417 Citrus aurantium flavonoid extract modifies the gene expression in the rumen of genes related to inflammation and behavior in Holstein bulls fed high-concentrate diets

Abstract

Abstract One hundred forty-four bulls (164.8 ± 5.91 kg BW and 135 ± 7.2 d of age) were randomly allocated to one of 8 pens and assigned to control (C) or Citrus aurantium (BF, 0.4 kg of Bioflavex® CA per ton of concentrate). Each pen had one drinker, one separate straw feeder, and one three-space feeder where mash concentrate rich in corn, barley, DDG and wheat was offered. Concentrate intake was recorded daily, and BW and animal behavior by visual scan fortnightly. Animals were slaughtered after 168 d of study (12 periods of 14 d), HCW and carcass quality were recorded. Rumen wall samples were collected from 18 animals per treatment to analyze the expression of 15 genes associated with inflammation and behavior. Data were analyzed with ANOVA. In the rumen, the expression of free fatty acid receptor 2 (stimulates PPY and serotonin secretion), pancreatic polypeptide receptor 1 (acts asNPY and PYY receptor), cholecystokinin receptor 4 (is a CCK and gastrin receptor), Toll-like receptor-4 (pattern recognition receptor), IL-25 (proinflammatory cytokine) and β-defensin1 (antimicrobial peptide) were greater (P < 0.05) in C compared with BF bulls (P < 0.05). Moreover, the expression of all bitter taste receptors (TAS2R, member 7, 16, 38 and 39) which are related with eating modulation and immune function were lesser (P < 0.05) expressed in BF compared with C bulls (P < 0.05). The supplementation with citrus flavonoids in these bulls fed high-concentrate diets tended (P < 0.10) to improve concentrate efficiency, reduced oral non-nutritive behaviors, agonistic interactions and sexual behaviors. The reduction on TAS2R expression is indicative of an inhibition of bitter taste receptor function by BF and the expression increase in the other genes could explain the changes observed on animal behavior within the gut-brain axis paradigm.