Alterations in bovine serum biochemistry profiles associated with prolonged consumption of endophyte-infected tall fescue.

Tall fescue (Festuca arundinacea) is a forage grass that is widely used in pastures in the eastern US for cattle, sheep and horses. The endophytic fungus Neotyphodium coenophialum is endemic in tall fescue pastures in the US. The turfgrass industry intentionally infects fescue cultivars with strains of the fungus to impart desirable growth and disease tolerance qualities to the plants. In contrast, ergot and pyrrolizidine alkaloid toxins produced by fungus-infected plants have been incriminated causally in bovine tall fescue toxicosis, a poorly defined syndrome of morbidity that occurs in cattle that consume endophyte-infected tall fescue (E+TF). We compared the serum biochemistry profiles from cattle that grazed E+TF with those from control cattle that grazed on endophyte-free tall fescue (E-TF). Cattle were bled on 7 dates from April 1 to August 30, 1996 and on 5 dates from May 1 to July 30, 1997. Cattle that grazed E+TF retained rough winter haircoats and had lesser weight gains, typical of tall fescue toxicosis, compared to those grazing E-TF. They had decreased activities of alkaline phosphatase and alanine aminotransferase. Compared to controls, they had lower values for serum prolactin and globulin concentrations. The concentration of creatinine and the albumin/globulin ratio were increased in the cattle grazing E+TF. Isozyme determination of alkaline phosphatase indicated that the decrease in serum activity of cattle grazing E+TF was due to decreases in both intestinal and bone isozymes. Serum protein electrophoresis indicated that the decrease in serum globulin concentration was due to decreases in both alpha and gamma globulin fractions of this protein. The data collected in these experiments add to our understanding of the alterations that occur in the serum chemistry profiles when cattle consume E+TF for prolonged periods of time.