The tryptophan requirements of pullets in the early production stage

Author: J.J. du Preez & J.S. Duckitt
Year: 1984
Issue: 2
Volume: 14
Page: 70 - 74

A trial was conducted with 1 152 Amberlink laying pullets from the ages of 30 to 35 weeks to determine the tryptophan requirements. The eight treatments consisted of a series of diets made by dilution of a summit diet with a dilution mixture. All amino acids in the summit diet were calculated to be in excess of the requirements and tryptophan was calculated to be the most limiting amino acid but still in excess. The daily tryptophan requirement was estimated by means of the Reading model, and a response equation was derived. The coefficients of the equation represent the amounts of tryptophan required per individual bird for egg formation and for body maintenance, being 2,017 mg tryptophan/g egg output and 8,256 mg tryptophan/kg body mass respectively. From a multiple regression fit of a parabolic curve, the daily tryptophan requirement for a bird, weighing 2,10 kg, with a potential egg output of 48,7 g per bird per day, was estimated to be 166 mg per bird per day (1,51 g per kg diet at a consumption rate of 110 g per bird per day). This estimate is valid for an economic situation when the marginal cost of 1 kg tryptophan is 20 times the marginal value of 1 kg egg. Under the same price structure and potential egg output the estimated daily tryptophan requirement for a flock was found to be 150 mg per bird per day (1,36 tryptophan per kg diet for a consumption rate of 110 g per bird per day) when the Reading model was implemented.



Keywords: Egg production, pullets, Tryptophan requirements
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