by Doug Toburen
Parsons, Kansas —
This past summer’s drought proved to be a challenge for beef producers and even with recent rains and greener pastures it doesn’t appear that the challenge of feeding cattle is over.
As fall weather seems to be here winter, won’t be far behind it and University of Missouri Extension Agronomy Specialist Tim Schnakenberg says that producers need to be aware of the possibilities of nitrate and prussic acid problems.
“This is the time of year we need to be concerned with nitrate problems in stored forages,” Schnakenberg says. “Whether it is dry hay bales, wrapped forages or bagged forages, all of are still at risk due to the fact that nitrate levels can still be the same as they were at harvest time.”
Although the specialist believes producers should test all forages to find their nitrate level, he says silage is likely the safest and he is less concerned about it.
“It is generally understood that nitrate levels in silage can be reduced 25-50 percent from what the concentration was when it was in the field,” he explains. “However, that all depends on how well it was ensiled.”
According to him, silage put in bags compared to silage that is chopped and put in a silo or bunker is at a higher risk. However, from what he has seen on the farm, silage and balage has been testing pretty good.
The big concern, when it comes to nitrate toxicity are baled forages such as johnsongrass, sor-ghum sudan, corn or millet.
“This concern is especially true if nitrogen fertilizer was applied to those crops,” Schnakenberg says. “These forages really need to be tested.”
Schnakenberg used corn as an example to explain why these crops are such a concern when it comes to livestock feed.
According to him, producers were likely to put 200 units of nitrogen on this spring in hopes of making a bumper corn crop. Yet, due to the drought, the corn crop didn’t make that much with some yields as low as 25 bushel to the acre.
“In this case the nitrogen hadn’t been pulled out of the soil. That, compounded by dry weather, made it accumulate in the plant,” he explains. “That nitrogen accumulates in the plant structure, which is smaller, and the plant isn’t able to metabolize it.”
The problem here, according to the specialist, lies in the fact that as the plant sits there accumulating nitrogen and not being able to use it, it puts the plant in a toxic state.
“Then when the cow comes along and takes a bite out of the plant she has been poisoned,” he says.
This same scenario is true of the other crops such as johnson-grass, sorghum sudan and millet.
Even though it might seem like it is hard to find anything good about this problem Schnakenberg says there is.
“Due to the amount of nitrogen fertilizer that is still in the soil and wasn’t utilized by the plant I think we will see a large carryover of nitrogen this year,” he explains. “This can be a good thing, especially for those who followed with a wheat crop.”
Another issue haunting cattle feeders as they head into fall and winter is the increased levels of prussic acid in forages.
The problem with prussic acid, according to him, is in those plants that have 18-20 inches of regrowth. In most cases prussic acid is not an issue in the tall, rank stuff that is out there.
“Prussic acid is a complex issue and one we don’t understand completely,” Schnakenberg says. “The biggest concern is in the fall when the plant cells get frozen, causing enzymes in the plant to mix together creating cyanide gas.”
The plus side of prussic acid problems, according to him, is that the gas usually will dissipate in a matter of days.
“Most of the time if producers wait at least a week the plant will fully dry down making it safe for cattle to consume.”
The reason testing for nitrate and prussic acid toxicity is so vital is because both can kill cattle that consume the plants in a very short time.
“Nitrate toxicity can come on in minutes to hours after ingesting a toxic forage,” Schnakenberg says. “In most cases you will see cattle get tremors and weakness in their back end. If an affected cow doesn’t die, it can cause abortions.”
According to him, producers might find out months later that the cow is open and never put it together that it was due to the drought.
“Abortions are one of the biggest economic losses that can occur in association with nitrate levels,” he says.
Cattle that ingest forages high in prussic acid levels, as opposed to those with high nitrate levels, almost always will be dead in a very short time.
“Cattle ingesting large amounts of prussic acid can have problems as fast as 45 minutes after consumption,” Schnakenberg explains. “After eating johnsongrass or sudan sorghum with heightened levels of prussic acid she can go down. Typically, if you are there fast enough to see it happen, cattle will have rapid breathing and nervous convulsions.”
According to him, there are some treatments for the poisoned cattle but rarely do producers have time to get the vet called and on site before the cattle die.
“Producers who experience any problems with either nitrate or prussic acid toxicity need to get cattle off the pasture immediately,” Schnakenberg concludes.£