Monday, November 2, 2009
Convention Center, Exhibit Hall BC, Second Floor
A number of studies have evaluated the behavior of sheep and cattle grazing adjacent monocultures of perennial ryegrass and white clover. In those studies, animals almost always chose a diet of around 70% white clover. Several theories have been proposed to explain why domestic ruminants have this pattern of preference and why they select mixed diets of grass and legume, but only a few forage species have been evaluated in this manner. Two different forage species were thus chosen for examination as adjacent monocultures; tall fescue (Festuca arundinacea Schreb. or Lolium arundinaceum (Schreb.) S.J. Darbyshire) and alfalfa (Medicago sativa subsp. sativa L.). The hypothesis that ruminants select mixed diets in part based on a plant’s ‘novelty’ was evaluated along with the theory that regardless of species evaluated, cattle will have greater preference for legume than grass. Cattle without previous exposure to alfalfa spent 78% of their grazing time consuming alfalfa, whereas cattle that had previously grazed alfalfa spent less time (P = 0.04) grazing alfalfa (72%). Overall proportion of the day spent grazing both forages was lower (P = 0.0001) when alfalfa was novel (40%), compared to when steers were experienced grazing both forages (46%). Proportion of the day spent idling was greater (P < 0.0001) when alfalfa was novel (35%), compared to when both forages were familiar to the steers (26%). The proportion of grazing time in alfalfa was greater (P = 0.02) in afternoon (76.8 %) than in morning (72.1 %). This result differs from previous studies that reported a decline in preference for legume over the day, with increased preference for grass in afternoon.