Effects of overseeding red clover in endophyte-infected tall fescue pastures on steer physiology and performance

Abstract

The objective of this research was to determine the effects of overseeding red clover on cattle grazing endophyte-infected tall fescue (E+ TF) pastures. A grazing study was conducted in the springs of 2016 (75 d) and 2017 (61 d). Before the start of the study, four 3-ha pastures with cool-season grass (predominately E+ TF) were blocked and randomly assigned to a control treatment (TF CON) or a broadcasted red clover treatment (TF+RC). Steers (n = 6 tester steers per pasture) were allocated to each pasture by BW. Pastures were divided into two 1.5-ha paddocks to allow for 14-d rotational put-and-take stocking. Serum prolactin was assayed on the last day of grazing, and selected tester steers from each pasture (n = 3) were moved to pens for Doppler ultrasound measurements, 7 d after grazing. Data were analyzed by repeated measures using the mixed procedure of SAS. Red clover was successfully established in TF+RC pastures (2016: 36% and 2017: 57%, pasture ground cover). The TF+RC pastures had less ADF and NDF and more true in vitro digestible DM than TF CON pastures after grazing ( P < 0.01, in all cases). However, there was no effect of TF+RC on forage mass ( P = 0.08) or pasture carrying capacity ( P = 0.19). Steers grazing TF+RC pastures had 53% and 58% greater ADG ( P = 0.03) and BW gain per hectare ( P = 0.01) than TF CON steers, respectively. Serum prolactin at the termination of grazing was almost 3 times greater in TF+RC steers than in TF CON steers ( P = 0.01). Additionally, 7 d after grazing, TF+RC steers had 44% larger caudal artery luminal areas than TF CON steers ( P < 0.01). Overseeding red clover in E+ TF pastures is an effective strategy for reversing the adverse effects of fescue toxicosis and improving cattle performance.