Abstract
ABSTRACTA total of 360 Hy-Line W-36 hens at 30 wk of age were assigned to 6 dietary treatments that consisted of 6 different (11, 15, 19, 23, 27 and 31) digestible Trp:Lys ratios. Hens were fed the experimental diets from 30 to 36 wk of age. Productive traits were recorded every wk and egg quality was measured at 36 wk of age. Total IgM, IgG, anti-sheep red blood cell antibody titres, plasma corticosterone, serotonine and glucose concentrations and heterophil to lymphocyte ratio (H:L) were determined at wk 6 of the experiment. Results showed a significant improvement (P < .0001) in egg production, egg mass, feed intake, feed conversion ratio and body weight by increasing the standardized ileal digestible (SID) Trp:Lys ratio from 11 to 19. Relative weights of shell (P < .05) and shell strength (P < .06) were affected by dietary treatments. Hens fed graded levels of SID Trp responded by decreasing the H:L ratio in a linear or curvilinear manner (P < .05). The study reported here indicated that the ideal SID Trp:Lys ratio for laying hens ranged from17.5 to 29 based on the response criteria and regression models.
Highlights
Tryptophan is one of the essential amino acids mainly used for protein synthesis
Based on the recent estimation by Bregendahl et al (2008), Trp requirement for true digestible Trp was 120 mg/d, which was similar to the 122 mg/d of digestible Trp reported by Coon and Zhang (1999) for 33–49-wk-old laying hens and the 149 mg/d of total Trp reported by Harms and Russell (2000) for 30–36-wk-old hens
Estimate digestible Trp to Lys ratio for maximum performance, immunity and welfare of Hy-Line W-36 hens using different non-linear regression models
Summary
Tryptophan is one of the essential amino acids mainly used for protein synthesis. In addition, it has numerous metabolic roles such as the conversion to niacin and the precursor of serotonin and melatonin. Estimate digestible Trp to Lys ratio for maximum performance, immunity and welfare of Hy-Line W-36 hens using different non-linear regression models.
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