Beef production. The 7 yearlings gained an average of 121 lbs during the 14 weeks of finishing. The average liveweight was 1,049 lbs at slaughter with a dressed carcass of 61 percent (Table 1). After one week of cooled hanging, the standard-grade beef had a respectable rating of 6 for tenderness, juiciness and no off flavor (Earl Wright, Tallgrass Prairie Producers, 11/25/96). The average daily weight gain during various stages of production was 1.6-1.9 lbs (Table 1), typical of rangeland beef operations (Bock et al. 1991).
The 14 acres of high TDN forages provided an average of 2.0 acres per yearling, or a gain of 60 lbs per acre. Our acreage per head is within the reported range of 2.0-2.5 acres of row crop stubble per overwintering calf or cow in several experiments, but the overwintering cattle received feed supplements while our yearlings on green crops without supplements (Larson 1995; Klopfenstein 1994). Our gain per acre is half the gain of 120 lbs per acre for steers finished during an equivalent period at a stocking rate of 1 acre per head with two rotations of grazing on pasture of mixed tall fescue-legume species in central Missouri (Martz et al. 1996). The larger gain in the Missouri study was most likely due to the greater precipitation resulting in more forage. Their daily rate of gain was 1.2 lbs per head, much lower than the 1.6 lbs per head during our finishing period (Table 1).
Based on the oven-dry weights of the clipped, ungrazed forages and the literature values of their TDN contents, the four high TDN forages in our study provided the following percentages of the total TDN consumed: cowpeas, 32; pearl millet, 30; eastern gamagrass, 24; and alfalfa aftermath, 14 (data not shown). Hence, it was not unreasonable to focus on cowpeas in our study of soil quality in the cropping system.