Three Common Genetic Defects to Review when Buying or Selling Sheep

Eastern Alliance for Production Katahdins (EAPK) Communications Committee – Roxanne Newton
(Previously published online with EAPK: June 7, 2024)

It’s important for buyers and sellers to be aware of a few of the more common genetic defects so that only the best quality animals are consigned and sold. It is the responsibility of sellers to consign high quality animals that are free from defects. Ask your veterinarian to perform a screening exam before consigning the animal if you are unsure. It is also the responsibility of buyers to do their due diligence by inspecting the animals they’re interested in buying before the bidding process begins. If the animal for sale is only available online, we strongly encourage bidders to contact the seller and request more information or photographs to make a more informed decision.

Jaw Evaluation
Defects of the mouth are highly genetic and can affect the sheep’s ability to nourish itself. This defect can become more pronounced with age. The lower incisors should properly meet the upper dental pad. An overshot jaw or parrot-mouth is the result of the sheep’s upper jaw being longer than the lower jaw. An undershot jaw or monkey-mouth is when the lower jaw is longer than the upper jaw.

Pastern Evaluation
Animals with “weak” pasterns have too much angle and length of the pastern. Pasterns can also be too straight with the sheep standing too high up on its toes affecting the shock-absorbing ability of the limbs. Improper angulations of the pastern are highly heritable, can occur in both front and back legs and can affect the breeding soundness of both rams and ewes.

Scrotal Evaluation
Scrotal defects are a common cause of infertility in rams. The scrotum of the ram should be smooth, firm, symmetrical and of adequate size for the age of the ram. Inspection and palpation of the scrotum will help to identify common defects such as scrotal hernia, partially descended (uneven) or undescended (missing) testicles. Inadequate scrotal development negatively affects breeding capacity.

Minimal Scrotal Circumference by Age:

  • 6-8 months of age  > 28 cm
  • 8-12 months of age  > 30 cm
  • 12-18 months of age  > 32 cm
  • Mature ram (>18 months of age)  > 35 cm

Technique for Scrotal Measurement below.