Livestock Update, March 2003
Scott P. Greiner, Extension Animal Scientist, Sheep, VA Tech
2003 Virginia Ram Lamb Performance Test
Nominations are currently being accepted for the 2003 VA Ram Lamb Performance Test to be conducted at the Virginia Sheep Evaluation Station located at the Shenandoah Valley Agriculture Research and Extension Center near Steeles Tavern. The test is open to sheep breeders in Virginia, and both registered and crossbred rams may be tested. Rams will be delivered to the test station April 29, and after a two week adjustment period, will be placed on gain test for 63 days. In addition to measurement of growth performance, rams will be evaluated for carcass traits with ultrasound during the test, and DNA genotyping will be conducted for spider syndrome and scrapie resistance. Eligible rams will sell on August 23. In 2002, 47 rams sold for an average of $384. Rams born September 1, 2002 to February 28, 2003 are eligible. For rules and regulations, as well as entry forms contact Scott Greiner at 540-231-9159.
Virginia Sheep Numbers Strengthen
Virginia's total sheep numbers have risen to 62,000 head, an increase of five percent compared to a year ago according to the U.S. Department of Agriculture's National Agriculture Statistics Service (NASS) sheep and goat report released January 31. Inventory numbers of breeding ewes one year old and older were reported to be the 39,000 head in Virginia, up 2.5% from the period January 1, 2002 to January 1, 2003.
United States total sheep and lamb inventory on January 1, 2003 totaled 6.35 million head, down five percent from 2002, and nine percent from two years ago. The U.S. sheep inventory peaked at 56.2 million total head in 1942. The national breeding sheep inventory declined to 4.68 million head on January 1, down 5 percent from 2002 and ewes one year old and older at 3.79 million head were 5 percent below last year. The U.S. sheep inventory peaked at 56.2 million total head in 1942.
Virginia's lamb crop for 2002 stood at 149 lambs born per 100 ewes one year old and older. This compares to a national average of 110 lambs per 100 ewes one year old and older. With an estimated 1,500 operations with sheep in Virginia, average flock size in the state is approximately 25 ewes one year old and older per operation. Counties in Virginia with largest total numbers of sheep include: 1) Augusta, 2) Rockingham, 3) Highland, 4) Shenandoah, 5) Montgomery, 6) Tazewell and Pulaski (tie).
Total sheep shorn in Virginia was estimated at 40,000 head for 2002, with an average fleece weight of 6.4 pounds. This compares to an average fleece weight of 7.5 pounds on a national basis. Virginia wools received an average of $.26 per pound in 2002, compared to $.20 per pound in 2001. National averages for wool prices per pound were $.53 in 2002, and $.36 in 2001.
Spring Breeding and the Ram Effect
Fall-born lambs marketed November through February have commanded high prices in recent years. These high prices have been the result of strong demand for lambs during these months coupled with relatively low supplies (particularly for lambs weighing 50 to 100 pounds). Consequently, production systems that utilize spring breeding (fall lambing) warrant consideration. However, the reproductive seasonality inherent to the biology of sheep makes this practice challenging, since many breeds are anestrous from April through July. Fertility in both the ewe and ram are affected by season of the year. Successful spring breeding starts with the utilization of genetics that have out-of-season capability. Breeds noted for this ability include Dorset, Polypay, Rambouillet, Finnsheep, hair breeds (Katahdin, St. Croix, Blackbelly), and crosses of these breeds. Considerable variation exists within these breed for fall lambing potential, and selection for this trait needs to be a priority for operations that utilize an extended breeding season.
Genetics, coupled with proper nutrition and management are key components for spring breeding success. One such management practice- the "ram effect" is commonly utilized to induce ovulation in anestrous ewes that have been previously isolated from rams. The ram effect is an effective, inexpensive, practical means to increase percentage of ewes lambing out of season. Utilization of the ram effect requires ewe isolation from rams for a minimum of one month, and preferably longer. Isolation from rams needs to be complete by avoiding fenceline contact and any association with rams (sight, smell, touch). Upon joining rams with ewes that have been previously isolated, ewes will ovulate with 7 days after introduction of the rams. However, less than 20% of the ewes will be in heat during these first 7 days (silent heat). Active estrus (heat) and ovulation will occur 17 to 24 days after introduction of rams, resulting in pregnancy. Breed of ewe is an important factor in response to the ram effect. Ewes will be more responsive to the ram effect as they reach the end of anestrous (are ready to start cycling), and therefore ewes with the genetic propensity to breed out-of-season respond most favorably to the ram effect in the spring. Vasectomized teaser rams are frequently used during the first two weeks since there is a delay in estrus with the ram effect. Fertile rams need to be placed with the ewes after 14 days. Aggressive rams (both fertile rams and teasers) with high libido are most effective in eliciting a response in the ewe. It is important that rams receive a breeding soundness exam prior to spring breeding to ensure fertility.