If you plan to feed out sorghums, there are several things to consider before feeding. Below, we talk about the various ways and what level of concern you should have. When in doubt, test before feeding.
Pasture. Grazing sorghum is considered to be the most dangerous option when HCN potential is a concern; however, proper management can reduce risk. Figure 6 shows a calf grazing sorghum-sudangrass that is more than 18 inches tall and shows no stress from frost or extreme drought, both conditions that could increase HCN potential. Residues from grain sorghum can be safely grazed after grain harvest, if the remaining plant is totally dead after a frost, or a week has passed since the frost occurred. Grain sorghum can have small tillers that can be high in HCN until after a killing frost.
Hay. It is recommended to use forage sorghum as hay when HCN potential is not a concern; plants are greater than 18 to 24 inches tall, and not drought or cold stressed. Drying does not eliminate risk. If in doubt about the degree of stress that might lead to elevated dhurrin in hay, collect a representative sample and test for HCN potential.
Silage. Silage is considered one of the safest options when feeding sorghum forage.
Green Chop. Use of green chop reduces HCN potential as compared to grazing but is not considered as safe as feeding silage.
If HCN is a concern, several steps can be taken to reduce the potential of cyanide toxicity. These steps include:
- use the sorghum before a frost occurs,
- submit sorghum sample(s) to a qualified lab to be tested for HCN,
- wait to graze 7 to 10 days after a killing freeze,
- do not apply more than 50 pounds of nitrogen (soil plus fertilizer) per cutting, and
- dilute the sorghum feed with another feed source.
If you suspect HCN poisoning in even one animal, call your local veterinarian immediately and remove the rest of the livestock from the feed. Accurate diagnosis of clinical signs and removal from feed is important in these cases. Your veterinarian may collect samples of forage, rumen contents, or blood to help confirm a diagnosis.
Overall, sorghum has many beneficial properties. If proper management occurs, sorghum can be a safe and beneficial forage crop. Soon, a new hybrid will be on the market that is dhurrin-free. This hybrid will not release HCN because there is no accumulation of dhurrin. This new hybrid will be a great option for removing the fear of cyanide toxicity.
Kansas testing information
Check with your local county extension agent or office for the closest option. https://www.ksre.k-state.edu/about/statewide-locations.html