Mefluidide treatment of tall fescue pastures: intake and animal performance.

Twelve Hereford heifers were used in a grazing experiment to determine intake and digestibility of tall fescue forage treated with the plant growth regulator mefluidide. Additionally, steer and heifer performance were evaluated after grazing tall fescue pastures or consuming hay harvested from pastures treated with mefluidide. Average forage OM intake by heifers was 47% greater (P less than .05) during July and 50% greater (P less than .05) during August for mefluidide-treated pastures than for untreated pastures. In vitro OM digestibility and indigestible ADF were compared for their ability to predict forage intake. The in vitro digestibility method produced more realistic intake data than the indigestible ADF method; however, trends in estimated forage intake were similar for both methods. Total tract particulate matter passage rates were similar (P greater than .10; 4.5 vs 4.1%/h), but mean retention times were shorter (P less than .05; 37.0 vs 46.9 h) when heifers grazed mefluidide-treated tall fescue. Steers grazing mefluidide-treated forage had greater (P less than .05) total weight gains than did steers grazing untreated tall fescue during a 168-d study (86 vs 69 kg). Heifers fed hay harvested from mefluidide-treated pastures also exhibited similar improvements in gain (49 vs 38 kg) because of increased (P less than .05) forage consumption (8.3 vs 7.3 kg/d) and greater (P less than .05) forage OM digestibility (65 vs 61%). Mefluidide treatment of tall fescue in early spring prolonged higher-quality herbage into midsummer and resulted in greater forage intake and animal performance.