Bruce Anderson is an extension forage specialist with the University of Nebraska – Lincoln
There isn’t a much more sickening feeling than to watch a group of hungry cows start falling over dead after feeding them a fresh bale of hay. Yet, that’s exactly what can happen when hay containing a high concentration of nitrates is fed incorrectly.
Eventually, most cattle producers who feed hay will have hay with high nitrates, especially when using millet, sorghum, oat or other cereal-based hays. But livestock losses do not need to occur if the hay is properly managed and fed.
Nitrate toxicity is a function of the amount and rate of nitrate consumption. Nitrates in feedstuffs usually are converted by rumen microbes first into nitrites and then into ammonia and bacterial protein, but they can do this conversion only so fast. “Nitrite” is one of the intermediate products in the breakdown of nitrate to ammonia and is the actual cause of nitrate poisoning. When more nitrates are consumed than what the rumen microbes can fully metabolize within a short time period, toxicity can occur.
For example, some fields have sites that are more droughty than other areas. Hay harvested from these sites might be expected to contain more nitrates due to drought stress. Samples could be collected just from this hay and tested. Other samples might be collected from the remainder of the hay.
When the results from the lab analysis for nitrates are received, check the units used by the lab. They can be reported as nitrates (NO3), nitrate nitrogen (NO3-N) or potassium nitrate (KNO3).
I’ve spoken with producers who had a lab value of 4,000 ppm, which they thought was pretty safe because the potentially toxic level for nitrates is around 9,000 ppm. Unfortunately, the lab analysis reported the results as nitrate nitrogen. In this form, the potentially toxic level is just around 2,100. Thus, the hay actually contained nearly twice the toxic level and was very dangerous. I’ve also seen the opposite, where they thought their hay was toxic, but it was actually quite safe. Also, see if the results are reported as a percentage of dry matter or as parts per million (ppm). You need to multiply percentage by 10,000 to get parts per million.
Mixing low-nitrate hay with high-nitrate hay is another way to dilute dietary nitrates to a safe level. It is critical, however, that animals consume both the high- and low-nitrate hays in the proper proportion. This may require grinding and mixing hays in a total mixed ration. Do not feed free-choice one bale of low-nitrate hay and another bale of high-nitrate hay. Animals will not adjust their diet correctly, and it practically guarantees that some cows that like the high-nitrate hay best will overconsume nitrates, which could lead to animal deaths.
Similarly, rolling out hay or using bale processors for separate low- and high-nitrate hays can lead to some animals preferring the high-nitrate hay or to boss cows eating most of one type of hay and timid cows only getting the less palatable hay. If hays cannot be mixed properly, it is better to feed the low-nitrate hay first. Soon after they finish, follow with the high-nitrate hay.
Since rate of nitrate consumption is important, never feed high-nitrate hay to hungry cattle. Frequent, small meals of high-nitrate hay allow livestock to consume more total nitrates daily than one large meal. It also can help cattle adapt to consuming hay with higher nitrate concentrations safely. If cattle are allowed to adjust to feeds that have potentially toxic levels of nitrates, they will develop a population of microbes in the rumen that convert nitrates to a non-toxic form.
Be extra careful if animals go off feed, like during a snowstorm. They probably will eat their first meal afterwards very rapidly. It needs to contain well below their previous nitrate levels to avoid a sudden, large influx of nitrates into their systems.
Do not feed hay that is high in nitrates when it is damp. Damp feed seems to be more toxic because some of the nitrate already has been converted to the more toxic nitrite before being consumed.
There also is a direct-fed microbial product available (Bova-Pro) that contains a specialized bacterial culture. It develops a large and stable rumen population that produces enzymes to convert nitrates and nitrites that enter the rumen to a non-toxic form. If this product is used to manage against high-nitrate feeds, all animals must get the proper amount to establish the needed microbial population. Also, it is still recommended to adapt cattle to the high-nitrate feed over a period of time.
Using feeds that contain high nitrate concentrations is not without risk, but feeds that contain nitrates can be fed successfully. Use the management practices mentioned above to reduce the chance of animal loss. FG
Eventually, most cattle producers who feed hay will have hay with high nitrates, especially when using millet, sorghum, oat or other cereal-based hays. But livestock losses do not need to occur if the hay is properly managed and fed.
Nitrate toxicity is a function of the amount and rate of nitrate consumption. Nitrates in feedstuffs usually are converted by rumen microbes first into nitrites and then into ammonia and bacterial protein, but they can do this conversion only so fast. “Nitrite” is one of the intermediate products in the breakdown of nitrate to ammonia and is the actual cause of nitrate poisoning. When more nitrates are consumed than what the rumen microbes can fully metabolize within a short time period, toxicity can occur.
Testing hay for nitrates
To use high-nitrate hay without causing nitrate toxicity, you first need to know how much nitrate is in your hay. The methods used to sample hay for nitrates often need to differ from those used when testing forage quality. Sampling for forage quality seeks to represent the average of the entire lot of forage. With nitrates, though, it often is important to know the worst-case scenario, or what is the highest concentration of nitrates that might be consumed by the animals.For example, some fields have sites that are more droughty than other areas. Hay harvested from these sites might be expected to contain more nitrates due to drought stress. Samples could be collected just from this hay and tested. Other samples might be collected from the remainder of the hay.
When the results from the lab analysis for nitrates are received, check the units used by the lab. They can be reported as nitrates (NO3), nitrate nitrogen (NO3-N) or potassium nitrate (KNO3).
I’ve spoken with producers who had a lab value of 4,000 ppm, which they thought was pretty safe because the potentially toxic level for nitrates is around 9,000 ppm. Unfortunately, the lab analysis reported the results as nitrate nitrogen. In this form, the potentially toxic level is just around 2,100. Thus, the hay actually contained nearly twice the toxic level and was very dangerous. I’ve also seen the opposite, where they thought their hay was toxic, but it was actually quite safe. Also, see if the results are reported as a percentage of dry matter or as parts per million (ppm). You need to multiply percentage by 10,000 to get parts per million.
How to feed high-nitrate hay safely
High-nitrate hay can be fed safely. The primary method is to dilute high-nitrate hay with low-nitrate forages or supplements so that the concentration of nitrates in the total diet (including water) is below dangerous levels. Feeding grain or other high-energy feedstuffs may be the most effective way to reduce toxic levels because the extra energy apparently helps speed and complete the conversion of nitrate to bacterial protein in the rumen.Mixing low-nitrate hay with high-nitrate hay is another way to dilute dietary nitrates to a safe level. It is critical, however, that animals consume both the high- and low-nitrate hays in the proper proportion. This may require grinding and mixing hays in a total mixed ration. Do not feed free-choice one bale of low-nitrate hay and another bale of high-nitrate hay. Animals will not adjust their diet correctly, and it practically guarantees that some cows that like the high-nitrate hay best will overconsume nitrates, which could lead to animal deaths.
Similarly, rolling out hay or using bale processors for separate low- and high-nitrate hays can lead to some animals preferring the high-nitrate hay or to boss cows eating most of one type of hay and timid cows only getting the less palatable hay. If hays cannot be mixed properly, it is better to feed the low-nitrate hay first. Soon after they finish, follow with the high-nitrate hay.
Since rate of nitrate consumption is important, never feed high-nitrate hay to hungry cattle. Frequent, small meals of high-nitrate hay allow livestock to consume more total nitrates daily than one large meal. It also can help cattle adapt to consuming hay with higher nitrate concentrations safely. If cattle are allowed to adjust to feeds that have potentially toxic levels of nitrates, they will develop a population of microbes in the rumen that convert nitrates to a non-toxic form.
Be extra careful if animals go off feed, like during a snowstorm. They probably will eat their first meal afterwards very rapidly. It needs to contain well below their previous nitrate levels to avoid a sudden, large influx of nitrates into their systems.
Do not feed hay that is high in nitrates when it is damp. Damp feed seems to be more toxic because some of the nitrate already has been converted to the more toxic nitrite before being consumed.
There also is a direct-fed microbial product available (Bova-Pro) that contains a specialized bacterial culture. It develops a large and stable rumen population that produces enzymes to convert nitrates and nitrites that enter the rumen to a non-toxic form. If this product is used to manage against high-nitrate feeds, all animals must get the proper amount to establish the needed microbial population. Also, it is still recommended to adapt cattle to the high-nitrate feed over a period of time.
Using feeds that contain high nitrate concentrations is not without risk, but feeds that contain nitrates can be fed successfully. Use the management practices mentioned above to reduce the chance of animal loss. FG
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