Abstract
Fescue toxicosis is a syndrome common in cattle grazing fescue containing an endophyte that produces ergot alkaloids. Our lab has previously demonstrated that chronic exposure of ergot alkaloids adversely effects innate immune response. Therefore, the objective of this study was to examine changes in cytokine profiles in heat tolerant heifers exposed to ergot alkaloids from endophyte-infected fescue compared to wildtype controls. Angus X Senepol heifers were blocked by weight and hair coat genotype, Slick (S) or Normal (N) then randomly fed novel endophyte fescue (EN) or endophyte-infected fescue (EI) haylage in a total mixed ration for 63d (n=5 per group). Weekly measurements were collected to monitor physiological responses during exposure to ergot alkaloids. Blood samples were collected for cytokine analysis on d 0, 14, 28 and 56. Cytokine concentrations were quantified using Quantibody® Bovine Cytokine Arrays. Data were analyzed using PROC MIXED of SAS with repeated measures. Statistical significance was determined at P< 0.05 and a tendency at 0.05< P< 0.10. Concentrations of TNF were greater in EN-S heifers (6.57 ng/ml) compared to other heifer groups (P< 0.05; 1.33, 2.34, 3.15 ng/ml for EN-N, EI-S, and EI-N, respectively). Concentrations of IL21 were greater in EN-S heifers (8.15 ng/ml) compared to other heifer groups (P< 0.05; 1.55, 3.43, 3.26 ng/ml for EN-N, EI-S, and EI-N, respectively). Concentrations of IFNA (P=0.0543), IFNG (P=0.0558), IL1F1 (P=0.0587), and IL1F5 (P=0.0738) tended to be greater in in EN-S heifers compared to other heifer groups. Interestingly, concentrations of chemokine CCL4 (953.5 vs. 183.7 pg/mL) and CXCL9 (2.57 vs. 0.69 ng/mL) were significantly greater in S heifers than N heifers (P< 0.05). No differences were observed for IL13 and CXCL10 (P >0.05). In contrast to previous data, exposure to ergovaline via endophyte-infected fescue, did not induce an innate immune response. Rather, cytokine concentrations were elevated in heifers with the slick hair genotype. Overall, developing a better understanding of the interaction between ergot alkaloids and the slick hair genotype will help to improve cattle health management.