This year, not many people harvested and stored good-quality hay on the northern Prairies. A cool spring and droughty summer capped by a couple of feet of autumn snow forced many producers to harvest thousands of mouldy hay bales. For many, this is their only forage supply to overwinter beef cows. Fortunately, we can set up some practical strategies to feed this forage and get cows in reasonable body condition for calving.
It’s started with the endless challenge that hay baled at above 14 per cent moisture is likely to have mould growth. The leaves and stems of “tough hay” may be rapidly covered with white mould when temperatures are above freezing. Cattle trials have demonstrated beef cows will eat most of this hay with about one to two per cent storage mould without much problem. However, when more than 10 per cent of it is contaminated, cattle tend to reject it unless they are close to starvation.
Even when mouldy bales are eaten by beef cows, we can be confident that it won’t be as nutritious as mould-free hay. That’s because microscopic organisms, namely fusarium and penicillium moulds, exploit these same essential nutrients to fuel their own growth. It is estimated that millions of mould strands found in damp hay typically reduce its dietary energy content by up to 15-20 per cent that could be otherwise utilized by gestating beef cows to maintain optimum body condition in the five to six score range during winter.
Unfortunately, moulds go one step further by reducing the nutrient digestibility/metabolism of forages within the cows’ bodies. Mould causes undigested forage fibre, soluble carbohydrates and proteins as well as forage minerals and vitamins to travel rapidly throughout the rumen and lower gut. It often shows up as chronic diarrhea in many afflicted cattle.
Various mould species also produce mycotoxins which are harmful compounds that can adversely alter animal metabolism. Although not fully understood, some mycotoxins display hormone-like properties, similar to those naturally produced by cattle. As a result, they can also damage organs, impede normal reproduction (including fetal abortions), as well as disrupt the immune system to fight disease. Such a mycotoxin-suppressed immune system may also cause a lack of natural response to producer-administered medications and vaccines.
Some research shows that cattle can adapt to eating hay containing moulds and mycotoxins because their rumen microbes have a moderate detoxication capacity. Yet this ability doesn’t mean that we should rest easy when cattle consume mouldy feed since specific mycotoxin tolerances are not well-established. And other natural factors are involved such as young livestock and sick cattle are very susceptible to myco-poisoning compared to more mature and healthy animals.
Mouldy forage strategies
Here are three basic strategies when it comes to feeding mouldy hay to overwintering cows as well as other classes of livestock:
1. Take a complete forage inventory. Separate out the good, the bad and ugly mouldy forage bales. For example, many beef producers should separate out their higher-quality and less-mouldy forage bales and save them to be fed to beef cows as they approach the calving season. Some extremely mouldy bales should also never be fed and discarded.
2. Add a specific allotment of mouldy forage. Add 15 per cent mouldy forage to 85 per cent clean forage, such as when making up a complete total mixed ration for beef cows. This strategy allows a specific and limited amount of mouldy feed to be provided. Avoid dilution of large amounts of mouldy forage with good forage, since this type of blending tends to create sole piles of significantly mouldy feed.
3. Alternate between forages. Feed clean mould-free (straw) bales, on one day and then the next day feed bales of moderately mouldy bale (hay). Make sure any lower-nutrient-quality feed (straw bales) is nutritionally supplemented by placing high-protein, low-moisture molasses lick tub near where cattle congregate. Ensure a well-balanced cattle mineral with complementary sources of calcium, and phosphorus as well as high levels of bio-available trace-minerals, vitamins and salt are fed.
It would be ideal to recommend that any mouldy hay should not be fed at all. This reaction is neither realistic nor practical in this special year when good-quality and mould-free hay is very limited and expensive. Therefore, many beef producers must cope with their own subpar forage supply, so they can overwinter their beef cowherd. Given the above reasonable strategies, a large portion of this mouldy hay should be safely fed.