Interactions between phytase and xylanase enzymes in male broiler chicks fed phosphorus-deficient diets from 1 to 18 days of age.

A total of 735 one-day-old male broiler chicks were used to evaluate the interactions between different levels of phytase and xylanase enzymes on performance and bone mineralization. Basal nonphytate P (nPP)-deficient diets (0.15%) were supplemented with different levels of phytase [0X, 1X, 2X, 3X, and 4X of recommended level (X = 500 phytase units per kg of feed)] alone or in combination with 3 levels of a xylanase preparation [0X, 1X, and 2X of recommended level (X = 0.1 g per kg of feed; a mixture with predominantly xylanase activity)]. A standard curve was developed using different levels of nPP (0.15 to 0.45%) to estimate the P equivalency of each enzyme combination. Treatments were replicated with 7 pens of 5 chicks each. The findings indicated that reducing dietary nPP level had a severely negative influence on bird performance and bone ash content. Results also showed that increasing levels of phytase significantly (P < 0.05) improved BW, feed intake, feed conversion ratio, mortality, and toe and tibia bone ash contents in a dose-dependent fashion. The P equivalency of phytase was also dose dependent, with estimates of 0.08, 0.11, 0.15, and 0.19 for 1X, 2X, 3X, and 4X supplementation levels of phytase, respectively. Xylanase preparation at 1X level failed to influence measured criterion; however, increasing the level of xylanase (2X) resulted in deteriorating BW and feed conversion ratio. The P equivalency of xylanase preparation at 1X and 2X was estimated as 0.010 and 0.014%. There were no interactions between phytase and xylanase preparation (P > 0.05). In conclusion, phytase was effective in improving bird performance and bone mineralization; however, xylanase supplementation failed to enhance phytase efficacy.

Effect of different levels of dietary vitamin E (DL-α-tocopherol acetate) on the occurrence of various degrees of white striping on broiler breast fillets.

White striping could be a potential reason for the rejection of raw breast fillets in the market. The condition is characterized grossly by the white striations occurring on the fillets showing myopathic changes on microscopic examination. Early research has shown similar lesions in the case of nutritional muscular dystrophy, which is a condition caused mainly by the deficiency of vitamin E in the diet. The present study was intended to evaluate the effect of different levels of dietary vitamin E (dl-α-tocopherol acetate) on the incidence of normal, moderate, and severe degrees of white striping, by modern description, on broiler breast fillets. Basal diets adequate for starter (0 to 18 d), grower (19 to 32 d), and finisher (33 to 49 d) age periods supplemented with 15, 50, 100, 200, and 400 IU of vitamin E/kg of feed were used in the study. Each of the 5 diet treatments were fed to 8 pens (53 birds each) of male broilers from a commercial strain. At 49 d, 5 birds were randomly selected from each pen (n = 40 birds/diet treatment) and were processed. Live weight, ready-to-cook weight, weight of the fillets, wings, tenders, legs, and the racks were obtained. The fillets were scored for the 3 degrees of white striping. There were no significant differences among the diet treatments with respect to the weight and carcass yield parameters. Furthermore, the diet treatments did not show any significant effect on the occurrence of normal, moderate, and severe degrees of white striping. However, fillet weight was the only parameter that had a significant effect on the occurrence of white striping. Higher degrees of white striping were seen associated with heavier fillets, which is in accordance with previous studies. Different levels of vitamin E levels used in the present study did not show any significant effect on the occurrence of 3 degrees of white striping. These results suggest that dietary vitamin E level is not associated with the modern condition of white striping in broiler breast meat.