Submitted to: Joint Meeting of the ADSA, AMSA, ASAS and PSA
Publication Type: Abstract Only
Publication Acceptance Date: 2/13/2007
Publication Date: 7/11/2007
Citation: Caldwell, J.D., Coffey, K.P., Coblentz, W.K., Ogden, R.K., Looper, M.L., Kreider, D.L., Jennings, J.A., Hubbell, D.S., Hess, T.W., Rosenkrans, 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 [abstract]. Joint Meeting of the ADSA, AMSA, ASAS and PSA. Journal of Animal Science (supplement 1). 85:498.
Technical Abstract: Fall-born calves grazing Neotyphodium coenophialum-infected tall fescue [E+) should benefit from early weaning because of reduced exposure to E+ toxins, but our previous research has not supported this hypothesis. Gelbvieh × Angus calves (n=238) were used in a 3-yr study to determine the optimal time to wean fall-born calves grazing E+ pastures. Cow-calf pairs were allocated randomly by weight and age to one of four weaning dates: 1) March 13 (177 d of age; MrW), 2) April 13 (204 d of age; ApW), 3) May 11 (236 d of age; MyW), and 4) June 8 (264 d of age; JuW). At weaning, calves were weighed, vaccinated, blood collected, and calves were moved to a 3.2-ha pasture adjacent to their dams. After 14 d, blood samples were collected a second time, and calves were weighed and moved directly to wheat (MrW and ApW) or bermudagrass (MyW and JuW) pastures. Calf BW did not differ (P>0.21) among treatments on the earlier weaning dates, but BW on the June weaning date, actual and 205-d adjusted weaning BW, ending BW (14 d following the June weaning date), and BW change between the March and June weaning dates increased linearly (P<0.05) across treatments. Response to bovine virus diarrhea and infectious bovine rhinotracheitis vaccination measured 14-d post-weaning increased (P<0.05) linearly, and that of bovine respiratory syncytial virus increased (P<0.05) linearly and quadratically across treatments. Total antioxidant potential at weaning and change during weaning increased (P<0.05) linearly across treatments. Predominantly linear trends were observed (P<0.05) across treatments for various serum minerals and red and white blood cell counts. Delaying the weaning of fall-born calves grazing E+ pastures until early June may be beneficial for calf growth and immune function.