Feed intake component of fescue toxicosis during short-term exposure to thermoneutral and heat stress conditions

Abstract

[ACCESS RESTRICTED TO THE UNIVERSITY OF MISSOURI AT AUTHOR'S REQUEST.] Fescue toxicosis is results from intake of tall fescue grass containing a fungal endophyte. It affects most of herbivore species, including rodents. The estimated annual loss due to decreased production and performance is more than $600 million. A large portion of this loss is due to reduced feed intake. The current study used the rat to determine if reduced feed intake contributed to many of the symptoms associated with fescue toxicosis. Animals were tested in both heat stress and non-heat stress environments. Feed intake decreased in rats fed the diet containing endophyte in both environments, with a greater reduction during heat stress. Core body temperature actually decreased slightly in the non-heat stress environment for rats on the endophyte diet. Reduced feed intake alone actually produced a greater reduction in body temperature. During heat stress, the rats fed the endophyte diet shifted its body temperature rhythm to a higher level. This did not occur for rats fed the reduced diet. Serum prolactin level was reduced for all rats fed the endophyte diet below the level for controls and those fed the reduced diet. The present study determined which symptoms associated with fescue toxicosis could be explained by reduced feed intake and which could not be explained using this approach.