|Hubbell Iii, Donald|
|Rosenkrans, Jr., Charles|
Submitted to: Arkansas Agricultural Experiment Station Research Series
Publication Type: Experiment Station
Publication Acceptance Date: 8/15/2007
Publication Date: 12/15/2007
Citation: Caldwell, J.D., Coffey, K.P., Coblentz, W.K., Ogden, R.K., Jennings, J.A., Hubbell III, D.S., Kreider, D.L., Rosenkrans, Jr., C.F. 2007. Growth performance and immune function of fall-born beef calves weaned from endophyte-infected tall fescue pastures on different dates in the spring. Arkansas Agricultural Experiment Station Research Series 553. Arkansas Animal Science Department Report 2007. 10:70-72.
Technical Abstract: Fall-born calves grazing Neotyphodium coenophialum-infected tall fescue [Lolium arundinaceum (Schreb.; E+) Darbysh.] should benefit from early weaning because of reduced exposure to fungal toxins, but our earlier work did not support this theory. A total of 238 Gelbvieh x Angus calves were used in a 3-yr study to determine the optimal time to wean fall-born calves grazing E+ tall fescue. Cow-calf pairs were assigned to one of four 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 ± 4.8 d of age; JuneW). Body weight on the June weaning date, actual weaning weight, ending BW (14 d following the June weaning date), daily gain between birth and the ending date, and BW change between the March and June weaning dates increased linearly (P < 0.05) with delayed weaning date. Antibody titers to bovine virus diarrhea (BVD) and infectious bovine rhinotracheitis (IBR) at the time of weaning decreased in a linear manner (P < 0.05), and bovine respiratory syncytial virus (BRSV) antibody titers tended (P = 0.09) to increase cubically across weaning dates. Response to BVD and IBR vaccination measured 14-d post-weaning increased (P < 0.05) linearly and that of BRSV increased (P < 0.05) linearly and quadratically across weaning dates. Antibody titers changes for BVD and BRSV between weaning and the end of the study increased linearly (P < 0.05) and that for IBR (P < 0.05) increased linearly and quadratically. Therefore, delaying the weaning of fall-born calves grazing infected fescue pastures until early June may be beneficial for calf growth and immune function.