Soybeans Could Provide Cow Nutrition in Drought

US - 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 utilise 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, says Jim Krantz from South Dakota University Extension.
calendar icon 15 August 2012
clock icon 3 minute read

Soybeans were actually introduced into the US 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 utilise 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 per cent to 20 per cent 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 per cent to 65 per cent 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.

Grazing soybeans is an acceptable harvest method although one that should be approached with caution. Recommendations involve an approach similar to that of grazing alfalfa. Cattle should be full when turned-in and late-day turn-outs are recommended. Soybeans are a legume and, like other legumes, may cause bloat. Further recommendations include only using soybeans as about 1/3 of the diet dry matter which would require some other available feedstuff along with the soybeans.

One very vital consideration when utilising soybeans as a forage source is that of pesticide residue. Some herbicides and insecticides are not labeled for use on soybeans intended for livestock consumption. Labels should be reviewed for determination. In addition, producers are reminded to obtain permission from their insurance agents prior to harvesting.

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