The choline requirement of the growing kitten in the presence of just adequate dietary methionine

Abstract

This study was conducted to determine the level at which choline is required by the growing kitten fed a 33% soy protein diet containing methionine just at its required level and total sulfur amino acids in excess. All experimental diets were isocaloric with a calculated metabolizable energy of 5.0 kcal/g. The soy protein used in each diet contributed 0.04% choline by analysis, and six levels of added choline were studied: 0, 0.10, 0.15, 0.20, 0.25, and 0.30g choline per 100g of diet. Kittens were fed the diets for 30 days in a 4×6 randomized block design, and food intake and body weights were recorded three times weekly. At the end of the feeding period, the liver was removed and analyzed for water content and total lipids, and a heparinized blood sample was taken for subsequent analysis of plasma methionine, albumin, total protein, glutamate-oxaloacetate transaminase (GOT), glutamate-pyruvate transaminase (GPT) and γ-glutamyl transpeptidase (GGT) activities. Weight gain and liver lipid response curves exhibited a plateau at approximately 0.2% added choline. GOT and GPT activities were significantly higher in the plasma of kittens fed the diet with no added choline than in any other of the groups. However, activities of both enzymes in that group were within normal range. No effect of dietary choline concentration was seen on any other plasma parameter measured. Assuming that the bioavailability of the choline contributed by the dietary protein is 100%, data presented indicate that 0.24% choline in a diet of 33% protein and 5.0 kcal/g, is adequate to support maximal weight gain and minimal liver fat in the growing kitten, when methionine is present just at its required level, and total sulfur amino acids are present in excess.