As drought conditions continue in the High Plains region, forage supplies remain tight and hay prices continue to increase. Sporadic rains have brought a flush of Kochia and Russian thistle in failed wheat fields and fallow areas. The option of grazing or harvesting these weeds for feed as hay is frequently considered by producers as a forage resource. These two non-native species, originating from Eurasia, when small and immature can be quite palatable to cattle and readily grazed. However, as they mature, they can become unpalatable, lose their quality, and can increase in concentration of compounds that are toxic.
Kochia
Kochia can be a high-quality forage when it is immature and can have protein content ranging from 11 to 22%. However, it also contains several compounds that contribute to its potential toxicity, including oxalates, alkaloids, saponins, nitrate and sulfate which tend to concentrate as the crop matures and sets seed and appear to have increased risk with drought conditions. Problems with acute, or short-term, toxicity typically occur when cattle are hungry and have been moved from drought-stressed pastures onto a post-harvest wheat field or an old dry lot where Kochia is the primary feed source and is high in nitrates or oxalates. Incidence of chronic or long-term toxicity also tends to increase when Kochia is being grazed, and cattle are consuming it almost exclusively for an extended period of time, ranging from 30 to 60 days.
Russian Thistle
Russian thistle like Kochia can be an average quality forage when it is immature. Like Kochia, it also can be high in nitrates and oxalates. This plant is most readily utilized when it is young and still palatable. If it is going to be harvested as hay, this should occur before spines form. Russian thistle can have a laxative effect for cattle when it is consumed.
Guidelines for Use as a Feed
If utilizing Kochia or Russian thistle hay as a feed, test for nitrates prior to feeding. While comparative research is limited on utilizing this as a feed resource, it is recommended that mature Kochia or Russian thistle not comprise more than 25 to 50% of the diet. It is also recommended that if it is utilized as a significant part of the diet, that it not be fed for extended periods of time lasting longer than 40 to 60 days.
When feed is in short supply or annual forages planted for hay are infested with weedy species such as Kochia or Russian thistle, it will often be utilized as part of cattle diets. Taking time to review potential toxicity issues as well as the risks and management practices that can be utilized to mitigate toxicity can help to minimize problems when utilizing these weeds as feed.
Sources
Thomson, et al. (2002) Feeding Kochia to South Dakota Livestock, Extension Extra
Hollis, et al. (2010) Kochia Toxicity, Kansas State Research and Extension
Lardy, Greg (2008) “Some Weeds Can Be Used as Emergency Forage Crop” North Dakota State University Extension and Ag Research News
Lardy, et al. (2022) Alternative Feeds for Ruminants, North Dakota State University Extension
