Switchgrass can replace straw in dairy rations

However, researchers caution against feeding too much to lactating cows or milk production could drop

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Switchgrass has potential as both dairy cow bedding and feed – especially for dry cows.

One of its benefits is that it is low in potassium relative to the more commonly used wheat straw.

High potassium levels can cause problems for dairy cattle, especially if they are calving during a dry season.

Gail Carpenter, a researcher at the University of Guelph’s Ridgetown campus, looked at the replacement of straw with switchgrass in lactating and dry cows.

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Why it matters: About 30 per cent of dairy farms now feed straw as part of their lactation, heifer and dry cow diets. In years when wheat acres are lower, like 2019, that can make straw more expensive and send farmers looking for alternatives – like switchgrass.

Carpenter spoke recently at a meeting on switchgrass at the Clinton-area farm of switchgrass innovator Don Nott.

Carpenter’s research was funded by the Ontario Agri-food Innovation Alliance and the Ontario Biomass Producers Co-operative.

She found that straw and switchgrass are similar nutritionally, other than the fact that switchgrass is lower in potassium than straw.

In order to reduce metabolic problems in dry cows, Carpenter says they are fed “salad”, volumes of lower protein and lower energy feed so that they are satiated but aren’t gaining weight during the dry period.

Reduced potassium in feed is also desirable because high levels are associated with milk fever at calving time.

Carpenter found that body condition score and dry matter intake were similar for cows eating straw and switchgrass.

But the most interesting finding was that switchgrass-fed cows who were in negative energy balance according to body condition score had lower ketone levels.

That’s important because higher ketone levels mean the cows are more likely to develop ketosis, which is a stomach imbalance that can lead to several health issues.

When it comes to lactating cows, the news wasn’t as good for those eating switchgrass.

Carpenter’s research shows that those animals produced slightly less milk and slightly less protein.

“It should be fed to lactating cows with caution,” she says.

Good for bedding

There’s been some Ontario research completed on bedding with switchgrass that shows it can perform well in that use.

Marlene Paibomesai, OMAFRA’s dairy specialist, says that there are several options for dairy farmers for bedding. They include sand, wood shavings, straw, dried manure solids, paper shavings, peat moss and even ground-up drywall.

Sand is the top choice due to its excellent cow comfort and udder health profile, but it isn’t always easy to come by and eventually the world could start to run out of sand, she says.

Switchgrass could be another alternative according to University of Guelph research that compared straw and switchgrass bedding and cow behaviour.

The research, conducted by Trevor Devries and colleagues at the University of Guelph and McGill University compared chopped straw on a mattress, with water, lime and switchgrass and also deep-bedded switchgrass.

In two experiments they found that deep-bedded switchgrass was preferred by cows over the lime and switchgrass and the wheat straw alternatives.

Paibomesai says the cows spent more time lying on the deep-bedded switchgrass and the number of times they laid down in the deep-bedded switchgrass was significantly higher.

She says there are examples from farmers who have been happy using switchgrass as well and that it can be used in place of straw.

The main challenge is consistency of availability of the switchgrass for bedding, as there aren’t that many switchgrass producers in the province. It also has to be competitively priced against wheat straw, which can vary significantly depending on wheat acres and harvest.

About the author

Editor

John Greig has spent his career in agriculture journalism and communications. He lives on a farm near Ailsa Craig, Ontario. Contact John at [email protected] or follow him on Twitter @jgreig

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