Efficacy of Endo-Fighter for Reducing Severity of Tall Fescue Toxicosis in Beef Cattle1

A field trial and 2 grazing experiments were conducted to determine the efficacy of Endo-Fighter (ADM Alliance Nutrition Inc., Quincy, IL), a product designed for cattle grazing wild-type endophyte-infected tall fescue (Lolium arundinaceum). A 126-d (June 1 to October 5) field trial with beef (Bos taurus) steers (BW  =  275 ±  2.3 kg) had 2 treatments: a control (n = 53; MasterGain mineral, ADM Alliance Nutrition Inc.) and Endo-Fighter (n = 67; MasterGain mineral with Endo-Fighter). There was no difference (P > 0.05) in BW gain between the control and Endo-Fighter treatments. During midday, more (P < 0.01) steers receiving Endo-Fighter were observed grazing than control steers. Two 84-d grazing experiments were conducted, in yr 1 (August 24 to November 17) with crossbred heifers (n = 60; BW = 325 ± 17 kg) and in yr 2 (June 14 to September 7) with crossbred steers (n = 60; BW  =  (267 ± 18 Jesup' wild-type endophyte-infected tall fescue pastures were used in each experiment. Cattle were allotted to pastures with 4 animals/1.2-ha paddock and with 5 replications/treatment. Mineral treatments were as follows: 1) MasterGain (control); 2) Endo-Fighter; and 3) a prototype (ADM Alliance Nutrition Inc.). Mineral consumption and grazing behavior were determined at 14-d intervals. Animals were weighed to determine ADG. Blood serum prolactin was measured at each weighing day. Animal performance and prolactin concentration were not affected (P > 0.05) by feeding Endo-Fighter or the prototype in either grazing experiment. Consumption of Endo-Fighter altered animal grazing behavior, but did not affect the BW gain of cattle consuming wild-type endophyte-infected tall fescue.