Effects of wheat cultivar, metabolizable energy level, and xylanase supplementation to laying hens diet on performance, egg quality traits, and selected blood parameters

A 2 x 2 x 2 factorial arrangement of treatments was conducted to evaluate the effects of two dietary apparent metabolizable energy (AME) levels (2,720 and 2,580 kcal kg-1 diet) and enzyme (0 and 0.3 g kg-1 diet, Grindazym® GP 15,000 with mostly xylanase activity) supplementation on the performance of laying hens fed diets based on two wheat cultivars (Marvdasht and Sardari). Experimental diets were formulated to have a constant energy to protein ratio and were fed to 65-wk-old Lohmann LSL-Lite laying hens for 7 wk. The lower level of AME reduced egg production and egg mass (p<0.05) and increased feed conversion ratio (p<0.05). Enzyme addition increased feed intake of the birds fed a diet with Sardari cultivar (p<0.05) but had no effect on feed intake of the birds fed a diet with Marvdasht cultivar (p>0.05). Nevertheless, birds receiving diets based on Marvdasht cultivar had higher feed intake and egg mass than that of those receiving diets based on Sardari cultivar (p<0.05). The birds fed diets based on Marvdasht cultivar produced less undesired eggs and had better yolk color as compared with the birds fed diets based on Sardari cultivar (p<0.05). The serum concentration of glucose increased by enzyme supplementation when birds receiving lower AME level (p<0.05). These results indicate that enzyme supplementation may have a positive effect on the feed intake of laying hens when fed on wheat-based diets; however, this effect is cultivar dependent and does not necessarily mean that enzyme supplementation always benefit production