Typical North American farm. Landscape

Soybean silage as an alternative forage for dairy cows

Alvaro Garcia

What are the advantages of including soybean silage as an alternative forage in the diet of dairy cows? Soybean plants are well-adapted to dry conditions, have high grain productivity per area, with high protein content, and low fiber to protein ratio. They may be harvested for forage when their yields have shrunk below the economic threshold for oilseed harvest.

As a result, they can help stretch out conventional forages when yields may be compromised. Additional advantages described are increased carbon sequestration, nitrogen fixation, and reduced greenhouse gas emissions during rumen fermentation.

To ferment adequately in the silo, their moisture content is very important, and needs to be like that of alfalfa silage. For soybeans, this ideal moisture occurs right before the pods are full. Waiting until complete maturity results in a drier, lower digestible forage that can lead to fermentation problems due to the high oil content of the seeds.

Nutrients in soybean silage

The nutrient composition of this silage can be expected to range from 16.0 – 20.6% crude protein (CP), 38.3 – 48.3% neutral detergent fiber (NDF), 27.3 – 37.3% acid detergent fiber, 6.0 – 7.4% lignin, 1.36 – 1.49% Calcium, and 0.26 – 0.31% phosphorus. Direct-cut soybeans have a dry matter (DM) contents between 22 and 30% and ensiling at this moisture will result in higher effluent losses and a greater risk of undesirable butyric fermentation.

It is thus better to aim for 35 – 40% DM. Buffering capacity of the forage is relatively high and can result in poor fermentation. Inoculants may help reduce these problems and reduce mold growth. Always verify herbicide restrictions for feeding when attempting to use soybeans for forage.

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