0.08%, and 0.12% DL-methionine. With increasing d ietary methionine level, liveweight gain, feed conversion, back muscle area, and the meat-fat ratio were improved. Furthermore, the basal di et high in methionine was superior to that high in cystine. In the 20- 60 kg period, pigs fed the high-cystine diet had a requirement for sul fur amino acids of 0.56%. At low dietary-cystine levels, 0.52% sulfur amino acids was already sufficient. During the second growth period, t he requirement. for sulfur amino acids was 0.47% with a high dietary-c ystine level and 0.43% with a low dietary cystine concentration. Consi dering the performance parameters growth and feed conversion, in the 2 0-60 kg liveweight range the methionine requirement was 0.37%, virtual ly regardless of whether the diets were low or high in cystine. During the second growth period, the methionine requirement of the pigs was more influenced by the dietary cystine ratio than during the first per iod. Here, the methionine requirement was 0.31% in relation growth per formance, and 0.33% with regard to feed efficiency.