Effect of Drug Additives and Type of Diet on Methionine Requirement of Chicks for Growth and Feed Efficiency

Abstract

Three short-term (2 week) experiments were conducted with broiler type chicks to determine the effect of monensin, lasalocid, and lincomycin on growth and feed efficiency responses in chicks to graded levels of methionine. Lasalocid and monensin were added at levels of 125 and 121 ppm, respectively. These levels are at the upper level of the range permitted for use in poultry feeds. In one of these experiments, two different types of diets (corn-soy and pea-corn) were used which differed primarily in the source of protein. Both types of diets, on a calculated basis, were deficient in methionine and total sulfur amino acids. The addition of lasalocid to the diet that was most deficient in methionine had a methionine sparing effect. Addition of monensin to both types of diets depressed growth and feed efficiency in most of the comparisons where it was used. Some of the differences were not statistically significant. Addition of lincomycin at a level of 2 ppm gave a marked growth response when added to the diet without a coccidiostat and to the one containing lasalocid. The response in the presence of monensin was greatly reduced. In two experiments out of three, growth plateaued at a level of .1% added methionine in the presence of monensin and at a level of .2% added methionine in the presence of lasalocid. In the third experiment, growth plateaued at the .2% level added methionine for diets containing no coccidiostat or monensin and lasalocid. The results indicate that a maximum response was not obtained to methionine because of the growth depressing effect of monensin. On an overall basis, lincomycin improved feed efficiency and the improvement was more striking in the presence of lasalocid than in the presence of monensin. No improvement was obtained in the latter comparison.