Well, 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…
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?
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?
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.]