Alternative forages can provide the nutrients cows need
Last year’s forage growing season and subsequent inventories were really messed up. Many farms planted alternative forage species and put up some “unfamiliar” feeds. These include small grain silages, cool-season grasses, sorghum-sudan grasses, forage peas, soybean silage, and whatever else that could be windrowed and chopped.
Feeding alternative forages comes with some nuances. Comparing alternative forages to alfalfa is a great starting point, but we must first recognize that our traditional quality metrics aren’t necessarily applicable to alternative forages. We are still learning how to evaluate, incorporate and manage these alternative forages. When strategically incorporated into the feeding plan, alternative forages can provide us the opportunity to fill in the gaps without leaving milk on the table.
The very first consideration of any alternative forage in inventory is its protein content. In general, if the crude protein (CP) content of the alternative forage is greater than 14% to 15%, the forage should be a prime candidate for inclusion in the lactating diet to help reduce purchased protein cost.
Cereal forages, such as triticale or rye silages, harvested early (at the flag leaf or early boot stage of maturity) may contain 15% to 18% CP and 42% to 48% NDF. Likewise, early vegetative ryegrass, soybean, and pea silages commonly contain 16% to 18% CP. The protein content of grass silages is largely dictated by soil nitrogen fertility status and harvest timing.
Grass forages are much lower in calcium and can be very high in potassium because grasses are luxury consumers of soil potassium. Dietary calcium and potassium levels need to be double-checked.
High potassium levels in grass forages can interfere with magnesium utilization by dairy cows. We often supplement a bit more magnesium in our diets when alternative grass forages are fed to lactating dairy cows.
As compared to alfalfa, cool-season grass forages will have less lignin and more hemicellulose. As a result, cool-season grass forages have less indigestible NDF and greater NDF digestion potential as compared to a typical alfalfa silage.
However, research has shown that legume forages, including alternative pea and soybean silages, have a greater passage rate compared to cool-season grass forages. This may result in slightly lower dry matter intakes in high-producing cows consuming diets with more cool-season grass inclusion, even when diets are formulated on an equivalent NDF basis.
Pay particularly close attention to the ash content in all your forages. High ash content can make some forages difficult to accurately test. It is also a risk to normal fermentation. A wet forage with heavy soil contamination can lead to the production of butyric acid and other harmful biogenic amines. Evaluating your harvest techniques and properly applying a quality inoculant can help manage some of these risks.
Cows need nutrients
Winterkilled alfalfa doesn’t provide any protein for your ration and late-planted corn may provide little to no starch in the silage. All the nutrients needed for the cows and their ration can be accounted for, we just need a plan for what we will have and what we will need to replace.
Despite nuances between feeding our cows traditional alfalfa and corn silage-based diets, we have observed excellent milk production and maintenance of milk components when alternative forages are included in diets.
This article was originally written for the February 10, 2020 issue of Hoard’s Dairyman.
Feed quality and nutrition