Its not just about the ewes when preparing your flock for breeding season; it is also time to semen test your rams before turning them out. Did you have low pregnancy rates last year? Low fertility in a flock is generally the result of one of the following: the males did not perform well, an infectious disease spread through the flock, or the females had a lack of cyclicity. When your rams have low fertility, you end up needing an increased number of rams to cover your ewes. You will also have a lower lambing percentage and more open ewes to cull, and possibly realize a prolonged lambing season due to the ewes requiring more cycles to get bred. Rams should be tested when they are bought or acquired for your flock, before every breeding season, and any time after an illness or injury that you think may have affected their breeding ability.
During a breeding soundness exam, the veterinarian does not focus only on the sperm sample to determine whether the ram will be a good breeder. A good veterinarian will look at his legs and confirmation, body condition score and teeth. They will check for foot rot or overgrown hooves causing lameness and be sure the ram is in good health overall. They will also measure his scrotal circumference and palpate his testicles for any abnormalities (Brucellosis infections can leave palpable lesions on the epididymis). Mature rams should have a scrotal circumference of at least 32 centimeters, yearlings may be a few centimeters smaller.
When it is time to use the electro ejaculator to get a sperm sample, the veterinarian will also observe how well the ram can extend his penis and look for any abnormalities on the penis. The sample will be grossly examined and ensured to contain no blood or urine. Motility, or overall movement and morphology, which are properly formed sperm get evaluated under the microscope. This evaluation can uncover the presence of defects in the sperm, an overabundance of dead sperm, or the presence of white blood cells in the sample. Major abnormalities may prevent fertilization from occurring, while minor abnormalities can indicate slowed sperm movement and therefore decreased fertilization rates. Some common causes of sperm abnormalities include heat or cold stress, infection in the testicles or epididymis, trauma, poor nutrition, age, systemic illness, or even genetics.
The results of the breeding soundness exam will determine whether the ram is classified as an excellent or satisfactory potential breeder, a questionable breeder (meaning a retest is recommended in 2-3 weeks as their condition may be temporary), or an unsatisfactory breeder who failed. The definition of a “satisfactory” ram is that he will impregnate at least 50 ewes under normal conditions in a 60-day breeding period. Often ram lambs that have not reached sexual maturity yet will test as questionable breeders and a retest is recommended, since their condition is defined as temporary.