ABSTRACT
To determine the digestible valine (dVal) requirement and dVal to digestible lysine ratio (dVal: dLys) for laying hens, this experiment was performed on three hundred sixty Hy-Line W36 hens during the peak egg production phase (28 to 40 weeks of age), based on a completely randomized design with six treatments and five replicates of 12 birds each. The six dietary treatments were graded levels of dVal: dLys ratios: 0.82 (basal diet), 0.86, 0.90, 0.94, 0.98, and 1.02. The dVal: dLys ratio of 0.82 led to the lowest performance, indicating that valine is the first limiting amino acid in this ratio. The graded increase in the dietary dVal: dLys ratio improved egg weight (EW, p<0.01), egg mass (EM, p<0.05), and feed conversion ratio (FCR, p<0.01). The highest performance was observed at the dVal: dLys ratio of 0.94. Serum albumin, uric acid, and triglycerides were significantly (p<0.01) affected by the dVal: dLys ratio; the highest level of albumin, and the lowest levels of triglycerides and uric acid were observed at the ratios of 0.98, 0.98, and 0.94, respectively. The graded increase in dVal: dLys ratio improved (p<0.05) the egg quality traits (albumen and yolk height, Haugh unit, albumen ratio, and yolk color). Based on regression analysis, the response curves for EW and EM showed the best fit with the linear broken line (LBL) model, while the quadratic polynomial (QP) model was the best fit for FCR. In conclusion, the optimum dVal: dLys ratio was estimated at 0.93, which equals 695 mg dVal/ hen/ day.
Keywords:
Dietary Valine; Laying Hen; Performance; Quality of egg; Serum Biochemistry