Use of water-treated black tea waste instead of wheat bran in laying hen diets
ABSTRACT We assessed the effects of different amounts of water-treated black tea waste (BTW) in the diets of laying hens on performance, egg quality, yolk peroxidation, and blood parameters in this study. The experiment lasted for 12 weeks, during which a total of 108 Lohman layers, of 24 weeks old, were randomly allocated to one of six dietary treatments (18 hens each); each treatment consisted of six replicate cages, each containing three hens. Experimental animals were fed a commercial diet that contained 0 (control), 20, 40, 60, 80, and 100% BTW in place of wheat bran. Providing BTW in diets for laying hens, instead of wheat bran, did not have a significant effect on egg production, egg weight, or body weight change. As the amount of BTW in the diet increased, feed intake, cracked egg rates, and feed conversion ratio linearly increased. Additionally, use of BTW in diets of laying hens did not influence some egg quality parameters, such as shape index or shell strength. Increasing proportions of BTW in the diet, however, had a quadratic effect on yolk color and shell weight, a linear effect on yolk index and shell thickness, and a cubic effect on albumen index and Haugh unit. In response to increasing BTW percentage, there were no differences in blood parameters except for albumen, triglyceride, alkaline phosphatase, and alanine aminotransferase levels. Malondialdehyde values in the egg yolks obtained from treatment groups fed diets containing BTW at different levels and stored for 14 and 28 days were lower than in those of the control group, but there were no differences at 56 days. Results of our study showed that supplementing diets of laying hens with different levels of water-treated BTW did not have adverse effects on either animal performance or egg quality parameters and resulted in strong antioxidative activity. Consequently, BTW may be used to replace up to 100% of wheat bran in the diets of laying hens, but the best outcomes are observed at 4% BTW level.