Effects of Clipping Heifer Hair Coats on Vaginal Temperatures and Performance of Fall-Born Heifers Stocked on Toxic Endophyte-Infected Tall Fescue During the Summer

Abstract

Achieving satisfactory levels of weight gain for developing replacement beef heifers is challenging when utilizing toxic endophyte-infected tall fescue (Schedonorus arundinaceus) as the primary forage. This is due to the intensifying impact of ergot alkaloids produced by the fungal endophyte on heifer heat stress in the summer. The purpose of this trial was to determine if clipping hair coats would reduce heat stress impacts experienced by fall-born heifers stocked on toxic endophyte-infected tall fescue. Heifers were randomly assigned to a control cohort and a clipped cohort. The heifers in the clipped treatment group were sheared along the body of the heifer. Vaginal temperature loggers were used to record core temperatures every ten minutes during several sampling periods. Hair coats on clipped heifers resembled hair coats of the control heifers by the conclusion of the 16-week trial. Average daily gains of the clipped heifers exceeded the average daily gains of the control heifers only in the first four-week period. There were no differences in seasonal average daily gain or pregnancy rates. Clipped heifers had cooler core temperatures by 0.2–0.3 °C in the morning compared to the control heifers. Clipping hair coats of heifers only provided short-term relief for cattle stocked on toxic endophyte-infected tall fescue.