Submitted to: Journal of Animal Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/20/2000
Publication Date: N/A
Interpretive Summary: The native grass, switchgrass, is a perennial warmseason forage that is showing potential for grazing, and as a hay crop in the Southeast. Switchgrass makes rapid growth in the spring, frequently producing more forage than can be effectively utilized when grazed. During this period, or when surplus forage is present, switchgrass can be made for hay and stored. Because of its high yield and thick stem, curing for hay may require up to six days. Such extended periods of dry weather seldom occur in this region causing hay making to be very risky. The potential of direct cutting switchgrass and storing it as silage, as opposed to making as hay was evaluated in this study. We found that switchgrass preserved adequately when well packed. Chopping and ensiling switchgrass reduced crude protein concentration, but steers fed the silage had higher dry matter intake and consumed less water than steer fed hay. Preservation as silage had no effect on steer eating behavior, except steers had a higher ingestion rate and made fewer eating chews, but ruminated longer and excreted smaller fecal particles. The higher daily intake of the silage enabled steer to counterbalance the nitrogen losses that occurred during the ensiling process. Making switchgrass as silage essentially removed the risk of forage loss due to frequent rain. Further, the chopping process improved animal utilization of the forage compared with hay. The ensiling of switchgrass is a viable alternative to grazing or to making it as hay for animal production systems in the humid Eastern USA.
Technical Abstract: Effect of preservation method on intake and chewing behavior was examined using a first, late vegatative harvest (mid-June) of Kanlow switchgrass (Panicum virgatum L.) cut with a commercial field chopper (1.5 to 4cm avg. chop length) and ensiled directly (S) or flail-chopped (7 to 15 cm avg. chop length) and cured as hay (H) in a drier at 77 degrees C. Diets of H and S were fed to six Hereford steers (338# 5 kg) in a single crossover design. Chewing behavior was montitored ovr 4 days with a computerized system. At feeding, H was higher in DM (P < .01), NDF (P < .01), CP (P < .01) and hemicellulose (P < .01), but lower in ADF (P < .02), and cellulose (P < .04), and lower IVDMD values (P < .01). Steers fed S had higher intakes of DM (P < .02) than animals fed H. Crude protein intake was similar between diets. Preservation method had no effect on eating time, number of boli ruminated, bolus duration and number of ruminating chews per bolus. Steers fed S made fewer eating chews (P < .10) and ruminated for a longer time (P < .05) while making a greater number of ruminating chews (P < .04) than steers fed H. Steers fed W ingested feed at a greater rate (P < .03), excreted smaller fecal particles (P < .03), had meals of shorter duration (P < .06), spent less time eating during main meals (meals following feed distribution: P < .05), had more ruminating periods (P < .01) and a shorter morning (P < .06) latency time (interval between end of main meal and onset of rumination) than steers fed H. These results indicate that preservation method with its concomitant difference in forage chop length affected forage chemical composition and voluntary intake and that differences in chewing behavior occurred mostly during eating.