In Spain today there are approximately 60 stations supplying boar semen for pig artificial insemination. This includes both the AI centres that sell doses commercially and those that produce and process the semen for use in their associated herds. But the total only counts those integrated centres that have more than 60 boars each. The Spanish AI scene also contains a number of pig units that collect semen from four or five boars to inseminate their own sows.

Representatives of the larger stations were invited to a round-table meeting in 2008 to hear about a survey of practices and protocols at boar studs nationally — the first full assessment of how artificial insemination programmes work, in a country known for having one of Europe’s highest rates of uptake for AI in breeding sows.

Talk about AI in Spain and the big operators that come to mind are names such as Semen Cardona, Vall Companys, Calpor, Gepork, Selección Batallé, Juan Jimenez and Cooperativa de Guissona. All these and more were represented at the round-table arranged by equipment company Magapor, as were networks from neighbouring countries including Italy and Portugal.

Critical control points

Those in attendance heard details of a survey led by Magapor’s R&D department that had started out with the aim of determining if the main Spanish pig AI centres followed similar or differing methods for collecting, processing and delivering semen from their boars. Other key objectives at the start were to identify the critical control points affecting the operation of a boar stud and to establish guidelines for optimising boar productivity.

Therefore, a set of 25 questions was compiled and submitted to the technical managers of 31 studs located across Spain. The questioning covered three main areas, being those relating to the boar, matters of collection and how the centres evaluate and process the semen.

Feeding methods stood out from the information obtained on boars. Almost three-quarters of the technicians questioned said they fed their boars a specially formulated type of diet rather than one prepared and sold for gestating sows, despite the extra cost involved. Nearly two-thirds of the people also reported that they occasionally used some sort of sperm-improving supplement in the boar’s feed. These tended to be complementary feed materials such as a proprietary one in which a vitamin-mineral blend has added amino acids. It is given in addition to the boar’s daily diet, for example during convalescence after stress or vaccination when sperm quality can drop and libido may be lowered.

In practice, the survey found most studs using a complementary feed of this type with the aim of mitigating or preventing heat stress and similar seasonal problems. The frequency of use varied quite widely. Whereas there were examples of administering the feed in alternate weeks all year round, other centres applied it only for a week each month or every two months.

Causes of culling

The AI stations also were asked how they decided when to remove boars. Poor semen quality showed as the main reason for culling, applying in 60% of all cases and being involved in a further 17% where it combined with lack of libido or leg weakness to cause the boar to be culled. Elsewhere in the survey it emerged that while the technicians did not administer synthetic prostaglandins as a matter of routine, some 87% agreed that they might apply them as a stimulant at collection time for boars with libido problems.

Semen centres have to vaccinate their boars at times, to secure health or meet current regulations. Vaccinating can increase the animal’s body temperature and this in turn potentially threatens semen quality. With that in mind, some 55% of the technical managers responded that they form batches of boars for vaccination and so avoid a major impact on the centre’s output. On the other hand, 39% called this an unnecessary precaution and were vaccinating all resident boars simultaneously.

There was one surprise in the answers on vaccination — when 3% of the respondents replied that they did not vaccinate at all. The other 3%, by the way, varied their vaccination protocol according to the nature of the vaccine.

Collection methods could also be variable, but 77% of the centres surveyed were collecting semen manually from their boars. The minority who had invested in automatic collection systems tended to be large operators.

From other answers, the attendant in the collecting area was expected to use the double-glove technique at 87% of the studs so semen would not be contaminated. The opposite end of the spectrum was that only 10% regularly flushed the prepuce against contamination and even occasional application was reported by under half of those in the survey.

Is it a common practice to place a small amount of extender in the collection flask in order to minimise spermatic shock? Apparently so, with 61% of people saying they did this routinely. Another 13% practised this occasionally or with certain boars, so the method was not being followed at all in 26% of cases.

Collection rhythms

Asked about the frequency of collection, the operators in Spain considered that an adequate rhythm to optimise the boar’s productivity without risking semen quality was to collect either once per week or three times every two weeks. These frequencies covered 87% of replies. But the centres added that they did collect twice-weekly if the boar was known to be extremely productive and when demand for semen doses was especially high.

Working patterns in AI operations were morning-intensive in 87% of studs and 71% reported processing doses on all weekdays Monday to Friday. Just 3% were preparing doses also at weekends. The remaining 10% in the survey varied their dose preparation schedule in line with demand or according to other factors.

When converting raw semen to prepared doses, the centres differed considerably on how to evaluate the concentration of sperm present in a sample. Their answers revealed only 6% currently employing a computer-assisted or CASA method of automatic evaluation. It was more common to assess density by spectrophotometer readings (26%) or by colorimeter (13%). A preference for determining sperm concentration by means of a haemocytometer or Bürker counting chamber was expressed by 45% of the managers surveyed.

The calculation of the number of doses to prepare per ejaculate was based for 75% of studs on the presence or absence of abnormal sperm. All of them discarded the semen entirely if its abnormality count exceeded a certain threshold level, which was most frequently set in the range 20-25%.

Slightly over half of the managers told the survey team that they subtracted the number of abnormalities from the total to guarantee there would be enough normal sperm. This compared with 23% saying they achieved the same objective by increasing the concentration of sperm in the dose.

No more than 20% of centres bought distilled water from a commercial source in order to prepare their doses. Four-fifths of those replying reported that they had their own water purification equipment. In this case, 76% conducted periodic checks on the quality of the water, either by referring a sample to an outside laboratory (63%) or by in-house assessment.

The type of extender user gave another surprise in that 17% of replies referred to adding some extra antibiotic to control bacterial contamination. Nearly two-thirds of centres said their doses were made with a long-term extender. They were asked what they did with any reconstituted diluent that was left over from the day’s semen processing activities. For 53% of respondents the answer was that they throw the unused liquid away because it could potentially contaminate if retained for re-use. But 47% of the managers told the survey they did store leftover extender and use it in dose preparation the next day.

Finally there was the question of packaging for the doses from these AI stations. Heat-sealed tubes were favourite for 45% and blister packs for 29%. The answers at that point were broadly for the size of dose in common use internationally. However, note also that 28% of the operators went on to say they now made some mini-doses — so reflecting the increased uptake in Spain of post-cervical insemination techniques involving fewer sperm per sow.