SOUTH Dakota ranchers making decisions about grazing their livestock can benefit from 70 years of data gathered at the Cottonwood Range & Livestock Research Station near Philip, S.D.
Managing livestock on rangeland is a balancing act, said South Dakota State University (SDSU) professor Patricia Johnson, a range scientist at the SDSU West River Ag Center in Rapid City, S.D. Many different factors, such as precipitation and dryness, affect how the land will be utilized. Additionally, producers can change their preferences based on the needs of the herd.
Ranchers have to determine how many cattle to run in their pastures, when and for how long. The main objective is to choose conditions that will maximize weight gain yet maintain and protect the pastures. The long-term grazing data generated at the research station provide scientists and ranchers with insight that a simple two- or three-year study cannot, Johnson explained.
For example, long-term studies have shown how changes in precipitation, such as drought, can affect plant community composition and production for years.
"It not just as simple as saying drought will produce this kind of vegetation and livestock production," Johnson said. "Drought can have effects not only during the drought years but for several years following the drought."
Researchers have also explored how the stocking rate, which is the number of cows per acre per month, affects the mixture of native prairie grasses. These studies looked at how to set stocking rates on pastures that were historically overgrazed with the goal of "getting back good native plant communities," Johnson said.
A heavy, long-term stocking rate turns rangeland with mid-grasses, such as western wheatgrass and green needlegrass, into one dominated by short-grasses like buffalograss, blue grama and sedges, according to Johnson. Lighter stocking rates are needed to maintain the mid-grasses in the plant community.
For many years, management professionals recommended that ranchers utilize light to moderate stocking rates. In the northern Great Plains, that will result in a mixture of native grasses dominated by mid-grasses, Johnson noted. However, recommendations have changed somewhat in the past 10-15 years.
"What's desirable now depends on what you're managing for," she said.
More plant biomass is produced with mid-grasses compared to short-grass-dominated pastures. With a relatively light stocking rate on mid-grass-dominated pastures, individual animal weight gains are maximized.
Short-grass-dominated pastures with a heavier stocking rate typically lead to lower individual animal weight gains, Johnson explained. However, the heavy stocking rate usually yields a greater total gain per acre because there are more animals per acre per month.
Many ranchers in western South Dakota maintain short-grass-dominated pastures, which tolerate a higher stocking rate and, therefore, produce a greater total cattle weight gain per acre of pasture.
"On a per animal basis, the cattle don't gain as well, but there are more of them," Johnson said.
For many ranchers in this region, there has been an economic benefit from maintaining the heavier stocking rates on short-grass pastures. However, there is a limit to how heavily native pastures can be grazed, Johnson cautioned. If the stocking rate is too heavy, the short-grasses will disappear, weeds will increase and bare ground will be exposed — and livestock production on both a per-animal and per-acre basis will be reduced.
The short-grass versus mid-grass dichotomy continues when it comes to watershed attributes — especially how much water and sediment come off these communities, according to Johnson. Short-grass pastures absorb much less rainfall into the soil, so they shed much more water than mid-grass pastures because they do so more frequently.
However, research conducted by SDSU and the U.S. Department of Agriculture at the Cottonwood field station showed that when enough water is applied to both types of rangeland to create runoff on the mid-grass-dominated pastures, even though more runoff occurs on the short-grass pastures, both produce about the same amount of sediment.
Johnson pointed out that this runoff scenario is important because all of that water moves off the rangeland, where it could be used for plant production, and then drains into streams, where it scours the banks and adds silt to rivers and lakes.
The sediment loss results of the watershed studies at Cottonwood, however, are not at all typical of other types of rangelands in the western U.S., Johnson explained. Sediment losses from most rangeland in the western U.S. are typically greater for plant communities associated with heavier stocking rates.
"Our plant communities are really good at hanging on to the soil, and our pastures don't fit the patterns that we see elsewhere," Johnson said. That makes the studies conducted at Cottonwood even more valuable to South Dakota ranchers.
High prices are providing an incentive to cattle producers to expand the nation's drought-riddled cow herd. With fewer cows in the nation's breeding herd, it is important to make each cow count, University of Illinois Extension beef specialist Travis Meteer said.
Meteer explained that management strategies play a major role in ensuring that cows rebreed.
"The most obvious management strategy a cattle producer can deploy is conducting a breeding soundness exam on bulls. All bulls that will be used in a breeding season need to be tested. Without a breeding soundness exam, producers are taking a huge risk," he said.
Meteer added that breeding soundness exams are low cost and provide a great return on investment. Bulls that are infertile or have poor fertility will fail to settle cows.
"Evaluating bulls is crucial to making sure that cows get bred. A (breeding soundness exam) should be conducted by a veterinarian each year prior to turnout. Environmental factors, age and injury can all affect a bull's fertility from year to year," Meteer said.
After a particularly harsh winter, checking bulls for frostbite damage, which can cause short-term and long-term infertility, is important.
Bulls should be evaluated for mobility, body condition score (BCS), age and other functional traits. Bulls need to display a free-moving gait with no signs of lameness. Hoof shape, joints and locomotion speed also need to be appraised.
Long toes, cracked hooves or signs of foot rot are characteristics that can cause lameness and the bull's subsequent failure to service cows. Swollen, fluid-filled joints may be signs of structural incorrectness or injury that may affect the number of cows a bull can cover.
Bulls need to be in good body condition, with an ideal BCS of five or six. Bulls that are too thin or too fat can pose problems. Bulls generally lose weight during a breeding season because they are focused on breeding and are traveling to service ready-to-breed cows, so it is important to ensure that bulls are in good condition.
On the other hand, bulls that are too fat may be out of shape and more fatigued when servicing cows. They are also prone to infertility during hot weather because fat around the scrotum limits cooling and thermoregulation.
Furthermore, bulls should be transitioned nutritionally.
"Feeding bulls a balanced diet in a drylot situation where feed is close and readily available is far different from a big pasture full of cows needing to be bred. Lush spring grass is not nearly as nutrient dense as hay and grain offered in the drylot setting," Meteer explained.
"Thus, transitioning bulls to pasture is important in making sure they don't 'melt' or 'crash' when they go to pasture to breed," he said. "I suggest feeding a low-protein, high-energy supplement at 2-4 lb. per head per day. This is very important if you are using yearling bulls. These bulls will have higher nutrient requirements than mature bulls because they are still growing."
Additionally, once bulls are in the pasture or breeding pen, they need to be monitored for libido, he said.
"Open cows are a major drain on profitability of a cow/calf operation. There is no doubt that reproduction is a sensitive mechanism and is vulnerable to several factors. However, evaluating bulls to ensure they are capable of servicing cows is the starting point to making sure your breeding season is successful," Meteer said.
Livestock producers may not be able to eliminate all of the stress the weather places on herds, but if they want to maximize animal performance, they should make management decisions to minimize animal exposure to mud and provide protection from adverse weather conditions, according to Chris Reinhardt, extension feedlot specialist for Kansas State University.
"Rain, snow, ice and extreme temperatures are a part of life in Kansas," Reinhardt said. "However, each of these factors can steal a measure of the animal's performance as that animal moves outside of its comfort zone, called the thermal neutral zone."
The thermal neutral zone for healthy cattle is 23-77 degrees F. When the temperature outside falls below or rises above the animal's comfort zone, the body needs to produce more energy to stay cool or keep warm.
After receiving moisture, feedlots and winter feeding sites can quickly become muddy when animals are active. If cattle are too tightly confined and the feeding grounds are not sufficiently spread out, even calving pastures can become muddy.
Reinhardt explained that producers should be concerned with the effects of mud in their pens for four main reasons:
1. Slogging through a muddy pen increases the amount of energy cattle expend;
2. Mud on the hide reduces the insulation effects of the hair coat, increasing cold stress;
3. Muddy lots in a feedyard make lying down to rest uncomfortable for the animals, resulting in more time spent standing, and
4. Muddy hides reduce dressing percentage at the packing plant, causing an increase in processing costs.
The first three of those concerns reduce the animals' energy left for gain.
"Under stress-free conditions, only about half of animals' normal daily energy intake goes toward gain," Reinhardt said. "All these increases in energy expenditures dramatically cut into what is left over for gain."
The National Research Council reported that 4-8 in.-deep mud can reduce the animals' feed intake by 5-15%.
When the temperature drops to 21-39 degrees F, mud that is dewclaw deep has the potential to create a 7% loss of gain, and the percentage doubles when the mud reaches shin deep.
Reinhardt recommended that producers prepare for muddy conditions by building and repairing mounds within the pen, increasing pen space per animal and smoothing pen surfaces whenever the weather allows.