Protein sources for finishing calves as affected by management system

Two beef production systems were evaluated in conjunction with an evaluation of escape protein sources for finishing calves. Two hundred forty crossbred steers and 80 crossbred heifer calves (BW = 267 +/- 2 kg) were split into two groups: 1) control, finished (207 d) after a 3-wk feedlot adjustment period and 2) grazing cornstalks for 74 d after a 3-wk feedlot adjustment period, then finished (164 d). Finishing treatments were sources and proportions of supplemental CP: 1) urea 100%; 2) soybean meal (SBM) 100%; 3) blood meal (BM) 50%, urea 50%; 4) feather meal (FTH) 50%, urea 50%; 5) SBM 50%, FTH 25%, urea 25%; 6) SBM 25%, FTH 38%, urea 37%; 7) FTH 25%, BM 25%, urea 50%, and 8) FTH 38%, BM 13%, urea 50%. Treatments 1 to 8 were fed in dry-rolled corn (DRC)-based diets. Treatments 9 and 10 were supplement Treatments 1 and 7 fed in diets based on high-moisture corn. Calves finished after a 74-d period of grazing cornstalks consumed more feed (P < .01) and gained faster (P < .01) but were less efficient (P < .05) than calves finished directly after weaning. Although not statistically different, calves finished after grazing cornstalks and supplemented with natural protein in the feedlot were 7% more efficient than calves supplemented with urea alone. Efficiency of calves finished directly after weaning was similar for calves supplemented with natural protein or urea alone. Supplementing SBM/FTH/urea or BM/FTH/urea improved feed efficiency compared with supplementing FTH/urea alone. These data suggest that allowing calves to graze cornstalks before finishing is a possible management option, but this system may require more metabolizable protein in the finishing diet to maximize feed efficiency if the calves are expressing compensatory growth.