Effects of supplemental encapsulated butyric acid and zinc on rumen morphometrics and small intestine histology of finishing lambs abruptly transitioned to a grain-based diet

The objective of this study was to determine if encapsulated butyric acid and zinc (BZ) fed to feedlot lambs abruptly transitioned to a grain-based diet influences rumen morphometrics and small intestinal histology. Polypay wethers (n = 84) were assigned to dietary treatment (CON: 0 g/kg BZ diet DM; BZ: 2 g/kg diet DM) in a randomized complete block design. Wethers were abruptly transitioned from a diet based upon grass hay (0.95 Mcal/kg NEg) to a finishing diet based upon whole corn (1.33 Mcal/kg NEg) upon study initiation. Four wethers were harvested on day (d) 0 to serve as a baseline, and the remaining 80 lambs were serially harvested on d 7, 14, 21, 56, and 63 (8 CON and 8 BZ per harvest date) for the collection of rumen, duodenum, and ileum samples. Rumen samples were stored in a 70% ethanol solution for storage until evaluation for papillae count, mean papillae area, and calculated rumen wall absorptive surface area. Duodenal and ileal samples were fixed in 10% neutral buffered formalin, embedded in paraffin, and stained with hematoxylin and eosin for microscopic evaluation of villus height, crypt depth, villi-to-crypt ratio, and mucosal thickness. Data were analyzed with individual wether as the experimental unit and fixed effects of treatment, harvest date, and their interaction. No treatment × day interactions (P ≥ 0.23) were observed for any variables. Additionally, BZ did not appreciably affect (P ≥ 0.26) any measures. A positive linear effect (P ≤ 0.04) of harvest date was observed for rumen papillae area, rumen papillae count, calculated rumen wall absorptive surface area, ileal villi height, ileal villi-to-crypt-ratio, and duodenal mucosal thickness. Supplemental dietary BZ had no effect on rumen morphometrics or small intestine histology in lambs abruptly transitioned from a forage- to grain-based diet. However, increasing days on a grain-based diet appears to affect these measures.

Key Words: butyric acid, histology, intestine, rumen, zinc.

Published in the proceedings of the 10th Symposium on Gut Health in Production of Food Animals 2022, St. Louis, USA.