Abstract:
CHOLINE ADDITION AND METHIONINE REQUIREMENTS OF LAYERS M.W. MCDONALD* A diet containing 2.1 g methionine, 4.3 g total sulphur amino acids, 860 mg choline and 12.0 mJ/kg was supplemented with all combinations of nil or 500 mg Each of the six diets were choline, and nil, 500 and 1000 mg dl methionine. fed to 108 pullets, 27 weeks old at the start of the experiment. The pullets Egg production, feed intake, egg weight and were housed in twin bird cages. body weight gain were observed. Analysis of the first 12 weeks of the trial showed that either choline or methionine increased egg production at the lowest level of each nutrient, but that choline had no effect on pullets fed the higher levels of methionine. The optimum methionine intakes were estimated (Fisher et al., 1973) with or without choline to be 303.9 and 305.6 mg/day respectively for the productions Using the parameters of the response curve derived from actually observed. this analysis, it is possible to predict the optimum methionine intake for a range of performance: TABLE 1 Optimum methionine (mg/day) and choline. The data indicate that methionine requirements were 10% less when choline was added to the diet than in its absence. Based on expected feed intakes (Waldroup, 1984) and current costs of methionine and choline, it is marginally more profitable to omit the added choline and add extra methionine to meet the slightly higher methionine requirement of the birds with no added choline, than to add choline and reduce the amount of methionine added. The effect of omitting choline and adding extra methionine ranges from an extra 47.6 cents per tonne of feed for 1.6 kg bird laying 50 g egg per day to a reduction of 34 cents per tonne for a 2 kf bird laying 40 g egg per day. FISHER, C., MORRIS, T.R. and JENNING, R.C. (1973). British Poultry Science, 14:469-484. WALDROUP, P.w., quoted by Smith, R. (1984). Feedstuffs, Dee 10, p.lO-18. *Queensland Agricultural College, Lawes, Queensland 4343. 7A