Resistant Weed Seed As Livestock Feed? Ask The Australians

Chaff Cart - Photo by Grain Research and Development Corporation, Australia

Chaff Cart - Photo by Grain Research and Development Corporation, Australia

Weed seeds may have value as a livestock feed in certain cases, based on results from an Australian demonstration.

In the project, Marino sheep from the same herd were randomly divided into two groups. One group simply grazed stubble in the field that included chaff spread by the combine during harvest. The other group could graze but it also had access to piles of chaff gathered during the harvest. The demonstration looked at chaff from several different crops, including Canola, wheat, oats and barley.

Sheep in the grazing-only group showed a weight loss of 4.4 pounds at the end of 6 weeks. The sheep with access to chaff piles didn’t lose weight and, in fact, gained a few ounces. A major producer-owned cooperative, Meat & Livestock Australia, funded the three-year project, which was conducted in eight different locations in the state of Western Australia.

Chaff Carts Make It Possible

The chaff was collected with a chaff cart, which a combine tows through the field as it harvests grain. A conveyor belt whisks the chaff and weed seed into the boxy cart. Chaff carts have gained a fit in Australia’s grain production regions. When full, a cart’s load is dumped and burned, which destroys weed seed brought along for the ride.

U.S. researchers evaluated chaff carts earlier this decade but largely backed away from the idea because of logistical concerns. For one thing, a combine and the pull-behind cart are a lengthy rig to maneuver around country roads in parts of the U.S.

Much of the early U.S. testing was in Arkansas, which has a far different terrain – and busier roads – than in Australia’s grain production areas. Those tend to be more like America’s Wheat Belt.

A chaff cart is an added piece of equipment, of course. In Australia, chaff carts retail for $80,000 (about $57,000 U.S.). Pulling the cart would likely add some wear and tear on the combine, too.

Feeding the chaff – gathered to control resistant weeds – is a way to offset some of those costs.

Return On Investment

To some degree, growers in Australia have been feeding chaff to sheep for several years. This specific demonstration provides a quick snapshot of possible economic returns when chaff and weed seeds are routed to sheep.

Obviously, the farmer gains some “free” feed. One economic analysis, based on a “model farm” scenario and a 3:1 feed conversion ratio, showed a 21% internal rate of return when the chaff is fed out in piles. That 21% return includes the cost of a new chaff cart, maintenance and then the sale of the cart after 20 years of use.

The economic analysis did not include any gains due to weed control, such as reduced competition or lowered herbicide costs.

One possible concern with feeding chaff has been whether sheep that eat weed seeds would later spread them across fields. That doesn’t seem to be happening enough to matter, according to a report on the project that appears on Australia’s Weed Smart website.

“Farmers who routinely use sheep to graze chaff piles say that there is no noticeable spreading of weeds across the paddocks (pastures),” writes Cindy Benjamin, the report’s author.

The Department of Agriculture and Food in Western Australia (DAFWA) has confirmed those observations, she points out. Of the weed seed eaten by sheep, only 3% will germinate “after passing through a sheep’s digestive system.”

For anyone working only with cattle, the kinds of weight gains cited here may not seem important, but with Marino sheep it’s enough to improve the flock’s condition score, boost lambing percentages and reduce summer feed costs, Benjamin notes. Among Australian sheep producers, the chaff piles, she observes, are “worth a serious amount of money.”

“When you add in the value of chaff management as a weed seed control measure to combat herbicide resistant weeds,” Benjamin adds, “the return quickly pays for the investment in a new chaff cart.”

To read Benjamin’s full report, click here.

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