Submitted to: Journal of Endocrinology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/17/1999
Publication Date: N/A
Interpretive Summary: Tall fescue is the predominant cool season grass in the humid pasture region of the eastern United States. Unfortunately, from an animal perspective, most of the 14 million hectares are infected with a fungus that produces chemical compounds that result in reduced animal performance which results in an estimated loss of over $600 million annually. Challenges to the immune system, such as might occur while grazing endophyte-infected tall fescue, can result in increase in one, or more often, all of the pro- inflammatory cytokines (interleukin-1, interleukin 6, and tumor necrosis factor-alpha). Results of this research showed that animals grazing endophyte-infected tall fescue did exhibit increased tumor necrosis factor-alpha when given lipopolysaccaride which suggests that exposure to endophyte-infected tall fescue and another immune challenge could result in more serious deleterious effects than when exposed to either one independently.
Technical Abstract: Fescue toxicosis in cattle is a result of consumption of ergot alkaloids found in endophyte-infected (E+, Neotyphodium coenophialum) tall fescue (Festuca arundinacea). The condition is characterized by pyrexia, decreased weight gains, rough hair coats, and decreased calving rates. The objective of this experiment was to investigate whether steers grazing E+ fescue have altered host response to lipopolysarcharride (endotoxin, LPS) challenge compared to steers grzing endophyte-free (E-) fescue. Angus steers (n=8) had continuously grazed either E+ (n=4) or E- (n=4) tall fescue for eight months prior to the experiment. The E+ steers had lower body weight, depressed average daily gain (ADG), and decreased basal serum prolactin (PRL) compared to the E- steers prior to LPS administration. Each steer received a single i. v. injection of LPS (0.2 ug/kg BW; Escherichia coli: 026:B6) dissolved in sterile saline and blood was serially collected every 30 min for 4 h and at 24 h post LPS administration. Lipopolysaccharide increased serum tumor necrsis factor alpha (TNF-alpha), cortisol, and haptoglobin (Hp) but decreased plasma glucose and insulin-like growth factor-1 (IGF-1). Importantly, however, TNF-alpha, cortisol, and IGF-1 responses to LPS were greater in E+ compared to E-. These results indicate that animals grazing E+ fescue had altered integrated metabloic host response compared to animals grazing E- fescue. Potentially, combined exposure to E+ fescue and LPS, could have greater deleterious effects to the animal compared with exposure to only one of the two and would likely lead to increased catabolism.