Growth of yearling horses compared to steers on high-and low-endophyte infected tall fescue

Abstract

A grazing study was conducted to determine whether grazing endophyte-infected tall fescue (Festuca arundinacea Schreb.) will adversely affect the growth and development of horses. Average daily gain (ADG), change in wither height, and rectal temperature were measured for yearling horses grazing paddocks with either high- or low-endophyte infection levels (≥ 75% or ≤ 25%). Yearling steers were grazed in paddocks of similar infection levels as a control group for comparing ADG and rectal temperature. Average daily gain for yearling horses on the high-infection level (.24 kg) was lower (P <.01) than for those on the low-infection level (.56 kg). Steer ADG was .23 and .69 kg for the high and low infection levels, and horse ADG was not different (P >.10) from that of the steers for either the high or low infection levels. Change in wither height for horses, and rectal temperatures for both horses and cattle did not differ between the high- and low-infection levels. Results of this study indicated that weight gain by homes grazing endophyte-infccted tall fescue can be reduced to a similar extent as that of cattle.