Stam looks at matching range plants to cattle nutrient requirements
Worland – “When we talk about forage nutritional values, we also need to talk about the requirements of cattle and making sure that what they need nutritionally is provided by forage available at different times of the year,” said Barton Stam, University of Wyoming Extension range management specialist.
Stam addressed a wide variety of producers at the 2014 WESTI Ag Days, held Feb. 3-4 in Worland.
“We need to be thinking in terms of what our animals need and what is provided at different times of the year,” he commented.
The challenge in looking at cattle management and range utilization is the diversity of species present from state to state, county to county or even pasture to pasture.
When considering cattle diets, Stam marked energy, protein and water as incredibly important for consideration.
“Energy is the component of the diet that is most limiting,” he said. “Every process that goes on in the cow’s body requires energy.”
While producers frequently look at only protein, Stam noted that most energy comes in the form of starches, such as the celluloses that makes up the cell walls of plants.
“Cellulose is a fairly low source of energy, but ruminant animals are unique in that they can change the cellulose to energy where humans can’t,” he said.
After energy, protein comes up when looking at cattle diets, largely because it is one of the most expensive components of the diet.
“With protein, we have a couple of considerations,” Stam comments. “Excess protein in the diet is converted to energy, but that is a very inefficient process.”
Water and others
“Water is probably the most important requirement,” Stam said. “Cattle die the soonest if they don’t have water, and a lot of times, we overlook the quality of water.”
Wyoming’s water, added Stam, is frequently high in minerals.
The time of year may also impact cattle’s consumption of water.
“This time of year, the water may be too cold or icy, discouraging cattle to drink,” he explained. “In the springtime, on the other hand, many plants are flush and green, meaning they are full of water.”
When plants are 75 to 90 percent water, it can be difficult for mature cattle to meet their requirements by consuming green plants.
“That is a great reason to leave leftover forages, so cattle have some dry matter to consume in the springtime,” he noted.
Consequences of lacking diets
“If the animals are deficient, negative consequences will start to be seen,” Stam noted. “We start to see impacts in terms of weight loss, decreased reproductive capacity and, eventually, death.”
Additionally, deficiencies may increase the likelihood that cattle may ingest poisonous plants.
Cattle requirements vary based on their stage of gestation, with the third trimester and lactation requiring increased requirements for mature cows.
“Heifers have even higher requirements,” Stam noted. “They are still growing themselves, in addition to growing a calf.”
In the third trimester, Stam noted that mature cows require a diet of 6.5 to seven percent protein and 44 percent of total digestible nutrients. Heifers, on the other hand, require eight percent protein or more and 55 percent total digestible nutrients.
In general, Stam also said that plants on the range vary greatly in terms of their protein and total digestible nutrient content.
Some grasses, such as crested wheatgrass and western wheatgrass begin with high protein content in the spring, at 23 percent and 31.6 percent, respectively. However, by the end of the season, the protein decreases to 4.5 percent and 7.9 percent, respectively.
“There are also other factors to consider aside from quantity of energy and protein,” Stam commented. “The fiber content may also affect palatability and negatively influence intake.”
As an example, crested wheatgrass has high protein content, but the season of use is in the spring and fall.
“It is the first to come up in the spring and be tolerant of grazing, but as we get into summer, it has all the palatability of a screen door, and cattle don’t like to eat it,” Stam noted.
Warm versus cool season
When looking at range plants, Stam also commented that warm season grasses maintain their protein content through the summer, where cool season grasses tend to decrease in protein through the summer.
“The warm season grasses hold their protein longer because they continue to grow during the summer,” he explained. “They can extend grazing seasons.”
Blue grama, he said, is a warm season grass that may help some pasture situations, although he also cautions that the plant will not cure all range problems.
Additionally, woody species tend to hold their protein content longer.
“A lot of the woody plants maintain their protein levels longer into the wintertime,” he commented. “Especially when we look at animals like sheep, and to a lesser extent cattle, woody species can be beneficial.”
Species such as fringed sagewort and low sagebrush, as well as four wing salt bush, are examples.
Stam also noted that a number of options are available for more information.
“Producers can find all the nutritional values of individual plants online,” he said. “They can also contact their local Extension personnel for more information.”
Saige Albert is managing editor of the Wyoming Livestock Roundup and can be reached at firstname.lastname@example.org.
An additional consideration in the diet is the minerals required by cattle.
“When we look at minerals, calcium and phosphorus are important,” UW Extension Educator Barton Stam noted. “The grasses on our rangelands are high in calcium, but phosphorus is usually very low on rangelands.”
Oftentimes, producers may need to provide a phosphorus supplement, and frequently, that can be coupled with a salt block or lick tub.
Vitamins, he added, may also need to be supplemented.
“Vitamin and mineral supplements need to be customized to the producer’s area,” Stam commented.