Tracking Weight And Condition Of Ewes During Pregnancy

The nutritional adequacy of ewes during the first 90 days of pregnancy can be assessed by tracking changes in body weight and body condition. During the first month after breeding, ewes should, if possible, maintain their weight and body condition. Short periods of either severe underfeeding or excessively high levels of feeding at this time can adversely affect embryo survival. In many cases, it is not possible to prevent some loss of weight and condition following breeding, but it is important that any losses are gradual and don't exceed 3 to 4 percent of the ewe's weight at breeding.

During the second and third months of pregnancy, changes in a ewe's weight becomes more difficult to interpret because of the increase in her weight due to fetal products (fetus, uterine wall, placenta, fluid, etc.). For example, at 90 days of pregnancy a 150 pound ewe carrying twins would have 10 to 11 pounds of fetal product included in her body weight or 6 to 7 percent. Taking into account this increase in weight due to the uterus and its contents, an acceptable body weight change during the second and third months of pregnancy would be a net loss of between 4.5 to 9 pounds (3-6% of ewe's body weight). Losses greater than this are likely to affect fetal growth and hence birth weight may become adversely affected.

Naturally such effects will be greater in ewes in poorer condition and that's why it is important to feed thinner ewes a higher level of nutrition during pregnancy to prevent body weight losses and minimize any loss in body condition.

In late pregnancy (last 60 days), the rapid growth of the fetus makes changes in body weight also difficult to interpret. The ewe's requirements for energy and protein increase rapidly during this period and especially during the final few weeks of pregnancy. Approximately 70% of the fetal growth occurs during the final six weeks. The difference in a ewe's weight between a single fetus and twin fetuses over this short period can be over 6.5 pounds. Although a ewe will generally be drawing on some body reserves during this time, her tissue weight loss should be more than offset by the increase in weight of the fetus or fetuses plus the uterine fluid weight.

As a general rule, a satisfactory level of feeding in late pregnancy should result in a body weight increase over the final eight weeks of about 10% in single-bearing ewes and 18% in ewes carrying twins. A 150 pound ewe carrying twins should increase her body weight by 27 pounds during the eight weeks before lambing.

Body condition is a more meaningful way than body weight change of assessing the adequacy of nutrition during late pregnancy because its evaluation is independent of number of fetuses. However, the time it takes to detect a meaningful change in body condition may be too great to allow for any necessary increases in nutrition to be made at the proper time. It is, however, a good practice to assess body condition about eight weeks before lambing and take out the leaner ewes for preferential feeding. Very often the period of greatest dependence on body reserves is during early lactation and if ewes are expected to have sufficient reserves for milk production, it is important that their body is in good condition.

Poor Nutrition During Late Pregnancy

The importance of ewe nutrition in late gestation cannot be emphasis enough. Poor nutrition during this period can have the following results:

1) An increase of ketosis (pregnancy disease).
2) An increase chance of losing ewes from pneumonia or starvation, especially older ewes.
3) An increase in light-weight lambs. In itself, light-weight lambs are not bad because you have fewer difficult births. However, some of these light lambs will be weak lambs as well and if weather conditions are rough, these lambs will be the first to die or will require more special care.
4) Milk production of the ewes will be reduced as will lamb gains.
5) If your ewes are not sheared before lambing, poor nutrition will reduce the value of your wool clip through wool breaks in the fibers, etc.

Managing Pregnant Ewe Lambs

* Ewe lambs should be fed to gain 35 to 40 pounds during gestation.
* Feed for growth as well as pregnancy. Be especially careful not to cheat her on energy during late pregnancy.
* Remember her calcium and phosphorous requirements are higher than an older ewe. A free-choice mineral supplement containing calcium, phosphorous, and a trace-mineralized salt should be made available.
* Feed high quality feedstuffs to the ewe lambs. Avoid screenings, straw, and other low quality roughage.
* Manage and feed the ewe lambs separately from the older ewes.
* If possible, put ewe lambs in your lambing area ahead of their lambing time to give them time to become familiar with the lambing area.
* As lambing time approaches, avoid disturbing ewe lambs as much as possible outside of feeding.
* Avoid mixing them with older ewes.