Effects of a bioactive olive pomace extract from Olea europaea on growth performance, gut function, and intestinal microbiota in broiler chickens

Abstract

The present study aims to investigate the effects of supplementing broiler diets with a bioactive olive pomace extract (OE) from Olea europaea on growth performance, digestibility, gut microbiota, bile acid composition, and immune response. To this end, three hundred and six 1-day-old broiler chickens (Ross 308) were housed in floor pens (6 pens/treatment, with 17 birds/pen). Animals were fed with a standard non-medicated starter diet for 21 D, and from 22 to 42 D of age with their respective experimental diet: a negative control with no additives (Control), a positive control with 100 ppm of monensin (Monensin) and the basal diet supplemented with 750 ppm of an OE (Lucta S.A., Spain). Feed intake and growth rate were monitored weekly throughout the trial. From 21 to 42 D of age, no significant differences in feed intake were observed among dietary treatments; however, lower average daily gain and higher feed conversion ratio (P < 0.05) was observed in birds fed the Control compared to Monensin and OE groups. Performance of birds fed OE or Monensin was similar throughout the trial. The apparent ileal digestibility of crude protein was higher in birds fed Monensin than Control treatment (P < 0.05). No significant changes on bacterial composition at a family level were observed in the caeca of birds fed the experimental diets. Moreover, no significant differences on plasma and intestinal bile acid composition were observed among treatments. Birds fed the OE showed a significant decrease of IL-8 expression in the ileum (P < 0.05). Additionally, the expression of TGF-β4, and Bu-1 was significantly upregulated (P < 0.01) in broilers fed the OE and Monensin diets compared to those fed the Control. In conclusion, the inclusion of 750 ppm of a bioactive olive pomace extract from Olea europaea in broiler chicken diets improved animal growth likely as result of its anti-inflammatory properties.

Keywords: broiler chicken; gut function; immune response; olive extract; performance.

Figure 1

Effects of feeding broiler chicken diets supplemented with 100 ppm of monensin or 750 ppm of OE on the relative abundance of bacteria families in caecal content (n = 6). Control, negative control with no additives; Monensin, basal diet supplemented with 100 ppm of monensin; OE, basal diet supplemented with 750 ppm of OE.

Figure 2

Effects of feeding broiler chicken diets supplemented with 100 ppm of monensin or 750 ppm of OE on the relative diversity of caecal microbiota (Shannon index) (n = 6). Control, negative control with no additives; Monensin, basal diet supplemented with 100 ppm of monensin; OE, basal diet supplemented with 750 ppm of OE.

Figure 3

Effects of feeding broiler chicken diets supplemented with 100 ppm of monensin (Monensin) or 750 ppm of OE (OE) on the expression of selected genes in the ileum. Gene expression values are fold change relative to the mRNA levels in the control diet (C) set to be 1.0 (horizontal axis). Bars indicate the 95% confidence interval (Fold change up—Fold change low) (n = 12; *: P < 0.05; **: P < 0.01; ***: P < 0.001).