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The use of compositional growth curves for assessing the response to dietary lysine by high-lean growth gilts
Published online by Cambridge University Press: 02 September 2010
Abstract
Growth modelling was used to characterize the response to digestible lysine in two experiments (114 gilts in experiment 1 and 96 gilts in experiment 2) from 34 to 72·5 kg and 72·5 to 136 kg, respectively. Maize-soya-bean meal diets were formulated to assure that lysine (5·4 to 10·4 and 5·4 to 9·4 g digestible lysine per kg for experiments 1 and 2, respectively) was the first limiting amino acid. Analysis of variance was used to test linear and quadratic responses in cumulative weight gain on test as digestible lysine increased. A time × digestible lysine interaction (linear, P < 0·001) was detected, indicating that a separate regression equation for each lysine level was necessary. In experiment 1, average daily gain (ADG) and carcass crude protein (CP) accretion were maximized for gilts given 10·4, 9·4 and 8·4 g digestible lysine per kg from 34 to 44 kg, 44 to 54 kg, and 54 to 72·5 kg, respectively. Lipid accretion was minimized for gilts given 7·4 to 8·4 g digestible lysine per kg. In experiment 2, ADG was maximized by feeding 8·4 g/kg from 72·5 to 92·5 kg and 7·4 g/kg from 92·5 to 136 kg. Carcass CP accretion was maximized by feeding 9·4 g digestible lysine per kg, whereas lipid accretion was minimized for gilts given 8·4 g digestible lysine per kg from 72·5 to 136 kg. If feeding graded levels of digestible lysine resulted in parallel lines for protein accretion, mean values would result in accurate data evaluation. However, responses to digestible lysine changed over the feeding period. Therefore, the use of body weight and compositional growth curves offers an approach to more accurately characterize the growing pig's response to increased digestible lysine.
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- Copyright © British Society of Animal Science 1996
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