ARS | Publication request: Post-weaning performance of fall-born beef steers weaned from endophyte-infected tall fescue pastures on different dates in the spring.

Submitted to: Arkansas Agricultural Experiment Station Research Series
Publication Type: Experiment Station
Publication Acceptance Date: July 15, 2008
Publication Date: December 1, 2008
Citation: Caldwell, J.D., Coffey, K.P., Coblentz, W.K., Ogden, R.K., Jennings, J.A., Hubbell, D.S., Krieder, D.L., Rosenkrans, C.F. 2008. Post-weaning performance of fall-born beef steers weaned from endophyte-infected tall fescue pastures on different dates in the spring. Research Series 563. Arkansas Animal Science Department Report 2008. (11):35-36.

Technical Abstract: Weaning fall-born calves grazing tall fescue infected with the toxic wild-type endophyte (E+) prior to early May should reduce exposure of those calves to E+ toxins, resulting in improved long-term animal performance. However, a previous study did not support this hypothesis. Gelbvieh × Angus crossbred steer calves (n = 118) 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 by weight and age immediately prior to the onset of calving to 1 of 4 weaning dates: 1) March 16 (177 ± 4.7 d of age; MarW), 2) April 13 (204 ± 4.7 d of age; AprW), 3) May 11 (236 ± 4.7 d of age;MayW), and 4) June 8 (264 ± 4.7 d of age; JuneW). The MarW and AprW calves were moved to wheat pasture whereas MayW and JuneW were moved to bermudagrass pastures following a 14-d fence-line weaning program. Steer BW at weaning increased (P < 0.05), and BW at feedlot shipment tended to increase (P = 0.06) linearly across weaning dates, but steer BW at the end of the feedlot period and ADG during the feedlot period did not differ (P = 0.19) across weaning dates. Hot carcass weight and backfat tended to increase (P = 0.10) linearly across weaning dates. Therefore, weaning fall-born steer calves from E+ pastures later had short-term benefits, but these BW benefits did not persist during the feedlot period.