effects of dietary protein level and betaine supplementation on nutrient digestibility and performance of japanese quails

ABSTRACT This study investigated the effects of dietary protein levels and betaine supplementation on nutrient digestibility and performance of Japanese quails. In total, 765 Japanese quails were randomly assigned to a 3×3 factorial arrangement, with five replicates of 17 quails each. Three basal diets were formulated to contain three crude protein levels (16.5, 18.0, and 19.5%). Each protein level was supplemented with 0, 0.06, and 0.12% betaine. The diet with 16.5% dietary crude protein with no betaine supplementation resulted in the lowest crude fiber digestibility, while the 18.0% CP diet supplemented with 0.12% betaine generated the highest crude fiber digestibility (p<0.05). The diets with 18.0 and 19.5% crude protein increased crude fiber digestibility, but reduced ether extract digestibility (p<0.01). Moreover, betaine supplementation increased dry matter, crude protein, crude fiber, and crude ash (p<0.01) digestibility and tended to increase ether extract digestibility (p=0.09). The increase in egg weight for the 18.0 and 19.5% protein diets was correlated with a decrease in feed conversion ratio (p<0.05). However, feed intake and egg production were not affected by protein levels. Betaine supplementation enhanced all performance variables (p<0.01). The diets with 18.0 and 19.5% crude protein resulted in heavier yolks and eggshells than the 16.5% crude protein diet (p<0.05), whereas betaine supplementation increased yolk, albumen, and eggshell weight (p<0.01). The 18.0 and 19.5% protein diets produced similar responses in most evaluated parameters. Laying Japanese quails can be fed diets with 18.0% crude protein. Moreover, betaine supplementation provided several benefits, and particularly improved nutrient digestibility, performance, and egg quality.