The pros and cons of grazing cover crops

Cover crops have traditionally been used to help hold the soil when transitioning between different types of cash crops, and are often plowed under before planting the next crop — to add organic material and fertility to the soil. Farmers with livestock often select cover crops that can be grazed, adding an additional benefit as feed and the advantage of animal manure.

Grant Lastiwka, livestock and forage business specialist with Alberta Agriculture and Forestry, says some of the alternative cover crops can be very beneficial for producers, to provide forage. “In conventional grazing systems, we either have an annual that starts growing later in the spring and finishes growing sooner than perennial forages, or we use a perennial pasture that lacks productivity. Many of our pastures in Alberta fall into that category and their ability to capture carbon is limited,” he says.

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“Also much of our land has gone out of crops that use a lot of water and are green for a longer period of time. More of our grain farms now manage water to get it off the land, and there is a lot of large equipment used. Weight per square inch has increased, as has our ability (via GPS) to travel on the same tracks. We are running into issues with our soils; they are being adversely impacted. The ability for these stands to take in water, hold it, release it, etc. has decreased. Using cover crops can help remedy this situation.”

“Also, if you add nitrogen to a system it improves water use efficiency. The cover crops mixes that some people are now using include a legume. This contributes nitrogen that is beneficial to the soil and also to the quality of feed,” he says.

Barry Yaremcio, an Alberta beef and forage specialist says some producers add different varieties of seed to establish an extra crop when planting a traditional crop, to provide more forage. “For instance, they might be planning to seed an oat crop or barley for silage, but also plant clover, winter wheat or another crop that will grow and be available for grazing after the silage is harvested,” he says. A person can plant their main crop and take it off for silage, but broadcast grazing turnips, kale or forage rape between the rows to provide a lot of biomass for grazing later.

“Grazing brassicas (turnips, kale, forage rape, forage radish), sorghum sudangrass hybrids, winter wheat or fall rye, winter triticale, etc. can provide high-quality forage for cattle or sheep late in the growing season. These species grow faster once the silage or greenfeed crop has been taken off,” says Yaremcio. This type of crop can provide a lot of fall/winter grazing for cattle.

Sometimes regrowth from a traditional crop can be used as fall grazing. “Last year, for instance, producers who harvested their silage earlier than usual because of the dry conditions saw significant regrowth when rains came in late July and early August. Some regions of the province were fortunate to have 12 to 16 inches of oat, barley and canola regrowth for fall grazing. Rain brought on second growth, reaching the heading stage when it froze. The quality of that regrowth material was as high as a good alfalfa-grass mixed hay, at 15 to 16 per cent protein, and very digestible (63 per cent TDN or higher), with low fibre content,” he says.

2HUNTER forage brassica

Winter wheat, fall rye or winter triticale can work nicely for grazing late in the year. “Even if you seed them in May or June (when their spring counterparts are seeded for a grain crop), they won’t grow much during early summer, but by August/September there will be a lot of leaf and bottom growth. The majority of the winter crop tillers won’t put up a head and seed until the next year. All those leaves at the bottom of the plant are very high quality and when they have a chance to grow they can supply a lot of feed for cattle,” says Yaremcio.

Nora Paulovich at the North Peace Applied Research Association has done a lot of work experimenting with various crop blends at the research farm near Manning, Alta. to determine what works and what doesn’t work in that area. The farmer-run executive board has made it a priority to increase total yields by adding cover crops. The group has been using various cocktail mixes of different types of species. A mix of plants can often be a good diet for cattle, including a legume such as clover to increase the protein and calcium content in the forage. Providing different species can help balance the ration, reduce supplement costs, and take advantage of moisture and growing conditions at different times of year. This can produce a better yield as well as a better-quality product that will be available through the entire summer. If one type of plant doesn’t do as well, some of the others might.

This is the advantage of some of the cocktail mixes because you can include a species that can take the heat and withstand a drought, so if it’s a dry year you’ve got that covered. There are other plants that have the ability to grow when it’s cooler, with more moisture. A good mix can cut down the amount of risk and help assure good feed for the cattle, whatever the year might bring.

“Our work with cover crops is still in its infancy,” says Paulovich. “We are still trying various things, and a dozen producers in our area are trying different combinations and species as well. We are still experimenting with seeding rates, also. We know that we need to include species from warm- and cool-season grasses, as well as legumes,” she says.

“We try to have species from each of these categories and hope to find the optimum seeding rate for all them. We like to have a spring cereal included, and oats or triticale are the cool-seeding grasses we are seeding. This (past) year in our cocktail cover crop mixes at the research farm we found that our seeding rate for the oats was a little bit high. So we are going to experiment with that,” says Paulovich.

“We’re also going to try different seeding dates — seeding every two weeks. It was so dry these past several years, that the more often you put seed in the ground, the greater the chance of success for one of those to catch some rain at the right time,” she explains.

Things to be aware of when grazing alternative crops

“Some of the problems we’ve seen this past year are related to soil fertility/nutrient uptake. Producers who put in forage brassicas like turnips, kale (or used late-germinating canola crops for grazing, silage or greenfeed) found that nitrogen content of the soils was quite high. The nitrogen may have come from commercial fertilizer or significant amounts of manure applied to the field. Nitrogen accumulation in some of these crops was sufficiently high that intake had to be restricted to prevent poisoning,” he says.

If a crop is grown in fields with high sulphur fertility, the plants will take it up with the soil moisture. “Brassicas species are known to accumulate sulphur. We’ve received feed test results with sulphur levels in the 0.6 to 0.8 per cent range. Sulphur content in a ration (including that which is obtained from water) should not exceed 0.4 per cent in the entire ration or it will reduce rumen pH. The bacteria responsible for producing thiamine are very sensitive to low pH and die off. A shortage of thiamine can cause polio. There have been some cows die this year because of this situation,” he says.

“In many parts of Alberta and Saskatchewan many canola crops did not germinate until the rains came in July and early August. It was in full bloom/early pod stage when they cut it for silage and greenfeed. It was excellent feed, at 16 to 17 per cent protein, with great energy and good levels of calcium, phosphorus and magnesium, but the sulphur and nitrate levels were high. The forage had to be blended down with other material to make it safe to feed. Control measures, such as electric wire, were needed to limit the amount of canola consumed daily. Alternative crops require awareness, and at times a bit more management compared to grazing conventional forages,” he explains.

“If you are putting some of these crops in to provide late-season grazing, feed testing is very important. With nitrates there may be no warning; you just suddenly find a dead animal. Polio takes a bit longer, but the outcome can also be dead animals.”

Another thing to be aware of is that immature crops or crop regrowth have low fibre levels, and a lot of the brassicas and other companion crops have very low fibre levels. “Without sufficient fibre the manure will become very loose, due to high water content and rapid movement through the digestive tract. It is beneficial to feed cattle some high-fibre roughage such as slough hay or straw to increase dry matter content and reduce feed passage rate. Animals that consume one or two pounds a day of the high-fibre material have improved digestive efficiency of the high-quality feeds, and greater opportunity to extract the nutrients before they go out the back end,” says Yaremcio.

“In some of these crops the magnesium levels can be fairly low, such as 0.12 or 0.13 per cent whereas you need about 0.2 per cent magnesium in the ration to have proper balance. A lack of magnesium, especially if potassium levels are high, could lead to tetany situations and downer cows,” he explains.

Most of the time, these alternate crops are grown on certain fields between other major crops. There’s usually no problem with intake; cattle really like them, even though it may take them a few days to adjust to the different taste or texture. Various crops may have differences from year to year in palatability and length of time it takes the cows to adjust to the new feed. For instance, he says some people were saying their cows didn’t want to eat their pea straw last year, and usually there was no problem. It may have grown a bit differently last year, or the leaves were a bit waxier.

“Sometimes cows that are accustomed to a really good pasture are fussy in what they want to eat. If you suddenly switch them to a cover crop it may take them a few days to get them to eat an alternate crop. If you don’t see them really going after it by the second or third day, you need to re-evaluate whether they are actually going to eat it or not. Usually by then the cows are hungry, they get used to the taste and texture of the feed and start eating it more readily,” says Yaremcio.

If a producer is trying an alternate crop for the first time, it helps to talk to someone else who has done this or knows about various forages, to glean some suggestions and guidelines.

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