Studies of the Renal Excretion of the Hydroxyl Analogue of Methionine by the Chick

Abstract

Athens-Canadian Random Bred adult cockerels and chicks were used to compare the metabolism of the free acid form of the methionine hydroxyl analogue (HMB-FA) to L-methionine (LMET). The first experiment was to determine whether HMB-FA was excreted by the kidneys, thus reducing the amount available for protein synthesis. Fasted adult male chickens were given a single oral dose of HMB-FA or LMET containing a radioactive tracer. Urine was collected and analyzed for the amount of radioactive tracer present; blood samples were subjected to blood gas analyses to assess the physiological status of the bird. It was concluded that LMET was the major methionine analogue excreted from roosters dosed with either HMB-FA or LMET, and that HMB-FA was not excreted by the avian kidney.The second experiment was to determine whether the acid-base status of the diet influences the utilization of HMB-FA. Two levels of dietary LMET or HMB-FA and six levels of dietary base were fed to chicks in a complete 2 × 2 × 6 factorial design for a period of 20 days, after which weight gain and feed consumption were determined. The results indicated that the acid-base status of the diet can play a role in maximizing the gain of chicks fed HMB-FA. Optimal dietary conditions for comparing the efficacy of HMB-FA with LMET and the poor performance of HMB-FA in crystalline amino acid diets are discussed.