Prescribed grazing can improve pastureland, eliminate problem plant speciesWritten by Gayle Smith
North Platte, Neb. – Management is the key to using prescribed grazing for improvement of livestock pastures. Casey Matney, Colorado State University Extension rangeland specialist, told producers how to control weeds with livestock during a recent rebuilding the cowherd meeting in North Platte, Neb.
“Controlling weeds with livestock can be as or even more effective and sustainable than using herbicides alone,” Matney explained.
He sees prescribed grazing as a way to improve pasture quality with less risk to target plant species while providing a free lunch for livestock.
“It has an added advantage of converting weeds into a saleable product,” he noted.
“Controlling weeds with livestock is like visiting a doctor and being given medicine,” Matney shared. “We need the proper prescription.”
The end goal is to alter the proportion of species in the plant community by harming the target weed species, which requires manipulation of defoliation patterns, he explained.
“Prescribed grazing is holding back the target weed species, so desirable plants can come back even stronger,” he continued.
Developing a prescription can be simple if producers know the plant community and S-T-M models, or state transition models. They also need to know their livestock and animal behavior and understand the complex plant-animal interactions.
“We will also need to determine the best season to graze those weeds, the defoliation intensity needed and the species of livestock needed to get the best control,” Matney added.
Breed, age and sex of livestock can also be factors. Producers need to think about age and class of animal, like a yearling compared to a cow/calf pair, when determining the stocking rate to use to achieve proper intensity of defoliation.
The key is targeting those undesirable weeds when they are most vulnerable.
“The prescription consists of determining the proper season, duration of grazing and intensity of grazing,” he explained. “We can harm the target plants by grazing them at a time and frequency when the weed is most vulnerable – usually, before the plant matures and is producing seed and biomass.”
Matney cautioned producers not to graze too early in the season but early enough that the targeted plants haven’t reached mature flowering and produced a seed set.
“Remember that some plants may put on a seed set at different times,” he said. “The goal is to graze them before they have matured so it will affect their seed production the next year.”
Some recommendations Matney shared are to graze in the early part of the season when the plant has developed a long stem. Producers will also want to graze when the plants have limited toxicity and are palatable and nutritious.
“Livestock won’t eat the plant if it is not palatable,” Matney explained. “It has to be tender and moist with good protein that will convert to growth.”
“Make sure the plant is low in fiber content,” he continued. “Once the plant becomes more stemmy, it has more fiber and less crude protein. Large infestations of plants that are unpalatable or less preferred may require heavy stocking rates, while small infestations of forbs that are palatable or preferred forage may only require a light stocking rate.”
Weedy plants may also be better consumed by one species of livestock over another.
Cattle are grazers that can handle fibrous herbaceous plants because of their rumen. Grasses and grass-like plants are also desirable to them.
Goats are browsers with narrow, strong mouths and large livers that allow them to deal better with secondary toxic compounds. They can digest those better than cattle, Matney shared, and they also prefer woody plants.
Sheep have narrow mouths and large rumens to handle herbaceous plants and forbs really well.
Matney encouraged producers to put together a solid management plan.
If the prescription works, producers should see significant damage to the plants targeted and limited damage to the non-targeted plants, he explained.
Once the livestock have grazed the undesirable plants, Matney said it is important to hold those animals in an area for two to three days to allow the majority of the seeds to pass through their digestive system.
“During that time, feed the animals clean feed and provide plenty of water,” he noted. “We don’t want the seed to pass through their digestive system into the clean pasture they move into.”