Selenium and Pregnancy

There are many different vitamins and minerals that a sheep needs, but one in particular is vitally important for pregnant ewes: Selenium. So much so I am giving it its own article.

Why is Selenium Important?

Selenium is an important mineral for muscle tone. This does not sound quite so vital until you consider what a ewe needs to give proper birth; good strong muscles for contractions. Sufficient selenium will help to strengthen those important muscles and make for an easier birth. But it doesn’t end there; selenium effects all muscles. This includes other skeletal muscles such as those in the legs, which may grow weak enough that the ewe has trouble getting around if she lacks appropriate selenium levels. This includes the diaphragm of the lungs; a selenium deficient ewe can start to get raspy breathing. Since there is already extra strain on the lungs due to the weight of the lambs, if the diaphragm grows weak on top of this, the ewe can get out of breath more quickly. Also consider that the heart is a muscle, and is likewise affected by a lack of selenium. (NAP, 20) There are more subtle benefits to a sheep with adequate selenium. Selenium aids in keeping cells healthy while slowing the division of damaged cells, giving them a chance to repair themselves before division. Selenium also aids in keeping toxins out of the blood, and in boosting immunity. This stronger immune system translates to lambs with stronger immune systems, as the ewe transfers her antibodies to her lamb in the colostrum. I do need to note now that all of the before mentioned benefits of selenium are contingent on one other nutrient; vitamin E. (Lawson, 289-90) However, I will get into that further in the section below.

Selenium is very important for the lambs as well, both before birth and after. Deficiencies in newborn lambs are much more serious than in adults; prevention is by far the best remedy, and can be accomplished by making sure the ewe has enough selenium herself. (Lawson, 289) Low selenium means weak muscles and lowered immune systems, which encompass a whole range of ills for a new lamb. Lambs born live may have weak hearts and die soon after. They may also have weak tongue muscles, making suckling difficult, or weak leg muscles, which make it hard to stand to nurse. Not nursing enough makes a lamb more prone to hypothermia. (Lawson, 287-291) A severe deficiency can lead to muscular dystrophy or white muscle disease, both of which can prove fatal to lambs. If lambs cease to grow, even if muscle wasting is not present, it could be a result of selenium deficiency. (Coleby, 110-11)(NAP, 20) The weakened immune system too makes a lamb more susceptible to disease.

Don’t Forget Vitamin E!

Vitamin E also needs to be considered here, as it is necessary for a sheep to properly synthesize selenium. Not enough vitamin E in the sheep means not enough Selenium can be utilized, even if the ewe has adequate levels; so a selenium deficiency could actually be an E deficiency. (Coleby, 111)(Lawson, 288) However, in more severe cases it is likely that both are lacking and will need to be supplemented. (NAP, 24-25) All the wonderful benefits of selenium above are only possible in the presence of adequate levels of vitamin E; the two are an inseparable pair that work together or not at all.

Signs of Deficiency

Signs of selenium deficiency tend to manifest in a ewe during late pregnancy, when the lamb is growing most rapidly inside and thus consuming higher quantities of nutrients. If there’s not enough selenium for both ewe and lamb, the ewe’s muscles can get weak. She may have more difficulty in walking, appearing more burdened than should be accounted for by pregnancy weight alone. Her legs may start to buckle, and if it gets bad enough, she may go down altogether. In lesser cases, she may have signs of labored or raspy breathing, due to her weakened diaphragm and the strain of the extra weight she is carrying.

A Case Study

Showing signs of selenium deficiency; note the buckled in front legs and the somewhat splayed stance that indicate that standing has grown difficult. Once I figured out what was happening, just a few days of SelPlex got her back to normal, and she delivered a healthy lamb not long after that. Taken 04.17.2012.

I had a ewe last spring whose legs started to buckle in enough that her hooves were wearing unevenly; you could see how the inside toe of each hoof was much shorter than the outside one. This is because she was placing her legs angled out from her body, so greater pressure was being placed on the inside of her hoof than on the outside. She also walked somewhat stiffly and reluctantly. I wouldn’t have suspected it to be selenium deficiency except for the advice of a wise old vet. You see, I live in a selenium adequate region, and there was selenium in the mineral mix I gave them. But the symptoms were there, so I bought some selenium yeast called SelPlex. She was walking straight within just a few days of dosing her with it. Now I add it to their minerals as an additional and regular source of selenium. During the last month of pregnancy, I also give extra selenium above what is in the minerals, as described below in the section on SelPlex.

What Forms of Selenium are There?


Organic selenium is found naturally in kelp. (Coleby, 111) For most of the year, adding this to my mineral mix at a rate of 1 pound kelp per 4 pounds minerals seems sufficient. However, different areas, with different soil selenium levels, will need different amounts of selenium supplementation. Thus, my rate will not necessarily be ideal for someone else’s farm. It just works for me. I should also note that I do not add the kelp for the sole purpose of selenium supplementation; it has other minerals, and especially iodine, that I am more concerned with adding to my mineral mix.


I have found that adding kelp alone to my mineral mix does not provide sufficient selenium for pregnant ewes, and thus I also add SelPlex 2000, another organic form of selenium, and far more potent than kelp. I have found 1 oz. per five pounds of total mineral mix (includes kelp) to be a good amount for maintenance, this learned from other farms who have found that rate to be sufficient. However, it is still not quite enough for late pregnancy. Thus I add additional SelPlex to the ewes’ diet during the last month of pregnancy, in the form of what I call “selenium mush”. I soak alfalfa pellets at the rate of about 1/2 pound, dry, per head, and then add a pinch of SelPlex to each bowl. The alfalfa pellets are both a vehicle to deliver the selenium, and a source of vitamin E to work alongside it. This I do daily, and have thus far had good results. No weak legged ewes. For more information about SelPlex, I’ve linked to the producer’s website here.

Sodium Selenite

Another selenium form that can be added to mineral mixes is the inorganic sodium selenite. 0.1 mg Se/kg DM was shown in several studies to be sufficient to prevent white muscle disease in pregnant and lactating ewes. This is also the USDA’s limit for selenium allowed in animals meant for food, when it is contained in a complete feed. Otherwise, as a supplement, up to 0.23 mg/kg per head per day is allowed. (NAP, 20-21) I have seen premixes of this sold at Pipestone Vet’s online store, and it likely can be found elsewhere. I personally do not have experience with this form.


There is also an injectable inorganic form of selenium and vitamin E called Bo-Se, but the label reads that this cannot be used for pregnant ewes, as it can cause abortion. I have never used it myself, but have heard of others who administer it to lambs as a preventative or treatment for white muscle disease resulting from selenium or E deficiency. It is a prescription medication, and must be dosed appropriately or else toxicity can occur. For more information, here is a link to the label.

Vitamin E

Vitamin E can be purchased as an injectable, though I’ve never had need to go that route, for vitamin E is also readily found in many easy to obtain feeds. Some of the best sources are wheat germ meal, dehydrated alfalfa, and vegetable fat. Some grains and hays are good sources too, but do vary. (NAP, 24)

How Much Selenium Do I Need to Give?

It’s good to know the selenium content of your soil; some places are more deficient than others, and will need greater supplementation. The northeast, southeast, and northwest United States are all known to have inadequate selenium amounts in approximately 80% of their soils. In contrast, parts of South Dakota, Wyoming, and Utah have problems with Selenium toxicity due to the high content in the soil. (NAP, 20) So it really is important to know. I’d highly recommend a soil test to be certain of the levels on a specific farm.

But even if you are in an area that seems to contain sufficient selenium in the soil, that does not guarantee that there will be enough for your sheep. Icelandic sheep seem to need more than other breeds. There is no good test for selenium or E deficiency, as other ailments can mimic these deficiencies. However, if you add either to the diet and improvement can be seen, it is a fair assumption that an E or selenium deficiency was to blame. (NAP, 24)

Finding out how much selenium other farmers use in your area is a great way to get an idea as to what your sheep should be getting as well. In the end, though, a little trial and error seems the best way to tweek what is just right for your farm. But whatever you do, do not ignore the importance of selenium in your pregnant ewes’ diet. It could literally be life or death.


1. Lawson, Laura. “Managing Your Ewe and Her Newborn Lambs.” 1993.

2. Coleby, Pat. “Natural Sheep Care.” 2006. Pp. 110-11.

3. National Academy Press (NAP). “Nutrients Requirements of Sheep, Sixth Revised Edition.” 1985. Pp. 20-22, 24-25.