056 Response of Growing Cattle to a Cumulative Management Strategy Including an Implant, Ionophore, and Byproduct Feed Supplementation While Grazing Tall Fescue Pastures with Varying Toxicity

• Published in: Journal of animal science 2016-12, Vol.95 (suppl_1), p.28-28
• Main Authors: Diaz, J., Gadberry, M. S., Beck, P. A., Hufstedler, G. D., Hubbell, D. S., Tucker, J. D., Hess, T.
• Format: Article
• Language: English
• ISSN: 0021-8812; 1525-3163
• DOI: 10.2527/ssasas2017.056

Abstract The objective of this study was to evaluate the growth response of steer calves to a combination management strategy while grazing low- to high-toxicity tall fescue (Festuca Arundinacea) pastures. Two short-term grazing seasons included fall 2015 for 91 d and spring 2016 for 84 d were studied. Sixteen pastures, 8 low- and 8 high-toxicity within season were used. Steers (n = 80) weighing 197.01 ± 15.43 kg and 116.93 ± 4.88 were stocked at 2.45 and 4.1 calves/ha in fall and spring, respectively. Within each of low- and high-toxicity pasture types, 4 pastures were allocated to a control, mineral (MIN) only management (MGMT) and 4 were allocated to the cumulative MGMT(CM) including Component TE-G implant, 150 mg/calf daily equivalent Rumensin, and 1% BW 50:50 corn gluten feed:soybean hull pellet supplement. Interim pasture ergovaline (EV) was measured within season. Data were analyzed within season. Pasture was the experimental unit and the statistical model included EV as a continuous covariate, MGMT as a fixed covariate and the EV × MGMT interaction. Reduced models were applied in the absence of interactions (P > 0.05). For fall and spring, the EV concentration was 1,476 ± 883.2 ppb and 1,173 ± 620.6 ppb, respectively. Mean forage allowance (forage DM/BW, kg/kg) was not affected by MGMT in the fall (4.5 ± 0.146) but increased with toxicity in spring (Forage Allowance = 2.17 + EV(0.0004), P = 0.04). In fall, there was no EV × MGMT interaction (P = 0.19) for BW gain. Fall ADG was negatively affected by increasing level of pasture toxicity (P = 0.01). In the fall, MIN calves gained 0.31 ± 0.027 kg/d, whereas, CM gained 0.95 ± 0.027 kg/d (P < 0.001). In the spring, there was an EV × MGMT interaction (P = 0.03) for ADG. For MIN, ADG = 0.7959 – EV(0.000278); whereas CM ADG = 0.936 + 0.000001835(EV) indicating CM improved ADG response as EV increased. Rectal and tail temperatures were not different (P > 0.20) among EV; rectal temperatures were not different (P > 0.20) for MGMT, however, fall final and spring interim and final tail temperatures were greater for CM compared to MIN (P ≤ 0.05). In conclusion, BW gain and skin temperatures may be increased by CM in steers grazing toxic fescue and the beneficial effects of CM on ADG are greater as plant toxicity increases.