Cool-season grasses produced more beef per acre than alfalfa or cicer milkvetch in a University of Wyoming irrigated pasture study. But the researchers point out that each choice involves tradeoffs.
Yearling beef steers were grazed on the three forages from May to September for three seasons. The cool-season grass pasture was a mixture of orchardgrass, smooth bromegrass, meadow brome and creeping foxtail.
Average daily gains were the same on the grasses and alfalfa, but lower on the cicer milkvetch. The grasses and alfalfa produced equal amounts of forage, but carrying capacity in steer days/acre was higher for the grasses. That’s due, in part, to greater trampling and waste in the alfalfa pasture, say the researchers.
Average per-acre gain was 862 lbs for the grasses; 634 and 503 lbs, respectively, for the alfalfa and milkvetch. But the grasses needed significant amounts of nitrogen fertilizer. That cost, plus the risk of polluting groundwater with nitrates, is eliminated with legumes. They’re more susceptible to trampling, however, plus the cost of preventing bloat on alfalfa pasture must be considered. Bloat isn’t a problem with cicer milkvetch. But it was the lowest-yielding forage in this test, and was slow to establish, say the researchers.