GUIDELINES FOR UNIFORM SWINE IMPROVEMENT PROGRAMS

VI. POST-TEST MANAGEMENT OF BREEDING STOCK

High priority should be given to the management of animals newly introduced into the breeding herd to achieve maximum reproductive efficiency. Good reproductive and nutritional management pays dividends through an increased number of pigs farrowed live and weaned. The following boar and gilt management practices will assist in the maximization of fertility and longevity.

Post-Test Management of Boars

  1. Upon completion of test, boars should be fed at a level of energy that will prevent excessive fat deposition. This practice should help ensure that they are physically adept and sexually active. Nutrients other than energy should be provided to meet the minimum daily recommended allowance of the National Research Council. See Appendix A for details.

  2. Boars tested individually or in small groups in close confinement should be managed upon completion of the test in a manner to develop physical hardening and to stimulate sexual arousal and libido. Where possible, this should be done before delivery to their new owners and might include the following: a) Shifting boars to different locations. b) Providing fence-line contact with cycling females. This may be especially important where the aggressiveness of the boars precludes mixing them together.

  3. Although boars tested in large groups and in less confined settings are likely to require less physical conditioning and sexual stimulation before use, they may also benefit from exposure to the management procedures described for boars reared in close confinement.

Post-Test Management of Gilts

At the end of the test, energy intake of selected gilts should be restricted to prevent overweight conditions. Nutrients other than energy should be provided to meet the minimum daily recommended allowances of the National Research Council (Appendix A).

Moving gilts to new pens, increased exercise, and daily exposure to boars beginning between 160 and 180 days of age will help stimulate the onset of estrus. Breeding should be delayed until the second or third estrus to increase the probability of large litters and prevent dystocia. Gilts that do not conceive after mating at two estrous periods should be marketed. Likewise, gilts that have not expressed heat by 9 months of age should be culled. During gestation, gilts should be fed to gain about 75 lb and not become overly fat.

Management of Newly Purchased Breeding Stock

Newly purchased animals should be transported in a covered truck or trailer that is bedded appropriately for the season. After delivery, animals should be isolated in clean, comfortable quarters for a minimum of 30 days. During this isolation period, boars and gilts should be acclimated to the environmental conditions (dirt, confinement, fluctuating temperatures, sunlight, etc) in which they are expected to function during breeding. Boars should be fed only 3 or 4 pounds of feed daily for the first week. If a breeding animal does not make the adjustment to this new environment satisfactorily, call the breeder immediately for assistance. After this initial adjustment period, producers should implement the following procedures:

  1. Provide protection against prevalent disease organisms. New breeding stock introduced to the farm should be blood tested after 21 days (or according to the state requirements) in isolation for pseudorabies, brucellosis, eperythrozoonosis, and leptospirosis. If breeding stock comes from a herd with a known disease profile, follow recommendations of the consulting veterinarian.

  2. After the period of isolation and before breeding, boars should be provided 3 to 4 weeks of fenceline contact with nonpregnant breeding females so the females may contract any new microorganisms brought in by the boars, and the boars may be introduced to any microflora on the farm. This period will provide sufficient time for recovery from any illness caused by the new disease organisms before breeding begins. The boars and females should both be observed closely during this period for elevated body temperature or signs of clinical disease. Similar procedures may be followed for newly purchased gilts.

  3. Boars should be evaluated early in the contact period for reproductive soundness. Any Claims of Nonperformance should be made by the buyer within 90 days of the date of purchase.

Evaluating Boar Reproductive Soundness

To be evaluated for reproductive soundness, boars should be at least 7 1/2 months of age. The evaluation should be completed before the breeding period so problem boars can be identified and culled. Boars should be evaluated on the following criteria.

  1. Mating behavior may be evaluated by bringing a gilt in standing heat into the boar's pen and observing the following: a) Libido: Observe the boar's aggressiveness and desire to mate. Boars may need assistance through at least one mating experience. b) Mounting: Boars must have the ability to mount correctly. Some boars may be interested in mounting but lameness, arthritis, or injury may prevent success. Boars that mount the front end of a gilt should be gently moved to the proper position. c) Mating: Observe the boar's ability to erect the penis and properly enter the gilt. Examine the boar's penis for normal size and condition. Penis abnormalities encountered occasionally are: (1) adhered or tied penis, (2) limp penis, (3) infantile penis, and (4) coiling of the penis in the diverticulum. These conditions may be heritable, and boars exhibiting these problems should not be used to produce breeding stock.

  2. Semen. A few boars fail to produce sperm cells. Hence, semen from young boars should be submitted to a check. The simplest way to collect semen from a boar is to allow the boar to mount a gilt in standing heat. First place a rubber glove (latex) on one hand and after the boar begins to extend his penis, grasp firmly the corkscrew end of his penis and bring the penis gradually forward once extended ejaculation begins. Collect the entire ejaculate into a wide-mouth container covered with a double layer of cheesecloth to separate the gel fraction. The volume of semen obtained is quite variable between boars but averages generally between 200-250 milliliters (about 1 cup). If the sperm concentration is high, the semen will be milky in appearance. Boars with watery or bloody semen should be evaluated by a reproduction specialist. Usually 70 to 80 percent of the sperm should be motile immediately after collection. Low sperm motility is not a serious matter unless the condition persists for several months. Boars that produce semen with no sperm or only a few sperm should be rechecked several times at weekly intervals. If the condition persists, the boar should be culled. The first ejaculate of a new boar may not provide an accurate test and should not be used for evaluation.

  3. Test Mating. To complete the soundness evaluation, two or three gilts should be bred and carefully checked as to whether they return to estrus within 4 weeks. Exposure to conditions or microorganisms on the new farm may have produced temporary infertility. High environmental temperatures, stress of transportation, illness, lameness, or injuries causing high body temperature can alter sperm motility and reduce fertility for up to 8 weeks.

Minimum Breeding Ages for Boars and Gilts

In order for the seedstock producer to measure performance to acceptable off-test weights, delivery of boars and gilts to the buyer is seldom earlier than 5 1/2 months of age. Sexual maturity and reproductive performance also are highly age dependent. The minimum age for successful breeding in boars is 7 1/2 months. Gilts should be bred on the second or third heat to take advantage of the expectd increase in ovulation rate that usually occurs following puberty.