|Hubbell Iii, Donald|
Submitted to: Livestock Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/21/2008
Publication Date: 11/3/2008
Citation: Coffey, K.P., Coblentz, W.K., Hellwig, D.H., Popp, M.P., Smith, T.F., Hubbell Iii, D.S., Scarbrough, D.A., Humphry, B.J., Turner, J.E., Johnson, Z.B. 2008. Weaning and Post-Weaning Performance of Fall-Born Calves Weaned on Different Dates from Endophyte-Infected Tall Fescue Pastures Managed with Two Different Rotation Frequencies. Livestock Science. 118:183-194.
Interpretive Summary: Designated calving season (spring or fall) may have a considerable effect on post-weaning calf performance in the southern Ozark highlands. This may occur because spring-born calves are weaned in the fall when ambient temperatures are cooler compared with fall-born calves that are weaned during periods of increasing ambient temperature. In most instances, limited information is available for post-weaning performance of calves weaned from fall-calving cows. In addition, other considerations are necessary for cattle grazing endophyte-infected tall fescue that produces toxic ergot alkaloids. Fall-born calves grazing endophyte-infected tall fescue prior to weaning should not be weaned at 189 days or earlier in order to avoid the most concentrated toxin loads in late spring. While early weaning appears to provide some benefits to the calf, such as higher antibody titers prior to vaccination and reduced transportation shrink, early weaning may have persistant negative effects on body weights of calves that even continue when they are moved non-infected forages or pastures following weaning.
Technical Abstract: A number of studies have reported performance by spring-calving cows grazing Neotyphodium - infected fescue [E+, Lolium arundinaceum (Schreb.) Darbysh.], but post-weaning calf performance from the majority of those studies is limited. Furthermore, both pre- and post-weaning information pertaining to fall-calving cows and their calves grazing E+ is particularly limited. A 3-yr study was initiated in April 2000 to investigate the impact of rotational management (twice monthly vs. twice weekly) program and weaning date [mid April (EARLY) vs. early June (LATE)] on production of fall-calving cow-calf pairs grazing E+ overseeded with ladino (Trifolium repens L.), and red clover (Trifolium pretense L), lespedeza (Lespedeza stipulacea Maxim.), and crabgrass (Digitaria sanguinalis (L.) Scop.). A secondary objective of the study was to evaluate calf performance both at weaning and after weaning until either breeding of the heifers or slaughter of the steers. Calves weaned later had greater (P < 0.05) actual weaning weights, but weaning date yr interactions were detected (P < 0.05) for most measurements at weaning. Weight loss during a simulated transport and sale, as well as the days required to regain the lost weight were lower (P < 0.05) by EARLY than by LATE in two of three years, and intake (kg DM/100 kg BW) was higher by EARLY than by LATE in two of three years. Antibody titers to infectious bovine rhinotracheitis and bovine virus diarrhea measured prior to vaccination and at weaning were greater (P < 0.05) from EARLY than from LATE. Heifer weight at breeding was greater (P < 0.05) from LATE than from EARLY in one yr and numerically greater (P > 0.11) from LATE in the other two yr. Heifer pregnancy rate only tended (P < 0.10) to be greater from heifers managed previously in a twice monthly rotation frequency prior to weaning. Initial and final feedlot BW and gain did not differ (P > 0.16) among previous treatments in two of three years. Therefore, carryover effects of weaning date or rotational grazing on calves previously grazing E+ tall fescue may be mitigated during a subsequent backgrounding period such that impacts on subsequent breeding or feedlot performance is minimized.