J. L. Goelz, D.V.M.
International SheepLetter
Vol. 19 No. 5, July 1999


Since the ram is responsible for 1/2 of the success of the breeding season it is appropriate that time and energy is invested to be certain that the ram is capable of fertilizing as many ova as the ewe flock can produce. Evaluation of the ram should not be left until the day of turnout, but rather should be performed at least one month in advance of breeding season. This will allow time for recovery of replacement if necessary.

HISTORY

Before you begin you may want to consider the history of the ram to determine if anything in his past may affect his breeding performance.Consider the age of the rams. Ram lambs should be at least 6 months old before they are used for breeding.Rams over four years will often become less athletic and may not be up to chasing ewes over rough pastures.Check your records on the ram's breeding performance last year. How tight was the lambing period? Determine if the ram was treated for a fever in the past 60 days. If the testicles get too warm the ram may become infertile for up to 60 days.

PHYSICAL EXAMINATION

A physical examination should be performed focusing on areas that are especially important in the next three months. Begin with the teeth. Check the wear on the incisors. Is the bite sound? Palpate the molar tips along the side of the face, are there any that are sharp? Next, check all four feet to ensure that the ram is free of foot rot and trim if necessary. Next, check the condition score of the ram by feeling over its ribs and spine. Lastly, watch the ram as it moves around the pen to be sure that he moves around pain-free and doesn't limp.

REPRODUCTIVE EXAM

The reproductive portion of the exam should include all parts of the reproductive tract that are accessible. Begin with palpating the testicles. They should be uniformly firm and freely movable in the scrotum. Next, measure the scrotal circumference. This is the distance around the largest part of both testicles. The ram should measure greater than 30 cm. This can easily be measured with a scrotal tape, a cloth tape, or even a piece of string and yardstick. Sperm production in rams is directly correlated to testicular width, which is measured by the scrotal circumference. Furthermore, rams with larger testicles will sire more prolific ewes, so if you are keeping replacements you will definitely want to be using large testicle rams. Next, it is important to palpate the epididymis. This is a sperm storage structure that is attached to the testicle on the top and wraps around it to the bottom. It can be visualized and easily felt on the bottom of the testicle. Any injury to the testicle or epididymis will result first in swelling of the testicle, then with time the testicle will shrink and atrophy. In this case the breeding value of the ram is zero and it needs to be culled. Finally, a semen examination should be performed on the ram. This involves collecting a semen sample with an electroejaculator and examining the semen with a microscope. The minimum acceptable standards are fair gross motility or 30% individual motility and 70% normal morphology. The semen portion of the examination will require veterinarian assistance. However, all other portions of the exam can be performed at home and poor rams can be culled early.

Lastly, plan your breeding season. If you plan for a short lambing season you will want to have plenty of ram power, such as one ram to 30-40 ewes. Higher than this ration may cause some ewes to get missed and the lambing season will be drawn out. If the ewes are synchronized the number of rams needs to be greater. Ram lambs should only be expected to breed 20 ewes.