|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
- 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.
- 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.
- 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
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
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:
- 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.
- 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.
- 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.
- 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.
- 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
- 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