THE VALUE OF CREEP FEEDING DURING THE LAST 84, 56, OR 28 DAYS PRIOR TO WEANING ON GROWTH-PERFORMANCE OF NURSING CALVES GRAZING ENDOPHYTE-INFECTED TALL FESCUE

To evaluate limiting the number of days that calves are creep fed, 84 crossbred cows (frame score 4) nursing steer calves were randomly assi gned to three replicates over 2 yr to receive one of four lengths of c reep feeding (0, 28, 56, or 84 d) for cows and calves grazing endophyt e-infected tall fescue. There were no differences in cow performance d ue to treatments. Calf daily gain increased (P < .001) as the length o f time exposed to creep increased. In yr 1, creep intake increased (P < .05) as the length to time exposed to creep increased. In yr 2, ther e was no difference in intake by period among 28-, 56-, and 84-d treat ments. Supplemental feed efficiency was best for 56 and 84 d, and the 28-d treatment was extremely poor. During the feedlot phase, there wer e differences in performance between the 2 yr and there were no differ ences in carcass composition due to length of time receiving creep fee d. Overall, creep feeding calves for 56 or 84 d improved performance, and the 56-d calves had the most efficient gain. Creep feeding calves for 28 d showed no advantage during the creep feeding period or in the feedlot. Four ruminally fistulated nursing steer calves were used in a 4 X 4 Latin square design to receive treatments of forage alone or . 68 kg, 1.13 kg, or 2.27 kg/d of creep plus high-quality, freshly harve sted forage available on an ad libitum basis. Forage OM intake and NDF digestibility tended (P = .11) to decrease as intake of creep feed in creased. The pH decreased (P < .001), molar proportion of propionate t ended to increase (P = .06), and acetate tended to decrease (P = .07) as the level of creep feed intake increased. Higher levels of creep fe ed tended to cause a decrease in ruminal fiber digestibility and forag e intake. Creep feeding calves for 56 or 84 d improved gain; 56 d had the most efficient supplemental gain. Creep feeding calves for 28 d sh owed no advantage during the creep feeding period or in the feedlot.