Performance of Sheep Grazing Tall Fescue Cultivars Containing Non-Ergovaline Producing Endophytes

Fescue toxicosis is one of the costliest animal disorders facing the livestock industry in the eastern United States, affecting over 8.5 million cattle and costing the United States beef industry nearly US $2 billion annually in lost revenue due to reduced reproductive and growth rates in cattle herds.  An study was conducted to determine the effects of  tall fescue (Festuca arundinacea Schreb.) containing wild-type ergovaline producing endophyte (Kentucky 31 E+), cultivars containing non-ergovaline producing endophyte (Martin 2 PROTEK, Martin 2 ISO 207, Duramax Gold), and tall fescues containing no endophyte (Martin 2, Au Triumph).  Three Polypay yearling ewes were assigned to one of 6 different pasture treatments containing either ergovaline producing endophyte, non-ergovaline producing endophyte or non-endophyte cultivars in 0.1 hectare replicated pasture treatments.  The 36 ewes were evaluated for changes in body weight, serum prolactin, and rectal temperatures during three grazing periods over three years (2009 to 2011) to determine animal performance and evaluate fescue toxicosis.  The nutritional quality of endophyte-infected tall fescue was shown to be comparable to other tall fescues that did not contain the Epichloë endophyte.  Ergovaline was only detected in the Kentucky 31 E+ forage, when sampled during each year of each grazing period (139 ppm).  Pre-treatment sheep body weight did not differ (P<0.9948) among treatments.  Mean total weight gain (P=0.0039) and mean average daily gain (P=0.0026) was lower for Kentucky 31 E+ compared to all other treatments.  Pre-treatment serum prolactin concentration did not differ (P=0.5526) among treatments.  Post-treatment prolactin level showed a highly significant effect in the 3-year mean (P<0.0001).  Serum prolactin concentrations in sheep consuming wild-type endophyte fescue were lower than those sheep consuming endophyte fescues that did not produce the ergovaline at detectable levels.  No differences in rectal temperatures were observed, either; pre-treatment (P=0.8404), treatment (P=0.7180), or post-treatment (P=0.5905).  However,  rectal temperature measurements can be subjected to confounding variables, such as sheep handling stress, and ambient air temperature.  Sheep grazing tall fescue cultivars inoculated with endophytes not producing ergovaline displayed total weight gains similar to sheep consuming cultivars not containing endophyte.  Lowered prolactin concentration and depressed weight gain of sheep grazing Kentucky E+ tall fescue indicates that the use of non-toxic endophyte tall fescue cultivars is a viable management strategy for minimizing the effects of tall fescue toxicosis.