The effect of variation of protein quality and protein level in diets on the performance of young pigs

Abstract

1. A feeding trial was conducted on 64 individually-fed pigs given diets varying in crude protein content, and containing as a protein supplement either white-fish meal or groundnut meal alone, or groundnut meal with L-lysine monohydrochloride or DL-methionine or both.2. Daily live-weight gain and feed conversion ratio of pigs given diets containing fish meal were best when the diet provided 18% crude protein on an air-dry basis (15·7% white-fish meal).3. Additions of L-lysine monohydrochloride to a diet providing 18% crude protein and containing 21% groundnut meal as the main source of protein produced highly significant (P<0·001) improvements in daily gain and feed conversion ratio and these measures were not significantly different from those of pigs given the control (fish meal) diet which provided similar total lysine and crude protein levels. The white-fish meal diet containing 18% crude protein produced pigs whose half carcasses were of higher specific gravity (P<0·05) and rib cuts with more protein and less fat (each P<0·05) than did the groundnut meal diet at the same protein level.4. DL-methionine did not significantly affect live-weight gain, feed conversion, fat or protein content of the rib cut or the specific gravity of the half carcass.5. Pigs on a 12% crude protein diet containing groundnut meal supplemented with lysine grew at the same rate as pigs on an 18% crude protein diet in which no lysine supplement was added to the groundnut meal. Their rib cuts contained more protein and less fat.