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Minerals and Vitamins

The next nutrient we want to talk about will be the minerals. From the standpoint of mineral nutrition in sheep, 15 minerals have been identified as essential for sheep, these include the macrominerals and the microminerals. And most needs will be met under normal grazing and feeding programs or feeding habits.

Some of the macrominerals that we are concerned about in sheep rations or feeding sheep are shown on this particular table along with the requirement for that particular macromineral.

Macromineral Requirements of Sheep
(% of diet dry matter)

Normally, I like to...when I talk about macro versus micromineral. Macrominerals are generally listed as a requirement as a percent of the diet and the others, the microminerals, are generally listed as parts per million or milligrams per kilogram of the diet. It's one way to kind of differentiate the two. Anyway, looking at the macrominerals, we have a requirement for calcium. Chlorine, the requirement really hasn’t been determined at any specific. Then, we have calcium which varies depending upon stages of production. Phosphorus, again, same thing. Magnesium. Potassium. Sulfur.

Moving onto the micromineral requirements of sheep. And here we want to look at maximum tolerable levels because even though there is a specific requirement, exceeding that requirement can result in some toxicities. Shown on this slide are the microminerals of concern in sheep nutrition: iodine, iron, copper, molybdenum, cobalt, manganese, zinc, selenium and fluorine.

Micromineral Requirements of Sheep and Maximum Tolerable Levels (ppm, mg/kg of diet dry matter)
Max Tolerable Level

We’re not going to talk about each one of these individually, but there are some that we are concerned with and those will be mentioned in more detail later on in this presentation on minerals as it relates to feeding sheep.

Looking at calcium requirements, again using the similar graph with the various stages of production.

Calcium Requirements for a 176 lb Ewe

Again, it follows the basic pattern that we noted previously. We do have an increase, of course, with fetal growth and development during the late gestation period and then, of course, an increased demand in our calcium requirements to accommodate the additional milk production that occurs during this time period. I’m not going to show the other ones, I just used this as an example to show what we would be looking at from the standpoint of grams of calcium per day. Similar requirements would show for phosphorus and the other macrominerals also.

From the standpoint of supplementation, we will talk a little bit about salt. The recommendation for sheep, from the standpoint of providing salt, is to supply loose salt, free-choice, no blocks. Sheep do not have the same tongue characteristics as cattle, they’re not very adept at licking from blocks. In fact, if they’re offered blocks, they tend to try and chew, this is hard on teeth, that is why we have the recommendation of supplying loose salt, free-choice for sheep as a way of providing salt. The recommendation is to feed at a level of a .25 to .4 of an ounce per head per day. This is going to vary, but if you would look at salt consumption over the year it would run very similar to this. Sometimes they have periods where they will eat a lot and then they’ll go back where they won’t eat as much. Trace minerals also are added when feeds are deficient in mineral content. Often times we feed a trace mineral salt to provide the trace minerals that are of concern in our particular area that we happen to be raising sheep.

Some problems that occur, as it relates to minerals and sheep, are mineral disorders. One is a situation that occurs with sheep with calcium to phosphorus ratio. We have a specific calcium to phosphorus ratio that we want to maintain. We get into a situation where we get urinary calculi. Then, with copper we have a situation where we have copper toxicosis or copper toxicity. And then, in certain areas of the United States, selenium plays a key role and with inadequate levels we get a disease called white muscle disease in sheep, especially in lambs, that do not have enough selenium in the diet. Let’s talk a little bit about each one of these mineral disorders.

First of all, urinary calculi. As I said, the calcium:phosphorus ratio is important in preventing urinary calculi. What we want is a 2:1 calcium to phosphorus ratio in our diets. And this is especially true when we feed young, growing lambs and especially when it comes to feeding males that is wethers or rams. Anytime we get our calcium:phosphorus ratio outside of this range, that is we get it less than 2:1, say 1:1 or 1.5:1 or 1.3:1, we increase the likelihood that urinary calculi can occur in these wethers and males. Generally, the problem occurs with animals on a high grain diet. Anytime you’re feeding lambs for market in a feedlot or you’re raising replacement rams where you want to get growth and performance, we do run into a situation where we have to pay very close attention to this calcium to phosphorus ratio, because grains tend to be high in phosphorus and low in calcium. We get this calcium to phosphorus ratio out-of-whack and we get problems with urinary calculi. One of the things that we need to do when we formulate these diets that have a high grain percentage is to add calcium to the diet to maintain that 2:1 ratio. Also, one of the other things that can be added to the diet is ammonium chloride or ammonium sulfate at .5% of the total. What this does, it tends to control the pH of the urine so as not to allow the formation of these calculi that develop and cause the problem.

The next mineral that I want to talk about from the standpoint of problems is copper. And with copper, we are concerned not only with toxicity, but deficiency. If we don’t have enough copper in the diet, we can get deficiencies. But what often occurs, in many cases, is that there is too much copper and we get copper toxicosis in more cases than we do deficiencies, in most areas of the United States. It’s a very fine line between the two as to when you have toxicity and when you have a deficiency. Toxicity is most likely to be the problem and this generally occurs because there is too much copper in the diet either in the mineral that’s being fed or mixing errors or whatever it might be. One factor that is involved, as far as copper requirements, is molybdenum. And molybdenum content of the diet effects copper requirements. If we have low molybdenum in the diet, we don’t need as much copper. If we have high molybdenum in the feeds, then we need more copper. Shown on this slide would be the recommended copper allowance for sheep, looking at molybdenum content in the diet.

Recommended Cu Allowance for Sheep
Molybdenum Content in Diet, mg/kg
Recommended Copper Allowance, mg/kg DM
< 1.0

Where we have less than 1 mg/kg or ppm molybdenum in the diet, we can get by on about half the level of copper as opposed to when we have over 3 ppm molybdenum in the diet. Molybdenum does have a sparing effect on copper. When we have low molybdenum in the diet, we don’t need as much copper in the diet to meet the needs of the sheep. Generally, where we see the problem is where we have low molybdenum in the feed and they tend to feed high or a little higher levels of copper, we get toxicosis occurring.

The other mineral disorder or mineral problem that we see in sheep and again it depends upon what area of the United States you might be living in, but selenium deficiency is the situation that occurs. In many areas of the U.S., feeds are low in selenium and so we need to supplement selenium again to provide and prevent the deficiency. Again, it’s a very narrow range in deficiency and toxicity. But it’s very seldom that we run into toxicosis, more often it’s the deficiency. And, of course, where we have inadequate levels of selenium, we get a situation in lambs called white muscle disease. This is from a deficiency, so that is why we recommend that we supplement sheep with selenium in the salt-mineral mix. And there are specific levels that have been established for providing selenium in the diet and these are set by the FDA. And 90 ppm is the maximum allowed in a salt mixture and no more than .23 mg of selenium per day per sheep as far as their total intake.

Moving onto...the next nutrient category would be vitamins. And here we're, when it comes to sheep, we’re mainly concerned with the fat soluble because sheep do require dietary sources of fat soluble vitamins that is A, D, E and K. We rely on rumen microbes for water soluble vitamins, the B-complex, as is the case with the other ruminant species. Vitamin A and E are the ones that are most likely to be deficient in diets of sheep.

Looking at vitamin A requirements, again for the various stages of production, to just kind of show the trend.

Vitamin A Requirements for a 176 lb Ewe

Similar trends would occur with the other vitamins, but only going to show you the situation with vitamin A. Again, we get into that late gestation, lactation period we have an increase in the international units required, but not nearly the difference in production level as we noticed previously for the other nutrients from the standpoint of low producing ewes, high producing ewes.

Some of the problems that we encounter with vitamin related disorders. There is an interaction of vitamin E and selenium. Low vitamin E also will result in white muscle disease. Sometimes it becomes very difficult to ascertain whether or not you have white muscle disease due to vitamin E shortages or selenium. Most cases it is selenium that’s in short supply. But it could be possible, in some areas, to have a vitamin E deficiency and have lambs exhibit the same symptoms as would be the case with a selenium deficiency.

One other vitamin related disorder that we often times see in sheep is a situation called polioencephalomalacia. Now, this is due to a lack of a B vitamin, in this case thiamin. Remember, I said earlier that we’re not so concerned with the B complex vitamins. But what happens, is there’s a situation that occurs where thiamin in the diet is destroyed or bound by thiaminase and so the animal can’t utilize it and thus, we get this situation called polioencephalomalacia or abbreviated PEM. The organ that is affected with polioencephalomalacia, as the name implies, is the brain. Most often we see polioencephalomalacia in young animals, in the feedlot, on high grain diets. However, there are some situations where you could find polioencephalomalacia-type diseases, poisonous plants can trigger this response, bracken fern is a classic example. But most all the time we see it in sheep it is in the feedlot and they come down with this situation called polioencephalomalacia. If caught early enough, injections of thiamin will take care of it and bring the animals out of the disease. But if it’s not caught early enough, it is pretty hard to correct.

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