During early gestation a ewe's nutrient requirements are only slightly higher than they are for maintenance. Ewes in good condition at the end of the breeding period can loose some weight without hindering normal production. This is particularly true of sheep that have recovered most of their lactational weight loss during the later phases of lactation. If the weight loss is entirely recovered before breeding, lack of gain for the first 60 to 90 days of gestation should not have a negative affect on subsequent production.
The last six weeks of gestation is the most critical period in ewe nutrition. Approximately 70 percent of the fetal growth occurs at this time. Nutrient restrictions during this period may result in lighter lambs at birth, increased postnatal lamb losses, lower levels of milk production, and possibly pregnancy disease (ketosis). In late pregnancy, ewes require approximately 50 percent more feed than they do earlier in gestation. If protein is limited during late gestation, lower birth rates and lighter ewe fleece weights can be expected. Very often inadequate phosphorus intake occurs during this period, especially with ewes on pasture or with ewes consuming hay.
Ewes in late pregnancy sometimes have difficulty consuming enough feed because of the space occupied by the fetus, particularly when they have twins or triplets. If the ewe is fed a high-roughage ration, she may not be able to consume enough to supply the necessary daily energy requirements. For ewes in late pregnancy consuming high roughage rations, it is generally advisable to feed supplemental grain.