Prussic Acid and Nitrate Poisoning in Grazing Forages: What You Need to Know

0:00 Hey everybody, welcome to the Green Cover podcast where we have really interesting conversations with some of the top farmers and experts in the regenerative agriculture world. Join us as we learn together how to regenerate God's creation for future generations.

0:15 Hey everybody, we're starting to get lots of questions already about issues that could come around grazing forages that are planted specifically around prussic acid poisoning and nitrate poisoning. Both of which are legitimate concerns. They're different, somewhat related but certainly different. And so we wanted to just have a conversation around what those are and how you manage around it. So to do that we brought in our friend Dale Strickler.

0:43 As many of you know, Dale used to work for Green Cover. He was part of the Green Cover team and now he has his own independent consulting business called Regenerative Wisdom. Dale, welcome. Thank you for sharing a little bit of your time with us today. Good, good to be back at it again. It feels like old times. Yeah, for sure.

1:02 Well, you know, we know that you're, you know, as good of an expert as there is in this field. And in fact, got your book right here, you know, managing pastures. And there's a section in here about prussic acid and nitrate poisoning. So we wanted to just have this conversation with you. If people want to take a deeper dive, they can go to your website regenerativewisdom.com. They can order your book. They can do all those sorts of things. But we thought it would be great to just to have a conversation.

1:30 So first of all let's talk about prussic acid poisoning and you know when that occurs, you know what's happening and then how do you manage around it because you may not be able to avoid it but you can certainly manage around it. Yeah. So prussic acid is, there are a number of plants that can have prussic acid. It's basically the toxic factor is cyanide and prussic acid can release cyanide under certain conditions and that's a bit of an oversimplification but yeah sorghums are probably the main two plants are actually cherry trees and sorghums and most of us in the plains are not grazing cherry trees but in places where there are wild cherry trees animals get prussic acid poisoning from eating the leaves of cherry trees. But sorghums, the real danger comes during frost.

2:43 So never seen a prussic acid toxicity during the green growing season on sorghum sudan. Now I have on fresh harvested grain sorghum that has regrown and people put animals out there but is that because part of the parentage of sorghum sudan is sudan grass which doesn't have as much, is that correct? If you do the hierarchy of all the sorghums, highest prussic acid potential to lowest.

3:17 Highest is actually probably Johnson grass, which is a sorghum, and then grain sorghum is higher or is less than Johnson grass, and then a little less is forage sorghum. Sorghum Sudan grass is quite a bit lower and the Sudan grass is lower yet. And a lot of the sorghum Sudan hybrids have, there are even within those categories some speed, some varieties are lower than others.

3:51 Amongst Sudan grass, green leaf and piper historically were very low prussic acid selections that's why they are used in almost all sorghum Sudan hybrids have as the pollinator green leaf or piper or some line developed from those. Now Purdue University has released some supposedly zero prussic acid breeding lines. So maybe hopefully this part of this talk becomes something we don't even worry about in the future.

4:32 Down the road that could be a mute point. Unless people are putting animals out on harvested grain sorghum in which case it's still a very real danger. And the reason that the two factors make this a bigger problem, I mentioned freezing. The other is young regrowth. It seems to be most concentrated in shoots regrowth that's less than 18 inches tall. And so if you can prevent animals from eating young regrowth, you eliminate a lot of the danger during the green season.

5:15 Which lines up with good grazing management anyway, you know, to have you don't want to be grazing that anyway. So yeah, I think graze a patch no longer than a week at a time, which means you need at least three patches. Four is better. Moving daily is better yet. But if you are rotationally grazing, then you can really almost eliminate the possibility of green season prussic acid poisoning.

5:44 The second factor, the freezing. This is when it becomes very dangerous. And the reason is if you look at the structure of a leaf, you got the leaf epidermis, you know, up and bottom, the skin cells of the leaf, and you have the mesophyll, which is all the cells in between. There are two compounds that have to come and basically get mixed in order for the cyanide to be released. One's in the epidermis, one's in the mesophyll, and they're separated by cell walls. So they don't ever under during the green season, they really don't come into contact with each other.

6:25 The animal when they chew, they'll break a few of those cells, but not much. And cyanide occurs at low levels in a lot of plants. The animals can detoxify small amounts of cyanide, a little at a time. So under normal grazing, this isn't an issue. At frost, however, those cells burst and then the whole thing becomes liquid, and you go out there the day after a freeze and you see sorghum leaves that look like you tried to grill lettuce on a skillet.

6:59 It's wavy, it's all mushy. And that is when it's very dangerous when it's in that fresh brazil state because all that cyanide is being liberated. Now once that plant dries out after a freeze, now it's completely safe when it turns that tan color. It's dry. It loses its moisture. Number one, it's liberated all it's probably going to and then it's no longer in a liquid state where those compounds can't really mix effectively and form any new proic acid. So there is a window there. And how do you manage around that freezing? Well, one I mean the obvious thing is don't have your animals out there when there's a risk of freezing.

7:56 So that sounds good on paper, but sometimes that doesn't work as a practical matter. Said, 'Well, I truck these animals an hour away to pasture this stuff and I can't, you know, haul them an hour back and then haul them, you know, they don't have anywhere else to go. So what can you do on practical matter?' And one thing that I say, well, if that's an issue, maybe one of your paddics can be a sorghum free mixture. You can have other plants, pearl millets on him, probably however many summer annual forages in your lineup that are not sorghums, sorghum sedans. So that's a possibility. Another one is to just create a very small area and put hay bales out there on a grid.

8:45 Usually you only need about a week after a frost where you need to be off and so maybe you have a pen fairly sturdy pen they're not going to get out of where you have hay bales already placed on a grid. Do a little bale grazing and if there's a risk of frost at, you know, at night if it's going to get below 40, you can run the animals in there. They've got good quality hay, keep them happy, and in the morning if nothing's frozen, turn them back out, lather, rinse, repeat.

9:26 One other idea is remember once the plants dry, they're safe because the cells aren't going to burst. You're not going to get that liquid effect. So if you need to, you could run a swather out there a few days before it, really only about one or two days of wilting will usually get that moisture content down to where the cells aren't going to burst. So you could swath a paddic or two, you know just enough for about a week and then do swath grazing on that.

10:06 Yeah, and just do small off grazing for a few days. And I think what you're talking about are all good ideas because you know with the with the value of animals and not only are you risk killing an animal but you could abort calves as well and so you just can't afford to do that. And it's not a question of if prussic acid will be a concern if you're grazing sorghum. It's just a matter of when unless you're far enough south where it doesn't freeze.

10:35 But for most of us, it's just going to be a matter of when, not if. So you just got to be prepared and have a management plan to go along with it.

10:42 Yeah. And sometimes you just get caught. You get bit. I mean, usually in Kansas, Nebraska, you know, where the bulk of your green cover customers are kind of centered, even though they're all over, it's kind of October is usually the month we have a frost risk. And that's a busy month. I mean, wheat planting's going on, corn harvest, sorting harvest. Soybean harvest. There's a lot going on and it's real easy to just get busy and just assume the animals are taken care of and then boom, you get caught.

11:24 Yeah. And so the easiest thing is to do all of the extra work up front and like you said, you know, plant 10, 15, 20% of your acreage to a millet base mix and then just kind of be saving that for that time frame. But otherwise, I like the swath grazing approach, you know, because then you're still getting the animals across the field. You're not pinning them up. But yeah, you just got to plan ahead. You just got to be able to manage around that.

11:52 Now, some people say when they call in and they talk to us, you know, they talk about nitrate poisoning and prussic acid poisoning is kind of the same thing. And they're very different. I mean, they both can have toxic, you know, terrible results for an animal. But talk to us now about nitrate poisoning and how that's different than prussic acid.

12:13 Yeah, they're very, they're somewhat similar in their effects because both of them basically cause cellular suffocation, but by completely different mechanisms. Now nitrate, lots of plants can have nitrate toxicity. Pearl millet can have nitrate, corn can have nitrate. Basically, just about any plant can potentially had one, one of the highest nitrate tests I've ever seen was in turnips and radishes that was planted into hailed out corn. You know, you're getting corn that had 200 units of nitrogen, got hailed off to the ground. Guys planted brassicas, which is good, and they did their job. They cycled that nitrogen, but man, were they hot. You know, they had to, you know, they were unfeedable the way it was. They had to blend that out.

13:09 But yeah, and you might be surprised because I'm glad you mentioned that because I will discuss that when we start talking about, you know, cautions with nitrate, but nitrate interferes with the blood's ability to carry oxygen. So the blood won't take oxygen from the lungs. So if you've got an animal out there in clear respiratory distress, you know, labored breathing, and if you poke a hole in her, poke a needle in a vein or I should say an artery, because an artery should have bright red.

13:51 Blood. If you poke a needle in an artery of an animal with nitrate poisoning, it will be brown colored blood, chocolate colored. Clear sign of nitrate poisoning. Now with proic acid, proic acid makes it so that the cell can't accept oxygen out of the bloodstream.

14:18 So it will have very similar symptoms to nitrate toxicity, but the blood will be an extremely bright red color. It'll be super set. Can't get rid of the oxygen. Right. Right. Right. So but I mean the end result's the same. The cells are starving of oxygen and so it's a cellular suffocation.

14:44 Preventing nitrate toxicity and one thing I want to stress is that people are especially in drier areas are terrified of nitrate. So they typically either I'd say no fertility is almost standard on sorghum sedan in dry areas. Would you agree with that? It. Yeah. And a lot of times people will ask about that and yeah, if they have a chance of being drought stressed, I say, boy, if you're going to put any on, you know, don't do much. 20 pounds, 30 lbs maybe. And take a soil test first. You may have that much in your soil. Yes. And I think I think the place you start is probably with a haney test so you can get a really accurate estimate of how much nitrogen is going to be released from your soil. Um, which a traditional soil test really doesn't predict very well. You know, we just put on estimates and go with it for grain crops. Well, that can be kind of hazardous with something prone to nitrate.

15:59 Um, but if you think about it and a lot of times I hear people say, 'Well, I was expecting this sedan to, you know, make this huge tonnage because I read the yield potential and so forth and it just didn't produce.' I said, 'Well, how much nitrogen did you put on?' Say, 'Well, none. I was scared of nitrate.' Now, nobody would put on zero pounds of nitrogen on a corn crop and then wonder why it didn't yield. But we do that on sorghum sedan for forage. And if you think about it, yeah, 1% nitrogen in a crop is 6% protein. You basically take the protein and divide by six and a quarter to get your amount of nitrogen. So if something is 12% protein, which you know, good green growing forage probably be in that neighborhood. It's 2% nitrogen. If all you have is 40, let's just say your soil naturally cycles about 40 pounds of available nitrogen. 2% of a ton is 40 lbs. You only have enough nitrogen to produce one ton of biomass.

17:29 Now, if you do any more than that, your protein contents are going to decline. Or if you, you know, you're either yield limited or protein limited, one or the

17:38 One or the other. And so I think a lot of people really short them the yield potential. And it's because of the very, I mean nitrate toxicity is very real. But if we can manage around that, all of a sudden you've got 4, 6, 8 ton yield potential on sword and sedan if you can supply nitrate or if you can supply nitrogen fertility without spiking nitrate. So it this is a big deal if you're planning on this as a source of pasture or hay. So how do you do it?

18:19 Well, one thing is you want to provide nitrogen in a form that won't spike nitrates. And there's all kinds of tricks to do that. Basically if you put synthetic nitrogen out there, it converts to nitrate and then gets taken up by the plant.

18:45 So is there a way of applying synthetic nitrogen without doing that? Well, people have come up with these recipes of putting like molasses or some sort of sugar source in with their nitrogen if they're applying liquid nitrogen, for example.

19:02 The idea being that when you apply sugar and nitrogen together, the microbes will use that as a source of energy and incorporate that nitrogen into bacterial bodies. And then you turn that basically nitrate releasing source into a very slow release, and not very slow release, but much as they die off and decompose. Essentially turn an inorganic into an organic form of nitrogen. And you can do that by adding molasses and sulfur to the mix.

19:45 Another, it's also very very important to realize that nitrate moves into the plant with water. So anytime the plant's taking up water with nitrate in it, nitrate comes in and then the nitrate has to metabolize into protein.

20:07 So how does that process happen within the plant? Well, you get the energy to do that from photosynthesis. So anything that's inhibiting photosynthesis can do that. That can be cloudy days, that can be drought, that can be anything really—diseases, different things like that.

20:29 Yeah, absolutely. If you got leaf rust or Sudan stripe or sorghum leaf aphids or sugar cane aphids, anything that's out there interfering with photosynthesis can slow that process and increase nitrates and slow the metabolism of nitrates.

20:46 So some things that I've noticed that are very critical—also to produce protein takes not just nitrogen and energy, but sulfur is also very very critical there. And so as far as soil fertility, you want a lot of phosphorus, you want adequate phosphorus, which can be real difficult on some soils, especially.

21:13 Higher pH soils. You want sulfur and a lot of our soils are very deficient in sulfur because we don't get it out of rainfall anymore like we used to. They've cleaned up with no that acid rain, right? Yeah. We don't get that acid rain so we don't get the free sulfur fertility that we used to.

21:34 Zinc can be very important especially on higher pH soils. And another one that very rarely tested for but is pretty important is molybdenum. Molybdenum is it takes only a tiny amount but if you don't have that tiny amount it's very important for converting nitrate into the next step in the protein production process.

22:08 And never really knew how prevalent this was until SAP testing came about. Once you start looking at SAP test, you're like, 'Holy cow, we have just a tiny fraction of the molybdenum supposed to have in this plant.' Often shows low. Yeah. And so molybdenum and cobalt, you know, like who ever heard of these things? And also very important for legumes.

22:36 And speaking of legumes and those are key nutrients needed just for the photosynthesis process. So if you don't have those photosynthesis slows down thus the problem that you just described before. Yes. Absolutely. So, if you can get balanced fertility out there, you know, when people are people will do this if they're growing corn, but if it's sorghum sudan, they'll put 40 lbs of nitrogen out there and call it good and forget all the other things.

23:07 But, and they're not just important for the plant. They're also important for the animal that's eating the plant. I mean, you're not feeding just one organism. You're feeding two organisms out there. And actually you're feeding billions of organisms below the ground, right?

23:26 I mentioned legumes. If you want to have a very slow release form of nitrogen that tends to be much less prone to spike nitrates, having a legume cover crop prior to your sorghum sudan is a fantastic way. Hairy vetch, winter peas, crimson clover, any of those winter annual legumes used as a cover crop and allowed to get a substantial amount of growth, terminate it and plant it in.

24:06 And not just because that's in the form of protein and releases slowly, but one of the key drivers of nitrate toxicity is drought stress. And if you have a mulch out there that can slow down evaporation, that can increase infiltration, you can help eliminate drought stress through your cover crop management.

24:33 How about how effective is it if I added a legume with my sorghum sudan? Say I mixed cowpeas in there with it. Is there going to be much nitrogen contribution

28:39 You're going to apply synthetic nitrogen, mixing some molasses in with it. Split apply instead of applying it all up front like people would normally for a grain crop. We know that if you side dress nitrogen on a corn crop, you get better nitrogen use efficiency and you also get less nitrate in the plant at any given time.

29:06 Split applying nitrogen on sorghum sedans can improve your nitrogen use efficiency and greatly reduce your risk of nitrate toxicity as well. If it turns off dry, you just don't apply. But once you save the money of not putting that second application on, right? If it's completely just boom dry.

29:31 There are slow release forms of nitrogen too. Polymer-coated urea, sulfur-coated urea that you can apply even in-furrow because they don't burn the seed. They can release 30 days, 60 days, 90 days after you put it in the soil. It times better instead of being all converted into nitrate 2 weeks after you put it in the soil. It's releasing that nitrogen later on when the plant actually needs it instead of all being up front.

30:13 If you're grazing, what we like to recommend is a lot of diversity because diversity is going to spread that out. It's pretty easy to get 8 to 10 different things in a nice grazing mix. You know, we'd have sorghum in there, but we'd have some millet, we'd have all these other things as well. But if you're putting up hay, it's a little more difficult to do all that diversity.

30:38 I want to make sure people understand that prussic acid will go away after you make hay, but the nitrate issue doesn't go away, does it? That's correct. Haying basically eliminates prussic acid as a problem, but it tends to make nitrate much worse.

31:06 In a grazing situation, animals tend to eat the leaves and ignore the stem. About 90% of your nitrate is going to be in the lower part of the stem. If you're not forcing animals to eat that stem, nitrate's seldom a concern in a grazing situation. But in hay harvest, you're cutting that stem and it ends up in the bale with the highest nitrate.

31:36 I always recommend cutting sorghum sedan for hay as high as is mechanically possible. If you're grazing it, never force them to eat that lower stem. There's no feed value in the stem. There's no point sticking it in an animal. Leave it for the soil, leave it for regrowth. It also dries out faster if you're not putting that thick part of the stem in a bale.

32:05 There's another thing at work and there was some German research a few years back on turnips actually because turnips tend to be really good nitrate accumulators and they took turnip green turnip greens essentially 20,000 parts per million nitrate which you get a test like that and you know the test glows in the dark. It's so hot.

32:35 That's hot. That's hot. What's a safe level is like is it I can't. Is it 1500 or about that? Yeah. Yeah. Yeah. So, you know, depend on whether you're talking nitrate in or nitrate or you know, potassium nitrate. There's several different ones, but you look at the chart and this was 20,000 parts per million nitrate, which is really hot. You know, more than 10 times the lethal level if you look at the chart.

33:05 And they took the turnip greens, put some of them, half of them in an artificial grooming and then took the other half and dried them in an oven, a drying oven overnight, like 150 degrees or 120 degrees, something like that, but dried them. Put them both into an artificial room into Roman fluid. The dried sample, all of the nitrate, 100% of the nitrate entered the rin fluid within an hour. In the green forage, it took 21 hours for the nitrate to leave the forage and go into the draining fluid.

33:56 That's significant. I mean, animals can metabolize nitrate. It, you know, when we eat kale, you know, nitrate in small amounts is healthy. It's good for you. It does things for your bloodstream and it's actually a healthy molecule in limited amounts. But too much overwhelms the system and causes potentially death. So, green grazing very very seldom has nitrate problems. You put the same exact forage in a hay bale, now you got problems. Look out. Look out.

34:38 Yeah. Yeah. That's really interesting. Talk a little bit too, Dale, about if you're going to graze this, there's tricks that you can do to bring that animal's rumen up to a level where it can metabolize that even better. If you go too fast, there could be detrimental effects. But if you kind of get them used to it, they can handle a lot more, right?

35:01 Yeah. I mean, of course nitrate can be a problem in drinking water for humans as well. I heard a story about an 80-year-old lady who spent her whole life, lived her whole life in this house drinking well water and never had a health issue until she finally passed away at a very old age and a young couple moved in and immediately started having problems. I mean, healthy young couple and they went to the doctor and they had found out their well water was like 80,000 parts per million nitrate. Just off the chart. Never bothered this.

35:37 Little old lady because she drank that water her entire life. So ruminance, not only can the body metabolism adapt to nitrate, but rumen microbes can adapt to nitrate. There are some rumen microbes in particular that are effective at it. If you can do a gradual adaptation, dilute the feed, you know, have something that would be very low in nitrate like prairie hay or alfalfa hay that would not typically receive any nitrogen fertilizer at all, can dilute that down.

36:21 Another adaptation technique is something called BovaRap. And BovaRap is a bolus that contains a live bacteria that is one of those bacteria naturally found in the rumen that eats nitrate. And the research with BovaRap, you can get it, you order it at any vet, has to be kept refrigerated, and then you got to run them through a chute and poke this bolus down them. But as soon as that bolus goes in the rumen and they are adapted to high nitrate feed, you know, almost let you get them out there right away versus the gradual buildup. So it provides an automatic adaptation to high nitrate feed, and that persists as long as they're receiving high nitrate feed. Those bacteria will keep reproducing.

37:18 The research shows that it will basically, you said like 1,500 is the toxic thing. Animals with BovaRap Pro can take about twice as much as animals without. So definitely a strategy there too.

37:35 And I always tell people too, you know, when you look at the value of these animals right now and you look at the cost of a nitrate test, which is easy and cheap. Why wouldn't you test for nitrates if you have any questions at all? Because like I say, it's an easy test to do. Almost any forage lab will do it. It doesn't cost that much. It doesn't take that long. So if you have any questions, just get a test.

38:03 And at least then you know what management techniques that you just described that you may need to employ and work on and try to figure out, and your vet can help you through some of that then too. Once they see what that test looks like, you know, if you need that bolus or if you know just a grazing strategy can work or dilution. If the plants in the field are high, putting the same field up for silage where it goes through a fermentation process, the microbes during the fermentation process tend to eliminate half to 2/3 of the nitrate, converted into other compounds. So versus dry hay.

38:48 I still prefer grazing because they just aren't eating the high nitrate parts and it's wet usually. Well, and you're not chopping it. You're not falling it.

38:59 You know, so much. That's a whole another topic though, isn't it, Dale? Yeah. Yeah. We don't have enough time to go into get you on that soap box, but all the reasons I hate silage.

39:13 So folks, you know, with the price of animals, you know, in the price of grain, we've got a lot of guys that are looking at planting some of their crop ground to forages, which totally makes sense in this economic scenario that we find ourselves in. Just know that, you know, there are things you can do to manage some of these toxicities, prussic acid, nitrates. Again, you know Dale's book Managing Pasture—a complete guide to managing pasture is a great resource for that and so many other things. It's regenerativewisdom.com. We'll, you can order the book on there. You can get a hold of Dale on there. And you know the Green Cover website. We've got blog posts. Oklahoma State has a really good paper on prussic acid poisoning that you can find on our website. There's lots of good resources out there. So don't, you know, don't take a chance. You know, do some research. Figure out what the management techniques that you need to do in order to safely graze your animals out on that forage because it just isn't worth losing an animal when it's totally preventable in most of these situations.

40:22 So Dale, last words. How would you encourage people as they work their way through some of these questions and issues? I would say the value of one animal saved by managing powderly could probably buy you about 100 acres of cover crop seed and a book on top. Absolutely.

40:48 All right. Well, Dale, we are going to have you back on another time as well because we know you've got lots of great information to share and to talk about, but we appreciate you taking your time to share about these two common questions: prussic acid and nitrate poisoning. So, thank you very much. Thank you everybody for listening.

41:04 My brother and I started Green Cover in 2009 because we understand what it's like to be a farmer starting out on the journey to improve soil health. We saw the power of plant and biological diversity on our own farm here in Nebraska, but we found that it was difficult to get the right cover crop seed mix. We also learned that there was a big learning curve in successfully implementing cover crops. That's why we build Green Cover so that farmers like you can access the highest quality cover crop seed put into the right diverse mixes along with the technical advice and the educational resources to help you successfully implement cover crops on your own operation. So contact us today and we'll help you with the right cover crop mix for your farm or ranch so you can regenerate your portion of God's creation for future generations.