Development of Replacement Ewe Lambs
Livestock Update, July 1998
Scott Greiner, Animal and Poultry Sciences, Virginia Tech
Nutrition from birth to first lambing has an influence on the lifetime productivity of the ewe. Ewe lambs should be in production by the time they are 12 to 14 months of age, as ewes that lamb first as yearlings rather than two year-olds have higher lifetime production. Therefore, development of replacement ewe lambs over the summer months prior to breeding has an impact on the overall productivity of the flock. Ewe lambs should be targeted to reach 70% of their mature weight at breeding.
Winter born ewe lambs generally have early rapid growth resulting from creep feeding and grain diets prior to forage being available. Winter born ewe lambs that will be kept for flock replacements should be prevented from becoming excessively fat. Excess fat deposition has been shown to reduce future milk production. Development of these winter-born ewe lambs is best accomplished through pasture grazing and additional grain supplementation as needed to enhance gains.
Early and late spring born lambs traditionally are developed primarily through forage-based systems. Potential replacements should be identified and weaned so they may be properly grown and managed. These ewe lambs may need to receive supplemental corn or barley (.5 - 1.5 lb./head/day) to achieve daily gains needed to reach target body weight prior to breeding. The amount of supplement needed will vary with forage quality and availability, as well as anticipated breeding date. As forage quality and availability declines during the summer, supplemental grain feeding will become necessary if breeding dates are early. Shearing of replacement ewes in July will enhance growth rates during the hot summer months. An effective deworming program is also crucial for optimum gains.
For commercial flocks, crossbred ewes should be retained due to advantages in reproduction and maternal traits compared to purebreds. Available records should be utilized in selecting replacements. Although lambing rate is lowly heritable, and effort should be made to keep twin and triplet born ewe lambs. Ewe lambs born earlier in the lambing season generally are more desirable as replacements as they are larger and older at breeding.