As the drought impact on South Dakota farms and ranches intensifies, feed resources surface as a major limitation to maintaining beef cow numbers. Fortunately, ruminant animals such as beef cows have the ability to utilize a “laundry list” of available feedstuffs to meet their daily nutrient requirements. While soybeans are one of those feedstuffs, they are rarely considered a livestock feed source except under drought conditions.
History tells us that soybeans were actually introduced into this country as a forage-feed, not for oil content or protein availability. Due to the extreme heat and marginal rainfall of the present growing season, their original purpose may provide a means to expanded cow diets this fall and winter.
If the decision is made to utilize soybeans as a forage crop, it should be made prior to the soybean plant reaching the R6 (full seed) developmental stage. Beyond R6, plant maturity becomes a factor in quickly reducing forage quality: Leaf and pod loss during harvesting will result in more of the feed being composed of a more fibrous stem.
Research at the University of Wisconsin documents soybean forage as a legitimate feed source for beef cows. Tonnage estimates range from about 1.0 to 1.5 tons per acre with tonnage increasing as the plants progress from R1 to R5. Relative feed values (RFV) diminish with maturity, reaching approximately 128 RFV as an R5. For comparative purposes, an acceptable dairy quality RFV begins at 150 which corresponds to the feed value of alfalfa harvested at mid-bloom. An RFV of 100, corresponds to what might be expected from alfalfa in full bloom. Crude protein ranges can be expected in the 15% to 20% range.
Harvesting options for soybeans used as a forage crop offer some flexibility for cattlemen in the way they choose to deal with a drought-damaged soybean crop. Ensiling, grazing and haying are the three most common methods recommended.
When harvested as silage, similar recommendations can be applied to those involved with processing alfalfa as haylage. A moisture range of 60% to 65% is ideal and this range is especially critical for soybeans. Moisture checks are required to insure this is the moisture range as harvesting soybeans with less moisture may be a potential fire hazard.
Baling soybeans as a harvest option provides more challenges than the ensiling one as the drying stage is difficult. Recommendations include tightening conditioner rollers to their tightest position to ensure extensive crimping of the plant stem which will require slower ground speeds. When the windrows are suitable from a moisture perspective, baling should only occur when leaves and pods have been exposed to levels of high humidity which results in less leaf and pod loss, usually late evening or early morning.