Methionine Essentiality for the Cat

Abstract

Two assays were performed to determine the essentiality of methionine for weanling and adult cats. Additional assays were conducted to establish whether cats could utilize the D-isomer and the DL-hydroxy analogue of methionine for growth. Both weanling kittens (750 g) and adult female cats (4,000 g) lost weight when fed a methionine-free crystalline amino acid diet containing 1.20% L-cystine, .70% K2S04 and .10% taurine. Adding .60% L-methionine to the diet resulted in daily weight gains of over 20 g/day in kittens and 14 g/day in adult cats. D-methionine appeared to be well utilized by cats, although performance levels fell somewhat short of those observed with cats fed L-methionine. DL-OH-methionine (Ca) was poorly utilized as a source of methionine activity when fed in a crystalline amino acid diet, but well utilized when used to provide supplemental methionine activity in a semipurified diet containing intact protein in the form of soybean meal.