“I had a question as I looked through the fleeces. One of them, Nettie’s, had banding across the lock. Is this truly color banding? I once purchased a little Shetland hogged fleece that had very black locks for the outer inch or so and gray in the inside of the fleece. Similar thing?
“I know some cat fur can have true color banding on one strand of hair, but I didn’t know it happened in sheep.”
She then asked if perhaps I would answer her question in the blog because she thought others might be equally interested—so here we are.
The banding one sees in sheep fleeces (and I am including a number of photos of our previously banded fleeces – both on the sheep and after shearing) is not at all related to the banding you might see on a rabbit or a cat. These other mammals actually carry genetic coding for such color changes along their hair, whereas domestic sheep do not. Yet there is no question that we occasionally run across banded fleeces. After all, you merely need to look at the photos here and you can see that it happens. And it has happened quite often here over the past four or five years! So, what causes this?
The answer is not quite as simple as the question. There are three possible causes for banding in a fleece, and the only way to know which is the true cause is to do some investigation. First, there are genetic patterns that can be inherited in a family line that can cause “sputtering” of the fleece color along a small portion of the fleece—usually around the shoulders—producing this banded affect in that area. It happens perhaps two times along the staple from light to dark and then perhaps light and dark again, and then it stays dark. This only happens in certain breeds; and my only experience with it is in the Romeldales. Because they can darken with age (the only breed I know of that does so), this sputtering can occur in the shoulder area as they make the transition to their darker fleece.
The other two causes of banding relate to a copper deficiency—either a primary or a secondary deficiency. First a bit of technical info. Those of you not interested in the technical aspects might want to jump down to the next paragraph. Fleece is pigmented most of the time by eumelanin. Sheep produce eumelanin in their wool follicles, and they need some copper to do so. However, copper can also be very toxic to sheep, and I’ve known many sheep who have died of copper toxicity. This is the reason we are always told not to supplement with copper. If sheep don’t get enough of the mineral—or their bodies don’t utilize what they do take in—they cease producing eumelanin and their wool turns paler and eventually white.
When I first researched copper deficiency as a possible cause for our banding, I was told that this would also cause weak fiber. Since none of our banded fiber had been weakened, I shifted focus to other things, never realizing that these bands were caused by a copper deficiency—but not a primary copper deficiency. We had a secondary copper deficiency, and they are not the same.
A primary copper deficiency occurs when the sheep don’t get enough copper. Our sheep get plenty of copper in their feed and water. The problem was that their bodies weren’t utilizing the copper they were getting. It took me years to figure this out, but eventually, armed with a ruler and samples from our sheep, I realized that this banding only occurred when the sheep were out grazing in our distant pastures. In some pastures, they would turn white. In others, their wool color would come back. The question was: why?
That took me to my local vet, who also became interested in the cause. Over the years, I had mailed samples and sent photos and emails to dozens of universities, without any results. In the end, with the help of Texas A&M’s Wool Lab, I was again pointed at copper, and after reading more about it, I put it all together. It wasn’t what they were eating out there; it was what they were drinking. You see, very high levels of other minerals can replace the uptake of copper. High iron and zinc levels can interfere with the utilization of copper. Molybdenum can also play with copper levels. When I heard this, I realized that our water tanks in five of the eight pastures were galvanized iron that had slowly begun rusting the first year we saw the banding (2010). As the rust became worse, so did the banding.
Last summer, we ran a test. We let our lambs drink from a rusty galvanized tank for two weeks, then we tested both the water in the tank and blood from two of our lambs. The water had 40-50 times the iron and zinc that should have been in the water, and the lamb’s blood showed remarkably low levels of copper and very high levels of zinc and iron. No surprise, I suppose, but it sure was a long time getting the confirmation! Six weeks later, the wool that emerged from the skin was white—just what we would expect, since it takes about six weeks for the wool to erupt from the skin.
So when you see this type of banding, now you know! The sheep was lacking copper for one reason or the other, either too much of other minerals or not enough copper (if that particular breed has higher copper requirements). I would not suggest that you supplement copper without close supervision by a vet. On the other hand, it is relatively simple to correct an overabundance of these other minerals. In our case, we simply sold our rusty tanks at a used equipment auction and bought the plastic tanks that we now use. It’s possible that we might still have an occasional banded fleece if one of our lambs is particularly sensitive to copper levels, but generally, our flock is now healthier overall. The fleece was an indicator of a larger issue that has thankfully been resolved.