Characteristics of swine semen extender

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Currently, swine artificial insemination is a reproductive technique widely used all over the world, although the extent of its usage in different countries varies significantly.

In general, in European countries, the application of artificial insemination is very high, reaching the rates higher than 80% in some countries (Holland, France, Germany, Spain, Norway, Finland, etc.), while, on the contrary, in the United States the percentage of use of artificial insemination use is still low (around 50%), although in recent years there has been a very remarkable increase. According to the latest estimates, around 19 million inseminations are carried out in the world; chilled semen at 15-20ºC is implemented almost always (in 99%)

What is an extender?

Diluent is the aqueous solution which increases ejaculated volume up to the required doses are obtained, preserves the functional characteristics of the sperm cells and maintains the adequate fertility level.

The proper conservation of pig semen in liquid state is essential to achieve acceptable fertility with artificial insemination. The principle factor to maintain the viability of the semen is the diluent in which this semen is being conserved.

In order to preserve the spermatozoa for a long time, it is necessary to reduce their metabolic activity by means of their dilution in a suitable medium and the temperature reduction.

In the ejaculate, the metabolic activity of the sperm cells can only be maintained for a very limited period. The particularities of porcine sperm cells make them very sensitive to a cold shock, which alters sperm viability. In fact, this susceptibility to a cold shock means that the seminal samples must be conserved at 15-20ºC, since a reduction in the storage temperature limits their viability.

Currently the results obtained with the technique of artificial insemination equal or even improve those obtained with natural matings.

One question we all ask ourselves is: Which semen extender maintains viability as well as possible in a certain time period? Unfortunately, it does not depend only on the extender, it can even vary depending on the farm conditions and climate

Focusing on the characteristics of the extender and reviewing its generic composition, we can try to determine the factors that influence the viability of the diluted semen.

The functions of any semen extender are:

  1. to provide energy for the sperm metabolism
  2. to neutralize metabolic residues
  3. to maintain osmotic balance
  4. to stabilize the sperm membranes
  5. to delay bacterial growth

The most commonly used ingredients in diluents to perform the five above-mentioned functions are:

1.- The source of energy most frequently used in the diluent composition is glucose. Other substances have been used (galactose, fructose, ribose or trehalose); however, their results do not surpass those of glicose

2.- The pH of freshly ejaculated semen is close to 7.4 ±0.2, and when this pH is reduced, energetic metabolism and motility of the spermatozoid is reduced as well. The addition of buffering agents therefore helps to control the pH of the medium. Simpler buffers include bicarbonate and citrate (sodium) with a limited buffering capacity, while more complex buffers (TES, HEPES, MOPS, TRIS) can regulate pH over a wider range and are not temperature-dependent (MOPS and HEPES).

3.- Porcine spermatozoid presents an osmotic pressure of 290-300 mOsm. Neither motility nor sperm viability are affected by osmotic pressure in ranges between 250 and 290 mOsm, whereas when it is reduced below 200 mOsm, a significant reduction in motility is detected. Isotonic thinners (300 mOsm) or slightly hypertonic thinners are the best performers in commercial conditions. Inorganic ion salts such as sodium and potassium chloride are mainly used to regulate osmotic pressure.

4.-Normally testicular tissue and accessory glands of the boar are free of bacteria and therefore bacterial contamination of the ejaculate occurs during the seminal collection process. To control microbial growth in the diluent it is necessary to add an antibiotic agent, since the components of the diluent (glucose) as well as the storage temperature of the doses (15-16ºC), allow the growth of most of the gram-negative bacteria such as E. Coli, Salmonella or Pseudomonas. The addition of penicillin and streptomycin (1 g/L) was initially the most widely used combination. Subsequently, aminoglycosides have been successfully used, including gentamicin, neomycin and kanamycin, in concentrations close to 200 mg/L. Recently, a new generation of antibiotics (ceftiofur, apramycin, etc.) is being applied, but we still do not have conclusive results on their use. We must bear in mind that the EU Directive 90/429/EEC regulates the use of an effective antibiotics combination against leptospira and mycoplasma, at the concentration that must have at least an effect equivalent to the minimum concentrations of 500 IU of Streptomycin/ml, 500 IU of penicillin/ml, 150 mg of lincomycin/ml, 300 mg of spectinomycin/ml.

Bacterial contamination mainly produces alterations such as motility decrease, sperm agglutinations, an increase in the percentage of altered acrosomes and a pH reduction up to acid levels (5.7-6.4), which lead to a reduction in the conservation time of seminal doses. Therefore, the addition of the antibiotic in the appropriate concentration will favor sperm survival and increase fertility results.

Classification of diluents

Diluents are currently classified in the market as short, medium and long term conservation diluents. This is determined by their composition.

Basically, energy sources and electrolytes added to diluents are very general. Which makes a difference when obtaining a short, medium or long-term conservation diluent, are the buffer systems (which neutralize metabolic residues) and compounds that are added to stabilize sperm membranes.

The choice of the diluent should be determined by the type of its use. When the storage time is less than three days, the right decision is to use a short-term duration diluent, which has lower costs and its results are equivalent to long-term diluents. When the aim is to preserve seminal doses beyond 4 days (long distances, sanitary evaluations of semen, etc.), long-term diluents should be used, and the dose concentration should be increased to compensate losses due to sperm ageing. In any case, a diluent must be chosen with the aim of optimising fertility and prolificacy under the conditions of a particular pig farm, since the impact on the economic performance is crucial.

Why should SEMEN-DILUYEND be used?

Because it is a diluent that WORKS.

From the entrance of the raw materials till the exit of our finished product and on each stage of manufacturing process, a range of controls that assure the maximum quality of the product are applied. Starting from the measurement of quality parameters (humidity degree, pH, microbiological characteristics, etc.) of the raw materials, controlling humidity conditions and temperature of the rooms where the manufacture and storage are carried out, using heating, refrigeration, dehumidification equipment... up to the packaging control.

SEMEN-DILUYEND is a diluent manufactured according to European directives and with the aim of obtaining maximum protection against bacteria by means of the inclusion of a combination of antibiotics in its composition in accordance with the European directive EU/90/429 EEC.