Nutrition during gestation: avoiding pregnancy toxemia

Nutrition is critical for any sheep flock, and even more so when the ewes are bred — particularly during the last trimester, when the unborn lambs gain about 70% of their growth. At this time nutrition can become a matter of life or death for both the ewe and the lambs she carries. The next couple of blogs will take a closer look at nutrition. That will allow new shepherds to better consider what they’re doing and those of you without flocks to better understand just how important some decisions can be, even if we don’t realize it at the time.

During the last trimester of gestation, a bred ewe will require increased levels of feed to meet the needs of her rapidly growing fetus(es). This is true regardless of how fat or thin she might be at the time — the last trimester is not a time to try to slim down a fat ewe or to control costs by reducing feed. At this point, every single ewe must have an increased nutrition if they are to produce healthy lambs.

In the first two trimesters, the ewe has been provided with a level of nutrition that the shepherd deemed appropriate. She has been eating approximately this same amount of feed for months and has stabilized her body weight according to that level of intake. In the last trimester, the lambs begin to put increasing nutritional demands on the ewe, above and beyond what she herself needs, requiring higher levels of nutrition from what she would normally ingest.

A ewe who does not get this increased nutrition in her own diet is at risk for pregnancy toxemia, a situation in which she burns her stored fat in order to provide for the energy needs of her own body and the growth of her unborn lambs. This fat-burning process introduces toxins into the ewe’s system and cause her to feel poorly and go off feed, which then causes more of her stored body fat to be burned. Once this cycle of deterioration begins, it is difficult to stop and can end up in the loss of the ewe and all of her lambs — often at very close to term. Pregnancy toxemia is much easier to head off before it begins. Even in “normal” conditions with a stable environmental temperature, the ewe’s level of feed should increase by up to 40% (depending on the specific situation) between maintenance and the time her lambs are delivered.

The number of lambs she is carrying will factor into the equation as well. If a ewe is carrying big twins, triplets, or more, she may be unable, at the end of her gestation, to ingest enough feed. Because her unborn lambs are taking up more space, she may no longer have space in her rumen to pack away enough hay to meet her high nutritional needs. This is the reason why we keep two different feeding groups on our farm after we ultrasound: the low-nutrition group, in which the ewes are carrying singles or twins and can likely meet their nutritional needs with the hay we provide, and the high-nutrition group carrying triplets or more, who will likely be unable to eat as much hay as needed near the end of gestation. We begin supplementing this latter group with a grain blend during the last trimester. Grain (particularly corn) provides a high level of energy in a compact form — just what these ewes need to successfully nourish both themselves and the lambs they carry. Eventually all of our lactating ewes will get some grain in their diet, but the low-nutrition group usually won’t need any until after delivering their lambs. They can usually meet their nutritional needs during gestation with high quality hay and, if needed, a very small amount of grain.

When I look across our high-nutrition group, which encompasses nine adults and four lambs (or just over 25% of our ewe flock), I find that they’re carrying  about 40% of this year’s lambs. These are the “workhorses” of our flock, consistently lifting our average for lambs. This group includes old productive ewes like Gabby, Hope, and Ivy, and this year’s new faces in Liberty, Nelly, and Naya, none of whom have produced triplets before. As their girths widen and lambing approaches, it only makes sense to offer them the nutrition they need to successfully deliver the next generation of lambs.

Friday’s blog will take a closer look at cold temperatures and how they impact the feed we offer our sheep.

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