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Legumes are best, but…

Nova Scotia researchers are looking at ways to maintain their percentage in forage mixtures under grazing

Research shows if cattle are given a preference, they want between 60 to 80 per cent of legumes in their pasture.

Not only are legumes a superfood for humans, but they are a superfood for cattle too. In fact, regardless of what type of livestock producers raise, the animals perform better on a diet of grass mixed with legumes than if just on a diet of straight grass, resulting in better weight gain and increased milk production.

They must know legumes are good for them too. John Duynisveld, a research biologist at Agriculture and Agri-Food Canada’s (AAFC) Nappan Research Farm in Nova Scotia, says research shows if cattle are given a preference, they want between 60 to 80 per cent of legumes in their pasture.

Researchers aim for 30 to 40 per cent in the Nappan pastures, but there are challenges to grazing and maintaining that level because of the growth patterns of the plants and the way animals graze. “Grazing management is important to maintain the types of pasture you want with the more desirable species you want to do well,” Duynisveld says.

Legume research

Considering the benefits, it makes sense researchers want to learn more about how they can increase, and maintain, legume content in pastures. That’s why, in recent years, the researchers at Nappan conducted cultivar research to look at grass species seeded with legumes and how the mix performs under grazing.

“Although most forage produced in Canada is comprised of species mixtures, there is limited research on identifying the best species, and cultivars, to include within forage mixtures,” says Yousef Papadopoulos, a forage breeder at the Nappan Research Farm. “The ultimate objective is to identify mixtures that enhance forage yield and nutritional quality throughout the grazing season, but particularly during all regrowth periods following the initial grazing.”

In a four-year study, the researchers determined the agronomic performance of binary mixtures of one of three legume species — birdsfoot trefoil, alfalfa and white clover — with one of three commercial cultivars of six grass species — timothy, Kentucky bluegrass, tall fescue, orchardgrass, meadow fescue and meadow brome. By using rotational mob grazing on the 54 binary mixtures over four years, they determined that a mix of legume, grass species and grass cultivars significantly affects annual dry matter yield (DMY) and seeded grass plant counts.

Results showed the most valuable players based on mid- and late-season yield and energy were Kokanee tall fescue with alfalfa or trefoil, Ginger bluegrass with white clover and Bg3 bluegrass with alfalfa. Yield and quality of grass species and cultivars in mixtures depended on the legume present.

Researchers aim for 30 to 40 per cent legumes in the Nappan pastures, but there are challenges to grazing 
and maintaining that level. photo: Supplied

Trefoil advantage

The researchers also found better animal performance when mixtures contained trefoil instead of alfalfa. This is attributed to the fact that studies of trefoil have shown it has condensed tannins which improve animal performance.

“Trefoil has better animal performance but it is harder to maintain in forages because it has a different growth strategy and animals will graze it to the ground so it can’t recover and regrow,” Duynisveld says. “Red clover and alfalfa have a big crown, so they grow back quickly once grazed off.”

Conducting the research while feeding cows on pasture gives the researchers a unique perspective. “Most research being done is with mechanical harvesting,” Duynisveld says. “But cows are selective about what they want to eat. Their hooves impact the fields and when cows eat, they wrap their tongue around and tear and pull on grass. This all has a different impact than what mechanical harvesting does.”

Management is key

How producers manage grazing will have a big impact on the type of legume they will see in their pastures, according to Duynisveld. At the Nappan Research Farm, they’ve seen fields start at the target of around 40 per cent legume content drop to eight per cent after three or four years due of grazing.

Studies led by Papadopoulos at Nappan have looked at three different grazing strategies: rotational, which is what they recommend for optimal pasture; rotational — with stockpiles to stop grazing in June — so the pasture is ready for grazing in August; and rotational — with stockpiles to stop grazing in July — so pasture is ready again for grazing in October.

“We’ve done this for 10 years, applying these strategies and found that for pastures with rotational gazing all summer, white clover stayed strong,” Duynisveld says. “Red clover and alfalfa did better when rested for stockpiling for fall. In that case, we were looking at how different species grow. We have to be able to allow the plant to grow the way it is meant to grow.”

Incorporating legumes also has a positive impact on winter grazing. “With legumes, we found the biggest impact if we got 30 to 40 per cent red clover. We didn’t have to add nitrogen fertilizer to get the same yield,” Duynisveld says. “That said, if legumes get too much frost, the leaves fall off and aren’t available for grazing.”

The researchers are now looking at what mixes producers should consider for different uses, such as finishing livestock or grazing for mature animals, and are working to develop recommendations for producers. They are also working on the best ways to increase legume content.

Past research looked at sod seeding and frost seeding techniques to introduce red clover into existing pasture and found that after two to three years, legume content can increase significantly.

“We don’t know how well this will work with trefoil and alfalfa,” Duynisveld says. “To get 30 to 40 per cent, that’s what the next research will focus on.”

This article originally appeared in the October 2017 issue of the Forage & Grassland Guide


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