Why Twinning in Lambs is a Winning Combination
A sheep that twins means increased farm profit.
One of the most productive measures of a ewe is her ability to have twins instead of just having one lamb. A sheep that twins is more likely to make you a profit. A sheep that has consistently just one lamb may cause you to lose money.
So, you would want as many ewes as possible to have twins. (Note to dairy and cattle farmers: when having a female and a male twin in sheep, the female will be fertile.) How do you get to a flock of sheep with a high twinning rate? Conventional wisdom is to take a twin-born ewe lamb and she will have twins. Unfortunately, it isn’t that simple. Not even close. I do get the occasional request to purchase only twin-born ewe lambs or a ram lamb that is twin or triplet-born with the expressed expectation that this will significantly increase the rate of twinning and will bring it close or all the way to one hundred percent. I even got a request from a person who culls all ewes the moment they don’t twin. In these cases, I decline selling the buyer any animals and state that I don’t have what they are seeking. Why? After all, almost all the ram lambs I sell are twin-born and so are most of the ewe lambs. So, why would I decline such request? I decline because those people will inevitably be disappointed in my sheep because there is no such straight line to getting a one hundred percent twinning rate.
Let me discuss my situation here at home. My adult White Dorper sheep have a lambing percentage on average of about 180 percent. That means on average I have 1.8 lambs per ewe. In some years I do a little better and get close to 190 percent. Slightly less than ideal conditions during breeding season will lead to a slightly lower average but will stay at or above 170 percent. I also expose the ewe lambs the year they were born to a ram. Most of these lambs breed at the age of 7 to 9 months of age. However, their lambing percentage stays below 150 percent and is not included in my calculation of lambing percentage.
A lambing percentage of above 200 percent is not possible with the sheep I have. Ewes having consistently twins year after year are rare. I do have ewes that have triplets on occasion as well. Still, a lambing season of 200 percent and above is not feasible. For those who seek it I have no advice other than suggesting a breed that naturally produces triplets often. There are breeds like these. Romanov sheep and Finnsheep are breeds like these and so are composite breeds or cross bred sheep that include these fertile breeds. I have found such high lambing percentage for a grass-fed system like mine unsuitable. While I have a number of sheep which get triplets, raising all three of them is a struggle and growth-rate is in my view not satisfactory. Of course, there is always the exception of a ewe that can do that but as a whole I find it undesirable. Therefore, I routinely find another mother for the third triplet and use my head gate to have a ewe with one lamb adopt a triplet and therefore have each ewe raise two lambs. In short, in a year when I have a 180 percent lambing percentage, I am where I want to be.
I don’t want to discourage you from selecting twins. I don’t attempt to advocate against it. Not at all. I do select mostly twins as well. Just don’t expect wonders. The increase in twinning rate will grow slowly and only marginally. Also, selecting just for twinning bears the risk of selecting against other traits like growth rate and body structure, as well as other economic factors. If you blindly select twin-born ewe lambs, you may not pay much attention to how well the mother’s mothering and milking ability was or how fast the lambs grew or whether the lambs are correctly structured and have good feet. In other words, you may decide keeping a twin-born lamb that has other flaws but will keep her because she is a twin and likewise, you may decide against selecting a perfectly good single-born lamb in the false believe it will bring down your lambing percentage. Keep that in mind.
There are other measures to increase twinning rate. You can do a lot of good by creating a good environment for your ewes, especially just before and during breeding season. They are as underappreciated as genetic twinning is overrated. Here is how.
Well-known and proven field trials and studies have shown that higher nutrition two to three weeks prior to breeding, especially an increase in energy, will cause ewes to ovulate more eggs. This increase in feeding is being kept up throughout breeding season. It is called “flushing effect.“ This works particularly well if the ewes had less nutrition until two to three weeks prior to breeding, are a little thinner, and are now put on this better feed or pasture, followed by introducing the rams two to three weeks later. The effect is less when the ewes are already in good shape. They already will ovulate well. Why does flushing work? Basically, mother nature tells the body of a sheep that times are good and are likely good to raise more lambs. As a result, more eggs are produced. As an aside because I was asked that question: Shortly after breeding season the nutritional needs for the ewes are not higher. The embryos are too little to require additional input. You do not necessarily need to keep up the high input unless you wish that your ewes still come in better condition for the winter.
Another very important management tool during breeding season is to cause no stress. Don’t train your herding dog during that time and keep any necessary work with your trained herding dog to a minimum. Don’t chase after a ewe to treat her, causing her and all other sheep around her to get stressed. Have all management issues, i.e. deworming, done before breeding season starts. In addition, you want your ewes to be healthy and fit at breeding. Sheep with a lot of parasites or are limping are stressed. If you have hoof rot that cause your sheep to limp you have a big factor that reduces ovulation and conception.
Here is the reason for a need to avoid stress: When the eggs are fertilized, they travel to the uterus wall and attach themselves to it. Stress can cause them to be aborted. If it happens to both eggs, you are “lucky” because the ewe will simply return to season three weeks later and breed again. All you might lose is time. However, it is entirely possible that one egg aborts and the other one stays attached to the uterus. This ewe will now have just one lamb.
It is also advisable to keep the rams away throughout the year until breeding. Ewes will come better into season and ovulate better when the rams are introduced at breeding time. In fact, switching rams out during breeding season has also a boosting effect as far as stimulation is concerned. Keep also in mind that rapidly decreasing day length, as we have it in late September and early October, will stimulate the ewes to come into season in large numbers.
So, the ideal scenario that I try to create during breeding season is this: Lots and lots of good pasture prior and during breeding season, forcing no one to eat anything clean, always grazing to the fullest. No stress, just a daily pasture shift. All other management was either done before breeding season or is put on hold. The same applies to the time shortly after breeding season has ended that no ewe aborts early. Create such environment and abide by such management system and I am certain, your twinning rate will increase significantly, regardless of whether your ewes were single or twin-born.
This article first appeared in the spring 2019 issue of “Farming Magazine” (Volume 19, Issue 1, No. 73).