AI has many benefits for producers. However, it is important that producers have realistic expectations from the results of AI programs. Many have expectations that are well beyond what is normally achieved. A good benchmark is to compare the results of small ruminant AI against the results of cattle AI programs - which have had many millions of dollars investing in improvements over 25 years. The average number of dairy cattle that get pregnant from a single insemination using frozen semen is reported from around the world to be about 50%. North American results are no better. Beef cattle AI results are often less.

FRESH SEMEN

Semen is collected and the sample is "extended" with products that increase the volume (so more animals can be inseminated). The extender also provides an energy source to keep it alive longer, and buffers that protect it from cooling damage. Semen can be collected and extended with reasonable fertility expected for the first 6-8 hours. Large doses of the extended -fresh semen (300+ million sperm) can be simply deposited into the vagina with reasonable success - pregnancy rates averaging 50% or better. Success is improved, and doses can be reduced, if the fresh semen is introduced into the cervix, or even better, into the uterus using trans cervical or laparoscopic methods. There are many examples of successful fresh semen AI programs. Because the results of fresh-semen AI are acceptable, the challenge for research is to extend the life of the semen to enable insemination to be done beyond the day of collection.

FROZEN SEMEN

The process of freezing and thawing semen damages the many of the sperm cells which causes reduced fertility. . Results are affected by the numbers of sperm that survived the freezing and thawing. Frozen semen rarely produces fertility as good as fresh semen. To get best pregnancy rates, frozen semen must be deposited into the uterus. The challenge for small ruminants is that the cervix of the sheep, goats and deer is not as insemination-friendly as it is in cattle or even swine. Until recently, it could not be penetrated at all for AI using practical systems.

Approaches used for frozen semen AI:

Laparoscopic AI uses a laparoscopic-surgical approach to injecting the semen through punctures made in the abdomen directly into the uterus. Animals are given a sedative/analgesic and undergo preparation as required for any minor surgery. Results are good but the procedure is difficult and costs are relatively high. Millions of sheep are laparoscopically inseminated annually. Almost all deer that undergo AI are done laparoscopically. It is less often required in goats because cervical and transcervical AI produces acceptable results Laparoscopic AI uses a laparoscopic-surgical approach to injecting the semen through punctures made in the abdomen directly into the uterus. Animals are given a sedative/analgesic and undergo preparation as required for any minor surgery. Results are good but the procedure is difficult and costs are relatively high. Millions of sheep are laparoscopically inseminated annually. Almost all deer that undergo AI are done laparoscopically. It is less often required in goats because cervical and transcervical AI produces acceptable results uses a laparoscopic-surgical approach to injecting the semen through punctures made in the abdomen directly into the uterus. Animals are given a sedative/analgesic and undergo preparation as required for any minor surgery. Results are good but the procedure is difficult and costs are relatively high. Millions of sheep are laparoscopically inseminated annually. Almost all deer that undergo AI are done laparoscopically. It is less often required in goats because cervical and trans cervical AI produces acceptable results Laparoscopic AI uses a laparoscopic-surgical approach to injecting the semen through punctures made in the abdomen directly into the uterus. Animals are given a sedative/analgesic and undergo preparation as required for any minor surgery. Results are good but the procedure is difficult and costs are relatively high. Millions of sheep are laparoscopically inseminated annually. Almost all deer that undergo AI are done laparoscopically. It is less often required in goats because cervical and trans cervical AI produces acceptable results

Cervical AI is used to introduce semen into the cervical canal. Cervical AI is used commonly in goats, particularly because many types of insemination equipment are not designed fro passage through the cervical canal into the uterus. Results are considerably better than depositing the semen into the vagina but far less than by depositing the semen into the uterus. Cervical AI with frozen semen should only be done in sheep when attempts to penetrate the cervix have failed the semen is simply "dumped" at the farthest possible site. Cervical AI is used to introduce semen into the cervical canal. Cervical AI is used commonly in goats, particularly because many types of insemination equipment are not designed fro passage through the cervical canal into the uterus. Results are considerably better than depositing the semen into the vagina but far less than by depositing the semen into the uterus. Cervical AI with frozen semen should only be done in sheep when attempts to penetrate the cervix have failed the semen is simply "dumped" at the farthest possible site.

Trans cervical AI (TAI) techniques have been developed to pass semen through the cervix into the uterus. TAI has been used successfully in goats for many years. An experienced inseminator can inseminate most does with acceptable results - as long as adequate number of live sperm are used. Sheep , because of the more complex cervix, have been much more difficult. A TAI technique has been developed at Guelph ( the Guelph System for Trans cervical AI) as an alternative to the laparoscopic technique. Ewes are positioned on their back and insemination equipment is manipulated through the cervix. Unfortunately, not all ewes can be penetrated successfully and pregnancy rates are less than with the laparoscope. An experienced inseminator can normally penetrate 75 % of ewes. The numbers that can be penetrated are higher with ewes on accelerated breeding program or having had multiple lambings. Of those penetrated, in well managed program about 40 to 60 percent lamb. So often only 30 % of those attempted lamb. Still, the system can be managed by trained producers and the success is good enough to introduce new, known health-status genetics into a flock at low cost. A similar system is used with success in anesthetized Fallow and White Tailed deer. The Guelph System works very well in goats, in which almost 100% can be penetrated and in inseminated into the uterus. Goats do not need, in fact would not accept, being positioned on their backs. Goats are simply bred standing. Trans cervical AI (TAI) techniques have been developed to pass semen through the cervix into the uterus. TAI has been used successfully in goats for many years. An experienced inseminator can inseminate most does with acceptable results - as long as adequate number of live sperm are used. Sheep , because of the more complex cervix, have been much more difficult. A TAI technique has been developed at Guelph ( the Guelph System for Trans cervical AI) as an alternative to the laparoscopic technique. Ewes are positioned on their back and insemination equipment is manipulated through the cervix. Unfortunately, not all ewes can be penetrated successfully and pregnancy rates are less than with the laparoscope. An experienced inseminator can normally penetrate 75 % of ewes. The numbers that can be penetrated are higher with ewes on accelerated breeding program or having had multiple lambings. Of those penetrated, in well managed program about 40 to 60 percent lamb. So often only 30 % of those attempted lamb. Still, the system can be managed by trained producers and the success is good enough to introduce new, known health-status genetics into a flock at low cost. A similar system is used with success in anesthetized Fallow and White Tailed deer. The Guelph System works very well in goats, in which almost 100% can be penetrated and in inseminated into the uterus. Goats do not need, in fact would not accept, being positioned on their backs. Goats are simply bred standing.

 SEMEN QUALITY AND QUANTITY

There is a considerable amount of difference between males in the quality of their semen. As well, individual males do not produce semen of consistent quality - one day can be better than the next. As a result, not all semen available for AI is of equal fertility. Especially for fresh AI when the semen must be used from that day's collection. Methods used to evaluate, particularly in the field (simple numbers and motility) are very crude methods of evaluation. In some cases, two samples, appearing to be similar using crude evaluation methods may have different success rates using AI. In many cases, the poor quality semen can be compensated for (at least partially) by increasing the numbers of sperm cells inseminated - trying to get more normal cells. In all cases, using more sperm cells are better.

SEMEN HANDLING

Semen is very sensitive to changes in temperature. High temperatures increases the metabolic rate and consumes sperm life. Chilling can damage the sperm.

Fresh semen is prepared with an extender that provides an energy source and protection against cooling. If chilled slowly to refrigeration temperature it must then be held at refrigeration temperature (4-5 C) until just prior to inseminating.

Frozen semen is thawed according to specific protocols provided by those freezing the semen. Typically, each straw is warmed according to protocol ( a typical protocol is to placed the semen straw in 35C water for 30 seconds) and used immediately without time for further temperature change. A severely cold or hot room temperature will affect results.

ANIMAL PREPARATION

In most AI programs adequate amounts of good quality semen are inseminated using the good technique. In such cases, variation in success is often due to animal selection, preparation and handling.

The goal of an AI program is to deposit semen at a chosen time in advance of when the animal ovulates - normally in the last 1/3 of the heat period. Fresh semen placed into the vagina should be deposited about 8 hours in advance of ovulation. Frozen semen has a shorter life and should be deposited closer to ovulation time - ideally about 4 hours before. The problem is that all animals in the group won't ovulate at the same time, even in synchronized heat programs. Animals are brought into synchronized estrus using progestagen hormones in vaginal pessaries and pregnant mares serum gonadotropin (PMSG). By following directions most will come into heat at about the same time. Still, there is considerable variation in the time of ovulation amounts animals in the group. Some will ovulate at less than 60 hour from pessary removal, most about 60-65 hours and some not until over 70 hours. So the inseminator is blind to the ideal time for each animal. Still, there are things we can do to further tighten the variation in ovulation. Dairy producers need to insure adequate drug withdrawal times following synchronization programs. A natural progesterone device (CIDR) should be considered.

By introducing a teaser (teasing with an intact male works reasonably well but not as good as actually letting the teaser breed ) at first signs of heat, the ovulations in those that would have ovulated later than others are moved ahead. Similarly, by injecting GnRH hormone about 24 hours after pessary removal, it is reported that most will ovulate sooner.

Goats, particularly dairy goats, can often be bred in natural heats. Single inseminations are done at about 36 hours after heat begins. Best program is to breed at 12 and 24 hours after first signs of heat.

TYPICAL SHEEP PROGRAM - PROGRAMS MAY VARY ACCORDING TO CIRCUMSTANCES 

TYPICAL GOAT PROGRAM

DRUGS USED