Grass silage: Success and challenges – Dr. Michelle Windle, Vita Plus

By Dr. Michelle Windle, Vita Plus forage products and dairy technical services specialist
Many factors may influence a producer’s decision to grow grass silage, such as a need for somewhere to put manure, a land topography that requires a cover crop, or a limited forage inventory that could use some quality feed to stretch it.  Grass silage can offer many advantages to both the animal and the producer.

Compared to grass hay, grass silage may offer better protein retention and a smaller chance of the crop getting rained on due to a shorter dry-down time.  Other advantages include more sugars and a lower buffering capacity, so it can be ensiled slightly wetter at 32 to 35 percent dry matter (DM), compared to the ideal haylage DM of 40 to 45 percent.  Grass silage also has the potential for a lot of high-quality neutral detergent fiber (NDF) and excellent yield, especially on soils not well-suited to grow legumes.

Cereal grass silages, such as winter triticale or winter rye, can also be double-cropped with corn silage.  Winter cereals are often planted after corn silage is removed from the field and harvested right before corn or soybeans are planted the following spring.  Furthermore, animals often prefer to consume grass silage over grass hay.

However, grass silage does have drawbacks compared to grass hay, as extra labor and equipment may be needed and the moisture content of the crop needs to be more closely monitored to ensure ideal ensiling conditions.

Discussing grass silages as a whole is difficult because of the wide variety of options.  These include cool season cereal grasses (rye and wheat), which are winter or spring annuals; cool season perennial grasses (fescue, orchard grass, timothy and brome grass); and warm season perennial grasses (sudan or sorghum-sudan grasses).

Digestibility is the main factor influencing grass silage intake and nutrient supply to the cow, so maturity of any grass at harvest is integral to forage quality.  For cool season cereal grasses, harvesting at the boot or early seedhead stage is ideal for lactating cows.

Optimizing the stage to harvest perennial grasses is harder to pin down.  Typically, the right time for the first cutting of cool season perennial grasses is after the plants go through a reproductive stage when the stem elongates and the grass produces a seedhead.  However, the same grass may not stem-elongate during the summer, making the ideal physiological stage for cutting difficult to define for later cuttings.

The bottom line for grasses, due to the large variation in species and maturities, is to understand what type of grass is growing and how to get the most value from it.  All of these grasses have different agronomic characteristics and need to be managed and harvested according to their specific plant growth characteristics.

From a feeding standpoint, little evidence exists that grass species are overly influential on dry matter intake (DMI) and/or milk yield of dairy cows.  The key to achieve the best-quality silage for lactating dairy cows is to harvest any grass for silage at early stages of maturity and ensile at the proper DM.  Of course, dairies also have dry cows and heifers to feed.  Later-harvested grass silage, which is lower in energy, makes excellent dry cow and heifer forage.