Alleviating Tall Fescue Toxicosis in Stocker Cattle Using Non-toxic Endophytes

To address the problem of fescue toxicosis in grazing cattle, non-toxic endophytes from New Zealand have been used to infect tall fescue varieties grown in Georgia. The objectives of the present study were to determine animal performance and evaluate toxicosis in stocker steers and heifers grazing non-toxic endophyte-infected (AR542), endophyte-free (EF), or wild-type endophyte-infected (EI) Jesup and Kentucky-31 (KY31) tall fescue. Replicated (n=2) 2-ac tall fescue paddocks were established at the Central Georgia Branch Station near Eatonton, GA and at the Northwest Georgia Branch Station near Calhoun, GA. Animals were stocked on the paddocks using put-and-take grazing management during Spring 1999, Autumn 1999, and Spring 2000. D-14+ serum prolactin (PRL) was depressed (P < 0.05) on the EI paddocks compared to the AR542 and EF paddocks in the autumn grazing season at Eatonton and during both spring and autumn at Calhoun. No significant (P > 0.05) differences were found in d-14+ rectal temperatures among the three treatments at either location, however, signs of heat stress were observed in the EI animals during periods of high ambient temperature. Average daily gain per head was significantly higher (P < 0.05) on the AR542 and EF paddocks than on the EI paddocks during spring and autumn at both locations. Similarly, gain per ac was significantly higher (P < 0.05) on the AR542 and EF paddocks than on the EI paddocks during the spring and autumn grazing seasons in both the central and northwest Georgia trials. These results suggest that incorporating non-toxic endophytes into tall fescue forage systems in Georgia is a promising alternative for combating fescue toxicosis in stocker cattle.