Influence of protein supplementation and implant status on alleviating fescue toxicosis

Heat stress is a major problem in transporting stocker calves with symptoms of fescue toxicosis. Removing calves from tall fescue pastures and offerin g diets devoid of endophyte-infected tall fescue could reduce the severity of toxicosis and precondition calves for transport to the feedlot. In the p resent experiment, a pasture phase was used to condition yearling steers to grazing tall fescue and induce symptoms of fescue toxicosis, and a pen pha se followed to determine effects of implanting at the start of grazing and protein supplementation (hay only vs hay plus supplement) on shortterm chan ges in rectal temperature and serum prolactin concentration Neither implant status nor protein supplementation affected (P > 0.10) white blood cell co unt or rectal temperature. White blood cell counts at the conclusion of the pasture phase averaged 8,778 cells/muL and were within a range indicating no immunological response. Changes in rectal temperature and serum prolacti n concentration during the pen phase were not influenced (P > 0.10) by impl anting or supplementation. Initial, rectal temperatures for the pen phase w ere high (39.9 degreesC) but declined linearly (P < 0.001) over the first 1 06 h and were below a normal temperature (39.2<degrees>C) by 82 h following removal from tall fescue pastures. Serum prolactin gradually increased (P < 0.001) to a peak by 82 h and stabilized thereafter. Results indicate that neither supplemental protein nor an estrogenic implant influenced recovery indices of fescue toxicosis, whereas removing calves from tall fescue past ures and excluding dietary tall fescue for 3 to 4 d may alleviate symptoms of fescue toxicosis.