Introduction

The impact of the boar stud on overall production in swine systems as they exist today is extremely significant. It is the beginning of every pig that is born in the system and is therefore a critical step for the success of the entire system. It cannot be viewed as more or less important than any of the other parts of the operation, just as a baseball team is more than a pitcher and a catcher. But, like the pitcher's influence on the outcome of a ball game, there is tremendous control over the success or failure of the operation by the boar stud. This success or failure is dependent on genetics, health, production, quality control, etc. Therefore, any risks associated with semen production which could jeopardize production in the entire system itself must be addressed before they have an opportunity to impact the system. The rest of the "team", in this case the breeding crew, have critical steps that must be followed properly as well to maintain optimum production.

Biosecurity

Some of the points of control may be out of the hands of the individual in charge of the stud, such as genetics or production schedules. There are, however, a number of points which must be addressed to prevent a breakdown in the system. The most important control point for the AI stud is biosecurity. Biosecurity means many different things to different people, depending on the situation, but should be looked at from a number of angles.

Site selection is the first consideration regarding biosecurity and would take into consideration location in relation to other swine units, as well as the location of sow units that will receive semen, if it is to be delivered directly. Location must also take into consideration traffic patterns and distance from main roads (is the stud on a main highway that carries high numbers of pigs to market?). Prevailing winds and proximity to homes or businesses that may be affected by swine waste odor are additional factors to consider.

Either the most or least important area of biosecurity, depending on geographic location, is control of external (nonpig) sources of contamination, specifically birds, rodents and other wild animals. Control at this stage includes chain link fencing, bird netting, rodent control (bait boxes) and possibly insect control. The specific location within a given geographic area can greatly impact the risk associated with these potential problems as well.

The point of biosecurity control with the greatest direct impact on the health status of the boars already present in the stud is the entry procedures for new boars coming into the stud. Isolation, including health monitoring, vaccination and acclimation, is critical and must be rigidly controlled to insure the continued health status of the stud. Status of the source animals as well as the current population in the stud will determine the vaccination and testing program, as well as the length of isolation. The impact of a particular disease on the entire production system may be manifested as reduced fertility due to poor semen quality or the spread of that disease into the sow population, or may be due to a reduction in sperm availability from the stud leading to an inability to perform matings at the production farm level. The second situation can be avoided as a problem for the sow farms by having a contingency plan in place to receive semen from an outside source, should that be necessary.

To most people, biosecurity refers mainly of the control of people entering the stud. The most effective method to control visitors is to simply not allow any, although this may not be an option for a particular stud. If visitors must be allowed in, set minimum exposure times to other swine, such as 72 or 96 hours. All persons, whether visitor or employee, should be required to shower in and wear only clothes from the unit. Jewelry, watches, cameras, etc. should not be allowed in, and any item which must be brought in, such as eye glasses, should be sterilized with 70% ethyl or isopropyl alcohol. In the case of the veterinarian who performs the routine health monitoring and blood sampling, scheduling can create problems and protocols, particularly down times, may not always be able to be followed.

Biosecurity applies to a number of other areas besides the boars and people entering the unit. Supplies and equipment should only be brought in through an off sight stores system, or at least not directly into the unit by the commercial carrier. Also, equipment and supplies should never be purchased from a supplier that would have exposure to swine. Most reputable suppliers are not a problem, but the commercial delivery companies may travel from one farm to another without consideration for your biosecurity standards.

As with the commercial delivery vehicles, you must also consider feed deliveries and distribution systems for the semen, whether commercial carrier or a private system, and the method by which the semen is transferred to them from the stud. If you are delivering semen through your own system of drivers and vehicles, they should not be returning to the stud from the farms without going through a vehicle wash and cleaning or changing shoes, and if possible, this return should be the next day at the earliest. Transfer boxes for delivery vehicles should not be removed from the vehicles, except for filling with semen at the stud. No item should ever go from a production farm back into the stud, such as semen for evaluation that was not used due to age.

Feed deliveries should be made as the first drop on Monday following a weekend in which the delivery truck is idle after being washed. Feed truck drivers should also disinfect all tires as they enter the unit off the road (a pull off area should be provided for this). Control of the quality and source of components for the ration need to guarantee that there is not potential contamination or disease introduction through the individual components.

The stud should have available a medicating system for the water, should it be necessary to treat all animals in the event of an outbreak or to prevent the spread of infectious disease. Medication of the feed is a second option, but can be delayed if storage bins are full and considerable time is required to empty them. Water medication is only practical with individual waterers, such as nipples. Common watering troughs may aid in the spread of disease through a barn and do not provide continuous access to fresh water, therefore they should not be installed in a boar stud. Because of the small number of animals in the unit, the economic advantage of constructing a trough versus installing nipples would at best be very slight.

Semen Collection

Several studies have recently indicated the importance of proper technique in the semen collection process. The presence of bacteria in the prepuce has been correlated with contamination of semen¹. The degree of contamination has also been quantified with sources of this contamination investigated². Both of these studies concluded that collection technique has the greatest impact on bacterial contamination of semen collected by the gloved hand technique. Therefore, following accepted protocol for sanitary semen collection³ is paramount to producing semen with minimal contamination. Techniques for removal of the preputial diverticulum have been described in the literature, which can be performed to reduce bacterial contamination as well^4,5.

Semen Processing

Hygiene in the laboratory is of utmost importance to insure that, once the semen is collected, further contamination does not occur. Basic procedures for maintaining a clean environment and keeping laboratory equipment and supplies clean or sterile were described in detail at this same seminar last year³. The key is to be certain that these procedures are always followed and monitoring takes place on a routine basis to verify that the procedures are in fact working.

The various steps in processing swine semen have critical points to consider as well. These include the collection of the semen in a prewarmed, sterile cup, immediate transfer of the semen to the laboratory and immediate processing. Swine semen is very susceptible to temperature shock (cold shock) and must not be exposed to cold or allowed to cool before it is extended. It also is susceptible to acrosome damage if kept above 32°C for more than 20 to 30 minutes, even if extended. It is therefore critical that the semen reach the laboratory, be analyzed, extended and packaged and then put into the incubator to cool as quickly as possible. Packaged semen may be allowed to cool to room temperature for up to two hours prior to being placed in the incubator, or may go directly into the incubator following packaging without adversely affecting motility and morphology⁶.

Once cooled to the recommended temperature for the specific extender being used, the semen can be shipped to the farms for use. Packaging methods are dependent on the type of delivery service to be used and the length of time in transit. It may be as simple as placing the cooled semen in a styrofoam box and driving it to the sow units, or as complex as double packaging in styrofoam boxes with gel packs in and between boxes for overnight delivery by commercial carrier. The gel packs can be heated or cooled as required to assist in maintaining the proper temperature. Keep in mind that gel packs placed in the same container with the semen should not be more than one degree centigrade different in temperature than the semen itself.

Semen Handling on the Farm

Once the semen has arrived at the farm, the next step is to insure that it is placed in a temperature controlled semen storage unit as quickly as possible. Doses must be stored laying flat, whether in tubes, bags or bottles, so the sperm cells do not collect into a confined area where they cannot be mixed back into suspension. Most extender manufacturers recommend once or twice per day mixing of the semen during storage, although one report has indicated that mixing semen may not be necessary for one specific extender⁷. If the semen is not at the desired temperature for storage when placed in the unit, it must be spread out with enough air circulation to allow for rapid and uniform cooling. This may require more than one semen storage unit for farms receiving large numbers of doses per delivery. Again, due to the sensitivity of swine semen to temperature fluctuation, it is recommended to store semen on the farms in a temperature controlled unit that maintains the set temperature within one degree centigrade and has the capability to heat or cool as required according to ambient temperature.

There is no scientific evidence that prewarming semen prior to insemination will affect fertility. There is a trial under way at this time to investigate this question further, but current recommendations are to inseminate the sow with semen directly from the semen storage unit. Semen should be transported to and maintained in the breeding area in a styrofoam box or cooler to prevent additional cooling and protect it from ultraviolet light rays which are spermicidal. If semen is warmed up, it should be inseminated as quickly as possible and not returned to the semen storage unit for use later.

Estrus Detection and AI

Determining the proper time to inseminate still remains the most difficult task in achieving optimum fertility with AI. Recommendations for timing matings depends on a number of factors, including frequency of estrus detection, parity and number of days between weaning and first estrus⁸. Inseminations performed early in the estrus cycle do not seem to be detrimental to fertility, but there is evidence indicating that inseminating sows or gilts after ovulation will decrease the number of viable embryos that survive to birth⁹.

The insemination process itself is a relatively simple procedure, but hygiene again becomes an important issue that must be addressed. From cleaning the vulva to using a clean (reusable) or new (disposable) catheter on each sow or gilt inseminated is critical. A widespread problem in the industry is that inseminators often do not understand the definition of the term disposable.

Future Prospects for AI

New technologies will be available to the swine producer which will improve efficiency or production and/or decrease the cost of production. AI itself has been around in the swine industry for six decades, but its use has only become widespread in the United States in the past ten to 15 years. Frozen semen has been used on a commercial, although limited, basis for over 20 years in the U.S. New techniques have improved fertility with frozen semen, but it still is more cumbersome and expensive than fresh semen and fertility lags somewhat. The principal use of frozen semen in the world today is to transfer genetic material between countries and store genetic material against some cataclysmic disaster in the swine industry.¹⁰

Semen sexing has received some attention in the press, but is not feasible for commercial swine production systems as it exists today. Due to the high cost of the equipment required and the low yield and slow processing time per ejaculate, semen sexing by itself does not appear to offer any advantages to the industry at this time. However, if used in conjunction with in-vitro fertilization and embryo transfer, both techniques which have experienced substantial advancements recently, semen sexing may have considerable merit. As with frozen semen, these technologies have a greater application for genetic transfer and improvement and limited use in commercial production systems as we know them at this time.

Cloning has also come of age, but may be of even less value than the three technologies mentioned above, due to the lack of genetic improvement that it offers. As of this writing, this author has not seen the perfect sow or boar which would merit being cloned.

Suggested Reading

¹ Martin Rillo, S., Shokouhi, V., Garcia Boix, E., Hernandez-Gil, R., Romero, L.: Contamination Of Semen Doses And Its Possible Relationship With The Bacterial Flora Of The Prepuce. Proc. 15th Int. Pig Vet. Soc. Congress, 3:60, 1998.

² Gall, T.J., Wilson, M.E., Althouse, G.C.: Quantification Of Bacteria In Fractionated Boar Ejaculates. Allen D. Leman Swine Conference, Suppl. 25:45, 1998.

³ Althouse, G.C.: Minimum Contamination Techniques For Boar Studs. Proc. North Carolina Healthy Hogs Seminar, 15, 1997.

⁴ Aamdal, J., Hogset, I., Filseth, O.: Extirpation Of The Preputial Diverticulum Of Boars Used In Artificial Insemination. J. Amer. Vet. Med. Assoc. 132:522-524, 1958.

⁵ Lawhorn, B., Jarrett, P.D., Lackey, G.F., Crabill, M., Peloso, J.G., Steiner, A.: Removal Of The Preputial Diverticulum In Swine. J. Amer. Vet. Med. Assoc. 205(1):92-96, 1994.

⁶ Lorton, S.P., Gall, T., Wilson, M.: The Effect Of Two Cooling Protocols On Quality Of Liquid Boar Semen. Allen D. Leman Swine Conference, Suppl. 25:43, 1998.

⁷ Simmet, C., Rath, D., Lorton, S.P.: Does Sedimentation of Liquid Boar Semen Influence Semen Quality During Storage. Proc. 15th Int. Pig Vet. Soc. Congress, 3:62, 1998.

⁸ Weitze, K.F.: Timing of AI and Ovulation in Breeding Herds I. Reproduction in Domestic Animals, 31:193-199, 1996.

⁹ Soede, N.M., Wetzels, C.C.H., Zondag, W., de Koning, M.A.I., Kemp, B. Effects of Time of Insemination Relative to Ovulation, as Determined by Ultrasonography, on Fertilization Rate and Accessory Sperm Count in Sows. Journal of Reproduction and Fertility. 104:99-106, 1995.

¹⁰ Didion, B.A., Schoenbeck, R.A. Fertility of Frozen Boar Semen Used for AI in Commercial Settings. Reproduction in Domestic Animals, 31:175-178, 1996.