Heifer eating Canada thistle

Spines on Italian thistle are 1/2" long. That's what the logo cow is eating.

Trainee eating distaff thistle. It's high protein helps the rumen process lower quality forage.

Whenever I tell folks that I've trained lots of cows to eat lots of different kinds of thistles, the first question I get is "Don't the spines/prickles hurt them?"

The answer: "Apparently not."

In 5 years of doing this, a trainee has never had a health-related issue as a result of eating thistle. Thistle-eaters gain weight at rates equal to or better than their non-thistle eating counterparts, they breed back, calve successfullly, and teach their offspring to eat the weeds too.

It seems that thistles don't affect them the way they affect us. I've seen cows stick their heads into patches of thistle just to reach a bit of grass, and those same thistles would stick right through my jeans. I've seen them start at the top of a plant and chew their way down to the bottom. I've walked into trainees' pastures to look for Canada thistle, only to find that every plant has been bitten off even with the grass. Finally, a herd I taught to eat late-season diffuse knapweed decided on its own to add Canada and musk thistle to their diets.

As with any plant, there are cautions to training cows to eat thistles. Canada thistle is a nitrate accumulator, so I have to allow time for the rumen to adjust and I make sure that animals are never put in a solid stand of that weed.

I highly recommend thistles as a forage. They've got good nutrition, it's generally available from spring through fall, and it's resilient.