Semen Placement

Semen Placement

The insemination process is quite straightforward. However, since relatively few sperm cells will be used, their placement is critical. The semen should be placed in the body of the uterus just in front of the cervix. You can recognize the proper site by the change in tissue consistency—from firm and hard in the cervix to soft and spongy in the uterus. To achieve the highest possible fertility rate, semen should be deposited at the very front end of the cervix. The internal (or front) end of the cervix is often called the anterior cervical os. To deposit semen at this location requires the use of a special device called Cassou pipette, or "AI gun." The rectovaginal insemination process is used. The inseminator places his hand in the rectum and manipulates the reproductive tract so that the gun passes through the vagina, then it is manipulated through the cervical rings, and then held at the internal opening of the cervix for semen deposition. In adequately restrained cattle this will take 30 seconds to 2 minutes. At first, however, passing an insemination syringe might not be easy because you might encounter natural obstructions on your way to the target.

Beware of obstacles. The front end of the vagina forms a circular blind pouch where it joins the backward projecting cervix.

Figure 2. Proper placement of insemination gun to deposit semen in the body of the uterus.

This blind pouch is usually from 5 to 1 inch deep, surrounding the entire dome-shaped back end of the cervix. You’ll meet other obstacles once you’re inside the cervical canal. Firm, finger-like projections arranged in three to four circular rings extend into the canal. These cause the passageway to be crookedand contain blind pockets, or dead ends. The circular blind pouch of the vagina and the winding cervical canal with its dead ends are the two major stumbling blocksfor anyone learning how to artificially inseminate.

Next to estrus detection, semen placement error (by the technician) is most likely to affect fertility. Correct semen placement is very difficult to confirm in the field. It is impossible to check pipette placement. The pipette position changes too easily. Postmortem tracts or examining culled cows inseminated with dye can be used to check semen placement after slaughter. Studies using dye deposition followed by slaughter have shown that up to 70 percent of the cows are inseminated incorrectly. The dye was placed in the vagina, posterior cervix, uterine horn, or bladder. The target for semen deposition is the anterior cervical os, a difficult site to find. Inexperienced inseminators often do not pass the pipette far enough, or they pass it too far into the uterine horns. Since the body of the uterus is only .5 to .75 inches in length, pipette passage 1 inch into the uterus results in most of the semenentering only one horn, effectively reducing conception. Semen deposition is often made too rapidly, and semen takes the avenue of least resistance. If one horn is not as open as the other, it does not receive enough semen.

Take your time while breeding a cow and depositing the semen. It only takes a few extra seconds to make sure semen is deposited correctly. The plunger should be depressed over a 5-second period, allowing the semen to flow slowly and evenly, divided between horns. In non-pregnant cows, walls of the uterus are soft and spongy. Inseminating syringes should never go beyond the front end of the cervix, because it is too easy to poke into or through the uterine wall. This could cause infection and perhaps even fatal peritonitis.

Retrieving Semen In the typical farm semen tank, dangerous temperatures exist in the upper half of the neck tube.
Exposure to these temperatures can occur when trying to locate a specific unit of semen or when transferring semen from tank to tank. Thermal injury to sperm is permanent and cannot be corrected by returning semen to liquid nitrogen.

In order to minimize thermal damage:

 Identify which canister contains the desired semen. A semen inventory which keeps track of the location of each bull prevents unnecessary searching.

 Remove the canister from its storage position to the middle of the tank. Raise the canister just high enough in the neck region to grasp the desired cane of semen. Keep the canister tops no higher than the frost line, or keep the tops of the canes no higher than two to three inches from the tank’s top.

 Immediately after the unit of semen is immersed in water, return the cane to the canister by raising the canister up over the cane. Return the canister to its storage position.

 Any time it takes more than 8 to 10 seconds to locate a particular cane, the canister should be lowered back into the tank to cool completely. Never return a unit of semen to the tank once it has been removed from the cane.

Figure 1. Diagram (side, or lateral, view) of the reproductive anatomy of the cow and radiograph (top, or dorsal, view) of the cervix, uterine body, and uterine horns.

Analysis of radiographs of all inseminations indicated that only 39 percent of the rod tip placements were within the uterine body. Placements in the cervix, right uterine horn, and left uterine horn were 25, 23, and 13 percent, respectively. Semen distribution, determined from the second radiograph, showed that 40 percent of the semen was located in the uterine body or equally distributed in both uterine horns. The remaining 60 percent was located in the cervix or disproportionately in one uterine horn. Accurate distribution of semen was significantly related to proper placement of the insemination rod. Figures 2a and 2b illustrate correct rod tip placement and semen distribution. Figures 2c, 2d, 2e, and 2f illustrate examples of incorrect AI technique.

Figure 2. Radiographs of excised cow reproductive tracts illustrating insemination rod tip placement (left) and distribution of radiopaque semen (right) following correct AI technique (a, b) and incorrect techniques (c, d, e, and

Conclusion

The semen storage tank is a large vacuum-sealed metal bottle with an extremely efficient insulation system. Because of the vacuum bottle construction, the temperature can remain at -320° F (liquid nitrogen temperature) as long as at least two inches of liquid nitrogen is present. Technical advances in design and construction have produced storage tanks with a liquid nitrogen holding time of six to nine months.
Although semen storage tanks are well constructed, they still are susceptible to damage from mishandling. Semen tanks should be kept in clean, dry, and wellventilated areas. Avoid excessive movement of the tank. The inner chamber, which contains liquid nitrogen, is suspended from the outer shell by the neck tube. Any abnormal stress on the neck tube, caused by sudden jarring or an excessive swinging motion, can crack the tube. This results in vacuum loss from the outer chamber.

To increase holding time, keep the tank in a cool location away from direct sunlight. Avoiding drafts from furnaces and outside air also helps prevent excessive nitrogen evaporation. However, make sure there is sufficient ventilation in the room to prevent possible suffocation which can be caused by excessive nitrogen gas in the air you breathe.
Protect the tank from corrosion by keeping it elevated above concrete or wet floors. Use boards or pallets. Pick a location that is safe from children and vandals, but do not hide the tank; it must be placed where it can be seen daily and where it can be monitored routinely for nitrogen level.

Finally, always be watchful for a lid that is left off and for frost or sweat on the tank. Give particular attention to the neck and vacuum fitting. Frost indicates that the vacuum insulation has been lost, and liquid nitrogen has been or is evaporating rapidly. If you suspect this has happened, use a wooden yardstick to measure the amount of liquid in the tank. If the tank contains liquid nitrogen, the semen must be transferred to a good tank immediately. Should the tank be empty of liquid nitrogen it is doubtful that the semen is viable; it should be evaluated before it is used.

References

§ Peters, J. L., P. L. Senger, J. L. Rosenberger, and M. L. O’Connor, (1984) “Radiographic evaluation of bovine artificial insemination technique among professional and herdsmen-inseminators.” Journal of Animal Science 59, 1671.

§ Gallagher, G. R., and P. L. Senger, (1989). “Concentrations of spermatozoa in the vagina of heifers after deposition of semen in the uterine horns, uterine body, or cervix.” Journal of Reproduction Fertilization 86,1

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