Boar Training Aid Tested

As the use of artificial insemination (AI) continues to gain popularity, commercial pork producers may want to collect semen from boars previously used for natural mating. These oexperiencedo boars are often more difficult to train for semen collection than novice, young boars with little sexual experience.

Virginia Tech set out to learn whether Prostaglandin-F2alpha (PGF2) could serve as an aid in training boars with natural mating experience.

Fourteen boars (four Hampshire, four Landrace, six Yorkshire) ranging in age from 1 to 4 years old were tested. Treatment groups were balanced for breed and age. Boars were moved to a semen collection pen twice weekly for four weeks. Training sessions lasted a maximum of 15 minutes.

Upon entering the collection pen, seven boars received an intramuscular injection of 10 mg. of PGF2alpha (Lutalyse, Pharmacia & Upjohn) to serve as the otreatedo group. The other seven boars received an intramuscular injection of 2 ml. deionized water to serve as the ocontrolo group. Boars were considered trained when, after a successful collection, they mounted the artificial sow and allowed semen collection on the next scheduled day without first receiving an injection of Lutalyse or deionized water.

Six of the seven treated boars and two of seven control boars mounted and allowed semen collection during the first exposure to the artificial sow. After four training sessions, all seven treated boars and four of seven control boars were successfully trained.

At the conclusion of the eighth training session, three remaining untrained control boars received the Lutalyse injection. Two mounted the artificial sow and were successfully collected.

Researchers note that the number of false mounts/session, in which boars mounted the artificial sow but did not allow semen collection was lower in treated versus controls. Likewise, the reaction time - that is the elapsed time after entering the collection pen until start of ejaculation - was lower in treated boars.

The research shows that the treatment has the potential to expedite training of oexperiencedo boars for semen collection. Once trained, injections of Lutalyse are unnecessary. Researchers also remind that the use of Lutalyse for training boars for semen collection represents product use under the Animal Medicinal Drug Use Clarification Act (also known as extra-label use). It is important that producers consult their veterinarian prior to implementing this procedure.

Researchers: Mark J. Estienne and Allen F. Harper, Virginia Tech u Tidewater Agricultural Research and Extension Center, Suffolk, VA. Phone Estienne at (757) 657-6450 ext. 114, or e-mail

Boar Exposure Linked to AI Success

University of Illinois researchers report that frequency of boar exposure to newly weaned sows can improve timing inseminations, increasing the chance of sows being inseminated within the preferred 24-hour period prior to ovulation.

Illinois research was aimed at evaluating whether increasing the frequency of boar exposure would affect the accuracy of determining the onset of estrus, therefore, the accuracy of predicting ovulation in weaned sows.

Between January and August 2000, sows of mixed parity were weaned 18 days after farrowing and then randomly allotted to boar exposure treatment by genotype, parity and lactation length. Sows were weaned into gestation crates. Boar exposure was initiated three days after weaning by moving boars through the alleyway at the front of the crate. Individual sow exposure lasted two to five minutes.

The three treatment regimes included 186 sows exposed to boars once daily (1X), twice daily every 12 hours (2X), or three times daily every eight hours (3X). Once estrus was detected, transrectal ultrasound was performed every eight hours to visualize the ovaries and determine time of ovulation. Sows in the 1X group were bred by artificial insemination at zero and 24 hours after first detected estrus. Sows in the 2X group were bred at 12 and 24 hours. And, sows in the 3X groups were inseminated at 16 and 32 hours after first detected estrus.

Researchers learned that wean-to-estrus was not influenced by frequency of boar exposure and averaged 4.5 days. Ninety to 100% of sows expressed estrus within eight days and were unaffected by treatment or month.

Treatment did, however, influence the percentage of sows ovulating. Sows exposed to a boar two or three times had an ovulation rate of 85%, while 98% of the sows exposed a single time ovulated.

The wean-to-ovulation interval was not influenced by treatment and averaged 6.5 days. The length of estrus averaged 58.5 hours and was influenced by both treatment and month, but no interaction was noted.

Estrus lasted longer in the 3X exposure sows (62-hour avg.) compared to the 2X exposure group (53-hour avg.) and the 1X group (42-hour avg.).

Researchers also reported the shortest average estrus length occurred in August, February and March (40-49 hours), while the longest lengths were recorded in April and June (75-58 hours).

The estrus-to-ovulation period was not influenced by treatment or month and averaged 45 hours.

The occurrence of ovulation to the end of standing estrus was influenced by month, with the shortest interval from ovulation-to-estrus in the February and March replicates (11 hours), intermediate intervals in late March and August (23 hours), while longest intervals were recorded in April and June (39 hours).

Researchers note that more frequent boar exposure improved the percent of inseminations that occurred 24 hours before ovulation. The increased exposure frequency improved the percent of first inseminations occurring within 24 hours from 10% in the 1X group to 29% in the 2X group, and to 46% in the 3X exposure group.

The higher exposure frequency also slightly improved the percentage of second services administered 24 hours before ovulation from 81% in the 1X group to 82% in the 2X group, and to 85% in the 3X group. But these were not statistically different.

"The results of this experiment indicate that the frequency of boar exposure for weaned sows can improve the precision for timing inseminations and the frequency of first and second services administered within 24 hours before ovulation," the researchers say.

Researchers: Robert Knox, Gina Miller, Kilby Willenburg, and Sandra Rodriguez-Zas, University of Illinois-Urbana. Phone Knox at (217) 244-5177 or e-mail at