Calculating Copper in a Sheep’s Diet

File:Copper sulfate.jpgWell, I can’t stop thinking about copper, and how much to allow my sheep to eat. And I’m going to keep blogging about it until I figure it out! 🙂 Sorry if it’s getting boring, eventually I’ll get past this phase!

So, as Kirk can tell you, when I’m in a period of indecision, I make a spreadsheet! I love spreadsheets. Looking at math and side-by-side comparisons of things always helps me think through a problem.

The Math is Unavoidable, so Get Out Your Calculator…

j0438673[1] I’m still thinking about Pat Coleby’s mix, and how it compares to commercial mineral mixes. But her book is vexingly non-mathematic, so at first I couldn’t figure out how her mix compares to the labels I’m reading.

And, it turns out that one is really forced to do some math anyway, because you have to figure out how much copper is already in your forage or hay, how much additional is in the supplement, and how much mass of both the sheep are eating, in order to calculate the dilution of the copper in the total diet. Well, it’s always good to stay fresh on our algebra and unit conversions! (And heaven forbid I’ve done any of this wrong, since my sheep’s lives are at stake here!)

Recommendations are Rare

Ok, so to start, it’s hard to even find somebody who is bold enough to give numerical recommendations for copper intake for sheep, because they’re probably afraid someone will sue them when their recommendation results in a dead sheep! This website from Montana Extension has the most useful quote I’ve found, so far, so I’ll start with this advice as a base guideline (and note how they give two disclaimers…):

Although it is impossible to give the exact requirements and toxic levels, the recommended copper allowance is 7 to 10 mg/kg DM when the Molybdenum content in the diet is below 1.0 mg/kg up to about 14-20 mg/kg when molybdenum content is above 3.0 mg/kg. It should be stressed that these are just guidelines and may vary drastically from situation to situation.

Ok, so probably 20 mg/kg is a minimum for what I should be shooting for, considering my copper tie-up problems.

ppm… mg/kg; what’s the difference?

j0436921[1] None. I think I figured out that mg/kg is the same as ppm (parts per million). I don’t think that’s always true in general, I think if you are talking to a chemist, he might be defining ppm as how many molecules of X compound are in Y compound, and those molecules may have different volumes and mass, so then ppm wouldn’t directly translate to mg/kg or ml/kl.

But, I’m pretty sure I’ve figured out that animal feed people are really just talking about mass (weight) when they say ppm or give a percentage concentration, not molecule concentrations, so then it really is the same thing as mg/kg. If there is a chemist and animal feed expert out there who disagrees, please correct me! But as far as I can tell, these are used interchangeably for animal feed; and that’s good to know, because you see both on labels and in forage analysis reports.

Copper Concentration In The Goat Mix

I’m going to start with this Purina Goat Chow Mineral mix that my sheep are loving so much and which has appeared to help them grow new feet. It has 1,800 ppm or mg/kg of copper in it. The label says to feed 1/3 of an ounce per head per day, for goats, if you measure it; but it also suggests feeding it free choice. I’ve been doing the free choice option, just to see how much the sheep will eat, given their druthers. They have been eating about 1.75 lbs per day, divided by 18 sheep, that’s 1.56 ounces per sheep per day- considerably more than the label recommends! (And I have concerns about their selenium intake at that clip, but boy, that’s another whole topic!), Ok, fine, so how much copper is that per sheep per day?

1.56 oz * 0.0283495231 kg/oz = 0.0441 kg per day of the supplement

0.044226 kg * 1,800 mg/kg = 79.38 mg copper per day per sheep consumed from the supplement

Assuming my sheep average about 120 lbs, and sheep eat about 5% of their body weight (dry weight) per day, I assume each sheep is eating about six pounds of feed. So, the above-mentioned copper amount is diluted, like this:

6 lbs feed * 0.45359237 kg/lb = 2.72 kg feed eaten per day

79.38 mg copper / 2.72 kg feed = 29.17 mg/kg (ppm) of copper from the supplement

But don’t forget my forage already has 12 mg/kg, so they have to be added together:

29.25 mg/kg+ 12 mg/kg= 41.17mg/kg copper diluted in feed

So, right now, my sheep are eating about double of the 20 mg/kg recommended above. But when I put it that way, it doesn’t sound all that shocking. When I was first looking at that 1,800 ppm number on the goat mineral label, I was thinking, whoo, that’s sure a lot of copper! But, it’s all a ratio of how much supplement to how much food, and it’s going to be different for every mineral mix. You can’t just focus on the concentration numbers of the mix by themselves.

Copper Concentration in the Pat Coleby Mix

So, how does this compare to what Pat Coleby recommends in her Natural Sheep Care book, and has been doing with thousands of Australian sheep for decades with record success? This took me a bit to figure out. Her book mostly focuses on feeding her mix free-choice, but she does, on page 37, discuss “shedded sheep” (by which, she means, sheep kept in a barn, not sheep shed in the shedding circle, like we Border Collie people would think!) and says they can be fed “the lick” at a rate of 4-5 grams/head/day. So, I’ll use five grams as an assumption of a likely amount sheep may eat.

The lick recipe is this:

25 kg dolomite + 4 kg copper sulfate + 4 kg sulfur + 4 kg kelp = 37 kgs total for a batch

The form of copper Pat’s book calls for is, I believe, Copper Sulfate Pentahydrate: CuSO4·5H2O. If I recall from chemistry, if we look up the mass of each one of those elements (1 copper, 1 sulfur, 9 oxygens, and 10 hydrogens) and add them up, copper accounts for about 25% of the total weight per unit. So, the copper component of this mix is:

4 kg copper sulfate * 1,000,000 mg/kg / 37 kg * 25% = 27,027 mg/kg of copper in the mix

Wow, now that’s a lot more than 18,000ppm in the Purina goat mix!

If sheep eat five grams of this stuff per day, that’s:

5 g mix * 0.001 kg/g * 27,027 mg/kg of copper = 135.14 mg copper eaten per day

In their overall ration, knowing from above the sheep are eating 2.72kg feed per day, that turns out to be:

135.14 mg copper / 2.72 kg feed = 49.7 mg/kg copper concentration in the lick

If I were to add that to my grass, my sheep would be getting:

49.7 mg/kg + 12 mg/kg = 61.7 mg/kg copper diluted in feed

So, that is 1.5 times what I’m feeding now, and 6-9 times the recommended “normal” range for people who don’t have high molybdenum. Now wonder some people consider Pat Coleby to be radical! And, no wonder a few people have had sheep die doing this. But this gives me some small comfort, knowing that most of the time, Pat Coleby followers an advisees do have success with this high of a concentration, and I’m still far below it.

How to Present Copper in Precise Increments?

image This is where the Pat Coleby advice breaks down for me. So, for one, I don’t think I’d be inclined to “force-feed” the Pat Coleby mineral mix at 5 g per day by sneaking it into grain. That is just a whopping dose of copper to be giving the sheep without their consent, so to speak. And, even if I offered the Colebly mineral mix free-choice, I question whether the sheep could manage their copper intake at a granular enough level. Five grams isn’t much, the sheep have pretty big tongues, it’s not like they could choose to precisely eat one gram or six- they are just going to get a several-gram mouthful every time they hit the box!

I like Pat’s suggestion of offering the minerals in individual bins, so the animals can choose how much to eat. But, putting out a bin of copper sulfate poses several problems, for me. If  you read MSDS sheets for copper sulfate, or see what it’s used for, holy cow, that is some nasty stuff! The MSDS warns of severe tissue irritation if inhaled or ingested. It’s sold as a product that can burn tree roots right out of sewer pipes, so it is extremely caustic. And yet, my sheep are currently eating 0.08 g of the stuff per day  (embedded in 44 g of crystals) in their goat mix. So I have to wonder, if I put a big bin of those blue crystals out, how could the sheep possibly manage to eat it in that small of a quantity? Even me handling the stuff regularly seems like a bad idea.

So, for me, some much greater dilution seems in order, to make sure that it’s palatable, that it doesn’t burn the sheep’s throats, and also that they have more precise control over how much they eat. But how to dilute it? In even more dolomite (which Pat Coleby says “buffers” copper, but I’ve never really found a good explanation for what that actually means). In salt? In kelp? Or, in water? Salt and kelp carry the risk that the sheep would over-eat on copper in craving the salt or kelp.

Doris, who comments on this blog a lot, told me that she has offered “copper water” to other livestock before, and they seem to prefer it over regular water. I like this idea from the standpoint that it seems much gentler. But, how much would I dilute it? And how would I track how much the sheep are consuming, given evaporation and spillage? I don’t know.

Still Shopping for a Solution

So this is where I am with this, today. I’m not quite happy with the Pat Coleby mix by itself, but I’m not quite happy with the commercial mixes I’ve found so far either, mostly because they are incompatible with my particular forage profile. I want to create a situation where the sheep can regulate their own copper, independent of whatever else is in their supplementation.

I am still studying the labels on as many mineral supplement bags as I can find in my area. This is another challenge, as many supplement manufacturers aren’t Web savvy, so I can’t find their information online. Today I’m going to actually have to drive to the feed stores and painstakingly hand-copy the information off the labels to put into my spreadsheet. How old fashioned! 😉

I know there is always the option of paying to have a specialized mix custom-made, and I haven’t eliminated that idea either.

[Note this post was edited for math corrections on 9/1/12.]

26 thoughts on “Calculating Copper in a Sheep’s Diet

  1. Linda says:

    WOW!!! Thank you for that Michelle! That comparison and breakdown is very good to know… it would not be hard to reformat Coleby’s mix to have a lower concentration of copper. Doesn’t Purina’s goat minerals contain mineral oil? When I was looking for minerals for my goats I had a hard time finding any without mineral oil. I finally settled on Manna Pro goat minerals (before Coley) because it was all I could find that did not have mineral oil in it.

    • workingcollies says:

      Linda, yes, I suppose I could re-do Pat Coleby’s mix and use much less copper, and maybe more dolomite; and I suppose one could weigh how much the sheep are eating, and tinker with the ratios to control how much they are taking in. But I also wonder if the mix is mostly dolomite and tastes that way, if they won’t crave it or eat it at all?

      I have some concerns about the mineral oil too, and of course it’s not clear how much of it is in the mixes. It’s usually low on the ingredient list, and I’m not sure why they use it- as a binder? So, I don’t know whether it’s an issue of blocking absorption or not; I imagine it depends on the quantity. Purina’s mix does have it, as well as Sweetlix.

      I just bought a small bag of the Manna Pro goat mineral to try out, as it has some attributes I’m seeking. But I have to say, it smells really awful, really strong chemical-ey; so I’m curious to see if the sheep will eat it. Right now,they have a buffet of four commercial mixes, the Purina, the Manna Pro, and two versions of Sweetlix- just because I’m trying to see what they prefer if they have the choice. I think the Purina mix smells the most wonderful, but then, maybe the sheep have different taste than I!

  2. Linda says:

    Oh wow, my Manna Pro smells like licorice or anise… which I believe is fennel. Perhaps you got something different than I do. It has vegetable oil in it as a binder and it only comes in small packages as far as I have found. I don’t want my goats ingesting ‘any’ mineral oil. Mineral oil floats around in the blood and picks up fat soluble vitamins so they are just excreted rather than utilized. No thanks!

    • workingcollies says:

      Linda, hmm, I just went and re-smelled the Manna Pro to see if it seemed like fennel to me, and I just can’t tell! I think it just smells like fertlizer to me, which I suppose, it is in some sense. But, who knows, maybe it smells good to animals, if they are craving minerals. It does say that it has natural and artificial flavorings in it, so maybe there is fennel in there and my nost just isn’t picking it up. I wondered about the small bag, I was glad to have that to just try it, but was thinking it’s very expensive, and that hopefully I could find it in bulk quantities and pricing if I decided to use it.

      I find it interesting that their product has what I think are digestive enzymes in it, which I haven’t seen in other products. Every company has their own spin on what they think is important, don’t they?

      Re: mineral oil, have you encountered some good reading on the subject? I’ve heard from a few people about the concerns, but I’d like to read more about it in a book or scientific journal. I haven’t been able to find many sources that discuss it.

  3. Linda says:

    I had forgotten about the artificial flavors! The fact that they are chelated minerals and the artificial flavors may have been the reason I chose to go with Coleby’s. And there is no sulfur in the Manna Pro. There is much controversy about the benefit of chelates. I prefer to not use them.

    The information I have cleaned about mineral oil is old and from books I have studied. I will look around the internet to find more resent information. Like anything I suppose, there is controversy pro and con.

    • workingcollies says:

      Linda, I’m concerned about the chelates too, that they might not be as digestible. Sulfur I don’t have to worry about as much, because our forage is very high in it already.

      What do you do about selenium- are your soils deficient there? If I do Pat Coleby’s mix, I’d have to figure out how to add that. Are you feeding the mix free-choice?

      I did hear from a researcher that mineral oil blocks nutrient absorption. I think in the parasite talk I attended at the Katahdin Expo, he discussed how some people were using mineral oil to make bolusing easier (or something, I can’t quite remember the context he was talking about of why people were using it) and how that is counter-productive, since the mineral oil dose would reduce the effectiveness of whatever drug you were trying to deliver to the stomach, and it’s not known by how much. And I think it’s used as a treatment for when animals eat toxic plants, to reduce the absorption of the toxin. But, I wonder if its presence in micro-quantities is still a problem, or if it’s just in high doses? Since I don’t know, I would like to avoid it too. My problem is that every supplement seems to have one thing I want to avoid! 😛 I guess I’m going to be forced to make my own Pat Coleby modified something!

  4. Linda says:

    I did look up some information. It’s enough for me… except for Wikipedia, I included a link to the document at the bottom of each quote.

    Mineral oil may decrease the absorption of fat-soluble vitamins and some minerals. (Wikipedia)

    There has been a great deal of work on the effect of mineral oil
    in impeding the absorption of fat soluble vitamins A (and precursors)
    D, E, K and essential fatty acids. There is no doubt that interference
    with absorption can occur, particularly of carotene if amounts in food
    exceed approximately 6000 ppm (Steigmann et al., 1952). Whether the
    amounts likely to appear in the food of children are of clinical
    importance is much less certain (assuming that it is not used as an
    ingredient as in (2) above). But the diets of many of these may
    contain amounts of these vitamins that are in any case marginal or
    inadequate and there seems no reason for the inclusion of mineral oil
    in foods which are specifically intended for infants with the possible
    exception of rusks (concerning which enquiries are being made which
    will be later reported as they may be subject to the same
    contaminating processes as bread).

    • research: While there is some disagreement, most research has found that mineral oil interferes with the absorption of many nutrients, including beta-carotene, calcium, phosphorus, potassium, and vitamins A, D, K, and E. Chronic use of mineral oil can cause a deficiency of vitamins A, D, E, and K, being fat soluble, as a result of their being not being assimilated properly. This is especially problematic during pregnancy as the regular ingestion of mineral oil may reduce the absorption of critical nutrients. As noted above, the malabsorption of vitamin K can result in an increased anticoagulant activity by coumarin anticoagulants due to this adverse effect of mineral oil.
    (Clark JH, et al. Am J Dis Child 1987 Nov;141(11):1210-1212 ; Holt GA.1998, 176.)

    • nutritional concerns: If using mineral oil for any extended period of time, regular use of a multivitamin supplement, containing more than 100 mcg of vitamin K per daily dose, would be beneficial. Malabsorption of fat-soluble vitamins due to ingestion of mineral oil can be minimized by administering mineral oil on an empty stomach or consuming vitamin or mineral supplements at least two hours before or after the mineral oil. In general it is advisable to limit the internal use of mineral oil to periods of less than one week.

    Personally, because of previous information I have read, I don’t want to ingest mineral oil, rub it on my skin, or give it to my goats. However, I do use salves and such that contain mineral oil on me and sometimes on the goats. I am working at making my own formulas of these things myself, so as to not use the mineral oil.

    • workingcollies says:

      Linda, thanks for all the links. The quotes imply that the researchers were concerned about people consuming mineral oil on a regular basis- I wonder why? Was that a diet fad or something, where people were purposely taking it daily? I just can’t imagine too many scenarios where humans would be eating mineral oil, but maybe we are and I’ve just never been aware of it?

      The discussion of fat-soluble vitamins intrigues me, because wouldn’t this concern be true in ingesting any oil/fat, that too much of it will dissolve vitamins and carry them away? Would vegetable oil, or say fish oil, in the feed be any better than mineral oil? And is it a matter of the presence of the oil, or just too much of it that causes the problem? And if so, how much is too much?

      Here is an interesting quote from Paula Simmons’ book “Raising Sheep the Modern Way”:
      “Researchers at the University of Illlinois have a new “flushing theory” which hey say promotes increased ovulations, thus increasing the number of lambs produced. They claim that a daily oral dose of just less than two ounces of mineral oil, given for ten days before mating, will decrease the steroid secretions that normally restrict the number of ovulations. The mineral oil, which in that quantity is said to have no affect on digestion, would be in addition to the normal seventeen day flushing with supplemental grains and/or better pasture.”

      So, it’s interesting that those researchers, at least, convinced themselves that two ounces per day wasn’t impacting nutrition. I would guess that the concentration in supplements, when used as a binder, is much less.

      The 6,000 ppm food concentration mentioned in the above quote is a threshold for children, who weigh less and eat significantly less poundage per day than a small ruminant; so I’m not sure how the threhold might scale up. The ingredient profiles on the supps don’t give a ppm concentration on the mineral oil. But, I can guess a bit. On Purina’s mix, the ingredient is after the calcium (9-11%) but before the magnesium (1%). So, the mineral oil concentration is somewhere between 10,000 and 110,000 ppm in that mix, and that’s by dry matter weight, so I’m not sure quite how that works once the mineral oil is dried out? On the Sweetlix mixes, it’s the last ingredient, after the selenium, so it’s somewhere lower than 50ppm.

      So, I suppose it’s possible that it’s in low enough concentrations in the supps to not cause a problem for an animal eating 5 lbs of food per day, and some of those supps add huge amounts of fat-soluble vitamins back in, too. So, I dunno. I’d still rather avoid it if I can, but I’d like to find more research on sheep to know if it should be of high concern to me, or if there are other things I need to worry about more. I’m attracted to the broader profile of minerals and vitamins that are offered in the commercial mixes, as compared to Pat Coleby’s mix, but then, maybe they don’t even need them, I’m not sure.

  5. Linda says:

    Mineral oil is used for many things, like the coating on cutting boards, the mineral wax (wax is a concentrated form of oil) on fruits and vegetables. Rubbing mineral oil on our skin is all taking in and absorbed to some degree. Cosmetics have mineral oil in them. Years ago people used to fry food in mineral oil because it is odorless, tasteless, and can stand very high temperatures. And if the internet keeps saying mineral oil is safe, it may happen again. As humans we can be gullible…

    Flushing as is suggested with mineral oil is compromising I think. If the animals are fed properly and get the proper minerals, they will naturally ovulate as they should without external manipulation.

    To some degree using vegetables oils too much can be harmful. Vegetable oils used in excess increases the need for vitamin E if I recall correctly. But in general vegetable oil are good for you because they contain the essential fatty acid that we all need – humans or animals. Mineral oil contains nothing that is needed.

  6. Linda says:

    I don’t know about the selenium. I did have my garden soil tested a couple of years ago. I give the pregnant does a small dose of selenium – E gel twice during their pregnancy, but other than that I haven’t seen any reason to give it to them. I would love to have the pasture tested, but I just can’t afford to do that and they get fed alfalfa and grass hay pellets as their main forage. I have no real idea where it comes from each time I buy it. Kelp meal has some selenium in it as well.

    • workingcollies says:

      Linda, my understanding is that the entire “northwest” is considered selenium deficient, though I don’t know how far that extends (aren’t you in CA?). Definitely all stores in my area *only* carry mineral supplements that contain it, as it’s generally presumed that everyone must supplement with it, even in the most basic supplements. I’ve read many authors who think the whole U.S. is deficient, as compared to Australia etc. Se is pretty important, and if your feed is potentially coming from all over the country, it might be worth considering having Se continually present in your mineral mix? I’ve read that Pat Coleby is working on a revision of her books, I’m really hoping she addresses this more for the American audience.

      The two kelp brand breakdowns I’ve seen are very low in Se, one was 3ppm and the other 0.3ppm. Of all the commercial supps I have in my spreadsheet so far, they range between 12-90ppm, with most being 25-30 (of course it depends on what the feed rate is how much they’re actually getting, just like with the copper).

      There is danger of overdose as well, I actually think I saw this in a lamb I had last year (long story). That’s actually what I’m more concerned about now for myself, because my sheep are choosing to eat more than the supplement label recommends, and some labels warn against this because of the Se content. When I get done obsessing about copper, I’m going to think about this next! 🙂

  7. helen galland says:

    i a glad someone is trying to do the math re amount of copper a sheep can safely ingest I have recently discovered the grass nuts i was given on a small scale have 47mg/kg copper! Now if i had been feeding 2kg feed to each sheep im sure they would all be dead now. Instead i am stuck with the dilemma- how much copper have they stored over the period of years they have had access to this feed? Was it below the recommended daily intake (and no-one will report a recommended daily intake…) I read on one website that the legal amount a sheep feed should contain is 17mg/kg copper- which feeding 2kg to a sheep would result in a daily intake of 34mg. As my sheep were only getting a max (i hope) of 200g per day of the suspect feed then that would be a daily intake of 9.4mg. add to that say 2kg hay (at a tested cu content <10mg/kg) plus 200g readigrass (ave 10mg/kg) then that would be a total (no other feed/ mineral offered) 31.4mg which is less than the site said of a ewe eating the sheep feed at 17mg/kg on a 2 kg ration per day (ie 34mg Cu per ewe per day).
    so i am thinking- do i treat all my (healthy looking) sheep for copper overloaded livers, or do i wait til a crisis happens and i lose a precious animal!
    what do you think? (i wont hold you to it!!)

    • workingcollies says:

      Hi Helen!
      Indeed it is a dilemma. The thing to remember is there are several other minerals in the diet that will bind with copper and block its digestion. So, it really depends on this dynamic of “all the other things”. If you had a lot of iron, or molybdenum etc it could be that the high copper you were feeding was just fine. And there is no good way to measure all that interaction to try to assess what they are really digesting in the end, the model is too complex to capture in an equation. Also, different sheep breeds, and different sheep, metabolize copper differently. So what might be fine, or even required, for one sheep might be lethal to another. A third complication is that apparently a lot of us have copper in our water- either naturally, or compounded from the copper pipes that it frequently passes through before it makes it into our sheep’s watering tanks! So in the end, there is just unmitigated risk…

      The fact that many people (hundreds? thousands?) have been following Pat Coleby’s recommendation for maybe decades, with that really high dose of copper- that implies to me that there must be some reason why it’s ok most of the time. And there is something special and unusual about the instances when it’s not, but we don’t know what that is. From the few accounts I’ve read where people have had sheep have a toxic event, it seems like it’s never the whole flock, it’s always just one sheep out of many. Why? I think maybe nobody knows?

      One thing you can do if you are butchering lambs is to submit liver samples to a lab for surveillance purposes, to keep an eye on how much your flock is generally accumulating. But I’ve also read that some people who are choosing to feed higher copper are having the tests come back reporting “your sheep should be dead…” but apparently they aren’t. So it sounds like even our lab tests can’t really tell us for sure what’s going on. Perhaps there is something we don’t yet understand about the actual toxicity “event” and what triggers it.

      You can run blood tests on it too, for live animals you aren’t butchering, but the local vet here whom I discussed it with felt that they aren’t terribly accurate. But if your concern was high and you were willing to spend the money, it might be worth a try, just to get some information.

      As far as treating sheep that may have a large accumulation, I’m not sure that you can? It sounds to me like the copper is just “safely stored away” and is not causing the sheep any difficulty unless and until they have one of these “dump” events where the copper is suddenly and completely released into the bloodstream. Then you can treat the acute phase, though the prognosis isn’t good. But it doesn’t sound like there is any definitive advice on getting a sheep to gradually bleed away that excess storage in a safe and controlled way. Maybe just feeding them low copper for a time? But maybe not zero copper, as maybe that’s part of what triggers the “dump”?

      It’s definitely a mystery! But I can say I’m in my second year of feeding high copper, and haven’t had any adverse affects that I know about yet. Knock on wood! Please share if you learn and experiment more!

  8. Thomas Riederer says:

    in the quest for more info on Pat Coleby’s sheep mineral feeding I found your blog. I am still not clear on what to think myself with her recommendations.
    I just went through your calculations. If you take copper sulfate equal with copper, you come out wrong by about a factor 4. There is approximately 25% copper in copper sulfate CuSO4*5H2O (it depends on how much water is bound in it as well, so it could be even less). You come to 211mg/kg and conclude: “Now we’re talking not double, but 100 times the recommended level I quoted above!” But above you were mentioning 20mg/kg. So in reality the Pat Coleby mix would be about 5 x recommended value (7-11mg/kg) of Cu, or 2.5 x of what you were aiming for (20mg/kg).
    A reason, why Coleby’s high Cu could work is because she is adding additional sulphur, which is another antagonist to Cu.
    Hope this helps.
    For more info on mineral nutrition read: Mineral Nutrition of Livestock, by Neville F. Suttle.


  9. Michelle Canfield says:

    Thomas, I think you are right- thanks for going through my math carefully, it always helps to have a second pair of eyes. I think this is where the ppm vs. mg/kg math gets more complicated, and where the units can’t be used interchangeably in chemistry as they are in other disciplines. So I went back and did a little more math to account for that, which hopefully I did right- I think copper ends up being about 30% (ish) per unit of weight in the form it’s in. I’ve edited the math, see if it looks better now!

    I think you are right, too, about the sulfur and copper binding, thus lowering the intake of copper. That is the ultimate variable, is how each of these things is interacting with other elements in the pasture system, and in the body. I have since done a lot more reading, thinking an writing about this problem, and I think the bottom line is that one recipe is never adequate- we’d each do best to analyze our own soils and forages, and design a supplement around that. Hard to believe this was three years ago when I wrote this, I have moved through a lot more mineral experiments since then, and am still tinkering!

    Thanks for the book recommendation, I’ll check it out!

  10. Thomas Riederer says:

    Don’t post this on your blog, but just consider it in your calculations:

    One more suggestion to the math. You write “copper accounts for about 36% of the total weight per unit. So, the copper component of this mix is:

    4 kg copper * 1,000,000 mg/kg / 37 kg * 26% = 38,920 mg/kg of copper in the mix.”

    First you write 36% and then in your formula you write 26% (I come to a rounded 25%, see below) but the math you still do with 36%.

    1Cu = 63.546
    1 S = 32.065
    9 0 = 9 * 15.999 = 143.991
    10 H= 1.0079 = 10.09
    Total= 249.692

    Cu content in % of Copper sulfate pentahydrate: (63.546 / 249.692)*100 = 25.449%. Round this to 25%.

    My suggestion: 4 kg copper sulfate pentahydrate provides 1 kg copper.
    Therefore 1 kg copper * 1,000,000mg/kg /37kg = 27,027 mg/kg of copper in the mix.
    Hope this helps.


  11. Michelle Canfield says:

    Yes, Thomas, you are right- thanks for good math and typo checking! Maybe someday the publishers of Pat’s book will issue an update where they just do this math for people, to relieve us of the extra work!

  12. Shivani says:

    I have been reading Colby’s book, too. It seems that the sensible thing to do is offer free choice. That won’t drive you nuts trying to figure out how much to feed, and the sheep will eat just what they need. And be sure to offer them dolomite as well, as Colby says she’s never seen a case of copper toxicity if they had the dolomite offered as well. The soils in Australia where Colby lives may have very different deficiencies from the soil where you live, so a mix appropriate for there could be bad news for you. If you insist on trying to figure it out and allowing them no choice, how about having their copper levels tested

    • Michelle Canfield says:

      Shivani, thanks for your comments. I wrote this post over 3 years ago. I do actually feed my sheep free choice loose minerals, as I don’t feed mixed feed, they are just on grass. But, it would be hard for me to offer each mineral free choice separately. I now supplement with quite a few different elements, and to keep them in a container which stays dry but is easily moved ever 2 days would be hard. So, I calculate the mix and blend it myself, using two different brands, plus adding dolomite, sulfur and zinc to get the correct balance I think I need here.

      I do now submit liver samples to a lab at least yearly, and that has been very enlightening- the results were not at all what I expected based on the tests of my soil and forage. It goes to show that minerals binding with each other is a very complex equation indeed. Since that time, I’ve adjusted my mineral mix every year, and I feel I’m getting closer and closer to optimal, and I feel I’m seeing the benefits in hoof health, which was my primary goal. But it’s a long experiment. I’m still feeding a lot of copper, but had backed it down from some higher levels I was feeding previously, and last year was the first time some of my lab results came back too low in copper. So, it’s proof that you can’t just go by general recommendations; that for whatever various factors, my sheep need more copper than is typical for most, and every farm and sheep breed combination is unique.

  13. jessica pykosz says:

    Love this. I graze sheep on an island and I believe there to be a chronic copper deficiency. I looked into it befor but vets and svhalors alike thought I was crazy. Copper deficient sheep. Here in the US. Not many folks have looked into mineral imbalances… I have been corresbonding with some folks that make mineral boluses with great success to sheep farmers in AUS NZ and UK. It makes the most efficient sence to me. The work to analyz the farm/flock imbalances in forage soil water and animal blood serum is essential to knowing if or which boluses will work for you. I would love to keep up with your work.

    • Michelle Canfield says:

      Jessica thanks. I have written a lot about this off and on, not sure how much you ran across on my blog. I test the livers of my butcher lambs and cull animals to monitor their trace mineral intake. I have indeed sometimes detected sheep which are too low in copper, so I do find that it helps to supplement them. I think getting my mineral mix right has helped a lot with foot health; and in general my flock is becoming more & more productive, so apart from genetic selection, I think tweaking minerals is a big piece of the puzzle to optimal health and productivity.

    • Michelle Canfield says:

      Nathan, I send them to our state land grand college veterinary diagnostic lab- for us, it’s Washington State University. Depending on where you live, you may also have an AG college with a vet lab; or you can find out where your vet normally sends them. They only need a small snippet, I freeze them first, then send them 2-day mail with an ice pack in the box. That seems to get them there in reasonable shape for doing mineral toxicology reports.

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