My first opportunity to train cows to eat Whitetop/Hoary Cress (Cardaria draba) was in June of 2010 in Harney County, Oregon. Cows belonging to the Roaring Springs Ranch, the Borelli Ranch, to Dennis Beurmann, and Carol and Alfred Dunten all learned to eat the weed. Some trainees were fed the weed in training for 2 days, and others for only one day, but they all started eating it in pasture right away.
The speed that the cows took to eating whitetop/hoary cress probably isn’t because Harney County cows are especially good students. It’s more likely because whitetop is very palatable, even to people. Whitetop is part of the mustard family and it’s leaves and flowers have a radish-like flavor. The USDA Forest Service’s Fire Effects Information System says that white top and other wild members of the mustard family are high in vitamin C and their nutrients make them suitable for human consumption.
Adding a few white top leaves and flowers to your salad won’t do much to reduce the weed in your pastures. But the high protein values might encourage you to get your cattle to work on it. Allreference.com provides the following information on the plant’s protein values through the growing season:
- Rosette: 28.5
- Bolting: 29.5%
- Early bloom: 20.3%
- Full Bloom: 11.3%
- Full Seed: 7.9%
Since feed tables show that cows and calves gain weight more rapidly when they get higher protein foods, white top could be part of your cows’s healthy diet.
Hoary cress (also known as whitetop in some areas) is a member of the Brassica family. This family of plants is known for its sulfur containing toxins primarily in the form of chemicals called glucosinolates. Glucosinolates are found in cauliflower, broccolis, Brussels sprouts, and more importantly to those feeding cattle in turnips, kale and rape. These last three have been known to cause “brassica poisoning” in cattle when animals graze them in very large quantities.
In the case of Hoary Cress, there are no records of animals suffering negative consequences from eating it. Ranchers in Nevada whose cattle ate large quantities of this plant during the 2012 drought reported no problems at all. In some cases glucosinolates can cause enlarged thyroids, but according to Jim Pfister of the Poisonous Plants Lab, ruminants are not too prone to thyroid problems from brassicas unless they are eating large quantities for many weeks. Adverse effects can be overcome by offering cattle and sheep a salt-trace mineral mix with .008% iodine.
Collecting Weeds for Training
I use a regular hedge clippers to clip plants and drop them in the tub. Then I cut them into “bite-size” pieces of about 4” – 6” each. This makes it so they can actually take a bite without the leaves and stems catching and being drug out of the tub. You’ll need about 2 loosely filled training tubs of hoary cress per training.
The idea of grazing hoary cress to manage it is a new one so we don’t have all the information we might like. In mowing tests, cutting plants before flowering did little to control hoary cress. Cutting or grazing plants in full flower resulted in smaller plants and less seed production. In research done by MicInnis et al, grazing hoary cress in its early growth stages reduces seed production. Finally, sheep grazing has reduced hoary cress populations, so the same should be true for other grazing animals.
As with any forage, the more often, and the shorter you graze it, the more difficulty it has resprouting. If you are in a situation where you need to reduce hoary cress populations, you can manage your animals to graze it more often and harder, keeping in mind that you don’t want to harm other forages in the process. For a less labor intensive option, I recommend using it as a forage throughout the growing season, managing it as you would other forages in your pastures.
Watch Cows Learning and Eating Whitetop
Here’s a 3 minute video showing the Harney County cows at work. Thanks to Ben Borelli who shares why he thinks this is a great idea.