8 Artificial insemination

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                                  Artificial insemination

     Artificial Insemination (AI) was first performed in the 1800s, but widespread commercial use did not occur
     until the 1950s, following the discovery of techniques to successfully freeze cattle semen. It is considered
     the most important technique devised for genetic improvement in cattle, since a few highly selected
     males produce enough sperm to inseminate thousands of females per year. In comparison, only relatively
     few progeny per selected female can be produced per year, even by Embryo Transfer (ET).
         Artificial insemination is widely used in the dairy industry. Its use is limited in the beef industry to
     beef studs because of cost.

     Feeding is very important. Cows in good body condition at calving come on heat and get in calf more
     quickly than cows in light condition. Table 8.1 shows the relationship between condition and conception

                        How condition at first calving affects time to first heat
                       Condition score at calving         Time from calving to first heat (days)
                                   3                                      46
                                   4                                      40
                                   5                                      34
                                   6                                      28
                     It should be emphasised that over-fat cows will often have difficulty calving.
               If a cow is provided with increased rations after calving she will begin to cycle sooner.
                           Cows in better condition at joining have higher conception rates.
                          Condition at joining                         Conception rate
                                  3.0                                       50%
                                  3.5                                       56%
                                  4.2                                       61%
          Cows gaining weight during joining have higher conception rates than cows losing weight.

                             Table 8.1: Relationship between condition and conception rate.

     Heat detection
     Once the herd is cycling well, the next task is to detect cows on heat. During mating, many farmers
     spend time between milkings checking for heat behaviour in their cows. Many have found that half an
     hour spent checking the herd two hours after milking results in more cows detected on heat than when
     the herd is only seen in the laneways and the shed.
        Accurate heat detection is necessary to maintain a 12-month calving interval, where at least 90% of
     cows should show standing heat within 60 days after parturition (i.e. 60 days after calving).
        Successful heat detection involves looking for one or more of the following signs at least twice a day:

32                                                                                            Cattle Breeding Technologies
•   Stand to be mounted by other cows
•   Have a swollen vulva and clear mucus on the tail
•   Have signs of being mounted including ruffled tail hair, mud on flanks and slobber on the back
•   Show unusual behaviour such as holding milk, bellowing, fence prowling, frequent urination,
    aggressiveness, restlessness and licking, sniffing and rubbing against other cows.
    There are several methods to aid farmers to detect a high percentage of true heats, including:
• Heat mount detectors which are pressure-sensitive and change colour when the cow stands for
• Tail paint applied as a strip going about 10 centimetres forward from the highest area of the tail.
    Cows being mounted have the paint strip rubbed or broken. This is a cheap method adopted by
    many farmers.
• Both hormonally treated steers and ‘marker’ bulls can be harnessed with a chin ball harness which
    leaves a dye mark on cows that they mount.
• Records of dates and services can be used to calculate the date of the next expected heat.
    Figure 8.1 shows the behavioural signs that can be used to detect cows in heat and the best time to
artificially inseminate.

       Coming into heat                      Standing Heat                              After Heat                      Life of Egg

       Increased activity         Signs of coming into heat                       Will not stand                      Mucus discharge continues
                                  Stand to be ridden                              Mucus discharge                     Vulva remains swollen
                                  Vulva swollen                                    thicker and cloudy                  and reddened
                                  Mucus discharge clear and thin                  Restless
                                  Attempts to ride others                         Sniffs other cows
                                  May bawl and withhold milk
                                                                                                                      Ovulation                     Bleeding

      1                           2                                      3                                   4                                             5
–10       –8   –6   –4   –2   0       2     4    6     8     10     12       14   16   18   20    22    24       26    28   30    –2     –4    –6     –8       –10 –12
                                          Insemination is best carried out within this 24 hour period

    1. Too early to breed.    2. Earliest breeding time.          3. Best breeding time.             4. Latest breeding time.          5. Bleeding may appear
                                 Note that latest breeding           Note this begins after the                                           24–48 hours after end
                                 time is still 30 hours              start of standing heat and                                           of standing heat and
                                 away.                               continues after cow no                                               indicates only that the
                                                                     longer stands.                                                       cow has been in heat.

                                             Figure 8.1: Heat detection and time of AI in cows.

Inseminate every cow on heat
The longer the time interval from calving until insemination, the higher the cow’s chance of becoming
   In seasonal calving herds, once mating has commenced every cow on heat should be joined regardless
of how long she has calved. For example, a cow calved for twenty-eight days may only have a 27 per
cent chance of becoming pregnant. This is better than a zero chance if she has not joined at all.

When to inseminate a cow
Best conception rates are achieved in cows inseminated 2–26 hours after first being observed on heat.
The ideal time to inseminate is 12 hours after the onset of heat.

Practical aspects of reproductive technologies for cattle breeding                                                                                                       33
        The average cow is on heat for 18 hours and releases the egg from the ovary about 12 hours after the
     end of heat. The egg must be fertilised within ten hours of ovulation, otherwise it dies. Sperm must
     spend several hours in the reproductive tract of the female before they are capable of fertilising the egg.
     During this time, the sperm undergo chemical changes, called capacitation.
        When the sperm are deposited either at the cervix by the bull or into the uterus by AI they are
     rapidly transported up to the oviducts (fallopian tubes), arriving there in three to four minutes. Transport
     of the sperm is achieved by wave-like contractions of the uterus, caused in part by the hormones
     prostaglandin and oxytocin. Rough handling of the cow and stress can cause the release of adrenalin, which
     stops these contractions occurring and may result in a lower conception rate.

     Twice-a-day insemination
     Some inseminators prefer to inseminate herds twice daily, thus reducing the number of cows requiring
     insemination at one time.
        They do this by timing insemination as follows:
     • Cows first seen on heat during the day or at the evening milking are inseminated the next morning.
     • Cows first seen on heat during the night or at the morning milking are inseminated in the evening.

     Once-a-day insemination
     Some inseminators prefer to inseminate all cows at one time during the day.
         Cows on heat in the last 24 hours are all inseminated at the one time. Inseminations should be done
     at a similar time each day. Cows on a rising energy plane will give significantly higher conception rates.

     Heat synchronisation
     Synchronisation of heat is used to reduce the time and costs involved in heat detection. It involves
     getting cows and heifers in heat so that they can be inseminated at the same time. However it requires
     the use of drugs, veterinary supervision and sometimes increased semen usage.
         Two different drugs are used to synchronise heat, prostaglandin and progesterone. Use of any of the
     following systems should only be done after consultation with a veterinarian or artificial breeding expert.

     1. Prostaglandin (e.g. Estrumate®, Lutalyse®)
     The hormone prostaglandin is produced by the non-pregnant uterus and destroys the corpus luteum on
     the ovary. It therefore induces heat.
        In heat synchronisation programs prostaglandin is injected. It does not work on cows in the first five
     days of the oestrous cycle and will cause abortion when administered to cows during the first 3–4
     months of pregnancy. Prostaglandin can be either administered as a single injection or as two injections.

     One injection technique
     The most common procedure is firstly to detect heat and inseminate for 5 days, then inject all the
     remaining cows with prostaglandin followed by a further 5 days of insemination at observed heat. This
     procedure involves more work, uses less prostaglandin and usually gives good fertility. It concentrates
     mating into a 10-day period.

     Two injection technique
     Two injections are given eleven days apart. Provided the cows are cycling and on good nutrition, most
     will respond to the second injection and will come into heat two to five days later.
        Cows are inseminated on observed heat. This procedure is commonly used in beef herds.

     2. Progesterone
     The hormone progesterone is produced by the corpus luteum and is responsible for the establishment
     and maintenance of pregnancy.
         In heat synchronisation programs, progesterone can be applied either as a vaginal implant (Controlled
     Intravaginal Drug Releaser (CIDR® – pronounced ‘cedar’)) or as an ear implant (Crestar®). Progesterone
     implants delay the onset of heat by acting as a substitute corpus luteum until removed. They have
     advantages over prostaglandins in that they will not cause abortion when used on the pregnant animal

34                                                                                       Cattle Breeding Technologies
and are still effective if used on cows that have just come onto heat. They may also be beneficial in
those cows which have not yet started to cycle.

Vaginal implants (e.g. CIDR®)
The CIDR® consists of a plastic core, coated with a layer of progesterone impregnated plastic, and
which is inserted into the vagina. The progesterone is absorbed through the wall of the vagina. Other
hormones may be administered either at the time of insertion (oestrogen) or removal (prostaglandin) to
improve synchrony.
   The CIDR® may be left in from 7–12 days, depending on what system is followed, and is removed by
pulling on an exposed piece of string. The animal usually comes into heat about two days later.
   Inseminations can be carried out at observed heat. Alternatively, a single blanket insemination of all
animals may be done 56 hours after removal, or two blanket inseminations at 51 and 75 hours. Blanket
inseminations may not give as good a result as inseminations following observed heat.

Ear Implants (e.g. Crestar®, Synchromate B®)
These work on the same principle as the vaginal implants.
   Injections are given at the time of implantation or at removal 9–10 days later. The timing of
insemination is similar to that with vaginal implants. A good cattle crush is required for this technique
since the implants must be injected into the ear.

3. Combination of Progesterone and Prostaglandin
This method involves using a progesterone device (CIDR® or Crestar®) for 7–11 days, with a prostaglandin
injection 1–4 days before the progesterone device is removed.
    This method is slightly more expensive but cost-effective in ET programs, e.g. where a high percentage
of treated animals have a heat on the one day, 48 hours after the progesterone device is removed.

Using AI in heifers
The cervix of the heifer is much smaller than the cow, therefore insemination may be more difficult.
The semen used should take into account ease of calving. In dairy heifers, semen from Jersey bulls is
commonly used, resulting in smaller calves and an easier birth.
   Heat detection in heifers is sometimes difficult. Synchronisation programs can be used to reduce the
time spent observing, yarding and inseminating heifers.
   Heifers generally take ten days longer to cycle after calving. If they calve late at their first calving
they are often late calvers at their second and subsequent calvings.

Factors affecting conception rates
Conception rate is simply the percentage of cows that have become pregnant to AI (or to natural service).
Semen handling and insemination techniques have a major effect on conception rate. Due to lack of
experience and lack of ‘feel’ inside cows, first year inseminators may have up to 10 per cent lower
conception rates than experienced inseminators. Low conception rates can also occur when experienced
inseminators use faulty insemination techniques.
   Again, nutrition is a critical factor affecting conception rates.

Semen handling
Straws containing frozen semen should be thawed in warm water (32°C to 37°C) for at least 30 seconds
to ensure that the semen reaches the temperature of the warm water.
    Exposing the semen to sunlight, dust, water, chemicals, sudden temperature change or rough handling
may reduce conception rates.

Insemination technique
Rapid gun withdrawal may allow the semen to flow back into the vagina. Passing the gun too far
forward or excessive movement of the gun in the uterus may damage the fragile lining of the uterus.
Poor hygiene resulting in contamination of the gun may introduce infection into the uterus.

Practical aspects of reproductive technologies for cattle breeding                                            35
     Semen placement
     Semen is often placed too deep (up one uterine horn) or not deep enough (in the vagina).
        Correct placement is two-thirds of the semen dose just through the cervix into the body of the
     uterus and the remaining one-third about 1 to 2 centimetres back from that point into the cervix.

     Splitting straws
     This is a very questionable practice, as semen producers put a lot of effort into optimising the semen
     diluent and the sperm numbers to suit each particular bull. There is also a risk of transferring bacteria
     and virus particles (e.g. EBL virus).

     Discharges and infections of the uterus
     Cows with infections of the uterus are very unlikely to conceive. Cows that have had a difficult calving,
     an induced calving, retained afterbirth or are discharging, can be held back and checked by a veterinarian
     3–4 weeks after they have calved, or at least 2 weeks before joining commences.

     Errors in heat detection
     Errors in heat detection include inseminating cows not on heat, inseminating the wrong cow, or
     inseminating too early or too late. These will seriously affect conception rates.

     Trace elements and minerals
     In some areas, trace elements and minerals can affect conception rates. Your veterinarian can advise you
     on the situation in your district.

                                     Artificial insemination conception chart
        Based on a cow receiving an average 12–15 million live sperm at time of insemination (natural mating 5–6
           thousand million), this chart shows factors that can make the difference between success and failure
                                                 with an AI programme.

         Million sperm                                                                                                  Acceptable
         per insemination                                                                                               conception

         12–15                                                                                                             70%
                                                                               Prolonged exposure and reimmersion
             11                                                                of semen into liquid nitrogen
             10                                                            Careless handling of semen
                                                                           (warm hands, tongs, gun)
               9                                                      Incorrect thawing temperature

               8                                               Contamination – dust, dung, water, alkali

               7                                          Faulty gun loading – cutting, sealing

               6                                      Incorrect semen placement

               5                                Speed in placement (deposition, withdrawal)

               4                           Hygiene – cow, equipment

               3                       Cow handling                                                                      17–19%

                                  Remember semen is fragile and highly perishable
                   Carelessness on one point may have little effect: carelessness on a number of points shown
                        could seriously lower results. Attention to detail with AI is the key to success.

                                       Figure 8.2: Artificial insemination conception chart

36                                                                                                         Cattle Breeding Technologies
Advantages and disadvantages of AI
Relatively inexpensive
Increased production               Increased production is the main reason for using AI on dairy cattle. AI-bred
                                   dairy cattle produce about 10–16 kg more fat and protein per lactation than
                                   their naturally-bred herd mates.
Disease control                    By using AI and licensed semen, venereal diseases (i.e. diseases usually spread
                                   by the bull during mating) can be eliminated from a herd.
Sire availability                  The wide choice of bulls within each breed allows flexible breeding programs
                                   and greatly facilitates crossbreeding.
Safety                             AI allows the elimination of dangerous bulls on the farm.
Better records                     AI requires good records which will aid better management of the herd.

Careless bull selection, semen processing, storage and careless use of semen, may result in damage to
the health and general production level of the herd.
   A dirty or careless inseminator may spread disease. Deep uterine insemination of a pregnant cow
may result in abortion. There may be some inconvenience in holding cows for service.

Semen collection and evaluation
At Genetics Australia, semen is collected from bulls from Monday to Friday, every week of the year.
Each bull is on a weekly roster depending on demand for his semen. Bulls can be used for collection of
semen generally by 12 months of age. Similar procedures are used at most bull collection centres.

Health testing
Bulls must undergo a series of health tests before semen can be collected from them. They must be free
from obvious physical defects such as undershot jaws and leg and feet problems. They must also be free
from the following diseases:
• Enzootic Bovine Leucosis (EBL)                       • Infectious Bovine Rhinotracheitis (IBR)
• Tuberculosis (TB)                                    • Brucellosis
• Johne’s Disease (JD)                                 • Trichomoniasis
• Leptospirosis (Lepto)                                • Ephemeral Fever
• Bovine Viral Diarrhoea (BVD)                         • Q Fever
• Campylobacteriosis                                   • Blue tongue
   Once they enter Genetics Australia, all bulls must be retested annually to ensure they remain disease-free.

Semen collection                                                                                  Artificial
Semen is collected using an                                                                       Vagina
artificial vagina (see Figure 8.3).
                                                              External view      0 50 100
                                                                                                      Semen collecting tube
    Live females, steers and                                                    Scale – mm

occasionally other bulls are used                                                Valve
as teaser animals.                               Rubber retaining band
    Two ejaculates are normally
taken from each bull on each
collection day. An average
volume of ejaculate is 4 ml,                    Lubricant                         Air                          Rubber funnel
which may contain anything
                                                                                               Warm water
from 500 to 2,000 million sperm                                                  Soft rubber   (approx 42°C)
per millilitre.                                               Radiator Hose      inner liner
    Once semen is inside the                                  Length: 30-40cm
laboratory, a small sample is                                 Diameter: 7cm
                                                                                               Figure 8.3: Artificial vagina

Practical aspects of reproductive technologies for cattle breeding                                                             37
     taken and diluted for analysis. The sample is placed in the precision analysis chamber of a computerised
     semen analyser. A series of images captured by the analyser assess sperm motion and concentration.
        Images are transferred to the computer in digitised format and separately analysed. Static and moving
     objects are distinguished, and all moving objects are identified and tracked.
        The machine calculates a semen profile covering total sperm count, concentration, motility, sperm
     swimming speed, linearity, straightness and a number of other characteristics. If there is not a high
     percentage of motile (moving) sperm or if there is a high percentage of defective sperm (eg. bent tails)
     the semen is discarded immediately.

     Semen utilisation
     Cattle semen can be processed as either deep-frozen or liquid semen (fresh):

     1. Deep-frozen semen
     Deep freezing is the most common technique for processing semen. It involves processing and freezing
     semen in liquid nitrogen at –196°C, which maintains the fertility of the semen. Stockpiles of semen
     from popular bulls can be built up and stored indefinitely. Successful inseminations have been performed
     with semen stored for over 20 years.
        The diluent used has been developed to minimise damage to the sperm cells during freezing and
     thawing. The semen diluent also maintains pH level and osmotic pressure, is a source of energy, a
     volume extender and an inhibitor of bacterial growth. The disadvantage of deep freezing is that
     30–40 per cent of the sperm are killed during the freezing and thawing processes.

     The semen to be deep frozen is diluted over five stages in either skim-milk or egg-yolk based diluent
     (extenders), with glycerol ( a chemical similar to ‘anti-freeze’) as a cryoprotectant.
        A diluent is added to the sperm to achieve a concentration of 15 to 20 million sperm per 0.25 ml (ie.
     one cow dose). The diluent contains reconstituted skim milk (extender), fructose (source of energy),
     antibiotics (to inhibit growth of bacteria) and glycerol (to protect sperm during freezing and thawing).
        The semen is then cooled to +4°C over several hours before being packaged into labelled straws,
     each containing 0.25 ml of diluted semen. The straws are sealed and placed on a freezing rack in a
     computer controlled freezing chamber.
        The straws of semen are frozen, packed into goblets and must be stored in liquid nitrogen at a
     temperature of –196°C until required for insemination. The semen can be stored at distribution points
     and by end-users around the country.
        Semen transfers between containers should be kept to a minimum – the more times it is handled, the
     greater risk of damage. Frozen semen should not be exposed to air for more than two seconds during a
     transfer. The recommended temperature for thawing frozen semen is 32°C to 37°C and any equipment
     that comes into contact with thawed semen should be kept warm to prevent cell damage. Semen starts
     thawing at –130°C.

     Quality control
     Following processing, sample straws from each batch of semen are thawed and visually appraised using
     a microscope with a specialised optical system that clearly shows living cells such as sperm cells.
         Semen is checked for motility percentages and swimming characteristics. Abnormal sperm cells and
     concentration are also assessed.
         If the semen does not meet strict minimum quality standards, the batch is discarded. The discard
     rate is approximately 10% of the semen processed.

     2. Liquid semen (also known as fresh semen)
     Liquid semen is diluted in two stages using an egg-yolk based diluent at a temperature of around +17°C.
     Less than 10% of the sperm are damaged by processing, as there is no stressful freeze and thaw cycle.
        This allows the sperm dose per insemination to be considerably reduced compared with deep-frozen
     semen, allowing for much better utilisation of the genetically superior bulls. Typically we see a two per
     cent increase in fertility with liquid semen.

38                                                                                     Cattle Breeding Technologies
   Liquid semen is packaged into labelled straws, each containing 0.25 ml of diluted semen. Straws are
stored horizontally to prevent sperm cells accumulating in one end of the straw and suffering a high
concentration of undesirable solutes. Quality control is described above.
   The disadvantage of liquid semen is that it does not last indefinitely. For best results it should be used
within three days of collection. This requires a different distribution system and does not allow any
build up of stocks.
   However, the rapid distribution of the latest genetics and the improved use of superior bulls are clear

Straw identification
Genetics Australia semen is packed in coloured straws, coded according to individual breeds.
    On each straw is printed the information required to correctly identify the individual bull (Figure 8.4).
Apart from the bull’s full name, there is a seven-character primary NASIS code, e.g. 11FFL77, which is
determined according to the following system:
• The first two numbers identify the collection centre (see Table 8.2).
• The next two letters identify the breed (see Table 8.3).
• The next letter determines the year of the birth of the bull (see Table 8.4)
• The final two numbers are specific to the individual bull.
    In addition there is also the name of the collection centre, the date the semen was collected and a
secondary NASIS code consisting of up to seven letters or numbers, e.g. SHOTIME, WINLUKE, SOONER,
77261. The secondary code is registered to ensure that it is unique for each bull. Whenever an abbreviation
is used to record a bull’s identity it is essential to use the correct code (either the primary or the secondary
NASIS code). The secondary code is used on Genetics Australia price lists and catalogues.
    If incorrect codes are used then essential breeding and production information will be lost to the
herd improvement industry.

                                                       Centre        Year of birth             Date of
                                 Bull name              code           of bull                collection

                     Strathaire Southwind Luke ET 11 FF L 77                     Gen-Aust     02-12-96     WINLUKE

   Plug                                                     Breed       Bull’s       Centre                Secondary
                                                                       number                                 code

                                   Figure 8.4: Sample straw showing identification details

   03     Livestock Breeding Services                                23     Riverina Artificial Breeders
   04     Northern Artificial Breeders                               27     Westralian AB Services
   05     Total Livestock Genetics                                   29     Riverina Artificial Breeders
   06     Tatiara AB Centre                                          35     New Zealand
   07     Hunter Bros Breeding Service                               45     England                85 Norway
   08     BSI Breeding Services                                      60     Scotland               87 Sweden
   09     Central West AB                                            65     Ireland                89 Denmark
   11*    Victorian Artificial Breeders                              69     Jersey Island          91 Finland
   12*    Genetics Australia                                         70     Canada                 90 Holland
   13*    Graham Park Artificial Breeding Centre                     80     USA                    93 Germany
   15*    Department of Primary Industries, Qld
   17*    Tasmanian Dairy Industry Authority                         (* All now Genetics Australia)
   21     Bovine Semen (Aust) Pty Ltd

                                                Table 8.2: Collection centre codes

Practical aspects of reproductive technologies for cattle breeding                                                     39
     Dairy breeds                                        Beef breeds
     Australian Friesian Sahiwal   FS    Red             Chianina                      CI Black
     Australian Milking Zebu       MZ    Red             Devon                         DD Clear
     Ayrshire                      AY    Blue            Droughtmaster                 DM Black
     Brown Swiss                   SB    Clear           Galloway                      GA Clear
     Dairy Shorthorn               DS    Pink            Hayes Converter              HV Dark Blue
     Guernsey                      GG    Yellow          Hereford                     HH Brown
     Holstein Friesian             FF    Grey            Highland                      HI Clear
     Illawarra Shorthorn           IS    Turquoise       Limousin                      LL Black
     Jersey                        JJ    Green           Lincoln Red                   LR Clear
     Meuse-Rhine-Issel (MRI)       MI    Purple          Luing                         LU Clear
     Milking Shorthorn             MS    Pink            Maine-Anjou                   MU Clear
     Red and White Friesian        RF    Grey            Murray Grey                  MG Salmon
     ACDC                          CD    Clear           Pie Rouge                    PR  Clear
                                                         Poll Devon                   PD  Clear
     Beef breeds
                                                         Poll Hereford                PH  Brown
     Africander                    AF    Red
                                                         Poll Shorthorn                PS Red
     Angus                         AA    Orange
                                                         Red Angus                     RA Orange
     Beefalo                       BO    Clear
                                                         Red Poll                      RP Clear
     Beefmaster                    BM    Dark Blue
                                                         Red Sindhi                   RS  Red
     Beef Shorthorn                BS    Red
                                                         Red Sahiwal                   SW Red
     Belmont Red                   BR    Red
                                                         Santa Gertrudis               SG Bright Red
     Blonde d’Aquitaine            BA    Clear
                                                         Simmental and Fleckvich      SI  Clear
     Brahford                      BF    Black
                                                         South Devon                  SD  Clear
     Brahman                       BB    Black
                                                         Sussex                       SU  Clear
     Brangus                       BG    Black
                                                         All breeds alternative allotment Clear
     British White                 BW    Clear
                                                         Unlicensed semen (custom collected) Wine Red
     Charbray                      CB    Purple
                                                         This system might not be used for imported
     Charolais                     CC    Purple

                          Table 8.3: Codes and semen straw colours for various breeds

                               A      1958       R      1972        F         1986
                               B      1959       S      1973        G         1987
                               C      1960       T      1974        H         1988
                               D      1961       U      1975        J         1989
                               E      1962       V      1976        K         1990
                               F      1963       W      1977        L         1991
                               G      1964       X      1978        M         1992
                               H      1965       Y      1979        N         1993
                               J      1966       Z      1980        P         1994
                               K      1967       A      1981        R         1995
                               L      1968       B      1982        S         1996
                               M      1969       C      1983        T         1997
                               N      1970       D      1984        U         1998
                               P      1971       E      1985        V         1999

                                     Table 8.4: Letter codes for birth year

40                                                                                      Cattle Breeding Technologies
Equipment required for artificial insemination
Aluminium vacuum-insulated vessel used to hold semen and liquid nitrogen (see Figure 8.9 on page 47).

Removable cylinder with a mesh or solid bottom to hold semen in the tank. It has a long hooked handle
to permit straw identification and access from the mouth of the tank.

Plastic cylinder with a sealed base, and which fits into the canister. It will hold up to twenty-five straws
in a bath of liquid nitrogen.

Each straw contains enough semen to inseminate a cow once. The volume of semen in the mini-straw
is 0.25 ml, which normally contains 20 million sperm cells with a usual minimum of 40% live at thaw.
    Semen produced in medium straws containing 0.5 ml of semen (also with 20 million sperm cells) is
sometimes available. These straws should be treated in the same way as mini-straws. An appropriate
0.5 ml insemination gun is required.
    Figures 8.5 and 8.6 show the size and construction of a typical straw.

                              Strathaire Southw
                                                ind Luke ET 11F
                                                                FL77 Gen-Aust
                                                                              03-12-96 WINLUK

                              Shoremar Perfect Star ET 11FFK43 Gen-Aust 02-11-96 SHOTIME

                                                                                96 SOONER
                                                                Gen-Aust 01-10-
                                               Franklin 11JJJ06
                              Stony Run Sooner

                                   Figure 8.5: Actual size of semen mini-straws (0.25ml)

                                                                               Crimped end
                                                                               (laboratory end)


                                                      Manufacturer’s Plug
                                                      Webbing plug
                                                      Poly-vinyl alcohol plug
                                                      Webbing plug

                     Figure 8.6: Straw construction showing crimped end and manufacturer’s plug.

Practical aspects of reproductive technologies for cattle breeding                                             41
     Artificial breeding is the most effective means of controlling certain diseases. To maintain its effectiveness
     precautions must be taken to ensure contaminants are not introduced into the cows uterus. Resulting
     uterine infection will interfere with fertility, increase mating costs and reduce conception rates.
          Inseminators careless with hygiene can easily spread disease from one cow to another or, more
     importantly, from herd to herd. Careless hygiene may also transfer certain diseases from cows to the
     inseminator. Hygiene precautions adopted by each inseminator should be based on the assumption that
     all cows may be a source of infection. Cleanliness is essential to good hygiene. Begin with clean equipment
     and keep it clean by cleaning contaminated equipment.

     A hygiene checklist
     Before and during the insemination:
     a New plastic glove.
     b New sheath.
     c Fresh paper towel.
     d Keep the ‘cow end’ of loaded gun uncontaminated, do not allow it to contact any surface in the dairy
        or breeding race.
     e Wipe the vulva as clean as possible.
     f Part the lips of the vulva and introduce the point of the gun as cleanly as possible.
     g Avoid inseminating too deeply, and excessive movement of the gun inside the cow, as these actions
        are likely to cause minor injuries that allow a better chance for infection to enter and reduce the
        chance of the cow holding. Deep inseminations can also abort already pregnant cows. For more
        information see ‘Insemination technique’ later in this chapter.
     Between cows on the same day:
     a Wash free hand if contaminated by dung or mucus.
     b Use fresh paper.
     c Then proceed as for points a to g above.
     At the conclusion of insemination:
     a Dispose of used sheaths, plastic gloves and paper in a waste bin.
     b Thoroughly clean contaminated guns before returning them to the kit box.
     c Scrub boots.
     d Wipe the kit box clean of contamination.
     e Remove gross contamination from the overalls.
     f Wash hands, particularly the non-gloved hand.

     Insemination technique
     Always ensure that your kit box and its contents are clean and contains the following:
     • gloves and paper towel
     • insemination gun
     • sheaths
     • thaw box and thermometer
     • lubricant.

     Thawing of semen
     1 Check, and if necessary, adjust the water temperature in the thawing flask to within a range of 32°C to 38°C. It is
       essential to use a thermometer for this. Thawing semen above 40°C may cause it to overheat and
       ‘cook’. Ensure that the water is deep enough to cover only about 4/5th of the straw. If the water is too
       deep and the end of the straw is broken, water may enter and kill the sperm.
     2 Remove the neck plug from the tank.
     3 Select the canister containing the semen required. Knowing the location of semen will avoid
       unnecessary handling of straws. Keep a semen location diary with the tank.
     4 Lift the canister to the top of the frost line in the neck of the tank. The frost line is about 50mm below the top of
       the neck. Do not bring the canister up to the top of the neck.

42                                                                                                Cattle Breeding Technologies
5 Select the required straw or straws from the mini-goblets using tweezers. Positive identification is
  essential. Use tweezers to avoid warming the straw and causing frost bite to fingers.
  Important: Provided the goblet is full of liquid nitrogen, the canister may be held in the neck of the tank for up to
  45 seconds before being returned to the bottom of the canister.
6 Whilst holding the laboratory end of the straw, give the straw a flick as this will dislodge any liquid
  nitrogen that has accumulated in the manufacturer’s end of the straw.
7 Place the straw in the thawing water as quickly as possible leaving it there for a minimum of 30 seconds.
  Thawing for a longer period does not cause any harm but the straw should be used within 20 minutes of
  removing it from the tank. Once thawed, straws must not be refrozen.
8 Replace the neck plug in the tank.

Loading the gun        (See Figure 8.7)
 1 Tear off approximately 20 cm of paper.
 2 Using fingers, remove the straw from the thawing flask and dry it with a paper towel. Drying is
   accomplished by following these steps:
   • Hold the straw by the laboratory end
   • Draw it through the paper once
   • Grasp the straw by the manufacturer’s (double wad) end.
   • Draw it through the paper once more.
   You should be holding the straw by the manufacturer’s end after drying is completed. Do not dry
   excessively as heat build up caused by friction may raise the semen temperature.
 3 Check the name of the bull printed on the straw. If the wrong straw has been selected it must be
   discarded. Never replace a thawed straw in liquid nitrogen.
 4 Remove the insemination gun from the clips on the inside of the kitbox lid.
 5 Pull back the plunger in the gun about 120 to 180 mm.
 6 Holding the straw by the end, to avoid damage to the semen through temperature shocks, thread
   the manufacturer’s end (double wad end) into the gun as far as it will go. There is an in-built stop
   preventing it going too far.
 7 Prepare to cut off the laboratory end of the straw by thoroughly cleaning and drying the scissors.
 8 Hold the loaded gun vertically at eye-level and with clean sharp scissors make a horizontal cut
   10mm above the gun to remove the crimped end. The cut must be at right angles to the straw so that a
   perfect seal occurs between the straw and the sheath.
 9 Clean and dry the scissors after cutting the straw and return them to their correct location in the
10 Replace the lid of the thawing flask to help maintain the correct water temperature.
11 Select a sheath from its protective package and place it over the barrel of the gun.
   Handle only the split end of sheath keeping the cow end clean.
12 Push the sheath through the beveled centre hole of the locking ring and twist it down on the conical
   seat of the gun. The sheath prevents gun contamination and holds the straw in place during expression
   of the semen. It is important that the seal between the sheath and the gun is secure, otherwise
   semen will leak into the gun.

                                           Figure 8.7: Loading an insemination gun

Practical aspects of reproductive technologies for cattle breeding                                                        43
     13 Press the plunger of the gun until the semen is just visible at the end of the gun. This reduces the
        stretching of fingers needed to handle the gun.
     14 Put the loaded AI gun in your mouth or place it across the kitbox ensuring that the cow end does not
        contact anything.
     15 Place the paper in your back pocket.

     Inseminating the cow         (See Figure 8.8)
     Always use a glove when inseminating. Plastic disposable gloves are preferred but reusable rubber gloves
     may be used.
      1 Don the glove and wet it by dipping the gloved hand into a bucket of clean water, scooping water
        up in your hand and letting it run back down your arm. Apply a small quantity of glove lubricant to
        the back of your hand.
      2 Carry the loaded gun in your mouth ensuring that the cow end does not become contaminated by
        contacting walls etc.
      3 Make the cow aware of your presence. A startled cow may kick.
      4 Retrieve the paper from your pocket.
      5 Protect your hand from contamination with a piece of paper toweling, then grasp the cow’s tail and
        lift it aside.
      6 Using the lubricated back of the gloved hand with the gloved hand, smear lubricant across the cow’s
        anus. Form a cone with the gloved fingers and insert your hand into the rectum. Pause at this stage
        and encourage the anus to relax by gently revolving your fingers. The wide part of your hand can
        then be eased in without dragging the rough dry skin surrounding the anus. Avoid rough sudden
        entry which can abrade the anus and cause the release of adrenalin which reduces conception rates.
      7 Thoroughly clean the vulva of all soap, dung and dirt by wiping it with the piece of paper used on
        the tail. Use a fresh piece if the paper is too soiled.
      8 Bear downwards with the wrist of the hand in the rectum which helps to part the lips of the vulva
        presenting a clean area for inserting the gun.
      9 Insert the gun cleanly between the lips of the vulva into the vagina. Take care to ensure the gun
        passes along the top of the vagina thus avoiding the bladder.
     10 Gently push the gun through the vagina until you reach the surface of the cervix which has a
        ‘grating’ feel about it.
     11 When the gun reaches the mouth of the cervix, hold the cervix in the finger tips. Maintain a light
        forward pressure on the gun and manipulate the cervix so that the gun passes through the cervix canal.
        If you are unable to hold the cervix you may pin it against the pelvis.
     12 While passing the gun through the cervix locate the forward end of the cervix with the middle or
        index finger. Gently push the gun forward but only as far as this locating finger. This is important


                 Insemination                                           Broad
                         gun                                         ligament
                                                    Cervix          Ovary
                                  bone            Bladder Horn of

                                      Figure 8.8: Uterine insemination of the cow

44                                                                                     Cattle Breeding Technologies
     when doing a repeat service as the cow may be pregnant. Avoid deep penetration of the uterus as
     the gun may cause damage and possibly infection thus reducing the chance of conception or in the
     case of a pregnant cow, an abortion (up to 5 per cent of pregnant cows show some signs of heat).
13   Begin to express the semen at this position ensuring that most of the semen (two-thirds) is expressed
     in the body of the uterus. The remaining one third should be placed near the uterus in the front 1 cm
     of the cervix. Take care not to draw the gun too far back. It is easy to pull back too far at this stage,
     even as far as the vagina.
         Occasionally the gun cannot be passed to the proper position. Avoid bruising and other injury to
     the cow by depositing the semen at the position reached after reasonable effort. Prolonged and
     forceful struggling will have a worse effect on conception rates than incorrect semen placement.
14   Gently express the semen being careful not to ‘spit’ it out.
15   Pause before withdrawing the gun allowing the semen to get away, then slowly withdraw the gun
     from the cervix. Rapid withdrawal of the gun can suck semen back through the cervix into the vagina.
16   Remove the gun slowly from the vagina.
17   Slowly withdraw the arm from the rectum of the cow.
18   Loosen the locking ring on the gun and remove the soiled sheath. The empty straw should come out
     with the sheath.
19   Dispose of the straw, sheath, paper and dirty glove in a waste bin.
20   If the unprotected parts of the insemination gun become soiled with the dung or mucus the gun
     should be thoroughly cleaned before it is returned to the kit box.
     Only clean equipment should be replaced in your kit box.

Unusual structures you might feel in a cow
A number of factors can cause an enlarged or misshapen cervix and uterus.

1. Recent calving
After calving the cervix and uterus may take up to 50 days to regain its normal size.

2. Pregnancy
About 5% of all cows show some sign of heat after becoming pregnant. Heat detection mistakes may
also mean that attempts are made to inseminate pregnant cows. Insemination of cows up to four weeks
pregnant can cause some pregnancies to abort. With later pregnancies, normal insemination procedure
(passing the gun no more than 1cm beyond the forward end of the cervix) and normal hygiene will
reduce the chance of abortion.
   Table 8.5 gives some indication of the size of the uterus during pregnancy.

     Months pregnant               Size of horn of uterus
            2                      Twice normal
            3                      Three times normal
            4                      Ten times normal
            5                      Vagina is stretched tight. Cervix may hang forward and down due to the
                                   weight of the uterus
             6 to 9                The calf may be felt as a hard structure freely moving

                              Table 8.5: Size of horn of the uterus and duration of pregnancy

3. Uterine infection
After calving some cows contract an infection of the uterus. This can progress, resulting in a large
‘doughy’ uterus which is full of pus.
    Although such cows often discharge yellow pus with a custard like consistency, some don’t. Veterinary
treatment is necessary to give these cows some chance of conceiving.

4. Age
Old cows usually have a larger cervix and uterus than young cows.

Practical aspects of reproductive technologies for cattle breeding                                               45
     Handling liquid nitrogen safely
     Liquid nitrogen is dangerous and must be handled with respect.

     First-aid for liquid nitrogen burns
     Immediately flood the area with cold water and apply a cold compress. Do not rub the affected area.
     Call a doctor if there is any chance that the eyes have been affected or the skin blistered.

     First-aid for lack of oxygen
     If a person becomes dizzy or loses consciousness while working with liquid nitrogen, immediately
     move the person to a well ventilated area. If breathing has stopped, apply artificial respiration and
     summon an ambulance.

     Liquid nitrogen — general safety precautions
     • Avoid contact with liquid nitrogen. The liquid or even the cold nitrogen gas issuing from the liquid
       can cause burns. Brief exposure which may not affect the skin of the face or hands, can still damage
       delicate tissues such as the eyes.
     • Be sure there is adequate ventilation. If enough nitrogen evaporates in a badly ventilated room, the
       percentage of oxygen in the air may get dangerously low. Never dispose of liquid nitrogen in a
       confined area.
     • Protective clothing should be worn when handling liquid nitrogen. Eye protection should be worn.
       Wear trousers outside boots and pour liquid nitrogen slowly to reduce splashing.
     • Secure liquid nitrogen tanks in the boot of the car. Carrying the flask in the passenger compartment
       may be dangerous. In the event of an accident dangerous levels of nitrogen gas will be present in the
       car if the car windows are shut.
     • Secure the flask at all times when it is being transported.
     • Never use a plug other than that supplied with the tank. Wrong plugs may interfere with the escape
       of gas and may cause the tank to burst.
     • Check the tank regularly for evidence of frost on the outside and for excessive loss of liquid. Either
       state could indicate a breakdown of the insulation. The amount of liquid nitrogen in the tank can be
       checked by the frosting on a dip-stick. Beware of using a hollow tube as a dip-stick as the liquid
       nitrogen will spray up through the centre.
     • The tank should be kept in a secure place so that children and unauthorised people unaware of its
       hazards do not have access to it.
     • Do not store the tank on bare concrete. Use a wooden plank to sit the tank on to prevent corrosion.

     Semen storage and handling
     Semen is fragile and must be handled properly to achieve the best results.
         Packed in mini-straws, and sometimes medium straws, semen is stored in liquid nitrogen at –196°C.
     Kept at this temperature, semen will last for years. Maintaining the correct temperature is important, as
     a temperature rise and subsequent refreezing will damage semen. Temperatures may rise high enough
     to damage semen if mini-straws are exposed to air for longer than two seconds.
         Make sure nitrogen covers the straws and fills the goblets while semen is stored in the tank. Semen
     straws may maintain their fertility when they are stored in liquid nitrogen vapour, but two problems
     may occur if the liquid nitrogen level is allowed to drop to a very low level.
     • The straws will be more susceptible to ‘temperature’ damage if they are lifted into the neck of the
         tank without liquid nitrogen present in the goblet. The temperature increases rapidly towards the
         top of the neck of the tank (see Figures 8.9 and 8.10).
     • Nearly empty goblets may float out of the canisters when the tank is refilled with liquid nitrogen.
         Although there is no need to panic if the liquid nitrogen level gets low it is much better to keep the
     straws covered with nitrogen.
         Remember, semen is a fragile commodity, handle it carefully. Exposure to direct sunlight, dust, water,
     soap, powder or rough handling might reduce conception rates.
         Positively identify the bull before removing straws from the tank.

46                                                                                      Cattle Breeding Technologies
                                                                     Figure 8.10: Temperatures increase rapidly
                                                                       towards the top of the neck of the tank.

       Figure 8.9: Typical semen storage tank.

Records inseminators should keep
Records that inseminators are to keep and have available are:
1 The number of cows inseminated with semen from approved bulls.
2 Name and address of the cow’s owner.
3 Total number of doses used.
4 Name and address of any other person supplied with semen and number of doses supplied.
5 The premises from which the semen has been received and the quantity of semen received.
6 Identity of cows inseminated.
7 The dates of insemination.
8 Identity of the bull used.
9 Batch number of the semen.
   These records could at any time be requested by the Chief Veterinary Officer.

Further reading
Hafez E.S.E. (Ed.) (1987), Reproduction in farm animals, 5th edition, Lea and Febiger, USA.

Practical aspects of reproductive technologies for cattle breeding                                                47

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