Many folks planted sorghum-Sudan grass hybrids and forage sorghum with the hope of refilling some hay traps.
We had some moisture early on and many of the fields were off to a good start. Unfortunately, now with over 100-degree days and a lack of moisture, many of those fields have stopped growing and are now just sitting.
Many of those planted acres may not have enough forage to cut for hay, but everyone could use the extra grazing these fields might supply. However, these plants do have the potential to create prussic acid poisoning issues. It is best to be extra careful when grazing forage with the potential to build up high levels of prussic acid.
Prussic acid poisoning is a threat to grazing livestock that are grazing forages that may accumulate prussic acid.
The threat of prussic acid accumulation is much greater when these forages are stressed from drought, frost, herbicide injury, or other types of stress. Forages that have the potential to accumulate prussic acid at high levels include: Johnsongrass, grain sorghum, forage sorghum, and sorghum-Sudan grass hybrids. Sudan grass, Sudan grass hybrids, and pearl millet have a low to moderate chance of accumulating prussic acid.
Prussic acid in livestock occurs when they graze forage with high levels of prussic acid otherwise known as cyanogenic glucosides. These glucosides are actually sugar compounds that are broken down in the rumen; this frees the hydrocyanic acid (HCN) otherwise known as cyanide from the sugar. Cyanide poisoning in l ivestock causes respiratory stress and is very fast acting; death will occur quickly. Treatment is possible with sodium nitrate and sodium thiosulfate and treatment can be effective but must occur quickly after the initial symptoms to be successful.
The best way to guard against prussic acid poisoning is to cut the forage for silage or hay. This will allow the HCN to volatilize. It is best to store the hay for some time to be sure volatilization has occurred. If you are forced to graze fields that have stands of grasses that are susceptible to storing moderate to high levels of prussic acid, I do recommend taking a few steps to help alleviate the chance of prussic acid poisoning. Since prussic acid is volatile and the levels in the plants can change quickly, even from one end of the field to the other, testing is not as accurate as we would like and usually only shows that there is prussic acid in the forage, but not the levels. I recommend that you never turn hungry cattle onto fields at risk, even those that have been tested. You should make sure the cattle are full of hay or other forages before turning them out, this will prevent the cattle from overloading on the at-risk forage and lessen the risk of prussic acid poisoning. I also recommend not turning out the whole herd, no one wants to lose any cattle, but 2 head loss compared to 20 head is a much better scenario. Gate cut a couple of head and let them graze for a day before turning the whole herd into the field. As always watch your cattle closely for a day or two after turning them out on at risk fields.