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 Knowledge for the CommonWealth

Sheep Update

Livestock Update, May 1997

Steve Umberger, Animal and Poultry Sciences, Virginia Tech

Final Results Of National Sheep Referendum Announced. On April 4, 1997, USDA released the final results of the National Sheep Referendum held in October 1996. The final results confirmed the preliminary information that was released last December, which indicated the Referendum had failed to pass. Of the 11,880 voters, 53 percent opposed the referendum. There were approximately 8,000 fewer voters in the second referendum. In Virginia, voter numbers were down by 150 people. Virginia producers approved the second referendum by 59 percent of the vote. That compares to an approval rate of 65 percent for the first referendum. As a result of this action, the American Sheep Industry Association was scaled back drastically in February. Their projected budget will allow them to continue to function through September 1999. A national task force met in early April to begin exploring the future direction of the countries' sheep industry.

Seed Dwarf Pearl Millet By May 15. Every summer, many of Virginia's permanent pastures, consisting of cool season grasses, decline in quantity and quality of production. A summer annual that has proven to be high yielding, high quality, and safe for ewes and lambs to graze is dwarf pearl millet. Dwarf pearl millet is kin to sudangrass but does not contain prussic acid and only reaches mature heights of 36 to 48 inches. It should be seeded between May 10 and 20 at a rate of 25 pounds per acre. If soil tests have not be taken, then the equivalent of 60 lbs NPK should be applied per acre. If soil tests have been taken, 60 lbs of nitrogen may be all that is required. Dwarf pearl millet can be seeded conventionally or with a no-till drill. With adequate early summer precipitation, it should be ready to graze by the first week in July or whenever it reaches a height of 16 to 20 inches. Dwarf pearl millet works best when rotationally grazed. Sheep should be moved once the millet has been grazed to a height of 6 to 8 inches and given time for regrowth before grazing again. Stocking rates of 20 to 25 lambs per acre in July and August have yielded average daily gains of .3 lb per day at the branch experiment stations where dwarf pearl millet has been tested. Lamb gain can be increased to 0.50 pound per day by supplementing one pound of corn per lamb daily.

Internal Parasite Control. Internal parasite control continues to be one of the biggest health problems with sheep flocks in Virginia. Internal parasites cause costly reductions in individual lamb performance, and when left unattended, death of the animal. We know a lot more about internal parasite control now than five years ago. However, to be successful, producers must understand the dynamics of internal parasite control, and most importantly the value of proper timing. Listed below are some factors to keep in mind as you plan your internal parasite control program this year.

  1. An effective internal parasite control program should not rely solely on the use of anthelmintics. Using anthelmintics as the only method of control often results in the increased incidence of internal parasite resistance. Whenever possible, sheep should be placed on "clean" pastures to slow down the rate of reinfection. Some examples of clean pastures are: 1) fields that have been without sheep for more than a year, 2) fields that were cut for hay since sheep last grazed there, and 3) fields grazed by cattle ahead of sheep. By strategically using clean pastures in combination with anthelmintics, the frequency of treatments can be lengthened. Treatments should be timed so that they occur just before sheep go onto clean pastures. Unfortunately, there is no cookbook recipe for the number of times to deworm sheep when used in combination with clean pastures. And, it should be stressed that clean pastures do not prevent reinfection but do help in slowing down the rate of reinfection.

  2. One of the most critical times to treat ewes for internal parasites is just before lambing or at lambing time. It is thought that physiological changes associated with lambing cause an increase in worm activity during late gestation. Preferably, ewes should be treated two weeks before lambing. But, unless producers have breeding dates on their ewes or do a good job of bagging and sorting during late pregnancy, many ewes may not be properly treated. The next best option to treating before lambing is treatment at lambing time. Ewes should be treated while in the lambing pen. They should be turned onto a clean pasture and should never be placed back in the same field with gestating ewes. By treating ewes in and around lambing time, ewe milk production and lamb performance are improved significantly.

  3. If anthelmintic treatments are not being administered in combination with the use of clean pastures, lambs grazing spring, summer, and fall pastures should be dewormed once every three to four weeks beginning at six weeks of age. The timing of these treatments is crucial. Letting treatments slip over into the fifth week, may result in unnecessary lamb death loss. Therefore, it is important to mark the calendar each time anthelmintics are administered. Treatments should start in late April and continue through late October. If lambs go into a drylot environment, treatments can be discontinued.

  4. Traditional pasture rotation programs are not effective in reducing internal parasite larvae levels on pasture. Larvae may survive on pastures for up to a year. Rotating sheep through pastures every two to three weeks is good pasture management and may help improve lamb performance, but it is only marginally effective in controlling internal parasites.

  5. Underdosing of anthelmintics results in accelerated resistance by internal parasites. Sheep producers should know the weight of the animals they are treating. If it is not possible to get a weight, it is better to err on the high side than to not give enough. Most anthelmintics approved for use in sheep, with the exception of Levasol (Tramisol), have wide margins of safety.

  6. Anthelmintics should be rotated on a yearly basis but not rotated within a year. By using a different product each time sheep are treated, internal parasites are given the opportunity to develop resistance against a number of products at the same time. Therefore, it is recommended that anthelmintics from different chemical families be rotated on an annual basis. For example, Levasol (Tramisol) could be rotated on an every other year basis with Ivomec.

  7. If you have questions concerning a specific system for controlling internal parasites, contact your Virginia Cooperative Extension Office. An extension publication entitled "Control of Internal Parasites in Sheep" is available upon request.

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