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Collecting semen from boars
Collecting semen from boars to use in artificial insemination (AI) is one way that owners and managers of piggeries can manage the fertility and health of their herd.
To ensure that the semen is of the highest quality, and to ensure good welfare for the animals involved, it's important that those responsible for collection are competent in all aspects of performing the procedure.
Hygienic techniques and controlled temperature changes are key elements of success in collecting boar semen.
Purpose and benefits of collecting boar semen
You can breed pigs through artificial insemination (AI) using semen collected from their own boars or semen purchased from commercial suppliers.
Using AI can help improve pig herds through introduction of improved genetics. Consult your veterinarian to check that boar care and semen collecting and processing steps reduce the low risk of diseases being transferred in the semen.
Collecting boar semen for AI helps:
- when death, lameness or refusal to work decreases the number of boars in the herd that are fit for service
- to spread the genetic influence of good boars more widely
- to maintain the health status of closed herds.
Collecting from on-farm boars
On-farm collection of boar semen is usually done in closed herds; however, it is also useful to introduce new genetics to the herd with new boars.
If you introduce boars, it's good practice to quarantine them and not place them with the herd until the potential risk of infection is eliminated. In large herds where biosecurity is a very high priority, boars may be kept in pens, in a purpose-built facility with 1 or more collection areas next to a processing room.
Benefits
- Young boars can be easily trained to mount dummy sows
- AI results using fresh collected semen are similar to results achieved from natural mating
- Can use undiluted semen from young boars to inseminate 2 or 3 sows and semen from older boars for 4-6 inseminations
Who can collect boar semen?
Under the Animal Care and Protection Regulation 2012, you must be a suitably qualified person, or under the direct supervision of a suitably qualified person, to carry out husbandry procedures on a pig.
For more information, see Chapter 3, Part 2 Code of practice and additional requirements for pigs.
Equipment for collecting boar semen
The successful collection of viable semen from boars depends on correct handling techniques and care of equipment.
When collecting semen:
- use an adjustable dummy sow (rather than an oestrus sow) to avoid any size differences between the animals, injury to sows, and any reluctance of the oestrus sow to support the boar's weight until ejaculation is complete
- make sure the collection area is shady and draught-free (the viability of semen decreases with exposure to ultraviolet light, sudden temperature changes and water contamination).
- use trained staff who implement documented workplace health and safety (WHS) procedures.
Required equipment
- Plastic insulated flask or polystyrene cups (minimum capacity, 250mL) for semen collection
- Semen filter (surgical or bandage gauge) that is fitted over the collection flask
- Polythene graduated measuring cylinder or flask (if evaluating by volume)
- Quality, calibrated thermometer to monitor the temperature of the semen storage container
- Small polystyrene boxes cooled with frozen glacial acetic acid to store diluted semen or specific temperature refrigerator (between 14°C to 18°C is best)
- Microscope slides and a microscope to evaluate the motility and quality of semen (if required)
- Temperature-controlled water bath and cabinet to warm equipment and slides that will come into contact with fresh sperm (if evaluating and processing)
- Personal protection equipment (PPE) to avoid injury to and infection of the stockperson
- Semen diluent (processing using diluent is usually not necessary for small AI programs)
- Non-slip surface or mat for the boar
Cleaning and storage
The proper care of equipment used to collect boar semen is crucial to the success of your breeding program:
- use hygienic methods when collecting boar semen
- keep equipment free from dust and dirt (store in dust-free cabinet or sealed plastic bag).
Carefully wash equipment after use:
- soak reusable containers in cold water immediately after use
- remove semen gel particles with a brush
- rinse several times in distilled boiling water (tap water leaves mineral deposits on equipment)
- allow to dry in a dust-free environment (dust-free cabinet)
- avoid using soap or detergent when cleaning containers as residues can affect sperm viability.
Care and training of boars for semen collection
The Model code of practice for the welfare of animals - Pigs describes how pigs must be handled and managed in Queensland. The code covers pig husbandry that is appropriate to pigs' physical and behavioural needs.
Boar training
Young boars are usually easy to train. Avoid rough handling when training a boar to mount a dummy sow. An injury or a fall may discourage the animal and make training difficult.
To encourage boars, the adjustable dummy sow should be:
- set at the correct height for the trainee boar
- stable, comfortable and free from sharp projections
- located on a dry, slip-free floor (a non-slip mat may be used) in an area that is familiar to the boar (e.g. his pen or the mating pen).
Sometimes the trainee boar may require encouragement to mount and thrust by:
- ensuring the smell of semen or saliva from another boar or urine from a sow is present on the adjustable dummy sow
- smearing some of the boar's own semen on the adjustable dummy sow (this is seldom required)
- using an oestrus sow to arouse the boar, then collecting a little semen and removing the sow
- implementing sound workplace health and safety procedures.
Collecting boar semen
Collect boar semen in a shady, draught-free environment. Exposure to ultraviolet light and any sudden temperature changes can cause deterioration of boar semen. Therefore, a warm (34°C), dry, insulated flask is required for collection.
Once the boar has mounted the adjustable dummy sow, the person collecting the semen should grasp the spiral end of the penis with their gloved hand (polyvinyl, not latex, and clean, dry and warm) and allow the boar to thrust a few times before applying pressure. The pressure caused by the clenched hand (some boars prefer more pressure than others, which becomes obvious with experience) imitates the oestrus sow's cervix and stimulates ejaculation.
To minimise irritation to the boar and disruption to the process, the long hairs around the boar's prepuce should be clipped.
To reduce the risk of dirt entering the semen sample, it's good practice to wear 2 gloves on the manipulating hand, removing one glove when the boar's penis is grasped.
Ejaculation process
A 4-phase ejaculation process occurs once the boar's penis is 'locked' in the hand and the boar relaxes. This takes 5–10 minutes to complete. Large amounts of gel signal the end of ejaculation. The boar should be observed after collection to ensure that the penis is fully retracted.
Phases
- First phase (pre-sperm fraction) consists of clear seminal fluid, some gel, and dead sperm cells, and is heavily contaminated with bacteria. This should not be collected.
- Second phase (sperm-rich fraction) is around 50mL in volume, creamy-white in colour, and contains the greatest density of spermatozoa. Collect in the pre-warmed thermos or cup.
- Third phase is about 80ml in volume, and greyish in colour due to the lower density of spermatozoa.
- Fourth phase (post-sperm fraction) is up to 250ml. Clear seminal plasma (free of spermatozoa) and gel is secreted from the accessory glands (the gel is separated from the collection by gauze, or similar material, fastened over the collection flask).
Cap the collection thermos or cup, place in a warm receptacle and transport to the processing area.
Filtering particles of gel from the semen prevents catheter blockage during insemination. Hair, skin or dust particles from the boar or dummy must be excluded from the flask during collection.
When semen is to be collected for dilution and storage over a few days, only the second and third phases of boar ejaculate are collected.
When to collect
Collection of semen (from the same boar) should be restricted to no more than 3 times a week. This ensures high sperm concentration and semen volume. Excessive collection over a short period of time results in low semen quality and quantity and can reduce the boar's sex drive.
Keeping records
It's important to maintain accurate records that identify the:
- name and number of the semen donor
- volume of the samples collected
- date and time the sample was collected
- use-by-date (for diluted semen) or use-by-time (for fresh semen)
- motility and density of each sample, including reference to abnormalities.
These records are especially important for diluted semen, which can be kept for several days. Accurate records will ensure that the oldest stocks are used first and that expired samples are discarded.
Evaluating boar semen
Evaluating boar semen is important for making sure the quality and quantity of the sample is satisfactory.
Evaluation of boar semen is rarely needed in small, within-herd AI programs where undiluted semen is used within hours (especially if the boar has a successful impregnation record).
However, if the boar has not previously provided semen, or if the semen is going to be diluted, then evaluating semen viability can be useful.
Volume
- Volume is measured in a warm (34°C), dry calibrated flask.
- Volume is usually 100–500mL (large volumes do not necessarily contain more sperm than smaller volumes).
When used undiluted, the volume determines the number of inseminations possible from each collection. The volume of semen per insemination is 50–100mL.
Motility
- Observing motility is the best way of estimating semen quality.
- Observing motility is not necessary for obviously fertile boars (unless dilution is required for inseminating a large number of sows).
To determine motility, place a sample on a warm slide (30–35°C) immediately after collection and under the low power lens (x50) of a microscope.
A typical 'wave' motion and movement of individual spermatozoa are both indications of good quality semen, whereas 'clumping' and weak motility indicates a poor quality sample. Motility depends on the volume of each fraction collected—higher motility and wave motion is detected in the sperm-rich (second phase) fraction, whereas accessory fluids dilute the semen (resulting in weak motility).
Density
- Accurate estimates are needed only when high dilution rates are used at artificial breeding centres.
- Density depends on the volume of post-sperm faction collected.
- Density varies from 100–500 million spermatozoa per mL (60–80 billion sperm are present in a normal ejaculation.
- Estimates of dead and abnormal spermatozoa are normally only performed at artificial breeding centres.
- Abnormalities include detached heads, bent and returned tails, broken tails, and twin heads or tails.
- Instruments such as the hemocytometer and the spectrophotometer help determine semen density.
Abnormalities
The presence of immature spermatozoa (which show protoplasmic droplets on their tails) indicates that a boar has been overworked. If the total abnormalities detected in a sample are less than 25%, then the quality of the semen is classified as 'satisfactory'.
Measure to manage
Record the results of all measurements to enable collection and processing procedures to be reviewed, evaluated and improved.
Processing boar semen
The method for processing boar semen influences the outcome of your artificial insemination (AI) program. During processing, sudden temperature changes and exposure to ultraviolet light reduces semen quality.
When handling semen after collection:
- use hygienic techniques (keep all equipment free from dust and dirt)
- treat the samples gently
- maintain a reasonably even room temperature and keep the semen temperature even or at a slow rate of change
- ensure that there is sufficient space in the collection area to lay out all equipment (e.g. storage box, collection flask)
- ensure good lighting and a non-slip surface
- supply facilities for disposal of waste
- wear personal protective equipment
- implement workplace health and safety procedures.
Undiluted fresh boar semen
Effective methods to process undiluted fresh semen for AI programs on most farms include:
- keeping the semen at the temperature collected (34°C)
- using the sample within a few hours of collection
- using 100mL of the gel-free fraction in the insemination process to obtain the best results
- rocking the container gently to disperse the spermatozoa that have settled on the bottom before dividing the sample into doses.
Diluted boar semen
Sometimes it's not practical to use undiluted semen. The use of a diluent will extend its 'shelf-life'.
A simple skim milk diluent protects semen for a few hours, whereas more complex diluents (preferable) allow chilled boar semen to be stored for several days.
For on-farm AI programs, 1 part gel-free semen is added to 4 or 5 parts diluent (e.g. 20mL of good quality semen is made up to 80mL or 100mL with diluent). For higher dilutions, accurate estimates of the total live and normal spermatozoa in the semen sample is needed.
Many commercially available diluents contain an antibiotic which will have a stated withdrawal period. Mated sows cannot be sold for slaughter before the stated withdrawal period for the antibiotic has been met.
The basic steps for diluting boar semen are to:
- dilute only the sperm-rich fractions when storage is to exceed 24 hours (seminal plasma does not protect semen during storage but some inclusion is not detrimental)
- warm the diluent to semen temperature (32–35°C) by standing the diluent in a warm water bath
- gently add the diluent to the semen, not the semen to the diluent (to avoid diluent shock)
- gently agitate the semen before pouring 80–100 mL of diluted semen into the inseminating bottles or bags
- allow semen to cool slowly for 1 hour to around 20°C
- cool semen further (to 14–18°C) over the next hour and store at this temperature range
- gently turn semen containers twice daily to prevent sedimentation.
Storing boar semen
There are simple ways to store semen to ensure that inseminations have a high success rate.
General principles:
- The storage duration of the sample affects the insemination success rate.
- All storage containers for boar semen should be kept clean (dirt, bacteria and moulds can contaminate your samples).
- It's important to keep good records of stock identities, numbers, date/time of collection and use-by-dates.
Undiluted boar semen
Undiluted semen should be kept at 34°C (i.e. the temperature at which it was collected) and used within a few hours.
Diluted boar semen
Store diluted semen at 14–18°C. Use refrigerators to store at this temperature or, for smaller quantities, store in small polystyrene boxes using frozen glacial acetic acid as a refrigerant. To avoid cold spots, fit the storage box with dividers to avoid the refrigerant directly contacting the semen bottles.
There is a reduced farrowing rate when using chilled semen that is stored for more than 72 hours.
Gently turn semen twice daily to prevent sedimentation.
Do not subject the semen sample to sudden changes in temperature.
© The State of Queensland 1995–2024
- Last reviewed: 08 Sep 2021
- Last updated: 08 Sep 2021