Sanguinarine improved nutrient digestibility, hepatic health indices and productive performance in laying hens fed low crude protein diets

A major mean to minimize feeding costs and faecal nitrogen excretion on poultry farms is to decrease the supplied dietary protein content. This, however, is associated with the declines in productive performance and systemic health indices. Sanguinarine may improve protein efficiency via decreasing the intestinal amino acid decarboxylation and stimulating the tryptophan‐serotonin pathway. The present study was carried out to investigate the effects of dietary supplementation of sanguinarine on the performance, egg yolk biochemical parameters, serum enzyme activities, nutrient digestibility, ovarian follicles, and hepatic health indices in laying hens fed decremental levels of crude protein (CP). For this purpose, 180 laying hens were allocated into nine dietary treatments with four replicates of five birds each. The experimental treatments consisted of three levels of CP (85.0%, 92.5%, and 100% of Hy‐Line W‐36 manual recommendation) and three levels of sanguinarine (0.00, 3.75, and 7.50 mg/kg) in a 3 × 3 factorial arrangement administered during a 70‐day feeding trial. Results showed that the decremental levels of CP led to significant increases in serum aspartate aminotransferase (p < .05), alanine aminotransferase, and alkaline phosphatase (p < .01) activities, egg yolk cholesterol concentration (p = .064), and hepatic fat and malondialdehyde (MDA) contents (p < .05). It also caused the significant declines in ileal dry matter (DM) digestibility (p < .05) and eggshell strength (p < .05), and also tended to decrease CP digestibility (p = .071), Haugh unit (p = .057) and egg production percentage (p = .062). The interaction effects of the experimental factors indicated that dietary supplementation of sanguinarine, especially at 7.50 mg/kg, led to significant improvements in serum aspartate aminotransferase and alanine aminotransferase activities (p < .01), egg yolk cholesterol (p < .001) and triglyceride (p < .05) concentrations, eggshell strength (p < .001), Haugh unit (p < .05), hepatic fat (p < .001) and MDA (p = .059) contents, ileal DM and CP digestibility (p < .01) as well as egg production, egg mass and feed conversion ratio (FCR; p < .05) in birds receiving decremental levels of CP. Taken together, the results indicate that dietary administration of sanguinarine could enhance productive performance via improving nutrient digestibility, hepatic health indices and fortifying systemic antioxidant capacity in laying hens fed low‐CP diets.