Abstract
Nutritional additives such as propolis seek to improve intestinal health as an alternative to the global ban on in-feed antibiotics used as growth promoters (AGP). The objective of this study was to evaluate the effect of propolis supplementation in diet of broilers. Four hundred and fifty straight-run Ross 308 AP broilers were fed with a basal diet (BD) throughout the whole experimental period. Birds were randomly distributed into 5 groups at d 14: negative control without antibiotics nor propolis (AGP-), positive control 500 ppm of Zinc Bacitracin as growth promoter (AGP+), and 3 groups supplemented with 150, 300, and 450 ppm of propolis. Every group included 6 replicates of 15 birds each. Propolis concentration was increased from d 22 to 42, in experimental groups to 300, 600, and 900 ppm of propolis, and 10% of raw soybean was included as a challenge in all groups during the same period. Analysis of productive parameters, intestinal morphometry, and relative quantification of genes associated with epithelial integrity by qPCR were performed at 21 and 42 d. The groups with the greatest weights were those that consumed diets including 150 (21 d) and 900 ppm (42 d) of propolis compared with all treatments. The lowest score of ISI was found at 300 (21 d) and 600 ppm (42 d). A lower degree of injury in digestive system was seen with the inclusion of 300 ppm (21 d) and 900 ppm (42 d). Up-regulation of zonula occludens-1 (ZO-1) was observed in jejunum of broilers supplemented with 150 and 300 ppm at 21 d. Up-regulation of ZO-1 and TGF-β was also evidenced in ileum at all propolis inclusion levels at 42-day-old compared to AGP+ and AGP-. The beneficial effects were evidenced at inclusion levels of 150 ppm in the starter and 900 ppm in the finisher. According to the results, the Colombian propolis inclusion can improve productive performance, physiological parameters, and gene expression associated with intestinal integrity.