Adverse Effects of Excess Methionine in Calves

Abstract

A nitrogen (N) balance trial was conducted for 2wk using 12 Holstein bull calves from 12wk of age (103kg initially) to verify adverse effects of excess methionine. The calves were trained to maintain reflex closure of the esophageal groove after weaning at 5wk of age, and received a diet based on corn and soybean meal throughout the trial at a level of 20g/kg of initial body weight. They were divided into three groups of 4 calves each, and assigned to three N supplements:(A) the mixture of 34.2g/d DL-methionine and 11.4g/d L-lysine monohydrochloride, (B) 35.2g/d casein, and (C) 39.3g/d diammonium citrate. All N supplements were iso-nitrogenous, and were administered through the esophageal groove. Administration of (A) resulted in reduced feed intake, body weight loss, and depressed N retention compared to the other N supplements, although N balance did not differ between (B) and (C). Extremely high plasma methionine concentration with the supplement (A) suggested adverse effects originating from excess methionine. Administration of (A) increased plasma concentrations of threonine, serine, cysteine, ornithine, proline and alanine, but decreased valine, leucine, isoleucine, arginine and phenylalanine in the plasma.