Preparing the Flock for the Breeding Season
Livestock Update, August 1998
Scott Greiner, Animal and Poultry Sciences, Virginia Tech
The ram's impact on the overall reproductive performance of the flock is often times overlooked. A highly fertile ram will settle a greater number of ewes early in the breeding season, and will also be more likely to fertilize a higher proportion of eggs than rams with poor fertility. Consequently, the fertility of rams is of great importance to the sheep operation.
Prior to the breeding season, rams should be evaluated for several aspects that may affect their serving capacity. A complete breeding soundness examination should be conducted on rams prior to turn-out. This is especially important in single sire groups, as conception is dependent on one ram. Rams should be in good physical condition heading into the breeding season, with sound feet and legs and free of internal parasites. Thin rams may have reduced stamina, whereas over-conditioned, fat rams that have had limited exercise may have reduced libido. Of greater importance is examination of the reproductive tract for sheath rot and epididymitis (B. ovis). Epididymitis is an inflammation of the epididymis that may result in sub-fertility or infertility. A complete exam conducted by a veterinarian that includes semen evaluation is recommended.
Sexual maturity in young rams is influenced by several factors including nutrition, age, weight, and genetics. In general, most ram lambs are fertile by 150 days of age and when they reach approximately 60% of their mature body weight. Ram lambs should be capable of breeding 25 ewes, whereas mature rams may service 50 ewes. Ram lambs and mature rams should not be used in the same breeding pasture, as the mature ram will dominate the young ram.
After turn-in, rams should be closely observed to confirm breeding activity. This is especially important with young rams. Utilizing a marking harness and changing colors every 17 days will help confirm that ewes are being serviced and settled. When feasible, rams should be isolated and supplemented with 3-4 pounds of grain daily to maintain condition during the breeding season.
Rams that will be breeding in August and September should be sheared 30 days prior to the breeding season to help minimize heat stress. Providing a cool environment and reducing heat stress prior to the breeding season will enhance the fertility of rams that will be used in the hot late summer and early fall. If weather is extremely hot during the breeding season, rams may be removed from the ewes during the day and kept in a cool place until returning to the ewe flock at night for breeding.
Ewes should be increasing in condition going into the breeding season. A complete flock health management plan that includes an effective deworming program throughout the summer months is important for having ewes in proper condition prior to breeding. Providing supplemental energy to promote weight gain prior to breeding ("flushing") has been shown to increase lambing percentage, especially with winter-lambing. This may be accomplished by moving ewes to higher quality pasture or feeding grain. For late summer breeding, supplemental grain is most commonly used. Starting 2 weeks prior to ram exposure, ewes should receive .5 to 1.0 pounds of corn or barley per head per day. Response to flushing will vary depending on the condition of the ewes with ewes in higher condition responding less than thinner ewes. Continuation of grain feeding through the breeding season will also maintain ewe condition and embryo survival. Removal of grain from the diet should be gradual so as to not cause stress by altering the plane of nutrition.
Ewe lambs should be kept in separate breeding groups from mature ewes, especially in larger flocks. This allows for increased nutrition to the young ewes, and eliminates competition for the ram from older ewes. Exposing ewe lambs later in the breeding season than mature ewes will increase maturity at breeding and body weight/size at lambing.
Like the ram, ewes are prone to heat stress during early breeding seasons. Minimize handling during the heat of the day and allow the flock access to a cool, shaded area to minimize detrimental effects on reproduction.
Finally, vaccinate ewes and ewe lambs for vibriosis and enzootic abortion (EAE) prior to the breeding season.