Effect of dietary energy level on methionine toxicity in chicks

To investigate the effect of dietary energy level on chicks fed excess methionine, 8-day-old Single Comb White Leghorn male chicks were fed 8 experimental diets for 12 days involving 2 levels of methionine (adequate and 1.5% excess)×4 levels of corn oil (4% to 16% in 4% increments). Supplementation of excess methionine significantly depressed body weight gain, feed intake and utilization of energy and nitrogen, independent of the dietary energy level. Supplementation of corn oil at the expense of corresponding amounts of cornstarch improved the efficiency of nitrogen utilization in both methionine-adequate and-excess diets. However, the growth rate was not improved because feed intake was not accelerated by the additional fat. When the chicks were fed the methionine-adequate diet, feed intake was gradually decreased with the progressive increase in the dietary energy level, so that metabolizable energy intake was kept constant. These chicks required several days to complete the adjustment for energy intake, while the depression in feed intake due to excess methionine was observed within 2 days after feeding.