ABSTRACT
BACKGROUND: High-energy diets of laying hens may improve roductive performance, although some negative effects may also appear with respect to egg quality and physiological parameters. Curcuma longa rhizome powder (CRP) has beneficial effects on health indices of the birds through antioxidant and antimicrobial properties, especially when the birds experience nutritional stress. RESULTS: Increasing dietary CRP enhanced egg quality by improving eggshell thickness and hardness but decreasing yolk cholesterol content (P < 0.05). The best feed conversion ratio was obtained in birds fed high-apparent metabolizable energy (AME) diets supplemented with 2.0 g kg-1 CRP (P < 0.05). Although increasing dietary AME elevated the serum concentration of triglycerides (P < 0.05) and enzymatic activities of alanine aminotransferase and aspartate aminotransferase (P < 0.05), dietary inclusion of CRP alleviates the blood levels of these enzymes (P < 0.01). Low level of dietary CRP boosted the immune responses to Newcastle virus (P < 0.01) and sheep red blood cells (P < 0.05) antigens but decreased the heterophil to lymphocyte ratio (P < 0.05). Inclusion of at least 2.0 g kg-1 CRP in the diet of laying decreased Escherichia coli enumerations in the ileal content (P < 0.01) and improved villus height, crypt depth and goblet cell numbers (P < 0.05). CONCLUSION: An improvement in the productive performance of laying hens fed high-energy diets might be associated with decreasing health indices and product quality, which could potentially be amended by nutritional modifications such as incorporating medicinal herbs in the feed. © 2016 Society of Chemical Industry.
