There are several concerns associated with grazing johnson grass hay for cattle. Prussic acid, a cyanide-based compound, has been linked to some cases of cyanide poisoning, so cattle owners need to follow certain guidelines when it comes to grazing johnsongrass. Southern Forages recommends waiting seven days after a frost to begin grazing a Johnson grass pasture. This will ensure that the amount of prussic acid present in the pasture is below dangerous levels.
Grazing johnsongrass
Grazing johnsongrass hay is safe for ruminant livestock in the right conditions, but it is not always suitable. It has several side effects, including nitrate buildup, prussic acid formation and toxicity. Some producers of hay have used a treatment to prevent johnsongrass from causing toxicity. There are also a number of other forage sorghums that may be toxic to cattle.
As a perennial grass, johnsongrass does not tolerate low grazing. Grazing johnsongrass needs to be done at a rate of six to eight inches per day, depending on the plant’s growth stage. When mature, its quality decreases rapidly. In addition, it produces a large amount of seed, so grazing johnsongrass for cattle is not always the best option.
A small proportion of cows will succumb to the Johnsongrass. Nevertheless, a farmer’s hay-raising efforts will pay off if he’s able to identify dead cows near the patch of johnsongrass. A farmer once described how he was hauling a bale of hay into a pasture. As he continued grazing the lush Johnsongrass that grew along the roadside, he was suddenly surrounded by dead cows and yearlings.
Prussic acid poisoning
If a farmer suspects his or her cattle of ingesting contaminated Johnson grass hay, the next step is to test the forages for prussic acid. The prussic acid concentration in the hay can be as high as 25 mg/100 g dry matter. Toxicological tests are available from the Toxicology Laboratory of Virginia-Maryland Regional College of Veterinary Medicine. For the best results, the samples should be stored well-refrigerated and frozen. Similarly, the University of Nebraska and Texas A&M have testing labs that can be used for the evaluation of hay.
To avoid this hazard, producers should consider different grazing practices for sorghums and Johnsongrass. While both contain high levels of this cyanide, sorghums can be a higher risk than Johnsongrass. If a farmer is unsure of which hay to use, he should test the forage with a methylene blue or sodium thiosulfate.
Prussic acid is a serious problem that many livestock producers do not fully understand. It can result in severe injury or death for an animal. The acid inhibits the absorption of oxygen and interferes with cell respiration. Even a small dose can cause asphyxiation in minutes. To protect livestock from this danger, producers should consider deferring grazing until the plant has dried out, which can take up to 7 days.
Keeping johnsongrass in check
Keeping johnsongrass in check when you hay cattle is an important practice for livestock producers. Although it can be a nuisance, the grass can also pose a health risk to cattle. This is especially true if the pasture is infested with the weed. The first application of a specialized herbicide should be made before the johnsongrass is more than six inches tall. If you see regrowth, apply another application of the herbicide. You must use a different herbicide for each regrowth application to avoid the selection of herbicide-resistant johnsongrass.
Keeping johnsongrass in check when you hay cattle is critical because the weed can damage crops. It is best to wait until the grass is 18-24 inches tall to begin grazing. It is especially important to monitor the weed before turning cattle into it, as this puts the animals at risk for prussic acid. Therefore, if you have cattle in a pasture with johnsongrass, you should use monitor animals to help you identify the weeds.
Luckily, if you notice signs of johnsongrass early on, you can treat the cows. You can administer a proprietary solution containing sodium nitrite-sodium thiosulfate to the animals. This medication must be injected intravenously and must be administered slowly. Depending on the severity of the infestation, a single dose may be necessary.
