Range Sheep Nutrition: UW Sheep Specialist and Extension educator provide tips for wintering ewes
“During the summer, rangelands have a lot of different plants and good diversity. But, as sheep producers, we sometimes forget there might be five or six feet of snow drifted in during winter months, and there are only portions of the rangeland our sheep can eat,” stated Brian Sebade, University of Wyoming (UW) Extension educator based in Albany County.
Sebade and his colleague Dr. Whit Stewart, UW Extension sheep specialist and associate professor, presented information on nutrition for ewes in rangeland systems during winter months at the Fremont County Farm and Ranch Days in Riverton on Feb. 8.
With the tough winter many Wyoming producers have battled the past few months, the two experts reminded attendees it is critical to ensure ewes wintered on rangeland systems receive extra care to meet their dietary needs and offered information on the nutritional makeup of different rangeland plants.
Flexible eaters
To kick off the discussion, Stewart cited research conducted at UW over the past few years, which has focused on understanding what sheep eat when they are out on rangelands.
With the help of UW Extension Rangeland Specialist Dr. Derek Scasta, Hot Springs County UW Extension Educator Barton Stam and UW Graduate Student Alexis Julian, Sebade and Stewart analyzed the percentage of grass versus the percentage of browse plants in a range ewe’s diet.
“What we found is sheep are very flexible when it comes to what they can consume,” Stewart stated.
He explained in the northeast corner of the state rangelands are dominated by crested wheatgrass, so sheep studied in this area had a diet of 95 percent grass.
Comparatively, in the southwest corner where rangelands have more plant diversity, the majority of ewes’ diets consisted of browse species.
“Sheep really make due with what they have,” Stewart noted.
Benefits of plant diversity
In addition to better understanding what sheep eat on rangelands, the team of researchers dived into how much of a ewe’s nutritional requirements are being met if their diet consists of mostly shrub species compared to a diet of mostly grasses.
“We determined ewes on operations with a lot of plant diversity were more adequately meeting their nutrient requirements than ewes exclusively grazing dormant grass,” said Stewart.
The research included collecting plant clippings and fecal samples from 25 different sites across the state.
“We looked at the percentage of crude protein (CP) in grasses compared to shrubs,” he explained. “A baseline of seven percent CP is needed for a sheep’s rumen to keep moving. We found grass was around four percent CP, which is far below necessary levels for sheep in the winter. Shrubs were around 10 percent.”
“We don’t necessarily assume our livestock are eating a lot of woody species out on the range, but they have some really high CP percentages,” Sebade said, noting research found juniper has around five percent CP, shadscale saltbush has eight percent, fringed sagebrush and silver sage have nine percent, Wyoming big sagebrush has over 11 percent, gardener saltbush has 12 percent and greasewood has 16 percent.
Comparatively, Stewart and Sebade found needlegrass has less than three percent CP, basin wildrye has just over three percent, blue grama and crested wheatgrass have less than four percent, Indian ricegrass and intermediate wheatgrass have four percent and bluebunch wheatgrass has 4.3 percent.
“Some other grasses including prairie junegrass, needle-and-thread grass, prairie sandreed and reed canarygrass all come in under four percent as well,” Sebade said.
Stewart noted research also found shrub species tend to have greater amounts of minerals such as calcium, phosphorus, potassium, magnesium, sulfur, sodium, zinc, copper and manganese than grasses.
Supplementation
versus substitution
The primary take home message Sebade and Stewart encouraged attendees to walk away with was the idea of supplementation versus substitution and when to use one or the other.
“I realize many producers understand this, but the principle of supplementation versus substitution is important,” Stewart stated, further explaining supplementation is the act of providing a certain amount of high-energy or high-protein feed to bridge the gap in nutritional requirements a ewe may not receive through grazing exclusively.
However, Stewart noted during some winters rangelands may see a lot of snow cover, which makes it hard for ewes to disperse and graze because they don’t have access to feed, and it requires a lot of energy to get around in the deep snow.
In this case, he said producers would need to pivot to substitution.
“With a lot of snow cover, we can’t just bridge the gap. We have to provide the base amount of material ewes need to make ends meet,” said Stewart.
He referred to feedback from across Wyoming which shows many producers in the state supplement ewes with alfalfa and side dress with corn.
“Generally speaking, alfalfa is the most cost-effective source of CP, but we have to think about how quickly nutrient requirements jump as we move from maintenance, flushing, early and late gestation and early and late lactation,” Stewart said.
“It’s good to hear producers are providing corn this time of year because corn provides a tremendous amount of energy to a ewe,” he added. “We have done work showing one-half of a pound of corn will yield nearly 40 percent of the energy requirements for a 160-pound ewe for an entire day.”
“We are knocking out close to half of her energy requirements simply by providing a little bit of supplemental corn,” he continued.
Stewart noted there is some controversy when feeding corn on rangeland systems, however.
“Don’t feed corn on range because it will reduce digestive ability – we hear this all the time,” Stewart noted. “But some excellent work done at UW long before I arrived shows providing corn at one-half of a percent of a ewe’s body weight or around 23 percent of her total daily intake will actually increase low-quality feed consumption on winter range.”
Hannah Bugas is the managing editor for the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.
