Replacement of dietary vitamin E by an extract rich in hydrox-ytyrosol, from the olive oil by-product “alperujo”, in broiler chickens: part II - effects on liver traits, oxidation, lipid profile and transcriptome.

The present study aims to evaluate the impact of replacing vitamin E (VE) by a liquid obtained from alpeorujo, an olive oil by-product rich in hydroxytyrosol (HT), on broiler liver traits, oxi-dation, lipid profile and transcriptomic analysis. There were 5 diets that differed only in the substitution of supplemental VE (0 to 40 mg/kg with differences of 10 mg/kg) by HT (30 to 0 mg/kg with differences of 7.5 mg/kg). A linear decrease (p < 0.05) of α-tocopherol concentration in the liver was observed with the replacement of VE by HT with no significant changes in tri-glycerides, cholesterol, and TBARs concentrations. The hepatic transcriptome showed 378 dif-ferentially expressed genes between broilers fed HT15 (20 mg/kg VE and 15 mg/kg HT) and HT0 (40 mg/kg VE) diets (p < 0.05 and Fold-Change less or higher than 1.3). Significant changes in cell cycle, cell nucleus activity, neuroactivity and necroptosis pathways and functions were observed. It is concluded that the olive oil by-product, rich in HT, could be used to spare VE as antioxidant in broilers diets without affecting liver lipids and TBARs concentrations. The differentially gene expression analysis showed a potential role of olive polyphenols in enhancing the chicken im-mune response. The experiment included 560 1-day-old male Cobb 500 chickens were randomly distributed among 35 floor pens with controlled environmental conditions(0.96 x 1.50 m) with 16 birds each and fed their respective experimental diets. The experiment was conducted with 5 treatments (HT0, HT7.5, HT15, HT22.5, and HT30) that consisted in 5 levels of supplemented vitamin E (0 to 40 mg/kg) with a difference of 10 mg/kg between diets. The vitamin E was substituted in these diets by HT (30 to 0 mg/kg) with a difference of 7.5 mg/kg between diets. Animals were provided with feed and water ad libitum. For microarray analysis, six liver total RNA samples per group were randomly selected for array hybridization.