Supplementing Citrus aurantium Flavonoid Extract in High-Fat Finishing Diets Improves Animal Behavior and Rumen Health and Modifies Rumen and Duodenum Epithelium Gene Expression in Holstein Bulls

Simple Summary Today, the commitment of beef production systems is to enhance their sustainability. Therefore, improving animal welfare and improving feed efficiency are both important challenges. Citrus flavonoids are polyphenols that have previously shown promising effects on reducing feed intake and modulating animal behavior in bulls fattened under commercial conditions. Moreover, increasing fat during the finishing phase in beef cattle diets has been used to increase dietary energy content and to reduce the risk of rumen acidosis. Therefore, the present study supports the hypothesis that a high dietary fat content does not interfere in the mode of action of these flavonoids and that the positive effects on feed efficiency and animal behaviors should be observed. Nevertheless, the mode of action of flavonoids is not known; it is speculated that digestive tract health (rumen) and changes in the expression of behavior- and inflammation-related genes (rumen and duodenum) may be involved, and dietary fat supplementation may also affect, antagonistic to flavonoids, these mechanisms. However, the present study data support that citrus flavonoid supplementation in high dietary fat diets may be a good strategy to face current beef production system challenges such as improving feed efficiency and animal welfare. One hundred and forty-six bulls (178.2 +/- 6.64 kg BW and 146.0 +/- 0.60 d of age) were randomly allocated to one of eight pens and assigned to control (C) or citrus flavonoid (BF) treatments (Citrus aurantium, Bioflavex CA, HTBA, S.L.U., Barcelona, Spain, 0.4 kg per ton of Bioflavex CA). At the finishing phase, the dietary fat content of the concentrate was increased (58 to 84 g/kg DM). Concentrate intake was recorded daily, and BW and animal behavior by visual scan, fortnightly. After 168 d, bulls were slaughtered, carcass data were recorded, and rumen and duodenum epithelium samples were collected. Performance data were not affected by treatment, except for the growing phase where concentrate intake (p < 0.05) was lesser in the BF compared with the C bulls. Agonistic and sexual behaviors were more frequent (p < 0.01) in the C than in the BF bulls. In the rumen epithelium, in contrast to duodenum, gene expression of some bitter taste receptors (7, 16, 39) and other genes related to behavior and inflammation was higher (p < 0.05) in the BF compared with the C bulls. Supplementing citrus flavonoids in high-fat finishing diets to Holstein bulls reduces growing concentrate consumption and improves animal welfare.

Automated summary

This study found that supplementing citrus flavonoids in high-fat diets for beef production can reduce feed intake and improve animal welfare. The positive effects may be attributed to the regulation of digestive tract health and gene expression.