Active healthy rams are essential for good insemination rates, especially high ewe:ram ratios (100+:1).
Check your current rams before buying a ram and eight weeks before mating to check the number of replacements needed. A quick check-up the day before the rams are removed leaves no time to treat health problems or find replacements.
Ram preparation is essential for good mating performance and sperm production starting eight weeks before mating.
Eight weeks before mating, check for the following:
- Wounds and fly strike.
- Genital health problems such as epididymitis, scrotal scabies, pizzle rot and penile abnormalities.
Immediately isolate rams with genital problems to reduce the risk of infecting healthy rams. Contact your veterinarian to examine these rams and do a blood test.
- Foot problems. Club legs and other lameness can reduce feed intake and therefore sperm production, as well as reduce ram mobility during mating.
A foot abscess will raise body temperature and cause infertility for up to two months.
Seek veterinary advice for treatment of genital problems or foot abscess.
Sperm development takes eight weeks, so all sperm present at the time of mating have developed before the mating period. Start eating well and exercising at least eight weeks before mating.
Avoid shaving for eight weeks after mating.
Brucellosis is caused by Brucella ovis and can appear as epididymitis in rams. Brucellosis, which often goes undetected, reduces ram productivity and therefore lamb percentage if enough rams are affected.
Brucellosis is considered mainly a ram problem, but when ewes become ill it sometimes causes abortion or small weak lambs.
Brucellosis is spread by ewes, which act as passive carriers during intercourse and mating between rams, and is transmitted when mating with more than one ram.
The vaccine is no longer administered. Buy rams from accredited brucellosis-free herds and be wary of infection brought in by males other than breeding rams – for example, a neighbour’s cryptorchid lambs run off with rams while waiting to be collected.
Isolate rams with epididymitis or testicular abnormalities (such as stiffness or odd sizes) and blood test as soon as possible.
Scrotal (chorioptic) scabies is a disease that causes infertility in rams by raising the temperature of the testicles. Mange is associated with infection by the Chorioptes bovis tick. A dried exudate appears on the skin, when scraped from an active lesion reveals damaged weeping skin.
Many rams carry ticks but no lesions, and there is no correlation between the number of ticks and the extent of lesions in individual rams.
Rams with minor inactive lesions may produce normal sperm, but rams with extensive lesions have poor quality sperm.
Inspect the rams carefully and reject any with active or extensive lesions—consider them temporarily healthy, treat, and retest. Rams with severe active or inactive lesions may be permanently healthy and should be replaced.
The tick can be carried by other animals (such as horses, cattle and goats). If rams have problems with scrotal itching, consult your veterinarian about a treatment program.
Sperm production is proportional to the amount of testicular tissue – meaning that rams with larger testicles generally produce more sperm. Large testicles and high sperm production allow sperm counts to remain high when rams serve many ewes per day.
Although sperm quality, ram motility and libido are also important, testicle size can indicate a ram’s potential to serve large numbers of ewes. This recommendation is for ram breeders only.
Simple practical measurements such as testicle girth can be used to estimate testicle weight and therefore sperm production to compare rams for likely serviceability.
Generally, 30 cm or more around the scrotum is sufficient.
Testicles need to stay cool for optimal sperm production and survival. This is especially important during the last eight weeks before mating, as heat or stress for any reason can reduce sperm quality and/or quantity.
If the rams are full wool, the testicles and underarms should be shaved, and the rams should be shaded in hot areas.
A decrease in sperm volume, sperm density and motility is observed in late spring and early summer (ie, when seasonal sheep breeds are not sexually active), peak values are observed in autumn. In practice, these changes are usually not important.
Semen quality tests with commercial rams are not guaranteed. Quality is most likely checked by rams with expensive rams used in single sire group matings.
Semen collected by electro-ejaculation are suitable for checking sperm motility and morphology, but sperm count is variable and is not a good check for density. Samples collected with an artificial vagina are generally more consistent and have a higher sperm density.
Two or three tests five days apart is a better predictor of fertility than one test.
If any factor is unsatisfactory in the first test, repeat the test before discarding the ram.
Sperm volume and density also often decrease after ejaculation, so the test after high sexual activity may give false results.
Rams with high serviceability
Identification of highly serviceable rams is best done with a serviceability test that measures the number of successful services over a period of time (eg, two or more ejaculations in 20 minutes in a stall with four estrous ewes. As mentioned above, such as testicle size, probably indicates the actual sperm production and possible serviceability.
Rams born from high-yielding ewes, preferably twins or triplets, have higher serviceability than rams born from low-yielding ewes. Rams co-twined with another ram have higher serviceability than rams co-twined with a ewe lamb.
Behavior and sexual experience
Ram libido and sexual activity changes significantly. In a number of studies, 27% of rams used were found to be inactive when first exposed to ewes during oestrus.
Although most rams improved with more exposure to ewes, some still performed poorly – such as low libido and low ejaculation rates.
Older, experienced rams typically seek out ewes during estrus, while inexperienced rams, especially lambs, may not be as effective at detecting ewes during estrus and may be less productive.
Use reduced rates of ram lambs (e.g. 50 ewes per ram lamb) and pair with older ewes that will seek rams.
Harnesses are useful for showing performance of ram lambs, especially for single-headed matings.
With a high ewe:ram ratio of 150+:1, use experienced rams if possible and avoid large paddocks.
Aries libido can outstrip sperm production, so rams continue to mate but may prove infertile.
Vasectomies must be performed by a veterinarian at least six weeks prior to use. Vasectomized rams can be used for:
- Encourage ewes to cycle earlier.
- Identify ewes in estrus for AI.
- Identify non-pregnant ewes after mating using harnessed vasectomized rams (e.g. 500 ewes per ram) after breeding rams have been removed. This method identifies non-pregnant ewes for early sale well in advance of pregnancy scanning.
- Encourage hoggets to cycle earlier.
- Introduce nonbreeding hoggets to vasectomized rams and train them in ram behavior.
– Excerpted from Making Every Mating Count by Beef + Lamb New Zealand