Estimation of methionine requirement of Japanese quails exposed to chronic heat stress during 7 to 21 days of age

The aim of this research is to estimate the methionine requirement of Japanese quails (Coturnix coturnix japonica) from 7 to 21 d of age using linear and quadratic broken-line regressions under chronic heat stress. A total of 480 quails were distributed according to a completely randomized design in 6 experimental treatments (diets containing 0.40, 0.45, 0.50, 0.55, 0.60 and 0.65% of methionine), with 4 replicates of 20 birds each. The basal diet was based on the corn-soybean meal and was formulated in mash form. Supplemental DL-methionine was added to the basal diet at the expense of corn starch to create experimental diets. The birds were fed a standard diet up to d 7, and then were weighed and randomly allotted to the experimental treatments. Birds exposed to chronic heat stress from 8 d of age for 6 h daily (37 ± 0.8°C from 10 AM to 16 AM). The optimal amounts of methionine for body weight gain, feed conversion ratio, and breast meat yield were obtained with 0.55, 0.57, and 0.60% of the diet as estimated by linear broken-line regression. However, based on the quadratic broken-line regression, the corresponding values were estimated at 0.58, 0.59, and 0.62% of the diet, respectively. According to the findings of this study, It seems that amounts of methionine higher than the usual recommendations are needed for Japanese quails to achieve optimal performance under chronic heat stress.