**1. Introduction**

16 A Bird's-Eye View of Veterinary Medicine

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Artificial insemination (AI) is widely used by veterinarians and veterinary specialists in most domestic as well as wild animal species. Reasons for use of AI instead of natural matings are diverse and different for individual species. As in humans, AI can be used as a tool to increase conception rate in animals that have fertility problems. This is usually performed in companion animals, like horses and dogs, where individuals are important as breeding animals. In these cases, breeding animals are mostly chosen for performance and pedigree instead of breeding soundness. Breeders go through a lot of effort to produce offspring of a specific female or male animal irrespective of potential reproductive problems.

In production animals, AI is a way to increase reproductive efficiency and production. AI has proven to be a very effective reproductive technology that selectively increases genetic gain through increased selection pressure on males. In Holstein cattle, for example, AI supported selection for the milk production trait and within 40 years milk production has nearly doubled. Farm animals, males as well as females, are usually chosen for breeding programs based on breeding soundness examinations (BSEs). These BSEs determine suitability and likelihood of females or males to participate successfully in breeding programs. Animals that do not fulfill certain criteria are identified. These "problem" animals are excluded from insemination programs. Estrus cycles of females can be manipulated to institute efficient insemination programs. With the use of these estrus synchronization programs, large groups of females can be inseminated at the same time. This does not only have the advantage of concentrating work on specific days during breeding, but will ultimately also simplify the herd management before and after the offspring are born. Group feeding of pregnant animals, partus observation, vaccination programs for calves and tail docking of lambs are just a few examples of improved herd management areas through the group effect achieved through AI.

Another reason for AI is to ensure effective use of semen. An increased number of offspring from a superior sire can be produced when AI is employed. For example, a stallion's ejaculate can be sufficient to inseminate 5-10 mares at the same time when split into doses instead of one live cover on a mare. Ram ejaculates can also be split into up to 15 fresh AI doses. Freezing bull semen can provide up to 200 straws of frozen semen from one ejaculate, equaling 200 AI doses. Overuse of males is prevented and commercial distribution

Artificial Insemination in Veterinary Science 19

been less successful for other species. Barker and Gandier reported the first pregnancy from frozen stallion semen in 1957 (Barker & GaPndier, 1957). Poor pregnancy results with the use of frozen-thawed stallion semen limited research funding for breeding trials in this species (Amann & Pickett, 1987). Only later the Chinese inseminated more than 110'000 mares with frozen-thawed stallion semen (between 1980 and 1985). The United States also did not have interest in developing improved procedures for freezing stallion spermatozoa in the seventies. Only in 1980 the Animal Reproduction Laboratory of Colorado State University began a long-range research program aimed at developing satisfactory procedures to freeze stallion semen. The acceptance of frozen semen as a method to produce registered foals by two of the largest breed associations, the American Quarter Horse and the American Paint Horse association in 2001 has furthermore stimulated new interest in the

Insemination techniques used depend on species, type of semen, breeding system, availability of equipment and expertise. Intravaginal (dogs), intracervical (sheep), transcervical intrauterine (cattle, horses, dogs, sheep), transcervical deep horn intrauterine (horses, cattle, pigs), laparoscopic (sheep), surgical intrauterine (dogs) insemination as well

In dogs, fresh, chilled extended and frozen semen can be used. AI using fresh semen is usually performed if the animals will not or cannot copulate naturally. There are certain breeds, like English bulldogs and other brachycephalic breeds that almost always require AI due to their anatomical incompatibility to mate naturally. AI is also used if time constraints are an issue as fresh semen AI in the bitch is much quicker than a natural mating where the coital tie between male and female can last up to 40 minutes or more. AI can be used in bitches with congenital vaginal abnormalities like vaginal strictures or septae which might cause copulation failure. These cases often have ethical implications as well. Owners need to understand that even though AI can be performed easily these bitches might require Cesarian sections as the vaginal abnormalities might also impair natural delivery or that certain vaginal abnormalities are heritable and offspring with the same problem might be produced. AI is also used if the semen quality of the specific male is poor and addition of semen extender or pooling of more than one ejaculate is required for one insemination dose. Fresh semen is deposited into the cranial vagina of the bitch using an insemination pipette that is inserted through the vulva and directed into the vagina. Once the semen has been deposited, the hindquarters of the bitch are usually elevated for a few minutes to facilitate movement of the semen from the vagina through the cervix into the uterus. Vaginal contractions can be elicited for the same reason at the same time by either tickling the vaginal wall or massaging the clitoris. An insemination dose of at least 150 x 106 sperm is recommended and most commonly the whole ejaculate is used which may contain

Pregnancy rates with the use of fresh semen for insemination is reported to vary between 65-84% on average depending on semen quality, timing of insemination and correct site of

semen deposition (Johnston et al., 2001; Linde-Forsberg & Forsberg, 1989).

as endoscopic semen deposition at the uterotubal junction (horses) is available.

frozen semen technology (Loomis, 2001).

**3. AI techniques in different species** 

250-2500 x 106 sperm (Johnston et al., 2001).

**3.1 AI techniques in dogs** 

facilitated. Other important aspects are the prevention of venereal disease transmission that plays a major role in the economic system of offspring production, and increased safety for valuable breeding animals as mating related injuries are avoided.

Venereal diseases that play a major economic role in cattle production are for example Trichomonosis and Campylobacteriosis both of which decrease reproductive efficiency through decreased pregnancy rates, high return rates to estrus and increased pregnancy losses. In general, shipping fresh and frozen semen nationally and internationally involves fewer health risks and welfare implications than transporting live animals.

Import and export of frozen semen is a huge economic market. Semen of a specific bloodline, a specific individual male or breed is imported. This is especially important in countries where breeds were introduced and are somewhat isolated with a small genetic pool. To eventually prevent breeding setbacks due to inbreeding and to expand the genetic pool, imported semen is used. Furthermore, AI can be used for frozen semen from males that have died or are not physically available for matings due to distance or physical inability. A great advantage of frozen semen in general is that it can be stored indefinitely and has the potential to outlive the male donor animal by years.
