Forage brassicas like turnips
help graziers beat the heat
They only started grazing turnips as part of Michigan State University research in 2006. But the brassica offers enough benefits that it has remained a part of their dairy’s forage rotation, say Terri and Rick Hawbaker, of Grazeway Farm, Pewamo.
“We’ve really come to like turnips. Our milk production increased, but we’ve come to like them for a lot of other reasons,” says Terri Hawbaker.
“It’s instant feed. We plant turnips with a pasture mix of alfalfa, Kentucky bluegrass, orchardgrass, perennial ryegrass, timothy and red clover. Thirty days later we have a crop. If we were to wait for the pasture mix, it would be much later,” she says.
Brassicas like turnips may not compete with conventional forages when it comes to tonnage. But the Hawbakers and other graziers find they do offer drought resistance, impressive nutritional qualities and can fill in the seasonal gaps for any grazing system.
“The product (turnips) has very close to the energy of corn, and it’s actually very close to the protein of alfalfa,” says Terry Gompert, University of Nebraska-Lincoln Extension educator in Knox County, NE. Planting costs are also terrifically low, with seeding rates of only 2-3 lbs/acre, he adds.
The most common forage brassicas – turnips, kale, rape and radishes – have been bred to fit as summer-slump pasture supplements when cool-season grasses are diminishing, or to extend the fall and winter grazing season.
For fall and winter grazing, Gompert recommends planting turnips with big bulbs that grow partially beneath the soil so cattle can harvest them even if the ground freezes hard.
Brassicas meant for summer grazing have small bulbs – or no bulbs at all – but have fast regrowth.
The best forage turnips for summer have multiple growing points on the stem, allowing for faster regrowth and a higher leaf-to-stem ratio, explains Richard Leep, Michigan State Extension forage specialist, who has studied brassicas extensively over the past 15 years.
“You can graze them down to about 4” of stubble, and they will regrow very nicely and be ready to regraze in about a month after the initial grazing,” he adds.
If soil erosion is a problem, Gompert advises planting forage rape. Cattle won’t graze to the bottom part of rape plants, which will leave stubble to hold soils in place. If soil compaction is an issue, he recommends planting radishes, which have a substantial taproot that can break soil apart.
If a dairy producer or rancher is going for a longer growing season, Leep recommends using kale.
“Kale is a little later-seasoned than either the forage turnip or forage rape, and you generally plant that in the spring, so it will be utilized in late fall or early winter,” he says.
Yearling cattle can easily achieve a gain of 2 lbs/day on a brassica forage, Gompert notes.
But because of the very low fiber content in brassicas, up to a third of the ration has to be supplemented with hay, resulting in higher hauling costs if hay has to be brought to the field. Leep recommends seeding a grass such as oats, triticale or sudangrass with the brassica so a fiber source is already in the field.
When it comes to feeding dairy cows, though, Gompert and Hawbaker urge caution.
“The issue with the turnips or any high-protein product is that it flavors the milk,” Gompert warns. “So if you’re using turnips, use them as a supplement and have them less than 25% of your ration so you don’t get the flavoring – unless you’re trying to do a niche market and have a turnip-flavored milk.”
Hawbaker chose Pasja turnips, which aren’t known to flavor milk. Yet she still takes care to limit her 100 crossbreds’ turnip consumption.
“They don’t get turnips 24 hours a day,” she says. Because turnips make loose manure, cattle graze them for 12 hours, then are moved to grass the next 12 hours. The Hawbakers get about four grazings from each turnip field, which gets them over their summer slump.
A big hurdle for brassicas, though, is the toxic levels of sulfur and nitrates that can accumulate in the plant – problems that Kenny Smith, custom cattle feeder in Connell, WA, knows all too well after grazing 850 cattle on forage turnips last fall.
An early October freeze sent nitrate and sulfur levels spiking to toxic levels in Smith’s turnips. He immediately noticed sick-looking cattle and quickly added more sudangrass hay to the diet to dilute toxicity. Nitrate levels were mitigated, but sulfur toxicity remained unchanged. Dead cattle even tested positive for prussic acid in autopsies.
After about three weeks of grazing, Smith had all the losses he could take and pulled the cattle off the field.
“We ended up losing about 10 cattle,” he recalls. “And I think we had about a dozen more that had polio symptoms, which are from sulfur toxicity. Basically, the cattle just get blind from the sulfur.”
Gompert says feeding iodized salt will help solve the high-sulfur problems commonly found in forage brassicas. Other livestock operators over the years have also reported problems with choking and pulmonary pneumonia, he adds.
Even with the management challenges brassicas present, Gompert foresees more livestock producers working them into their grazing systems.
“Like everything, there are some management things with brassicas we have to look at,” he says. “But I think time has really proved them to be just an outstanding opportunity.”