Standardized ileal digestible tryptophan requirements for japanese laying quails
Abstract
This study aimed to estimate the nutritional requirement of standardized ileal digestible (SID)
tryptophan for Japanese quails during the initial laying phase and to assess its effects on egg quality,
organ weights, leukocyte differential count, and heterophile: lymphocyte ratio. The experimental
design was completely randomized, with 5 treatments (0.14%, 0.19%, 0.24%, 0.29%, 0.34%) and 5
replicates, resulting in 25 experimental units with 12 quails per unit, totaling 300 birds aged 42 to 126
days. Based on the results, a SID tryptophan level of 0.14% was optimal for the laying phase. Oviduct
weight exhibited a quadratic effect, suggesting a requirement of 0.24% SID tryptophan. A decreasing
linear effect was observed in heterophiles and basophils, while lymphocytes and monocytes showed
an increasing linear effect. The heterophile: lymphocyte ratio demonstrated a quadratic effect,
indicating a requirement of 0.31% SID tryptophan. However, for birds aged 63 to 126 days, 0.14% SID
tryptophan was sufficient for optimal performance, with a SID tryptophan: lysine ratio of 13% and a
SID tryptophan intake of 34.67 mg per bird per day. Thus, reducing tryptophan levels in the diet did
not adversely affect bird performance.
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