Ruminal motility, reticulo-ruminal fill and eating patterns in steers exposed to ergovaline

Authors: AHN, GYUCHUL - University Of Kentucky; RICCIONI, KARA - University Of Kentucky; AVILA, SUELEN - University Of Kentucky; Klotz, James; HARMON, DAVID - University Of Kentucky

Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/17/2019
Publication Date: 12/18/2019
Citation: Ahn, G., Riccioni, K., Avila, S., Klotz, J.L., Harmon, D.L. 2019. Ruminal motility, reticulo-ruminal fill and eating patterns in steers exposed to ergovaline. Journal of Animal Science. 98(1):1-11. https://doi.org/10.1093/jas/skz374.
DOI: https://doi.org/10.1093/jas/skz374

Interpretive Summary: Cattle suffering from ergotism or fescue toxicosis exhibit significant drops in feed intake. This causes significant drops in body weight gain and can lead to substantial financial loss. Ergot alkaloids are the toxins that cause this problem and are known to alter smooth muscle function. Thus, it was hypothesized that these toxins could alter digestive smooth muscle function and digestive motility causing the aforementioned decrease in feed intake in cattle. Several experiments were conducted using numerous dosages and durations of toxin exposure while measuring reticuloruminal motility. The data in this paper demonstrate that ergot alkaloid exposure does change ruminal motility and slow eating patterns. These data contribute to our understanding of this applied aspect of fescue toxicosis and will benefit scientists conducting future research on how to mitigate this problem.

Technical Abstract: Fescue toxicosis is problematic for growing steers, causing lower DMI and productivity when fed endophyte-infected (E+) tall fescue. A complete understanding of underlying mechanisms of how fescue toxicosis affects growing steers is lacking. Therefore; the overall objective of this multi-experiment study was to determine if ruminally dosed ergovaline (ERV) impacts rumen motility, rumen contents and eating patterns. In Exp. 1, an 8-h period of rumen motility collection began 4 h after feeding by monitoring pressure changes using a wireless system for 21 d. Eight cannulated steers (283 kg BW) were pair-fed with alfalfa cubes (1.5 × NEm) and assigned to endophyte-free (E-; 0 µg ERV/kg BW) or E+ treatment (20 µg ERV/kg BW). Overall, E+ steers had more frequent rumen contractions (Seed P = 0.05 and day of feeding P = 0.02). On d 7 to 9, both treatments showed lower frequencies and E- steers had greater amplitude of contractions (P < 0.001) that corresponded with decreased DMI. In Exp. 2, steers remained in pairs assigned in Exp. 1 (322 kg BW), but reversed seed treatments while increasing ERV levels (titrated 0, 5, 10, 15 and 20 µg ERV/kg BW over 57 d). There were no differences between E- and E+ for frequency (P = 0.137) or amplitude of contractions (P = 0.951), but increasing ERV dosage, decreased frequency (P = 0.018) and amplitude (P = 0.005), coinciding with lower DMI. In Exp. 3, 8-steers (589 kg) were pair-fed and ruminally dosed 15 µg ERV/kg BW and rumen motility data was collected for 21 d. E- steers showed higher amplitude and lower frequency of contractions than E+ steers with seed (P < 0.0001), day (P < 0.001) and seed × day (P < 0.04) effects, but rumen fill was not different between E- and E+ (P > 0.29). Serum prolactin concentrations were lower in E+ steers in Exp. 1 to 3. Eating patterns of pair-fed E- and E+ steers were relatively slower in E+ than E- (Exp. 4) by measuring every 2 h across 24 h. Number of meals were higher in E+ than E- steers, but meal duration and meal size were not different between treatments. Rumen content (DM%) tended to be higher in E+ than E- when steers were fed once a day (P = 0.07), but there was no difference for rumen content (DM%) when E- and E+ steers were fed 12 times a day (P = 0.13). These results suggest the changes in rumen fill associated with fescue toxicosis may be driven more by changes in feeding behavior and eating pattern rather than by changes in motility.