Excess dietary tryptophan mitigates aflatoxicosis in growing quails

A biological assay was carried out to evaluate the impact of dietary tryptophan (TRP) in aflatoxin B₁ -contaminated diets (AFB₁ -D) on performance, blood parameters, immunity, meat quality and microbial populations of intestine in Japanese quails. Six experimental diets were formulated to include two levels of dietary TRP; 2.9 (moderate high: MH-TRP) and 4.9 g/kg (excess: Ex-TRP); and three levels of AFB₁ (0.0, 2.5, and 5.0 mg/kg). Each experimental diet was fed to the one of the six groups of birds from 7 to 35 days of age in a completely randomized design with 2 × 3 factorial arrangement. Decrease in feed intake, body weight gain and gain:feed in birds fed 5.0 mg/kg AFB₁ -D was restored to the control level by 4.9 g TRP/kg of the diet. The hepatic enzymes in blood were elevated in quails fed on AFB₁ -D but attenuated by 4.9 g TRP/kg of the diet (Ex-TRP; p ≤ .01). High serum uric acid in birds challenged with AFB₁ significantly decreased by Ex-TRP (p ≤ .01). The skin thickness to 2,4-dinitro-1-chlorobenzene challenge suppressed by AFB₁ but increased by Ex-TRP diet (p ≤ .02). The AFB₁ increased the malondialdehyde in meat, whereas TRP efficiently diminished malondialdehyde production (p ≤ .01). The greatest drip loss and pH in meat were observed in the birds fed 5.0 mg/kg AFB₁ -D but Ex-TRP augmented the adverse effects of AFB₁ (p ≤ .01). The Ex-TRP reduced the total microbial and Escherichia coli counts (p ≤ .01). The adverse effect of AFB₁ on ileal Lactic acid bacteria was completely prevented by Ex-TRP (p ≤ .03). This study showed that tryptophan supplementation could be considered as a powerful nutritional tool to ameliorate the adverse effects of AFB₁ in growing quails.