Title: Dietary cysteine cannot replace dietary methionine for protein accretion in growing broiler chickens
Abstract: In a 14-day dose-response study, we studied the effect of increasing sulfur-containing amino acid (SAA) concentration in the diet on feed intake, growth rate, feed conversion and composition of gain in male growing broilers. SAA were supplemented to two basal diets (calculated to be equal in Met and Cys with 4.5 g/kg total SAA) in 7 graded levels by replacement of equivalent masses of NEAA with either pure DL-Met or a 1:1 mix of DL-methionine and L-cysteine. An upper level of 10.5 g/kg SAA was achieved. Broilers responded non-linearly to increasing concentration of SAA with increased feed intake, improved growth rate and better feed conversion and a plateau was achieved in all cases. The 1:1 mix of Met and Cys failed to match the growth performance of Met-alone diets in the range of suboptimal SAA supply. SAA intake and feed conversion were similar between the two alternatives. Response in protein accretion was also non-linear over the entire range of SAA intake. Content of Met but not Cys increased in gained body protein with increased SAA intake. 95% of ymax in protein accretion were achieved with a SAA concentration of 5.9 (Met alone) and 8.1 g/kg (1:1 mix of Met+Cys), respectively. The maximum in marginal efficiency was 88% in case of Met alone and 45% in case of the 1:1 mix of Met and Cys. It is concluded that cysteine cannot replace at all dietary methionine for protein accretion.
Publication Year: 2003
Publication Date: 2003-10-10
Language: en
Type: book-chapter
Indexed In: ['crossref']
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