Introduction

During the past ten years, there has been a dramatic increase in the use of artificial insemination (AI) by commercial swine producers. In 1990, less than 7 % of sows and gilts in the United States were bred by AI. Today, over 50% of the United States sow herd is bred via AI and within the next decade, nearly all swine producers will probably utilize this technology. Producers adopting AI obtain semen in a variety of ways:

1. Semen is purchased from commercial studs, the majority of which are located in the Midwest.
2. In the Midwest, some producers have created cooperative boar studs from which members obtain semen.
3. Semen is obtained from studs that are structured so individual producers retain ownership of their boars.

For a fee, the stud provides "room and board" for the boars, as well as semen collection and processing services. A fourth option for obtaining semen is to collect it from boars housed on the farm or at farm-owned, off-site studs. This method is advantageous in that a supply of fresh semen is readily available and the producer maintains complete control of genetic and semen quality decisions. However, specialized labor, techniques and equipment are necessary for semen collection, evaluation and processing. This article focuses on one aspect of this process, namely training boars for collection of semen off of a "dummy sow".

The Semen Collection Area and Dummy Sow

Semen can actually be collected from boars in one of two ways. It can be collected from the boar while he mounts a sow or gilt that is in estrus. Two problems with this method are: 1) the boar may be too large to be supported by smaller females and 2) females may begin to walk around the pen, making it difficult to collect semen. The preferred approach is to collect semen from a boar trained to mount a dummy sow.

Dummy sows can be purchased from AI equipment dealers or can be constructed at the farm. Dummy sows certainly need not be elaborate but should be solid in construction, well secured to the floor and have no sharp edges. For example, a dummy sow can be a simple box frame made of metal with large pieces of pipe welded to each end to form legs. One-half of a small barrel or old water heater can be welded on top of the box frame and covered with rubber or canvas. The height of the dummy sow should be adjustable. When a boar mounts the dummy sow, his sheath should be below the back of the dummy sow. For designs and specifications of dummy sows, see Levis (1989).

The dummy sow should be located in a designated semen collection room or pen that measures at least 10' x 10' and has a non-slick floor. Rubber breeding mats provide excellent footing. Once in the semen collection area, the boar should be subjected to no distractions (i.e., no feeders, waterers, etc.). The room or pen should provide a means of escape for the producer in the event a boar becomes hostile.

Training the Boar

Ideally, the boar should be trained when he is between 8 and 10 months of age, although older boars that may have been used for natural service may also adapt to collection of semen off of a dummy sow. The majority of boars can be trained for semen collection; however, a very small number may refuse to mount the dummy sow indefinitely.

With regard to training the boar for semen collection, the key word is patience. To begin, the boar is moved to the collection room or pen two or three times at daily intervals, with the purpose of getting him acquainted with the dummy sow. The boar being trained should be exposed to the dummy sow immediately after collection of semen from an already trained boar. Many boars mount the dummy sow during one of the first few training sessions.

A boar that does not mount after two or three exposures to the dummy sow, can be "tricked" by the producer into mounting by his sprinkling semen from another boar, or spraying SOA Boar Scent (Intervet Inc., Millsboro, DE), on the dummy sow. This technique is necessary only until the boar has been trained to mount.

Another option is letting the boar mount, but not breed, a sow that is in estrus and in same area as the dummy sow. After removing the sow by letting her exit near the dummy sow, the boar may be stimulated to mount the dummy sow. Alternatively, the sow in estrus is penned or caged near the head of the dummy sow.

A producer can also allow the boar to mount a sow that is in estrus and is standing parallel to the dummy sow. The producer can begin collecting semen and after approximately two minutes, have an assistant gently push the boar over onto the dummy sow while the collection continues. The sow in estrus is then removed from the room.

After a successful collection, the boar is collected several times within the next 7 to 10 days. This procedure helps the boar associate the dummy sow with ejaculation.

Use of Lutalyse (Prostaglandin F2a [PGF2a]) for Training Boars

At the Tidewater Agricultural Research and Extension Center in Suffolk, we are researching another method of stimulating boars to mount a dummy sow. Our experiments have focused on the effects of Lutalyse (Pharmacia & Upjohn Company, Kalamazoo, MI) on the training of boars for semen collection.

Anecdotal evidence from observations in the field suggested that the administration of Lutalyse enhanced libido in boars and increased the willingness to display mounting and mating behavior. There were, however, very few published research reports to justify this practice. Hashizume and Niwa (1984) reported that PGF2( improved libido to some extent and increased the volume and total number of sperm cells in the sperm-rich fraction of ejaculates. However, only 3 boars were evaluated.

Szurop et al. (1985) reported that treatment of young boars with a PGF2( analog increased the number of individuals that mounted a dummy sow at the first training session for semen collection. Researchers at Oklahoma State University, however, found that treatment with PGF2( did not increase the number of low-libido boars that mounted and mated gilts (Wettemann et al., 1992).

The objective of our experiment was to determine the effects of Lutalyse on the ability to train boars for semen collection. Fourteen boars (4 Hampshire, 4 Landrace and 6 Yorkshire) that were experienced with natural mating but naïve to a dummy sow were utilized. Boars ranged in age from 1 to 4 years, and treatment groups were balanced for age and breed.

Boars were moved to a semen collection pen twice weekly and each individual training session lasted a maximum of 15 minutes. Upon entering the collection pen, 7 boars received an i.m. injection of 10 mg Lutalyse (2 ml) and the other seven boars received i.m. injections of 2 ml deionized water (controls). After a successful collection, the boar was moved to the semen collection pen again on the next scheduled day in order to confirm that the boar was actually "trained". Prior to the attempt at a second collection, boars received no injections.

Six of 7 Lutalyse-injected boars mounted and allowed semen collection during the first exposure to the dummy sow. In contrast, only 2 of 7 control boars were collected during the first training session (P < .03).

All seven Lutalyse-injected boars were "trained" by the end of Week 2 of the experiment (Figure 1). In contrast, by the end of the fourth week of the experiment, only 4 of 7 control boars had been trained. After the last, unsuccessful attempt to get the three untrained control boars to mount the dummy sow (i.e., end of the fourth week), they were injected with Lutalyse. Two of the three boars mounted the dummy sow and allowed semen collection after Lutalyse injections.

Table 1 shows reaction time (elapsed time from entering collection pen until the start of ejaculation), duration of ejaculation, the number of false mounts (mounts with no collection), and gel-free semen volume for boars collected after receiving injections of Lutalyse or deionized water, or no injection. Note that for most items, there were no significant differences between groups. However, boars injected with Lutalyse exhibited fewer false mounts prior to collection of semen, compared to boars injected with water or boars receiving no injections.


Based on our results, it appears that Lutalyse can be used as a tool to expedite the training of boars for semen collection. Certainly, indiscriminate or routine use of Lutalyse in boars is not recommended. Indeed, in our experiment, Lutalyse was used only to "train" boars for semen collection. In subsequent collections, it was not needed nor used to entice boars to mount. The long-term effects of repeated injections of Lutalyse on boar health, libido and semen quality have not been determined. Finally, Lutalyse injections for enhancing libido in boars is technically an "extra-label" use of the drug and should only be administered after consultation with a producer's herd veterinarian.

Semen Collection

Before attempting to collect a boar, clip the long hairs on the sheath because it interferes with the collection process. During the actual collection process, patience is again important. Allow the boar to mount and make a few copulatory thrusts, extend the penis and display an erection. The corkscrew end of the penis is grasped with a bare or gloved hand. If gloves are used they should not be latex because chemicals on these type gloves are spermicidal. After a few moments, the boar will cease thrusting and begin to ejaculate. Semen is collected into a thermos. The gel fraction should be filtered out of the ejaculate during collection using gauze or cheesecloth, which has been placed over the mouth of the thermos. The grip on the penis should not be loosened during ejaculation, which on average requires 5 to 6 minutes. Once semen is collected it should be protected from abrupt temperature changes, water, soap residues, nicotine, or sunlight, each of which can damage or kill sperm cells. Semen handling procedures are described in Levis (1989).

References

Hashizume, T. and T. Niwa. 1984. Effect of administration of prostaglandin F2( (PGF2() on the properties of sperm rich fraction of boar semen. Japan. J. Anim. Reprod. 30:182.

Levis, D. G. 1989. Artificial Insemination of Swine. Nebraska Cooperative Extension EC 89-264.

Szurop, I. et al. 1985. Stimulation of libido in pubertal and mature boars with prostaglandin F2( analogs: Clinical observations. Zuchthygiene 20:83.

Wettemann, R. P. et al. 1992. An attempt to stimulate sexual behavior of boars. Oklahoma Agricultural Experiment Station 1992 Animal Science Research Report. pp. 410-412.

Source: Virginia Cooperative Extension - January 2001