Ask the expert: Wet alfalfa – Dr. Michelle Windle, Vita Plus
Question: I cut alfalfa almost one week ago but, due to rainy weather, I can only just now get out in the field to chop it. How can I salvage this crop?
Answer: In many areas across the Midwest, alfalfa is ready to be harvested, but this last week brought a lot of rain and next week looks like more of the same. Alfalfa is already prone to a higher pH than corn silage due to the presence of minerals and proteins that resist a pH drop.
When a crop is rained on, sugars that are necessary to fuel fermentation get washed out, preventing an adequate and quick pH drop. The crop will probably also have higher-than-ideal ash content. Couple this with a crop that is wetter than ideal and you have the perfect breeding ground for a clostridial fermentation. Clostridia can only grow in wet forages with a high pH. These bacteria consume valuable nutrients (proteins) and produce detrimental byproducts (butyric acid, ammonia and biogenic amines) that can cause animals to go off feed, make animals sick, and kill animals, in extreme situations. Clostridia have been considered a major contributing factor in hemorrhagic bowel syndrome (HBS).
That being said, this crop can still retain value through good management. Ideally, this crop would be wide swathed and chopped at 35 percent dry matter (DM) and ensiled around 40 percent DM. Typically, in narrow swaths, the bottom of the swath will develop a slimy layer of some detrimental bacteria. If the crop is narrow swathed, tedding may help dry it. Fortunately, Clostridia are slow-growing microorganisms and take about two to three months to do their damage. Segregating the feed will allow this crop to be fed as quickly as possible before it has a chance to turn butyric. Using a high-quality upfront inoculant at the label-recommended dosage is crucial to lower the pH as quickly as possible. Running a fermentation analysis on the feed before you feed it is essential to determine if it can be used in lactating rations or if it needs to be diverted to heifer feed.
If you have a crop that has gone butyric, it is important to determine how much butyric acid the animals would be consuming. Butyric silages should be diverted away from pre- and post-fresh cows, and animals should not consume more than 50 g of butyric acid a day. It may be beneficial to “air out” silages to allow some of the acid to volatilize. Because butyric acid is a strong antifungal, these silages will not spoil while they are “airing out.”
As usual, planning and good management can go very far in this situation.
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