Preparing the Flock for the Breeding Season
Livestock Update, September 2002
Scott Greiner, Extension Animal Scientist, Sheep, VA Tech
With the hot and dry weather recorded throughout much of the state, several management practices are critical for sheep producers for the upcoming breeding season.
High temperatures can be detrimental to ram fertility, reducing pregnancy rates and lambing percentages. Heat stress occurs when the scrotum is not able to reduce the temperature of the testicles below normal body temperature. Although heat stressed rams may not be infertile, they may have reduced semen quality. Poor sperm morphology, motility, and viability may reduce the capacity for fertilization. The effects of heat stress on ram fertility may last for up to 60 days. As a result, hot weather a few weeks prior to turn-out can have pronounced effects on ram fertility. Therefore, it is imperative that rams have a breeding soundness examination given by a veterinarian prior to the breeding season.
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.
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 2-4 pounds of grain daily to maintain condition during the breeding season. 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.
Like the ram, ewes are prone to heat stress during early breeding seasons. Prolonged exposure to high temperatures can have an effect on ewe fertility and embryo survival. Embryo loss due to temperature stress normally occurs during the first week of gestation. To help reduce these embryo losses and resulting decrease in lamb crop, minimize handling during the heat of the day and allow the flock access to a cool, shaded area.
With shortage of forage experienced through the summer months, many ewes are likely in moderate to poor body condition heading into the breeding season. To improve lambing percentage, ewes should be increasing in body condition going into the breeding season. To improve body condition, supplemental energy must be provided. This practice, commonly referred to as "flushing", may be accomplished by moving ewes to higher quality pasture or feeding grain. For late summer breeding, supplemental grain is most commonly used. Starting two 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 poorer body condition responding more favorably than over-conditioned ewes. Therefore, with the dry conditions this year, flushing ewes may provide an opportunity to increase the number of lambs born. Continuation of grain feeding through the breeding season will also maintain ewe condition and enhance embryo survival.