Effect of dietary level of methionine on growth performance and immune response in Japanese quails (Coturnix coturnix japonica)

BACKGROUND: Methionine (Met) being the first limiting amino acid in maize/soybean-based quail diets, its supplementation provides scope for improvement of protein quality and reduction of dietary protein concentration. The question remains to what extent it can be incorporated in the diet of genetically improved quails. Therefore the effect of dietary Met level was assessed on growth performance and immune response in growing Japanese quails (n = 400) divided equally into 20 groups. Five dietary treatments (similar to 230 g kg(-1) crude protein and 12.14 MJ kg(-1) metabolisable energy) were formulated with 3.5, 4.5, 5.0, 5.5 and 6.0 g kg(-1) Met respectively, and each was offered to four groups of birds from 0 to 35 days of age. RESULTS: Live weight at day 35 increased (P < 0.0001) up to 5.0 g kg(-1) dietary Met level but did not improve further at higher Met levels (5.5 and 6.0 g kg(-1)). Improved (P < 0.039) feed conversion ratio was achieved at 5.5 g kg(-1) Met level, which was statistically similar to that at 5.0 g kg(-1) Met level during 0-14 days of age. Cellular (phytohaemagglutinin from Phaseolus vulgaris) immune response increased (P < 0.0001) with increasing dietary Met concentration, whereas humoral (sheep red blood cells) immune response did not differ. CONCLUSION: The optimal requirement of Metwas 5.0 g kg(-1) for growth and 5.5 g kg(-1) for maximum cellular immune response. (C) 2009 Society of Chemical Industry