Thanks to Brad Schick and Ben Beckman, Nebraska Extension Educators, and BeefWatch for this timely article!
There is often fear associated with grazing alfalfa due to bloat potential or hurting the alfalfa stand. These are very valid concerns, but with additional management and timing alfalfa stands can provide supplemental forage. In a haying system during the spring and summer, fall and winter grazing may be an option to harvest quality feed.
Alfalfa grazing in the fall provides high-quality forage and eliminates any issues of poor drying if attempting to make hay. In the fall, other pastures may already be fully utilized and crop residue unavailable or temporarily unavailable. All classes of livestock can benefit from grazing alfalfa. Studies at the University of Nebraska-Lincoln have shown yearlings can have 1.5 to 2.5 lb/d ADG (average daily gain) and cows can increase body condition score before harsh winter months.
Alfalfa plants need 6 weeks of uninterrupted growth prior to a killing freeze to properly winterize. Winterization allows for accumulation of energy in the roots of alfalfa plants. While alfalfa can be grazed during this time, it is not recommended unless needed. As with a late cutting, any harvest will increase the likelihood of winterkill and impact spring productivity. Also, if the stand is old, has had high pest pressure, or has been under high stress throughout the season, it is not recommended for utilization. Ultimately, the decision to be made is whether to have forage in the fall or have forage later in the spring. If forage is needed and cannot wait until next spring, then utilizing alfalfa now may be a viable option, just with additional management.
Fall grazed or hayed alfalfa can be incredibly high-quality but low quantity, so if it must be utilized, graze lightly leaving at least 8 inches of stubble on average to minimize the stored energy used for regrowth. Graze using a rotation, so animals are less selective and are less likely to overgraze a given area. Because grazing can leave more growth behind, properly managed grazing may allow plants to better winterize than a late hay cutting but is still a risk for the stand.
Plans should be made so that grazing can be done when the field is dry and firm. If the soil is too wet, animal hooves can damage plant crowns. The same principle applies to driving equipment on the fields as well. Having a sacrifice area or an adjacent lot ready to pull animals into if conditions get wet, can avoid excessive damage to the stand. Pairing with crop residue fields will allow for less pressure on the alfalfa and provide good roughage.
Usage of alfalfa should follow a killing frost (29-24°F for 4 to 6 hours) to limit damage to alfalfa stands. Once the hard frost occurs the stand can be harvested. Cutting or grazing needs to take place shortly after following the killing freeze to salvage as much of the nutritive value as possible. Compared to fall alfalfa, the forage quality and quantity will decline rapidly as the alfalfa plant desiccates. For this reason, winter alfalfa stands will seldom provide enough nutritional value to be a primary forage source for animals. Grazing soon after a killing freeze will aid in capturing the best value from the alfalfa. In most cases, grazing will occur incidentally when alfalfa fields adjacent to crop residue being grazed is not fenced off.
Once the ground is frozen, the danger of hoof damage to plant crowns is reduced. However, keep an eye out for warm periods where the upper soil layers may thaw and the crowns once again become vulnerable. Protecting the plant from weather extremes is critical to prevent stand winterkill. When winter grazing, be sure to maintain at least 4 inches of stubble height.
As with all high-quality, fresh forage, bloat is a concern that must be addressed when grazing growing alfalfa. The risks are highest three to five days after a freeze, when cattle are first introduced to an alfalfa field for grazing, when heavy dew is present, and if the cattle have low rumen fill. To prevent bloat, animal management should limit the amount of high-quality forage grazed. When initially turning animals out to graze an alfalfa stand, pre-feed animals before allowing grazing access, and then only allow grazing for an hour or two. Moisture from rain or dew can also aid in bloat, so initial grazing should occur later in the day. Slowly build up the time allowed to graze over a period of several weeks to allow the rumen to adjust to the high-quality diet.
More mature alfalfa stands will be lower quality and pose a lower risk for bloat. Providing a lower quality roughage source like crop residues or grass hay can provide animals fill and reduce risk. In these cases, strip grazing alfalfa can help balance animal intake even further. Some animals are naturally more sensitive to high quality forage and pose a higher risk. Avoid issues by separating these animals from the herd during the alfalfa grazing period or, if grazing alfalfa is regularly planned, culling them permanently.
When grazing in the fall, freeze events followed by warm days also raise the risk of bloat, so pull animals off or limit grazing for three to five days after a freeze. Freezing damages cell walls in the plant, making proteins and minerals more readily available during digestion, causing problems even in animals that have already adjusted to grazing growing alfalfa. Once cold temperatures set in, bloat risk decreases and becomes very low once 50 to 70% of the alfalfa is frozen and dried. Typically, this will occur in late fall, but warm and wet fall conditions may keep alfalfa growing until the early winter months.
To truly safeguard against bloat beyond herd management, supplements like nonionic surfactants (vegetable fats and mineral oils) which reduce the rumen foam production, antifoaming or tension-active agents such as poloxalene (typically in a “bloat block”), and fed ionophore antibiotics can be used. These products can be successful but depend upon regular daily intake to maintain effectiveness. These products have various forms that can be administered through water, feed, or salt/mineral. Ensuring regular consumption of water and salt/mineral, or supplying daily supplemental feed further complicates use.
Need more on bloat? Here you go!
For more on dryland alfalfa grazing, check out this week’s Lunch With Forages presented by the Oregon Forage and Grassland Council!