Effects of Stocking Rate and Corn Gluten Feed Supplementation on Growth and Intake of Bred Heifers Grazing Stockpiled Tall Fescue-Red Clover Forages During Winter

Abstract

Two 30-acre fields at the Iowa State University Beef Nutrition Farm were seeded with ‘Fawn’ endophyte-free tall fescue and red clover in 2000. In 2001 (yr 1) and 2002 (yr 2), forage was harvested from these fields as hay in two cuttings and stockpiled for winter grazing beginning in early August. Each field was divided into four pastures of 6.25 or 8.75 acres subdivided into 8 paddocks. On November 7 and October 23 of yr 1 and 2, 24 Angus and Angus x Simmental heifers in mid-gestation were allotted to the eight pastures to strip-graze stockpiled forage and 8 similar heifers were placed in a dry lot to be fed hay. Corn gluten feed was supplemented to heifers in pastures at each stocking rate and in the two dry lots at levels to meet the target weight gains for pregnancy and growth while heifers in the remaining pastures were supplemented at levels to meet the target weight gains for pregnancy only. Mean seasonal concentrations of in vitro digestible dry matter (IVDMD) were greater (P < 0.05) and concentrations of neutral detergent fiber (NDF), acid detergent fiber (ADF), and acid detergent insoluble nitrogen (ADIN) were lower (P < 0.05) in stockpiled forage than hay. Average daily gains and body condition score increases of heifers grazing stockpiled forage were greater (P < 0.05) than heifers fed hay in a dry lot even though heifers grazing stockpiled forage required 49 and 90% less corn gluten feed at the high and low stocking rates in yr 1 and required no corn supplementation while heifers in the dry lot required 1.8 lb/day in yr 2. Mean production costs were $0.86, $0.87, $0.64, $0.65, and $1.17 /heifer/day for heifers grazing stockpiled forage at the low stocking rate at the low or high level of corn gluten feed, grazing stockpiled forage at the high stocking rate at the low or high level of corn gluten feed, or fed hay and corn gluten feed at the high level.