Effects of excess methionine or lysine for broilers fed a corn-soybean meal diet

Three experiments were conducted to examine the consequences of over-supplementing DL-Met or L-Lys (as L-Lys.HCl) in diets for chicks fed a corn-soybean meal diet (23% CP, 3,200 kcal MEn/kg, .2% supplemental Met) during 1 to 3 wk posthatching. New Hampshire x Columbian male chicks were used in Experiments 1 and 2 and Hubbard x Hubbard males were employed in Experiment 3. The basal diet was supplemented with .5, 1.0, 2.0, or 4.0% DL-Met, or .4, .8, 1.6, or 3.2% L-Lys in Experiment 1. Weight gain, feed intake, and feed efficiency decreased linearly at supplemental levels of DL-Met between 1.0 and 4.0%. Weight gain of chicks fed diets with supplemental L-Lys levels greater than 1.6% was less than that of chicks fed the basal diet, but feed efficiency was not significantly affected. Adding K2CO3 to the diets containing 1.6 or 3.2% added L-Lys did not improve performance. Experiment 2 evaluated the effect of 1) adding 1.0% Gly or 1.0% L-Thr to the diet supplemented with 2.0% DL-Met; and 2) adding NaHCO3 to the high-Lys diets in order to buffer the excess chloride provided by L-Lys.HCl. Addition of these amino acids or buffer ameliorated but did not totally correct the negative effects of excess Met or Lys. Experiment 3 examined the tolerance of commercial broilers to supplemental DL-Met or L-Lys levels of .5 or 1.0%. Weight gain and feed efficiency were not affected by these excesses, but feed intake was reduced at the 1.0% level of inclusion of either amino acid.(ABSTRACT TRUNCATED AT 250 WORDS)