When it comes to the quality of cooled shipped semen for artificial insemination (AI), all semen collection centers are not equal. They're far from it, in fact, according to a new study by Austrian researchers. The huge variation in the quality of the sperm processed by the collection center has an impact on the probability of the broodmare becoming pregnant.
"Results show--and confirm--that semen processing is far from standardized, and it can be much improved," said Christine Aurich, DVM, PhD, professor at the Graf Lehndorff Institute at the University of Veterinary Sciences in Vienna and senior author on the study. "An improvement of semen processing would certainly help to increase pregnancy rates."
In her study, Aurich and her colleagues tested 201 doses of cooled shipped semen coming from 67 stallions in 36 semen collection centers that have received the European Union (E.U.) certification of approval. In countries around the globe where there is no official approval process for semen collection centers, processed semen quality is likely to be even more varied, Aurich said.
The semen used in the study was ordered from different E.U.-approved semen collection centers in Europe for the insemination of mares. Stallions and, thus, semen collection centers were always chosen by the owners of the mares to be inseminated.
The greatest discrepancies Aurich found in quality among the collection centers involved semen concentration. Less than 50% of semen doses in her study had the optimum concentration rate (25-50 x 106/ml). Concentrations of sperm higher than 100 x106/mL lead to impaired motility and morphology of the sperm, which might cause reduced fertility, Aurich said. While a lower concentration means fewer sperm, appropriate processing and dilution will yield a better-quality dose than a high concentration of poorly diluted sperm.
Time of year also affected the quality of the insemination doses, as it appeared that more doses were prepared from single ejaculates during the busiest months--April and June. "At times when a high number of mares per stallion have to be bred, the total number of spermatozoa included into one AI dose may thus decline to suboptimal," she said. However, if the processing was well done, and the AI technician is skillful, the mare can still become pregnant, she added.
Temperature of the doses at arrival also varied significantly and averaged around 9.8 ° C (49.6 ° F). In Europe, semen is frequently transported in plastic foam boxes as opposed to the Equitainer boxes which are more popular in the U.S., she said. The Equitainer boxes--which provide thermal exchange conditions, plus insulation and shock protection needed for storage and shipping--maintain a more constant and lower temperature, but if the doses are delivered in a plastic foam box within 30 hours of collection, the temperature does not appear to affect fertility.
"Most mistakes in semen processing may be based on inaccurate evaluation of semen concentration," Aurich said. This might be because handlers rely on spectrophotometry (based on the principle of light absorbance, the sperm concentration is proportional to the optical density), which she said is less reliable than sperm-specific analysis.
Although it will not be a quick transition, improving and standardizing semen collection will require improved education and longer training programs, Aurich said. In the meantime, mare owners should be careful about the stallions they select. Not only should the stallions have good fertility, but their semen should also be processed by professionals at reputable collection facilities.
The study "Quality and fertility of cooled-shipped stallion semen at the time of insemination," is slated to appear in an upcoming issue of Theriogenology.
Disclaimer: Seek the advice of a qualified veterinarian before proceeding with any diagnosis, treatment, or therapy.