Selenium Deficiency and Toxicity in Goats

Episode 37
For The Love Of Goats

 

 

Selenium is a very important mineral in a goat’s diet. However, since most soil in the U.S. is deficient in selenium, and the U.S. government limits the amount of selenium that can be added to goat feeds and minerals, it’s not that easy to make sure your goats get enough selenium. 

In this episode, I’m talking to veterinary and ruminant nutritionist, Dr. Robert Van Saun, a professor of veterinary science at Pennsylvania State University. He talks about the notorious history of selenium, as well as symptoms of deficiency. You’ll learn how much selenium goats need in their diet and how to make sure they are getting it.  We also talk about the good, the bad, and the ugly in terms of selenium supplements. (Spoiler alert: So-called “selenium gel” does not actually have enough selenium in it to be helpful for a goat that is actually deficient in selenium.)

If you are listening to this episode while driving or milking goats, and you have an urge to start taking notes, remember that the transcript is below, so you can review all of the numbers that Dr. Van Saun shares.

Listen right here by clicking on the player above, or on your favorite platform:

TRANSCRIPT

Deborah Niemann 0:18
Hello, everyone, and welcome to another episode. Today, I am really excited to be joined by Dr. Robert Van Saun of Pennsylvania State University, who is a professor of veterinary science there. And, I first saw him speak way back in 2011 at the conference of the American Dairy Goat Association. And he was talking, he did two separate sessions, he talked for an hour each, on one on copper a nd one on selenium. And today I asked him to join us to talk about selenium, which I know is a huge challenge for a lot of people with goats. Welcome to the show!

Robert Van Saun 1:00
Well, thank you very much, and glad to be here and talk about nutrition, one of my favorite topics.

Deborah Niemann 1:07
Yes, it is always exciting. I love nutrition. One of the things I learned very early on— because we dealt with all kinds of deficiencies, like severe copper deficiency and borderline selenium deficiency—and I discovered very quickly that, if you’ve got the nutrition wrong, there isn’t much you can do with your goats. Like, they’re just not going to be very productive, they’re not going to be healthy. They’re not gonna have long lives. And, once you get the nutrition right, it’s incredible. They’re extremely hardy animals.

Robert Van Saun 1:39
It’s amazing, the turnaround, in how things can go. I’ve had a few cases, just recently, not necessarily all in goats, but I had one case of a beef cattle farm that had lost actually fifteen animals over a year and a half period of time. And it was a small herd, so this was a fairly substantial loss. And ultimately, I diagnosed that it was a copper deficiency due to high molybdenum in their forage. And, within just a few weeks of getting more copper into those animals, I got an email from the client. And he said, “It’s amazing. You wouldn’t even notice the same herd. The color is better, the animals are eating…” And, you know, so it’s just such a turnaround.

Deborah Niemann 2:25
Yeah, it is really incredible. So, today, let’s get started talking about selenium. Can you first just explain why is selenium important for goats’ well-being?

Robert Van Saun 2:38
Alright, well, selenium has kind of a notorious history. And we’ll get into this a little bit. Selenium was discovered, you know, back in the late 1800s. But it was used because of its chemical properties in electrical equipment and things like that. And it wasn’t until 1959—1956 to 1959, there was research going on at Cornell University and out at Oregon State University. And they related this selenium to a disease process in sheep called “white muscle disease” at the time. And now, we know this as nutritional myodegeneration. But, selenium works in the body as a form of antioxidant. So you hear a lot of commercials today about drinking pomegranate juice and so many things because of its antioxidant activity. And antioxidants are important because our body generates many oxidizing agents in its normal metabolism, plus, we’re exposed to things like air pollution and tobacco smoke and things like that, that all have oxidating activities that can damage proteins or cell membranes. And so, having a certain level of antioxidant activity keeps us protected from these things. And selenium, in concert with vitamin E, plays a very important role in that.

Deborah Niemann 4:17
Okay, and so if somebody’s goats are deficient in selenium, what are some of the symptoms that people will see?

Robert Van Saun 4:25
So, we can talk about this in two different ways. When I talk about nutritional diseases, most of what I describe in my classes are what we call the “textbook” or “clinical” disease. And a clinical disease, the animal shows very specific clinical signs—outward physical changes—that you would pick up on that is associated with the loss of function of a nutrient. So, for example, you know, maybe people could relate to vitamin D deficiency causing rickets. Okay? So that’s a clinical disease, all right? With selenium, it’s a little more challenging. Clinical selenium deficiency is essentially white muscle disease. All right? So the muscles, typically of the hind legs, but could also be heart muscle, tongue muscle, muscles of the abdomen, as they burn energy to move—so as the animal just moves around and uses these muscles, they’re generating oxidizing kind of compounds: hydrogen peroxides, oxygen radicals, nitric oxide. And it’s selenium’s responsibility in the form of the compound glutathione peroxidase—this is an antioxidant compound that can squelch these oxidants and correct that status and maintain normal function. But when selenium is deficient, glutathione peroxidase activity in all our tissues is deficient, then we can get oxidative damage to the cells. The cells scar over, basically, the muscle fibers turn into basically scar tissue, you get calcium deposits, and then the animal walks around either very stiff or can’t get up. Or, if it’s a young animal, like a newborn animal, maybe they can’t nurse very well, they don’t absorb colostrum very well. Or, a fast-growing animal, we might see an acute death, basically a heart attack, and we see the lesions in the heart. So that’s clinical disease.

Robert Van Saun 6:47
Now, we also discovered in the late 1990s that selenium is important in converting thyroid hormones into the active form. So your thyroid gland, which controls all metabolism—the rate of metabolism, the animal’s ability to maintain body temperature, and growth and everything—that hormone is called “T4” or “thyroxine.” And, at the cell level, thyroxine is taken in by the cell and has to be converted to T3, has to have an iodine compound taken off, a molecule taken off, to become the active form to help the cell do its actions. And it turns out, there is a selenium-based enzyme, a deiodinase enzyme, that is responsible for converting T4 to T3 in the cell. And without selenium than the body can’t make active, or have active, iodine thyroid hormones in the cells. And so we can see unthriftiness. The animals are poor doers, their hair coat’s not very good, they’re not growing very well, they don’t perform very well…. And so that’s another clinical. This has really been highly characterized in sheep populations in New Zealand and Australia, where they have real problems with selenium deficiency. But that would be another clinical disease. The probably bigger issue with selenium, or selenium deficiency, is what’s called a “subclinical” disease. And this is where the selenium status of the animal isn’t as good as it could be, but it’s not low enough to cause clinical disease. And so, in this case, again, probably due to selenium’s effect on many aspects of the immune response—the immunology of the body—as well as the thyroid function, we see animals that just aren’t doing well, maybe a little slower-growing, more prone to infectious disease, maybe you can’t get rid of the coccidia even though you’ve treated that animal a number of times, or you have a higher rate of respiratory disease and it keeps coming back… That would be classically what we call “production effect diseases” that we consider subclinical diseases, and I would estimate based on the surveys and the diagnostics that I’ve done that that’s probably a bigger problem in our herds, our goat herds, and sheep flocks than, you know, the straightforward deficiencies.

Deborah Niemann 9:47
And I know one of the things that, it seems, the government is, like, very concerned about is selenium toxicity. Because selenium is the only nutrient I’m aware of that the government has placed a maximum limit on in feeds and minerals, and this seems that it’s not enough for some people. So this is like a very multi-pronged question here, like, do we really need to be worrying about toxicity—selenium toxicity?

Robert Van Saun 10:14
You know, this is a classic, classic issue, and selenium is such a unique element in this way. So, let’s start at the very basics: Why is the government so concerned about selenium? Well, selenium, as I said earlier, has sort of a notorious history. Selenium is one of the nutrients that has a what we would call a “narrow optimal zone.” In other words, the amount of selenium necessary to meet nutritional needs and have normal performance, and what might cause toxicity, is very close. Only maybe 2, 3, 10 times what the requirement is. And that’s very similar to, like, vitamin A and vitamin D; both of those elements you have to be careful of in not overdosing, unlike, say, vitamin E, where you could give 100 times the normal dose and it wouldn’t be a problem. And what had occurred is—there’s certain regions of the United States, like out in the Great Plains area. So from North Dakota, South Dakota, down through Colorado, through all the way down to Oklahoma and Nebraska, that in the Great Plains, the traditional buffalo or bison range, there is unique plants that naturally accumulate selenium, and the soils are such that they are alkaline in nature in terms of pH—a higher pH—that makes the selenium in the soil more available to the plant. And so we get these plants that are, in various ways, accumulating selenium to a very high level or an extremely toxic level. And so a disease process called “alkali” disease was discovered in the 1930s. And this was seen in horses predominantly, but also seen in cattle, where they consumed the selenium accumulator plants when there weren’t other things around. And what selenium toxicity will do is it adversely affects the skin. You get flaking of the hooves, cracks in the hooves, you lose hair in horses in the mane and the tail, cattle will lose the swish of their tail, and they become extremely lame and basically die. And the story that I’ve heard through my time at Cornell with Dr. Skip Hintz, who was, you know, a long-time equine nutritionist, he said that it was selenium toxicity that’s responsible for Custer’s Last Stand going the wrong direction for Custer. It turns out that General Sherman was supposed to come to Custer’s rescue, but his horses were all lame due to, ultimately, what was discovered to be alkali disease from selenium intoxication. And then, in the 1940s, selenium was being used in rat studies. And somehow the design of the studies was not that great, but the conclusion of these studies was that increasing selenium resulted in cancer in rats. And so selenium had this toxicity history, and then, on top of that, was perceived by these studies in the 40s to be a cancer-causing agent. And so, with that history, once we figured out around the late 1950s that it was an essential nutrient, the government basically said, “We’re not going to allow this.” And selenium was considered a food additive, and thereby came under the purview of the Food and Drug Administration, and is regulated by the Food and Drug Administration. So it’s this notorious background.

Robert Van Saun 14:16
Now, another part of your question. It turns out, because of the unique differences in the digestive tracts of our ruminant species, like sheep and goats and cattle, they are less sensitive to selenium toxicity than, say, you or I, or a horse, or a pig, or poultry. So, our traditional nonruminant species are highly sensitive to selenium and toxicity. So the requirement for selenium is approximately 0.1 to 0.3 parts per million in the diet, according to most of the published reports on nutrient requirements for the various species, but for nonruminant animals—like horses, pigs, poultry, dogs, cats—the upper, or what’s called “maximum tolerable level” of selenium, is only 2 parts per million. So, basically, just under a tenfold difference between what the perceived requirement is and what the toxic or potentially beginning toxic level is. And so, because of that, you know, the Food and Drug Administration, they didn’t allow selenium to be added to the diet—it wasn’t until 1984, I think it was, when selenium was allowed to be incorporated into poultry diets. And then it was in 1987 that selenium was allowed to be added to the diet, at a level of 0.1 part per million, for any of our ruminant species. And, as you sort of alluded to, we found that that wasn’t sufficient enough. Our ruminant species… We just were not curing or treating or preventing white muscle disease in our animals, our calves, our kids, or our lambs, or in the adult animals very well. And so again, some more research had been done, and some work out of Michigan State University by Duane Ullrey and others showed that we actually had to supplement at 0.3 parts per million. And so, with that information, the FDA allowed increase the level of supplementation up to the 0.3 mark. And that’s where we stand today.

Robert Van Saun 16:58
There was a situation out in California, where wild waterfowl were having congenital birth defects and weak eggs, and, ultimately, the Game Commission diagnosed selenium intoxication. And so it was being blamed on the agriculture, the big dairy industry in Southern California, and stuff at the time. However, what was shown is when ruminant animals consume inorganic selenium—this would be, if you read the labels on your products, if it says “sodium selenite” or “sodium selenate,” those are what we call inorganic or mineral sources of selenium. It turns out that selenium is such a unique element. It’s very positively charged, like, the selenium atom in selenite and selenate has a +4 or a +6 charge on it. And that’s important in the rumen. Because when the microbes are fermenting all the fiber in the rumen in that we expect ruminant animals to process and make into good-quality meat and milk and so on for us, there’s lots of negative charges from electrons from fermentation looking for positively charged things. And so what happens is, this positively charged selenium atom gets reduced to elemental selenium—a valence or charge of 0 or -2. And, it turns out that if selenium is in that form, it no longer can be absorbed in the small intestine. And so it just passes out through the feces. And so, ultimately, now we’ve recognized that ruminants, because of that issue, are much less prone or susceptible to toxicity, and the maximum tolerable level of selenium in a ruminant diet is, like, 5 parts per million, but it probably could even be 10. So it’s two and a half times what it is for the nonruminant species. And we’re just fortunate enough that in the early 2000s, where they developed the new form of selenium called “organic selenium”—this is where selenium is actually incorporated into an amino acid called “selenomethionine.” We’re still allowed to feed that or supplement that at the 0.3 parts per million in the diet so that it’s much more biologically available. And then, that allows us to have much better animal performance and animal health, you know, by using a combination of these sources.

Deborah Niemann 20:00
Wow, that is really fascinating! One thing I just want to clarify, because sometimes I will get an email from somebody who is freaking out because they will see something like what you said about, like, 0.3 ppm selenium, you know, is considered ideal. And then they see that, you know, like a mineral has 20 ppm selenium or 50 ppm selenium. And they’re like, “This is bad.” And it’s like, “No, no, it’s not.”

Robert Van Saun 20:27
No, no.

Deborah Niemann 20:27
That other number is total. So, like, it’s averaging out.

Robert Van Saun 20:31
Okay, so let’s address that, because that is really an important point. So, let’s come back and say the requirement for selenium is 0.3 parts per million. That’s 0.3 milligrams per kilogram of diet. All right, so that’s a pretty small amount, but that’s a concentration. And we need to remember that our animals do not eat concentrations, they eat amounts. And so what’s important is the milligrams per day that they consume. So, a typical goat in the range of about 150 to 160 pounds of body weight, if she was just a maintenance goat, not doing anything, not lactating, not growing, not being pregnant, or anything like that, she would need to consume, basically, about 0.3 to 0.4 milligrams a day. Now, she would normally eat maybe 3, 3-1/2 pounds of feed. So, if I convert that to kilograms, that’s 0.3 milligrams divided by 1.5 kilograms, so you’re looking at a concentration in the diet, the total diet, of somewhere around 0.2, 0.25 parts per million. And so that gets us to this kind of 0.3 parts per million. Now, the important thing to know is what the FDA regulates is not the selenium that is already in the diet. It’s just how much you can add to the diet. Okay? And so, the current regulations for sheep and goats, which is the same, is we can supplement up to 0.7 milligrams per day, total amount. So, living here in the East Coast, we’re very selenium deficient. The selenium content of our forages here is probably 0.01 parts per million. So we basically ignore that, because, again, that selenium probably is only about 30% available. So then, if we gave 0.7 milligrams as supplemental selenium, that’s basically twice what she needs. Right? So that would be okay.

Robert Van Saun 23:09
Now, the question is, how do we get that? So, the Food and Drug Administration in their regulations, there’s two ways we can supply selenium. We can feed selenium in our diet by adding a selenium premix. And, unfortunately, most of these premixes are highly concentrated, so the only way to really add them in is to blend them in with other minerals, and then blend that in with the rest of the feed. But not too many people are feeding, like, completely mixed diets, like we typically do for dairy cows, you know? I mean, I work with a large goat dairy in Northern California, and we feed a total mixed ration to those dairy goats, but most people with goats, you know, feed hay and maybe, you know, commercial product or something. So, that way, the other option is we can provide selenium at 0.7 milligrams per day in a free-choice trace mineral salt that has selenium. So a selenized trace mineral salt. So, to figure that out, we’d have to know how much salt the animal consumes—how much of that salt block or granular salt. And so the FDA assumes that your salt blocks are basically 90% to 95% salt. So that you would have to read off the label. And, they assume that they’re going to consume between 1/4 to 1/3 of an ounce on average per day. And so, if you do the mathematical gymnastics of calculating 1/4 to 1/3 of an ounce into, ultimately, grams or kilograms, and you want 0.7 milligrams to come into that amount, the legal limit is 90 parts per million. So, if you want to provide 0.7 milligrams a day to a goat with a free-choice salt mix, it would have to be a high-salt mix where they consume 1/4 to 1/3 of an ounce per day on average. We know that varies by animal, but it would have to be 90 parts per million.

Robert Van Saun 23:09
Now, if you look at many products out there, it’s all over the board. I see products that are only 10 parts per million, and I see products that are 20 parts per million, and I see products that are 50 or 60 parts per million. And that’s what’s very confusing. And what you have to do with those is you have to look at the labels, look at the feed tag, and there’s two things to look at. You look at how much salt is in there, and what the label says is what the intake should be. And the problem that I have is, even these products that are, say, 25% to 30% salt, I still only see about that 1/3- to 1/4-ounce per head per day intake. But, they’ll claim that they’ll eat an ounce per day. And so, if they’re eating an ounce per day, the company that makes the product is liable to the FDA to make sure that, if they’re saying they’re an ounce per day, then they have to back down the selenium content so that when they eat an ounce per day, they would only get that 0.7 milligrams. Again, I know this a lot of numbers and everything, but let’s just say, “Okay, if an animal is going to eat 1/4 of an ounce per day, and it’s 90 parts per million, and that’s what the FDA allows. Now I’m going to make a product with selenium, but I expect the goats to eat an ounce per day, so four times as much. So that means the selenium concentration has to be one-fourth, so that the total delivery of selenium per day is that 0.7 milligrams.” So you take one-fourth of 90, so that gets you down to, you know, 25 parts per million.

Deborah Niemann 27:31
Wow, this is great. Because I just, a couple days ago, was talking to the nutritionist at Premier 1, which has a mineral that is so unlike anything I’ve ever seen. I have no idea what to say to people when they contact me and say, “Is this a good mineral?” I’m like, “I don’t know.” But it sounds like exactly what you’ve just described, really, because… And that’s the thing I was looking at, I’m like, “Well, it’s 90 ppm selenium, which I’ve never seen in a mineral before, but it has a really high salt content. So I guess that it balances out.” And, after talking to the nutritionist a couple days ago about the product, that’s exactly what he said. Because so many of the more popular ones have somewhere between 30 and 50 ppm, but their salt is much lower. It’s like 15%, 20%, 25%. And I know some of them, they say that the goats should eat, like, 1/2 an ounce to 3/4 of an ounce per day. So it sounds like this is all adding up to exactly what you just explained.

Robert Van Saun 28:34
Yeah. And so the question is this: Is will they really eat that amount? And I deal with this in many different species, whether it’s beef cattle, sheep, or goats, or llamas and alpacas, I’ll talk to somebody, a client, and say, “Look, let’s weigh out the amount of trace mineral salt, and leave it out for a month or so. And if you add any, make sure you weigh how much you add, and know how many animals who were there.” And then you can calculate, based on the number of days and the amount of weight of salt that was lost, kind of an average intake. And every time I’ve done that, at least in sheep and goats, we come back to that 0.25 to 0.33, you know, ounces per head per day. And not these 1 or 2, or in beef cattle 2 to 4 ounces, per day. The other thing that people need to remember, is goats don’t have nutritional sense, you know, per se, at least from a mineral standpoint. Like, they can’t sense that they’re selenium deficient and specifically eat selenium. Goats have an appetite, just like any other species, for sodium. They need sodium to maintain their blood volume, and to maintain electrolyte balance in their body. And so they will seek out salt for their sodium source. So, if you put out white salt, iodized salt, and red salt, then you’re completely messing up any trace mineral program, because those goats are going to pick and choose whatever sodium source that they want to have. So they don’t know that, “Oh, I’m deficient in copper, so I better go to the red salt.” And so that’s a problem, because I see a lot of people putting out multiple sources of different kinds of salt, but they’re planning on their trace mineral salt providing the appropriate amount of selenium, or copper, or whatever.

Deborah Niemann 30:40
Right. Yeah. I know, so many people think, “The more, the better.” And, like, one of the big new things is cobalt blocks, which drive me crazy, because it’s like 98% salt. And there’s actually less cobalt in it than in some of the mixed minerals that are on the market.

Robert Van Saun 30:58
Right, right. Well, it’s the nutritional fadism, you know? Somebody reads some stuff and finds out… I mean, cobalt deficiency is a very significant disease process, although it’s not very common. It’s seen around the Great Lakes here in the United States. Or, it can be seen when you have high interfering elements, like iron and manganese and some of these others. But, you know, most trace mineral products have a balance of cobalt and copper and stuff. But again, as you know, you know, with copper, it’s all over the board, too. I mean, you find products that are really low in copper and products that are high. The other issue, then, or the other source is if you buy a commercial product, like a grain product, a pellet, or some kind of mixed grains that you’d like to supplement to your goats, that might have selenium in it, too. So, we need to account for that. And again, I see a lot of products that have 0.3 parts per million. But that’s inadequate, because unless you’re going to feed that entire concentrate as the only source of diet, then you’re not going to get the total diet to the 0.3 parts per million. So, if you’re feeding 50/50 forage/concentrate, then the selenium concentration of your concentrate has to be at least 0.6 parts per million, because it’s half of the diet, right?

Deborah Niemann 32:26
So, how does somebody know that they actually need to supplement their goats with selenium? That they’re not getting enough? Because you don’t want to wait until you’ve got animals down with white muscle disease. So how do you know that you need to have more selenium in their diet?

Robert Van Saun 32:40
Yeah, so that’s a great question. And one fortunate thing, unlike our situation with copper, is that blood selenium concentrations are very diagnostic for selenium status. Now, we can also measure selenium in livers, so I always recommend to my production people… You know, we never want to lose an animal. But, if we do, it might behoove you to take a piece of liver. And that liver can be frozen and held for as long as you want. And then, you know, should something happen, or you want to monitor your selenium program, we can measure the selenium in that piece of liver. And, if you have a couple examples, then that gives you a little better perspective. But, we could also just take blood samples, and where the debate comes in here is serum selenium is more sensitive to the current status of selenium. So, if you just increase Selenium in your diet, if you wait a day or two, you can take serum seleniums and see that increase. But whole-blood selenium, which is what a lot of labs run, that’s more of a chronic evaluation of what the selenium status has been historically. And the reason is, is selenium is incorporated into the red blood cell as glutathione peroxidase, and red blood cells have about 101- to 105-day lifespan. So, you can incorporate selenium into the red blood cell once it leaves the bone marrows where it’s made, so that all the red blood cells that are in the blood, you know, have started out their lives at different points in time. And the selenium status at that point in time is reflected in them. And then, they’re a mosaic of all the cells over, you know, a three-month period. So, whole blood selenium would tell you that, you know, you historically have had a good selenium program or not, and then serum would tell you where things are right now.

Deborah Niemann 34:59
Okay. And then, when you send in your labs, they will… Your lab report will come back and tell you where it should be. And so, the lab report—because values can vary a little bit from one lab to another, and your lab report should tell you where it should be. So let’s assume that it comes back, and it’s low or borderline-low. I know our liver samples have shown borderline-low selenium, usually. It’s usually like right smack at the bottom of what the normal range is.

Robert Van Saun 35:27
You know, and that would be okay for an individual animal. But, if you had multiple animals showing that, then I would be worried.

Deborah Niemann 35:33
Yeah. And so, because I used to feed Purina, which has 50 ppm selenium in the feed, but then another goat breeder locally said, “Hey, we can get the local mill to make feed for us.” And I said, “Okay,” and she showed it to me, but it was only 0.3 ppm. So, the Purina goat chow is 0.5 selenium. The local mill was like, “No, we can’t do more than 0.3.” And they said, “because that’s what the legal limit is.” And I’m like, “Well, how can Purina do 0.5 then?” But the price difference was huge, so I’m like, “Okay, I’ll figure out another way to get selenium into them.” And so, for five years, I did. I was getting extra selenium from Caprine Supply, and then they stopped selling it, and since then I haven’t found anything really good like that. And this is a really common question I get from people, like, so what are the options available now for selenium supplementation? And how should people choose one over the other?

Robert Van Saun 36:32
Okay. So to me, you know, again, being a veterinarian and a nutritionist, the best way to deliver selenium is through the diet. All right? Now, we do know that there are selenium injections, the BO-SE, the MU-SE, those kind of things. But, I only describe those as BAND-AIDs of trying to fix something that’s really bad. So if I come into a herd, and I got a bunch of does that are… I know they’re selenium deficient, they’re going to be kidding, I’m going to probably try and fix that, because I know that she’s going to share that selenium, to a great extent, with those fetuses. And, if she doesn’t, those fetuses are going to be very prone to either dying in an abortion or being stillborn or being weak neonates. So, what the problem is, is when you inject selenium, it’s very biologically available. It increases blood concentration quite rapidly. And that exceeds the kidneys’ ability to retain it in the blood. So, there’s been some interesting research done at the University of California, Davis, where they injected selenium deficient beef animals, and collected urine. And they did the calculations that, basically, in 24 hours, they peed out about 40% of the selenium they injected. So, injections can help you in a very short order, but they’re not the way to go. We used to have selenium boluses that were slow release, but they were taken off the market, unfortunately. But that would be a good source if you couldn’t do it through the diet.

Robert Van Saun 38:23
So, how do we do it through the diet? Well, as we already talked about today, we can go with an appropriate level of selenium in a trace mineral salt. We could get a commercial grain product, if we were going to feed at a certain level, to have the right amount of selenium that it delivers, you know, the amount that we want. We could also look at a custom product, like what you were talking about. Now beyond that, there are products out there, and one that I would look at very carefully is two what we call “organic selenium products” that I think a lot of the feed mills have for horses that are in smaller quantities. These products contain the selenomethionine, which is the organic form of selenium that I mentioned earlier is much more available. And even some of the commercial products that you see, if you look on the ingredient list, they may have “selenomethionine” or “yeast selenium” or “selenized yeast”—those would be all the different names that that would be. And that’s going to be a much more available source of selenium, and that would be what I might want to use. Now, I want to caution everybody: Organic selenium is good, and it is absorbed, but I am seeing, in cases when people use exclusively organic mineral, especially the organic selenium, that liver concentrations and tissue concentrations get really high. It’s makes me scared. I almost get into, you know, potential toxicity, although I’ve not seen any clinical signs. So, my recommendation is no more than about 50% organic selenium and 50% inorganic.

Deborah Niemann 40:19
One of the things, in case people had not thought about this: Once in a while—even though I have raised Nigerian Dwarves—once in a while, we do butcher some, and when we butcher them, I send in livers from those animals.

Robert Van Saun 40:31
Yep, that’s a great way. That’s… I did that for a study with some beef cows. Every time they sent an animal to slaughter, you know, they would take a piece of liver and start to build up a database there.

Deborah Niemann 40:44
Yeah, and whenever you change anything, so, like, once you introduce a supplement like this, it’s always a good idea, a few months down the road, to do another liver check.

Deborah Niemann 40:54
So, one of the things I wanted to mention in terms of the selenium supplements, is that so many people think that the selenium gels are adequate. But, if you look at the labels of most of them, they have, like, 1 ppm of selenium in them, which seems like a waste of money. Like, that just does not seem like very much, especially when people talk about doing it once a month, maybe once a week. Like, how often would you have to be giving a goat that extra 1 ppm of selenium to make a difference?

Robert Van Saun 41:31
So 1 ppm? One part per million?

Deborah Niemann 41:34
I found one of the labels and it says, “Each 2 mil dose contains 23.2 micrograms,” and they put “1 ppm” in parentheses.

Robert Van Saun 41:44
Okay. 23.2 micrograms. Per 2 mls.

Deborah Niemann 41:53
Yes.

Robert Van Saun 41:53
That would be 11.6 micrograms per ml, so that’s per gram. Okay?

Deborah Niemann 42:02
Okay.

Robert Van Saun 42:03
Now, we have to convert that. That’s not parts per million. So, per 11.6 micrograms, that would be 0.0116 milligrams per 1 ml. So that means they would get 0.02 milligrams in that dose.

Deborah Niemann 42:30
Which is next to nothing.

Robert Van Saun 42:31
Next to nothing.

Deborah Niemann 42:32
Okay. That’s what I’ve been saying for years. So, I’m like, “This has next to nothing in it.”

Robert Van Saun 42:37
Remember, we can feed as high as 0.7 milligrams per day.

Deborah Niemann 42:43
Yeah.

Robert Van Saun 42:44
Right? 0.7 milligrams—to put it on the same thing—a microgram is 1/1000 of a milligram. So, if we take 0.7 milligrams and multiply it by 1000, that’s 700 micrograms.

Deborah Niemann 43:01
Wow. So you could give the whole tube to a goat, and you wouldn’t hurt it?

Robert Van Saun 43:07
Well, you’d hurt your wallet.

Deborah Niemann 43:09
Yeah, yeah. Exactly. But there’s just so little selenium in here.

Robert Van Saun 43:15
That’s right. And that’s why they’re not seeing any good selenium response.

Deborah Niemann 43:21
Yeah. Okay. I’m so excited to finally have somebody look at this and verify what I’ve been saying, because I just… I’ve crunched the numbers, like, so many different ways, and I’m like, “I just don’t understand how this is going to be helpful.”

Robert Van Saun 43:37
Yeah. Well, and the thing is, is the companies that do this, you know, they’re betting on people being somewhat math-phobic and not knowing how to convert back and forth. You know, a lot of times they’ll put—instead of putting parts per million, they’ll put selenium on a percent basis, you know? So, you know, because it’ll look like it’ll be 0.009%.

Deborah Niemann 44:03
Yeah.

Robert Van Saun 44:05
Well, you got to move the decimal place four places to go from a percent to a parts per million. So, if you’ve got 0.009, then you go “1, 2, 3,” that would be 90 parts per million.

Deborah Niemann 44:20
Right. Another question that I have, because this is something that is just… It’s so incredibly common in social media groups and stuff. If somebody posts that they have a kid that is weak at birth, there’s always people going “BoSe, BoSe, BoSe, BoSe,” and, without even asking, like, “Well, is it 10 degrees where you’re at? Could the kid have hypothermia?” Like… So, one of the things that I’ve always believed is that if a doe is fine on selenium—she’s not deficient—then she should not be giving birth to a kid that is so selenium deficient that it can’t stand or suckle. Is that accurate?

Robert Van Saun 45:03
That is correct. And that’s an area that I’ve been doing a fair amount of research in now, and looking at maternal fetal interrelationships and minerals. Now, the problem we have is, not every lab that measures selenium in tissue does it on a, what we call a “dry weight basis.” They measure it on a wet weight basis. And what has been shown in the literature over the last 30 or 40 years is that the fetus is actually capable of concentrating many trace elements to a level above what’s found in the in the maternal liver. And if we think about this… This is some of the work I did for my master’s degree at Michigan State. I went to slaughterhouses and collected fetuses and livers from the mom in the slaughter process. And, when we measured these and put them on a dry weight basis, the fetus was about two and a half times what mom was in her liver, but the fetal blood—the serum concentration—was very low in the fetus compared to mom. And the reason is, is mom’s got to transport those minerals from her blood into the fetal blood across the placenta. So there needs to be a concentration gradient. So the liver, the fetal liver—and I’m not sure why yet—but the fetal liver is capable of basically sucking all the mineral out. And that way, the blood of the fetus is just marginal, and allowing for this concentration gradient. But, we’ve been working on defining, or better defining, fetal values for trace minerals, because many labs… The fetus is much wetter in its tissue, like, the dry matter content of the fetal liver is only about 18%, whereas, in the adult, it’s about 32%. So, if you have something that’s more concentrated, you know, or has higher amounts, but it’s in a wetter environment, it’s diluted out. And so that, on a wet weight basis, the two numbers look the same. And so that misinterprets the numbers. And so, I’ve worked with my old lab at Michigan State, we basically developed fetal mineral recommendations for all the trace elements in our ruminant species, because what I found is, of many aborted fetuses where you get back the proverbial answer “they couldn’t find anything”—because the only thing they look for is infectious agents—well, we’re finding vitamin A deficiency, we’re finding copper deficiency, zinc deficiency, and selenium deficiency are all highly associated with abortions or weak neonates. And that would be in situations where mom is in tough shape.

Deborah Niemann 48:04
Wow, this is great! This has been so much fun. You now officially have the longest podcast episode of anyone I’ve interviewed. And it’s been amazing. I love it! Do not apologize. I’m so excited about being able to dive into selenium at such a deep level. I think this is just going to be so helpful for people in terms of, you know, figuring out how to help get their goats better nutrition in terms of selenium. Is there anything else that you feel people need to know that I didn’t ask you about?

Robert Van Saun 48:35
No, I think we’ve kind of covered that whole gamut. I know that the numbers and the calculations and reading things are always challenging. And that’s probably something that just needs to be addressed over and over again, to kind of get that through.

Deborah Niemann 48:53
And I will be listening to this podcast episode over and over again myself to really get all these details absorbed, because this is great information. So, thank you very much for taking the time to be with us today and help educate all of our listeners. Thank you.

Robert Van Saun 49:09
All right! You’re very welcome.

 

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9 thoughts on “Selenium Deficiency and Toxicity in Goats”

  1. Phew! what a lot of information! Not to add to your burden, but I’ll count on you to digest a lot of it for your listeners and summarize with info re. a solid nutrition plan : ). Thanks so much for doing that podcast!

    Reply
    • One of my biggest takeaways was that before people get too worried, they should just do blood work and see what their goats’ selenium levels really are. Blood isn’t accurate for copper levels, but it is for selenium, which makes this a lot easier.

      Reply
      • And whole blood vs serum. Serum will give you the snapshot but whole blood will give you the big picture, or at least the 3-month average.
        (Red blood cells are recycled every three months so the whole blood reflects the average amount of selenium in all of the red blood cells that have been circulating over the last 3 months – kinda like glycosylated hemoglobin vs blood glucose in terms of diabetes). Cool!

        Reply
  2. Yes, thank-you to you and your guest. That was really fascinating and informative. I’ll be listening (or going over the transcript) again for sure. And I’ll be going back to my dairy ration and my loose supplements to crunch some numbers, that’s for sure.
    One quick Q that I’ll be re-reading (or listening) is that it seemed to me like selenium toxicity could look like copper deficiency in terms of hair loss. I know there are a lot of other signs of copper deficiency but it makes me wonder…
    Thanks again!

    Reply
    • But you can do a blood test for selenium levels, which you cannot accurately do for copper, so this is MUCH less complicated. No guessing required! 🙂

      Reply
  3. Does Sweetlix Minerals have enough copper and selenium to keep a goat healthy and not become deficient in copper or selenium? I feed this to my 3 month old goats. And need to know if it will also keep them from becoming deficient, as adults. They have it available during the day, but not a night. Should it be available 24/7?

    Reply
    • Sweetlix Meat Maker loose minerals is excellent. However, there is no one-size-fits-all mineral. Conditions vary from farm to farm. I had a friend four miles away who had goats for 20 years and never had to supplement with copper like we did because we have well water that is high in sulfur and iron, whereas their well had run dry, and they were hauling out city water. On the flip side, they had problems with vitamin E deficiency because their goats were on dry lot and not getting a lot of green forage. You might want to sign up for my free copper course to learn more:
      https://thriftyhomesteader.teachable.com/p/copper-deficiency/
      There are also lots of articles on here about other minerals.

      Reply
  4. I’ve gone through this episode multiple times and recently came across a mineral that doesn’t seem to follow the idea of high salt and high selenium. It’s min salt is 9.5% to a max salt of 11.4%. selenium is 80ppm. Feeding amount is .25 to .31oz daily so still within range for .7mg/head daily. Sweetlix meat maker is higher in salt and lower in selenium with higher feeding amounts, but fits in line with the above 50ppm selenium to a 15-18% salt. My only guess as to why so far is it’s a mineral meant for meat goats on pasture or browse in the southeast so maybe no feed in the diet? Any ideas?

    Reply
    • I’ve talked to a few different nutritionists about the level of selenium in minerals, and some have told me that you can put more selenium in a feed or mineral, depending upon how you label it in terms of consumption. If they are saying to top dress that amount of the mineral, I could understand the logic behind it. But if they are saying that it’s free choice, that’s trickier. You could put it out and do the math to see how much they consume. If they consume 1/4 to 1/3 ounce per day, that would be 7 ounces for every 3-4 goats per week. So you could weigh out whatever they should consume in a week and then see how fast they actually consume it. If they are +/- a day or two on either side, then you could probably put it out free choice. If you wanted to do a measured amount for 2-4 weeks initially to get a baseline, you could then see what they’re consuming. And if they do wind up a little selenium deficient, and they are willing to eat more, that’s a good thing. It would provide a more consistent selenium level that BoSe shots.

      I don’t normally recommend that people weigh the minerals because we know that goats do well when the salt is 15-18% and selenium is 50 ppm. But in a lot of areas, goats do still wind up selenium deficient. You definitely don’t have to worry about toxicity with the typical ratios though. When in doubt with selenium, you can always have blood testing done to see where the levels are in your goats. (This is NOT accurate with copper though.)

      Reply

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