|Hubbell Iii, Donald|
Submitted to: Journal of Animal Science
Publication Type: Abstract Only
Publication Acceptance Date: 11/19/2007
Publication Date: 3/17/2008
Citation: Caldwell, J.D., Coffey, K.P., Coblentz, W.K., Jennings, J.A., Hubbell Iii, D.S., Kreider, D.L., Rosenkrans, C.D. 2008. Post-Weaning Performance of Fall-Born Beef Steers Weaned from Endophyte-Infected Tall Fescue Pastures on Different Dates in the Spring. Journal of Animal Science. 86 (e-Supplement 3): 91.
Technical Abstract: Earlier weaning of fall-born calves grazing Neotyphodium coenophialum-infected tall fescue (E+) in the spring should reduced exposure of those calves to E+ toxins, resulting in improved long-term animal performance. However, a previous study did not support this hypothesis. A total of 118 Gelbvieh × Angus crossbred steer calves were used in a 3-yr study to determine the optimal time to wean fall-born calves grazing E+ fescue. Fall-calving cow-calf pairs were allocated randomly by weight and age immediately prior to the onset of calving to one of four weaning dates: 1) March 16 (177 d of age; MarW), 2) April 13 (204 d of age; AprW), 3) May 11 (236 d of age; MayW), and 4) June 8 (264 d of age; JuneW). The MarW and AprW calves were moved to wheat pasture whereas MayW and JuneW where moved to bermudagrass pastures following a 14-d fence-line weaning program. Steer BW at weaning increased (P<0.001) linearly across weaning dates and tended to increase (P=0.06) linearly at the time they were shipped to a feedlot, but steer BW at the end of the feedlot period and average daily gain during the feedlot period did not differ (P>0.19) across weaning dates (MarW 592, 1.8; AprW 577, 1.8; MayW 597, 1.8; and JuneW 609, 1.9 kg, respectively). Hot carcass weight tended to increase (P=0.10) in a linear manner across weaning dates. Quality grade did not differ (P=0.84) across weaning dates, with 47% of the steers grading choice and 53% grading select. Yield grade, and during the first 2 yr of the study, ribeye area, and marbling score did not differ (P>0.12) across weaning dates, but backfat thickness tended to increase (P=0.09) linearly across weaning dates. Therefore, weaning of fall-born steer calves from E+ pastures later may have short-term benefits, but those benefits may not persist throughout a feedlot period.