Livestock Update, January 2003
Scott Greiner, Extension Animal Scientist, Sheep, VA Tech
Late Gestation Ewe Management
Proper management during the last four to six weeks of gestation is critical to ensure a healthy, vigorous lamb crop. Approximately two-thirds of the growth of an unborn lamb occurs the last six weeks of gestation. During this time, the ewe should gain approximately 0.5 pound/day. Proper management during this last portion of gestation will help prevent pregnancy disease, promote strong lambs at birth, enhance milk production, and prevent disease. Following are a few points to consider during late gestation:
Energy/Protein: Requirements for both energy and protein increase during the last 4 to 6 weeks of gestation. Mature ewes weighing 150 to 175 pounds require a diet of approximately 65% TDN and 11.5% crude protein. In most cases, energy is the deficient nutrient during late gestation. Feeding high quality grass/legume hays normally provide adequate protein concentrations for the late gestation ewe. However, hay samples should be analyzed to make appropriate ration formulations. General recommendations include supplementing 1 pound of corn or barley during the last 4 to 6 weeks of gestation. It is important to gradually work ewes up to the 1 pound/day: 1/2 pound per day 4 to 6 weeks prior to lambing increasing to 1 pound by 2 to 4 weeks prior to lambing. Grain should be introduced gradually to prevent enterotoxemia, and appropriate bunk space should be provided to prevent crowding and potential injury to unborn lambs. If hay supplies are short, 1 pound of corn may substitute for approximately 2 pounds of hay. It is important that ewes receive a minimum of 2 pounds of roughage per day to maintain rumen health. Additionally, supplemental protein will likely be necessary if grain is used to replace a significant portion of the roughage in the diet. Inadequate energy during late gestation may result in small, weak lambs at birth as well as decreased milk production in the ewe. Additionally, pregnancy ketosis may occur as a result of a diet deficient in energy during late gestation.
Selenium: Virginia is largely a selenium deficient state. Deficiencies in selenium result in weak lambs and white muscle disease. Ewes should have access to a selenium fortified trace mineral salt (up to 90 ppm selenium) during late gestation. Providing selenium mineral mixes specifically formulated for sheep should meet the ewes' requirements. If feeding a selenium mineral is not feasible, injections of selenium and vitamin E can be given. Ewes should receive 2.5 to 3 mg of selenium per 100 pounds of bodyweight. Injections of selenium/vitamin E are not recommended when a selenium mineral mix is being fed as high levels of selenium may be toxic.
Enterotoxemia and Tetanus: Vaccinate ewes for overeating and tetanus approximately four weeks prior to lambing. Vaccination at this time will provide passive immunity to the lambs at birth through the ewe's colostrum.
Antibiotics: Vaccines for prevention of abortion diseases (vibrio and chlamydiosis) have not been widely available. Chlortetracycline (Aureomycin) fed at a level of 80 mg/head/day (approved dosage) during the last six weeks of gestation has been shown to aid in prevention of these diseases. Injections of oxytetracycline (LA 200) at 2 week intervals the last 4-6 weeks of gestation have also been recommended as a preventative measure.
Deworming: Ewes should be dewormed 2 weeks prior to lambing. Research has documented that worms increase egg shedding just prior to and continuing after lambing. During this time, the ewe has a reduced ability to deal with the increased worm load. Therefore, deworming prior to lambing is an important aspect in an effective parasite control program.
Shearing: Shearing prior to lambing has several advantages: facilities remain cleaner and drier, ewes require less space, ewes about to lamb are easier to identify, and the newborn lamb and ewe are easier to manage. Shearing prior to lambing does require that adequate facilities be made available, especially immediately after shearing so that ewes have protection from adverse weather. Cold weather will increase the energy requirements of the ewe the first couple of weeks after shearing. Shorn ewes are more apt to seek shelter for lambing in adverse weather. Shearing can be done up to one week before lambing. Shearing ewes very close to lambing may result in some premature births. If shearing is not feasible prior to lambing, ewes can be crutched. Crutching involves the removal of wool around the dock and udder of the ewe. Although crutching enhances the shepherd's ability to manage the ewe and her newborn lambs, it will not enhance the lambing barn environment or reduce space requirements needed for the ewes.