Does Dietary Yeast Extract Improve the Performance and Health of Quail Breeders Reared under High Stocking Density?

This study was designed to study the effects of stocking density without or with yeast extracts supplementation on productive and reproductive performance, digestive enzymes, blood biochemical parameters, and antioxidant and immune measurements of quail breeders. A total number of 336 Japanese quail birds at 8 weeks old were used. Quails were randomly distributed into 6 groups and 4 replicates maintained / each group in a complete randomized design. The 1 group contained 36 birds (24 females and 12 males) was stocked at a rate of 9 birds /replicate (control, ND; 36 quails/m) and fed the basal diet without any supplementation; the 2, 3, 4, 5 and 6 groups contained 60 quails (40 females and 20 males) and stoked at a rate of 15 chicks/replicate (HD; 60 quails/m) and fed on a basal diet supplemented with 0, 1, 2, 3 and 4 mg YE /kg diet, respectively. Egg number, egg weight and egg mass were significantly decreased (P<.0001) due to increasing stocking density from ND (9/cage) to HD (15/cage) and fed without dietary YE supplementation. The activity of SOD (p<0.0001), TAC (p<0.0001) and GPX (p=0.0047) was improved with HD plus YE when compared to HD. Digestive enzymes (amylase, lipase, and protease) activity was decreased with HD when compared to ND. It could be concluded that addition of yeast extract can positively mitigate the stress applied to quail raised under high stoking density by enhancing productive and reproductive performance, lipid profile, antioxidants and immunity as well as egg quality criteria.