What to consider when grazing alfalfa this fall

Pasture conditions this fall have been less than adequate, leading producers to consider grazing hay fields this fall as an option to extend the grazing season. Much of these hay stands contain a significant portion of alfalfa, making bloat a bit of a worry.



The moisture conditions this year have been less than optimal for hay production. Hay yields have been sub-par to where there's little point in cutting for hay. At this time of year also, hay stands are getting over mature, which impacts forage quality compared to stands with plants still growing and beginning to flower.


Because most hay stands contain a significant amount of alfalfa, the hay harvested is guaranteed to normally be higher quality. Alfalfa-grass hay generally contains sufficient protein and energy to meet most animals’ needs. When it comes to grazing, the grass portion stands to be more beneficial than pure alfalfa stands. This legume species poses a bloat risk in the fall.


Ideally, the best time to begin grazing alfalfa-grass stands is after mid-September when plants have begun to slow growth and go into dormancy. This time period is also past the 45-day critical growth period, starting from the first of August. This period is important because alfalfa plants need to put energy stores into their crowns and roots to get ready for winter. They use these stores to regrow in the spring. Compromising this ability to put down these stores makes these plants more prone to winterkill.

Should a producer be looking to take out a hay stand, this critical growth period isn’t as important as how frost makes alfalfa plants more bloat prone. Frost freezes plant cell contents, which causes the cell size to expand beyond what cell walls can handle. The walls burst, releasing cell contents. When they get eaten by cattle, rumen microbes can quickly access the cell contents and just as quickly convert them into proteins. The foamy “slime” that comes of such rapid digestion encourages bloat. Waiting a few days for the leaves to slough off is one practice to consider when grazing alfalfa. Another is to make sure animals are already adjusted to grazing alfalfa prior when frosts arrive.


Alfalfa that is overmature and going into dormancy has higher fibre content and lower digestible protein and energy content. That makes them harder for rumen microbes to break down. In this regard, it lowers bloat risk especially when cattle are first introduced onto hay stands. However, bloat risk is still present, so it’s still best to implement management practices to reduce any incidences that may occur.


Animals should not be hungry when they are first introduced to the stand. Also, they should be first put out in early afternoon, after much the plants have dried up after frost and before sugar levels reach their peak. Providing access to hay or straw is another good plan, and these should be available for the first week. This provides an extra source of fibre they wouldn’t otherwise get. Access to another forage stand that is predominately grass works too, especially if hay is in short supply. Finally, check on them at least twice a day for the first week. Chronic bloaters can be a headache and should be removed as soon as possible.


Bloat-prevention products such as Bovatech (contains lasolacid), rumensin or a bloat block is also worth considering. These should not be a replacement of the management practices above, but as another tool in the tool chest of bloat prevention. Be sure to follow product labels and ensure animals have consistent access over the time they are grazing the hay field.


Such management practices above are also good if there’s a worry about fog fever in older cows. Fog fever comes when animals are moved from a brown, dry, mature stand to a more lush, green one. It causes fluid to build up in the lungs from an overproduction of tryptophan, an amino acid. Slow introductions as previously mentioned reduces the chances of cows coming down with this forage-related illness.


When it comes to nitrates and alfalfa, there’s very little, if any, issue. Alfalfa’s nitrogen-fixing capacity basically eliminates nitrate risk. This is true for all legumes. Also, most hay stands are usually not fertilized. Nitrates are more of a problem with annual cereals such as barley or oats.


Once animals are adjusted to the stand, it is best to not remove them, even for the night. They will have to be re-introduced using the same management practices when they first entered the field. It is best to leave them there for as long as they are needed to graze that forage stand.


When faced with overmature forage, high fiber content can impact the ability of animals from better utilizing it. Overmature forage is a little better in quality than straw. Providing some form of protein supplementation to improve feed intake and feed utilization is a great advantage. This helps rumen microbes to better break down the fibrous forage, releasing much-needed nutrients for the cow to use.


Options include free-choice protein tubs or feeding three to four pounds per head of peas every two or three days. Adding a non-protein nitrogen source like urea to barley or oats will also help. Feed this to cows every two or three days at three to four pounds per head.


Legumes to provide sufficient protein and energy to meet animals’ needs. The grass component of a hay stand is more beneficial for grazing than a pure alfalfa stand; however, alfalfa still poses a bloat risk in the fall, particularly with frosts.”


Don’t be too alarmed if you start grazing and you get frost on the alfalfa when it comes to nitrates,” adds Lindquist. “Nitrate toxicity with alfalfa is not an issue because of its nitrogen-fixing capacity - as with all legumes - and most hay stands are usually not fertilized. Nitrates are more of a problem with annual cereals such as barley or oats.”

“The most significant factor against producers is over-maturity of hay stands,” says Lindquist. “Consequently, over-matured stands will not have the forage quality that younger, more vegetative stands will have.”


Fibre content is higher and digestible protein and energy content are lower when plants have already reached maturity and are going into dormancy. “That makes the plants harder for ruminants to digest,” says Lindquist. “It lowers bloat risk especially when cattle are first introduced onto hay stands. However, there is still some risk of bloat, so management practices to reduce incidences are still good to keep in mind.”


Lindquist says that the best time to begin grazing alfalfa-grass stands is after mid-September when plants have gone into dormancy. “This time frame is also past the 45 day critical growth period, starting from the first of August, that alfalfa plants need to prevent winterkill. Alfalfa must be able to put energy down into its crown and roots to survive winter and to use those energy stores for regrowth in the spring.” Lindquist also recommends grazing alfalfa two weeks after a killing frost as bloat risk lowers considerably compared with grazing at or before a frost.