Behavior and inflammation of the rumen and cecum in Holstein bulls fed high-concentrate diets with different concentrate presentation forms with or without straw supplementation.

Twenty-four individually housed Holstein bulls (395 ± 7.3 kg BW and 252 ± 3.1 d age) were exposed to a 2 × 2 factorial design (meal vs. pellets; with vs. without straw) to evaluate the effect of concentrate form and provision of straw in finishing diets on behavior and expression of rumen and cecum epithelium genes related to inflammation and behavior. Concentrate and straw consumption were recorded monthly and behavior (self-grooming, social, oral nonnutritive, tongue rolling, eating, drinking, ruminating, and lying) was recorded every two weeks. Bulls were slaughtered after 64 d of exposure to treatments, lesions on the rumen and liver were assessed, and samples of the rumen and cecum were collected. Straw supplementation tended ( = 0.08) to increase concentrate intake (8.0 vs. 7.4 ± 0.26 kg/d), increased ( < 0.01) the proportion of time ruminating (9.4 vs. 3.1 ± 1.02%), and decreased ( < 0.01) the occurrence of oral nonnutritive behaviors (0.52 vs. 1.34 ± 0.123 times/15 min) relative to bulls deprived of straw. Provision of straw increased ruminal pH, but the magnitude of the change was greater when the concentrate was provided as meal compared with pellets (interaction, < 0.05). When straw was not supplemented, all rumen samples had papillae fusion, whereas only 16.7% of bulls fed pellets and straw had papillae fusions (interaction, < 0.05). Vacuole grading of the rumen papillae was less ( < 0.01) in bulls provided straw compared with bulls without straw. For the ruminal epithelium, straw provision tended to increase the relative expression ratio of (which stimulates peptide YY, PYY, and serotonin secretion; = 0.06) and α (which modulates immune reactions and behavior; = 0.09) and increased and (tight junction proteins; < 0.05), along with β and (proinflammatory cytokines; < 0.01) and ( < 0.01) in the rumen. Moreover, it also tended to increase the relative gene expression ratio of β (an antimicrobial peptide; = 0.10) and ( = 0.10). Bulls fed pellets had a decreased ruminal relative expression ratio of α ( < 0.05). Bulls without straw had increased ( < 0.05) the cecum relative expression ratio of β. In conclusion, the lack of straw supplementation in bulls fed high-concentrate diets modifies behavior and affects rumen macroscopic morphology and expression of epithelial genes that could be related to behavior and inflammation.