Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/19/2009
Publication Date: 9/18/2009
Citation: Akins, M.S., Coffey, K.P., Caldwell, J.D., Lusby, K.S., Coblentz, W.K., Kegley, E.B. 2009. Comparison of Bloat Potential Between Soft-red and Hard-red Winter Wheat Forages. Journal of Animal Science. 87:3278-3287. Interpretive Summary: Livestock grazing lush wheat pasture are known to exhibit pasture bloat. This study evaluated differences in bloat risk within livestock grazing hard-red and soft-red winter wheat in northern Arkansas. There were no differences in bloat incidence for stocker cattle grazing either hard-red or soft-red winter wheat. However, ruminally cannulated heifers grazing soft-red winter wheat had slightly greater bloat incidence than those grazing hard-red winter wheat. Rumen fluid from cattle grazing soft-red winter wheat had greater foam production and strength, and was more viscous than rumen fluid from cattle grazing hard-red winter wheat. Bloat was positively correlated with in vitro organic matter disappearance and negatively correlated with neutral detergent fiber and environmental temperature. In conclusion, soft-red wheat had greater bloat-causing potential than hard-red wheat when grazed by cannulated heifers, but no differences were observed with stocker cattle. Hard-red winter wheat may have produced less bloat in this study, but since bloat is unpredictable and associated with several factors, more research is needed to conclude that particular wheat types exhibit more or less potential for bloat.
Technical Abstract: Some aspects of wheat pasture bloat have been researched extensively, but little research has evaluated the effect of wheat type on bloat. Forty-eight Angus heifers (238 ± 12 kg BW) and 8 Gelbvieh by Angus ruminally cannulated heifers (515 ± 49 kg BW) grazed 1-ha pastures of either hard-red or soft-red winter wheat (Triticum aestivum L.) to evaluate the effect of wheat type on bloat potential. In Exp. 1, cattle grazed from Nov 11 to 22 and from Nov 26 to Dec 7, 2006 in a crossover design. In Exp. 2, cattle were shrunk for 20 h and then grazed from Dec 19 to 20, 2006 and from Jan 19 to 20, 2007. In both experiments, bloat was scored at 1000 and 1600 daily. Rumen samples were taken in Exp. 1 the last 2 d of each period at 0600, 1200, and 1800 then evaluated for pH, foam production and strength, and consistency. Rumen samples were taken during both days of each period of Exp. 2. Forage availability was not different (P > 0.05) between hard-red and soft-red winter wheat in the stocker cattle pastures. Respective initial and final forage availabilities for the stocker calves were 1,366 and 1,154 kg DM/ha for hard-red, and 1,447 and 1,089 kg DM/ha for soft-red winter wheat. Bloat incidence was low (2.1%) for the stocker cattle, with no difference between hard-red and soft-red winter wheat (P = 0.52). The cannulated heifers grazing soft-red had a greater percentage of observed bloat (21.8 vs. 5.6%) than the heifers grazing hard-red winter wheat (P < 0.01). Consistency of the rumen fluid had a wheat type x time interaction (P = 0.03) with soft-red at 1200 and 1800 being more viscous than soft-red at 0600 and hard-red at all times. Also, consistency of rumen fluid differed across wheat types (P < 0.0001). Rumen fluid from heifers on soft red flowed 7.4 cm and hard red flowed 9.5 cm in a consistometer. Foam production as determined by bubbling CO2 gas through rumen fluid had a wheat type x time interaction (P = 0.02) with both wheat types similar at 0600 but soft-red having greater foam strength at 1200 and 1800. In Exp. 2, no bloat was observed. Also, no differences between wheat types were observed for any of the rumen foam measures. Therefore, soft-red winter wheat had a higher bloat potential than hard-red winter wheat based on results from the cannulated heifers, but no differences were observed in the frequency of bloat in stocker cattle. In this study, shrinking of cattle prior to grazing wheat pasture did not induce bloat.