Adverse effect of excess methionine or methionine hydroxy analog on feed consumption in cattle

The toxicity of DL-methionine and methionine hydroxy analog infused into the rumen or abomasum was gauged by relative feed consumption. A continuous intraruminal infustion of at least 3 days' duration of DL-methionine equalent to about 2.5% or more of dietary dry matter intake was required to reach a toxic amount. This was approximately four times the amount necessary when it was infused into the abomasum. Methionine hydroxy analog equalent to about 1% or more of dietary dry matter intake was toxic when infused into either rumen or abomasum. This is in large excess of suggested amounts of analog supplementation. Reduced palatability is likely to occur in advance of reduced intake due to toxicity.