REPRODUCTION PIH-64
PURDUE UNIVERSITY. COOPERATIVE EXTENSION SERVICE.
WEST LAFAYETTE, INDIANA
Artificial Insemination in Swine
Authors
John R. Diehl, Clemson University
Billy N. Day, University of Missouri
Emmett J. Stevermer, Iowa State
University
Reviewers
Harold H. Hodson, Jr., Cambridge, Iowa
James W. Knight, Virginia Polytechnic
Institute and State University
Don Levis, University of Nebraska
Pam Miller, Chokio, Minnesota
Vernon Pursel, USDA-ARS, Beltsville,
Maryland
The techniques and equipment necessary for artificial
insemination (AI) in swine are readily available. When consider-
ing whether or not to use AI, the following advantages are
noteworthy.
AI allows more extensive use of older boars on lighter
weight females, and decreases the number of boars and time
required for breeding when heat is synchronized. It promotes
development of a closed herd where no animals are brought into an
existing herd. This makes it possible for any size operation to
maintain a more effective disease control program and to bring
new genetic material into the herd with minimum risk of introduc-
ing new disease organisms.
When sows are placed in gestation crates after first ser-
vice, AI removes the necessity of taking the sow out of the crate
for a second insemination 12-13 hr. later. Experienced herdsmen
may not have to remove her for the first breeding or heat check-
ing, depending on their system.
One drawback with the use of AI is that a higher level of
management is required. However, several benefits result from the
greater input of managerial skills. For instance, with better
records, a greater awareness of the true reproductive status of
the breeding herd will result in more effective selection of
breeding stock.
Only healthy disease-free boars should be used as semen
donors. Minimum standards of health and sanitation for those
interested in merchandising semen have been published by the
Livestock Conservation Institute, 239 Livestock Exchange Build-
ing, South St. Paul, MN 55075. Anyone using AI should be
thoroughly familiar with these guidelines in order to evaluate
the health status of semen donors regardless of source, i.e.,
farm or boar stud.
Heat Detection
The most critical factor in achieving maximum conception
rates with AI is to inseminate females at exactly the right time.
To accomplish this, the breeder must practice proper heat detec-
tion. The normal estrous or heat cycle of the pig is 20-22 days
in length, but it can range from 18-25 days. The estrous cycle
can be divided into segmentsthe period of receptivity to the male
(standing heat or estrus), lasting from a few hours to several
days, and the nonreceptive period. The average length of estrus
is 1-2 days for gilts and 2-3 days for sows. If the length of
estrus is longer or shorter, the chances of picking the right
time to inseminate a female are lower.
Estrus detection is a simple technique. The difficulty is in
being sure that detection is carried out correctly. When the
female is in heat, she often will try to find the boar herself.
There may or may not be evidence of swelling of the vulva. In the
presence of a male, the female will assume the mating stance;
that is, she stands solidly when pressure is applied on her back.
The final sign of standing heat is the ``ear popping response,''
where the female's ears will repeatedly move toward an erect
position as she assumes the mating stance. Determining the
correct time to breed is based on the time the female first shows
heat. Therefore, the more frequently heat detection is done, the
more likely it is that insemination will be carried out at the
appropriate time.
The best method of heat detection is to check each female in
the presence of a boar by applying pressure to her back (try to
sit on her back) to see if she will assume the mating stance as
described (Fig. 1). Unless these criteria are met, the time of
ovulation cannot be estimated accurately. Using a boar in combi-
nation with hand pressure is the most accurate method of finding
females in heat. Researchers have shown that the presence of a
boar increases the chance of detecting all females truly in heat
by 30 to 40%.
If you must use a boar to check for heat, how does he fit
into the AI program? First, the heat check boar can be raised on
the farm. As the heat checker, he should be vasectomized. Second,
by using AI, fewer, but genetically superior, boars can be used
to breed many more females than with natural service. Currently,
researchers feel 3-4 billion live sperm per insemination are
required to insure good fertility. The average boar produces
enough sperm to impregnate approximately 1,200-2,000 females a
year. In a normal pen breeding system, a boar rarely breeds more
than 100-200 females per year.
Boar Training and Semen Collection
Training a boar for collection of semen can be the most
frustrating part of AI unless extreme patience is used in han-
dling the boar; but with this patience, semen collection can be
easy. Boars can be trained to mount a dummy sow or a sow in heat.
The dummy sow is preferable since there is no size incompatabil-
ity, nor is there a problem with a sow that won't stand still
long enough for ejaculation to be completed. A simple plan for a
boar collection dummy is shown in Figure 2. It is usually easier
to train a young boar that has had no sexual contact with females
than to train an older, experienced boar. Some boars probably
can never be trained, although these are infrequent. These are
likely to be the ``shy breeder'' type.
As soon as a young boar starts to rant, or at approximately
7-8 months of age, he can be brought into contact with the dummy
sow to start training. Don't expect a boar to mount the dummy at
first contact. Patience is very important. Handle the boar with
care so that he will get acquainted with the collector and the
dummy. Be sure the dummy is placed where there is adequate room
to move around and where the floor is not slick. The dummy should
be securely anchored so it can't be turned over.
If no mounts occur the first time or two, sprinkle semen,
boar urine, or fluid from the sheath of a strange boar on the
ends of the dummy. Urine from a sow in heat is much less effec-
tive than the odor of a strange boar. If there are still no
attempts to mount, try bringing several females in heat into the
same area as the dummy, and allow the boar to mount a female in
estrus several times. If there are further failures to mount, try
collecting semen from the boar by placing a sow in heat close to
the dummy; later, try collecting the semen using the dummy alone.
An alternative method is to start collecting from the boar using
a female in heat adjacent to the dummy, lifting the boar over to
the dummy after he has stopped thrusting. If all attempts to use
a dummy fail, then you may be restricted to using a sow in heat
for each collection.
The stimulus for ejaculation in the boar is pressure applied
to the spiral portion of the penis (Fig. 3). Once the boar
mounts, allow him to start thrusting, then quietly ease down
beside him from his rear and grasp the penis firmly enough to
retain a grip, using your bare or gloved (rubber) hand. At the
same time, begin pulling the penis (gently) from the sheath, and
rapidly increase the pressure and pulling action until thrusting
stops. Prior to collection, it would be helpful to clip the long
sheath hair to aid in gaining a grip. Some boars require what
seems to be tremendous pressure to stimulate ejaculation; others
require only slight pressure.
Occasionally a boar will start backing off or sliding off
the dummy or even a sow when your hand touches his penis. To help
prevent or correct this problem, one of the following may be
helpful. If you're collecting from a dummy (Fig. 2), try attach-
ing a piece of pipe or a board, 2 in. x 4 in., to the bottom side
of the dummy perpendicular to the length at about the halfway
point. This will give the boar something to hook his front legs
around. Normally an artificial vagina is of no value, but in the
case of the shy-breeder type boar, it may facilitate obtaining a
collection impossible to get otherwise. Fill the outer jacket of
the device with 100o F. water, and lubricate the open end. Guide
the boar's penis into the open end, and wait for ejaculation to
take place. Finally, a combination of artificial vagina and hand
pressure may be used.
There are several phases to ejaculation. The first portion
may consist of clear fluid and some gel-like substance. There are
no sperm in this portion so it need not be collected. Then the
sperm-rich fraction starts (creamy white), followed by more gel
and clear fluid. Some gel will be noticed along with the sperm-
rich fraction. There will be several alternating phases of
sperm-rich and sperm-free fluid; the sperm-free phases do not
necessarily need to be collected. The time for ejaculation can be
as short as a minute but may be as long as five minutes. The
average volume will vary with each boar, but approximately 50-500
cc. ( 1/3 - 1/2 pt.) can be expected (see Table 1). Volume
varies with breed, age, and collection frequency.
__________________________________________
|Table 1. Semen characteris- |
|tics and sperm output of |
|boars. |
| |
|_______________________________________ |
|Number of semen |
|collections per week 1-5 |
|Volume (ml.) 50-500* |
|Sperm concentration 150-750 |
|(million/ml.) |
|Total sperm/ejac. (billion) 20-120 |
|Total sperm/week (billion) 80-200 |
|Motile sperm (%) 80 |
|Morphologically normal sperm (%) 80 |
|_______________________________________ |
|* Gel-free volume |
|________________________________________|
Semen Evaluation
Figure 4 shows the equipment necessary for collecting semen.
A wide-mouthed thermos bottle or a plastic (pint size) bottle
with a narrow mouth can be used. If the thermos is used, place a
couple of layers of cheesecloth over the mouth to strain out gel
and prevent dirt from falling into the semen (Fig. 3). To ease
cleaning, a plastic bag may also be used as a liner in the ther-
mos. The plastic bottle should be covered with 1 in. of foam
rubber for insulation against cold shock.
During and following collection, protect the semen from a
rapid change in temperature. The insulation from the thermos or
the foam is sufficient protection to prevent sperm damage for
5-10 min. at 20o F. In a warm room (60-70o F.), strain the gel from
the semen (through a couple of layers of cheesecloth) if not
strained during collection. Note the volume of semen, since this
will dictate how much extender you will need to add, depending on
the number of females to be bred and whether or not semen will be
stored. Throughout the collection and insemination process, care
should be taken to be sanitary.
Normally semen will have a chalky, creamy appearance. This
shows that sperm concentration is high. As concentration gets
lower, the opaqueness diminishes. A microscope is not essential
to make an AI program work, but it is useful to verify concentra-
tion and motility as well as to check for abnormal sperm. An
expensive microscope is not essential, but one that has two or
three power settings ranging from 30 up to 1000X would be needed.
Accurate sperm counting would require additional equipment. A
hemacytometer can be used to accurately evaluate concentration of
spermatozoa. This is a critical factor only when extending semen
to ratios that would reduce concentration below three billion
live sperm per insemination. For details on using this or other
equipment properly, contact your state Extension service.
Visual observation of sperm is not a sure indicator of fer-
tility. The only way to be certain is to test-mate prior to the
breeding season. The test-mating does not, however, insure that
the boar will remain fertile for the entire season.
Frequency of collection depends on the need for sperm.
Ideally, a boar should be collected no more than two or three
times a week to maximize sperm concentration and semen volume.
When the need arises, collection once or twice a day can be main-
tained for 3-5 days; however, volume, sperm numbers, and sex
drive diminish rapidly. This does vary to some extent with the
individual boar.
The average ejaculate contains enough sperm to inseminate at
least 6-8 females. The best rule to follow is to use the sperm as
soon as possible after collection. Two factors are considered in
insemination: Number of sperm and volume of fluid. It has been
shown that a minimum of 2 billion live sperm in an adequate
volume of fluid are required to obtain adequate conception rates.
Since some sperm will be dead, more than 2 billion are needed.
Researchers have shown that 50 cc. fluid volume is close to the
minimum, and it is recommended that 100 cc. total volume be
inseminated to maximize conception rates.
How much an ejaculate must be extended depends on the volume
of the ejaculate collected, the number of females to be insem-
inated, and whether or not short-term storage will be used. If
five females are to be inseminated with fresh semen, a total
volume of 500 cc. of extended semen is needed. If the ejaculate
contains 100 cc., then 400 cc. of extender is required to obtain
the required 500 cc. for five females. If some semen is to be
stored for future use, then a higher rate of extension would be
used, and microscopic verification of sperm concentration may be
advisable. However, AI should be a routine procedure in herd
management before short-time storing of semen is considered.
Storage for more than two days is not advisable in most
instances. Until ``longlife'' extenders (greater than 3 days
storage time) are proven effective by unbiased investigators,
producers would be well advised to be cautious regarding their
use.
Before extending the semen, measure the temperature of the
ejaculate with a thermometer, and raise or lower the temperature
of the extender to within 2 degrees of the semen. Gently but
thoroughly mix the two. If extension rates greater than 1:5 are
used, it is good practice to add only half of the extender at a
time. The extended semen is now ready for insemination or
storage. For storage, allow the mixture to cool to room tempera-
ture, 70-75o F. Place the container of semen in a small styrofoam
box or in a pan of water (same temperature as the semen), and put
both in a refrigerator, or Koolatron, to maintain a temperature
of 60-65o F. (15-18o C.). Since temperature varies greatly among
refrigerators, check ahead of time to be sure the appropriate
temperature can be maintained. These precautions are necessary to
prevent the mixture from cooling too rapidly, thus causing damage
to the sperm. Higher temperatures (65-70o F.) may be used if there
is no bacterial contamination, which is not likely with on-farm
collection.
Usually, semen can be extended at a ratio of 1 part strained
semen to 3 parts extender without any problem. Higher rates of
extension are not likely to result in a decrease in conception
unless a ratio of 1:10 or greater is used. Then it is advisable
to get an estimate of actual sperm concentration so at least 3-4
billion sperm are inseminated. To maximize litter size and con-
ception rate, investigators have shown that the use of two or
more ejaculates pooled from different boars can be advantageous.
Two formulas for semen extender are presented in Table 2.
These extenders, available commercially, can be stored in dry
form until needed. Both extenders can be stored frozen. Freezing
into cubes or in plastic 125 cc (4 oz.) bottles is a good storage
method that is convenient to use.
Skim milk may be used as a semen extender if the following
steps are taken prior to mixing with semen: (1) Heat in a double
boiler to a temperature of 88-90o C. (190-195o F.) for 8-10 min. Be
careful not to scorch the milk. (2) After cooling to room tem-
perature, break one egg and add the egg yolk only (minus the mem-
brane) to 1 qt. of milk. Carefully mix for about 2 min; so as not
to raise a froth. (3) Equalize (within 2o C.) the temperature of
the milk with that of the semen. (4) Add the extender to the
semen by slowly pouring the milk down the side of the container.
Semen extended with skim milk should be used immediately. Addi-
tional information regarding extenders, as well as other informa-
tion, can be obtained with the aid of your state swine Extension
specialist or boar stud technician.
Table 2. Extenders for use with liquid boar
semen.
___________________________________________________________
BTS* Kiev
____________________________
Component 1 quart1 liter1 quart1 liter
___________________________________________________________
Distilled water (cc.) ** ** ** **
Glucose (gm.) 39.1 37.0 63.4 60.0
Potassium chloride (gm.) 0.79 0.75
Sodium bicarbonate (gm.) 1.32 1.25 1.27 1.2
Sodium citrate (gm.) 6.3 6.0 3.96 3.7
EDTA (gm.) 1.32 1.25 3.91 3.7
Penicillin (million Int. Units) 1.1 1.0 1.1 1.0
Dihydrostreptomycin (gm.) 1.1 1.0 1.1 1.0
___________________________________________________________
*Beltsville Thawing Solution.
**Put ingredients in a clean beaker and fill to the
appropriate line with distilled water.
Insemination
Based on frequency of heat detection, Table 3 presents a
``rule of thumb'' to determine the appropriate insemination time
for sows and gilts using fresh semen. It is recommended that
insemination be done at least twice during estrus (Table 3). How-
ever, at this time there is conflicting evidence regarding the
value of inseminating more than once during estrus using frozen
semen. At this time frozen semen is not equal to freshly col-
lected semen. On the average, conception rates will be 10-20%
lower, and litter size is likely to be about one to three less
pigs per litter. Apparently the freezing and thawing process
alters the sperm in such a way as to make them more fragile.
Because they are more fragile, the sperm must receive special
handling as outlined in the thawing procedures received with the
semen shipment. When using frozen semen, twice daily heat detec-
tion should be the rule, and insemination should be delayed until
30-35 hr. after the onset of estrus. Ovulation occurs about
37-45 hr. after the onset of heat.
________________________________________
|Table 3. Optimum time to |
|inseminate females in heat |
|using fresh semen. |
| |
|_____________________________________ |
|Frequency of Best time to inseminate |
|heat detectionafter the onset of heat |
|_____________________________________ |
|Once daily Every day they stand |
|Twice daily 12 and 24 hr. after the |
| onset of heat* |
|_____________________________________ |
| |
|*Breed at 48 hr. if in heat 3 |
|days. If in heat longer than 3 |
|days, discontinue insemina- |
|______________________________________|
After having estrus females penned conveniently, take a
breeding catheter, and apply light mineral oil, vegetable oil, or
KY jelly to the catheter for lubrication. Both the rubber
spirette or the plastic type catheters will work; however, there
are advantages and disadvantages to both. Many producers prefer
the spirette because it is shaped much like a boar's penis, and
the female's reproductive tract grips the spiral end just as it
would during natural mating. This helps minimize backflow of
semen and also is a fair indicator of estrus. In addition, the
spirette is flexible, and there is very little chance of injury
to the female. The disadvantage is that it must be cleaned
promptly after use. A modified spirette is commercially avail-
able, which combines the best of the rubber spirette and bovine
catheter, being disposable yet retaining the spiral tip.
In contrast to the spirette, the diameter of the plastic
bovine or bent-tip type of catheter is small enough that the
female tract cannot grip it. Consequently, there is a greater
chance for backflow to occur. Usually backflow is not a serious
problem unless sperm numbers are expected to be at the minimum
requirement, such as with frozen semen. With hard plastic
catheters, there is a greater risk of injury to the female. Also,
if the female is nervous or jumpy, the bovine catheter will slide
in and out with every move, unlike the spirette type which is
gripped tightly, flexes and bends, and usually doesn't fall out,
even if the sow jumps away from the inseminator. Unless used in
a purebred herd or unless a known disease condition is present in
the herd, the same catheter can be used for several females. When
a positive record of ancestry is required or herd health status
is uncertain, use a clean catheter for each female.
Seldom do females need more restraint than being confined to
a small pen. Tight restraint or snaring should be avoided. Some-
times having a boar close by will help a nervous female to stand
more solidly for insemination. Putting out a small quantity of
feed can also be helpful.
For insemination, put about 100 cc. extended semen in a
squeeze bottle (4 oz. size) with a cone-shaped tip (see Fig. 4).
A large syringe can be used but is more difficult to handle. Dur-
ing cold weather, put the bottle of semen in a protected area,
such as a styrofoam box or your shirt pocket, until ready to
inseminate the female.
Place a few drops of lubricant on the tip of the rubber
spirette (not needed for the bovine type), and insert the tip
into the vulva, pointing it toward the backbone to avoid the
opening of the urethra. Slide the catheter along the top of the
vagina until rather firm resistance is felt. The cervix is usu-
ally 8-10 in. (16-25 cm.) inside the vulva but could be deeper in
larger females. In some gilts, resistance may be encountered
about 4 in. (10 cm.) inside the vulva. This may be the remains
of a nonfunctional membrane (hymen). When the cervix is detected,
start rotating the spirette counterclockwise (left-hand thread)
until it becomes ``locked'' into the cervix. The opening into the
cervix is nearly impossible to miss as it has the shape of a fun-
nel. Occasionally, a female will not clamp down on the spirette.
This occurs mostly in sows or if the female is not in heat.
Insert the bovine catheter until the tip is deep into the cervix,
being careful not to penetrate into the uterus where injury could
result.
When the catheter is in place, connect the semen container,
and begin squeezing the semen through the catheter. If semen
starts running out of the vulva (backflow), release the pressure,
wait momentarily, and start again. Allowing the female to move
around often helps minimize backflow. There are times when it
seems nearly impossible to force the semen into the femalethe
opening of the catheter may be jammed against some tissue. Work
the catheter around and continue. Check the opening of the
squeeze bottle; it should be about 1/32 in. in diameter.
Cleaning AI Equipment
Following use, do not allow semen or other material to dry
in the equipment. Use plenty of clean water for rinsing. Do not
use soap or detergents to clean anything that will come in con-
tact with semen since there are likely to be residues harmful to
sperm. Clean thoroughly with a brush and tap water to remove any
gel particles left. Rinse all pieces in distilled or deionized
water; then boil in distilled or deionized water for 20 min. Do
not boil in tap water as this will leave a mineral deposit on the
equipment. If you are not able to boil the equipment, a temporary
sterilizing method is to rinse thoroughly with 70% alcohol. How-
ever, do not depend on the alcohol for continued use since some
organisms are immune to its effects. Use of disposable equipment
is encouraged to minimize the chances of a breakdown in sanita-
tion, i.e., catheters, insemination bottles, and plastic bags in
the collection thermos and styrofoam thaw box.
Commercial Semen
Frozen semen is available, as is liquid semen, in the United
States and Canada. However, before obtaining semen from Canada,
be sure the shipment is cleared with customs and with the Animal
and Plant Health Inspection Service (APHIS). Check the records
accumulated for each sperm-donating boar being considered. Your
choice is just as important as if you were buying him for a per-
manent replacement. Evaluate the usual data regarding boar per-
formance, but more importantly, evaluate data on his conception
rates, litter size, and his progeny's performance whenever avail-
able. Remember, the sperm of some boars do not survive well dur-
ing the freezing and thawing process; therefore, it is important
to check the performance record of the boar before using him.
Records
A certain amount of record keeping is advisable. Records of
female identification and the dates in standing heat are valuable
in scheduling breeding and in determining the volume of semen
required at the next breeding period. In addition, through
records, irregular cycle lengths, anestrus, and other reproduc-
tive problems will become more evident, allowing corrective meas-
ures to be taken. A record including date of semen collection and
strained volume should be maintained for each boar. These records
may also include notes of the type and duration of any sickness
the boar may experience. Anything that causes body temperatures
to go up as little as 1-2o F. can result in a 60-80% decrease in
total number of viable sperm for several weeks. The normal body
temperature is approximately 102o F.plus or minus 1 degree F.
Summary
To introduce new genetic material into your herd at a
minimum risk of disease and to increase the use of a particular
sire, the pork producer should consider an AI program. Providing
a viable possibility for herd improvement, an AI program will
require greater managerial input but will result in greater
awareness of any reproductive problems in the herd. A minimum of
specialized equipment is needed to carry out a successful pro-
gram. One of the best uses of AI is in bringing new genetics into
the herd using commercial semen and semen collected on the farm
for expanded use of fewer but superior boars. If a few simple
suggestions are followed, AI will yield conception rates and
litter size equal to or better than natural service using fresh
semen. Use of frozen semen is likely to yield less favorable
results. AI training courses are available through many state
Extension service shortcourses and boar studs. Supplies are
becoming more widely distributed by boar studs and other sup-
pliers. Be certain to follow directions for use of equipment and
extenders as closely as possible to maximize pregnancy rates.
Don't be afraid to ask questions no matter how insignificant.
________________________________
Reference to products in this publication is not intended to
be an endorsement to the exclusion of others which may be simi-
lar. Persons using such products assume responsibility for their
use in accordance with current directions of the manufacturer.
REV 10/84(5M)
Figure 1. Method of detecting estrus in females. Note the erect ears and rigid
stance with pressure applied to the back in the presence of the boar.
Figure 2. Boar collection dummy.
Figure 3. The stimulus for ejaculation in the boar is pressure applied to the
spiral portion of the penis.
Figure 4. Equipment used in Al.
______________________________________________
Cooperative Extension Work in Agriculture and Home Economics,
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