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The production of breeding material with a good health status

by 5m Editor
9 November 2007, at 12:00am

By Geertjan van Groenland, veterinary surgeon, Topigs. Animal health and breeding go hand in hand. The top breeders in the sector work with material with a good health status. By starting eradication programmes at these nucleus breeding farms, it has been possible to banish a number of infections from the sector.

Pig breeding is the top of the production chain for pork. This is one of the reasons why it is extremely important that the breeding companies aim for the highest level of health. It may be obvious that enhancing stock health status is far more difficult than losing it. For this reason breeding farms do everything possible to prevent infections at the top of the breeding pyramid. This pyramid is not only top in the domain of genetics, but also in that of health.

The value of health

Food safety and animal welfare are important reasons to work with farms that have a low infection risk. After all, the fewer germs animals have to fight, the less reason for preventive or curative action. This is for the benefit of the animal, for each treatment is one that also influences the animal's welfare.

Food safety procedures require assurances regarding the absence of foreign substances and their metabolites that are harmful to the consumer. In addition to the prevention of residues, it is also increasingly important to provide proof that food is free from infectious agents that may also be harmful to man. Salmonella and campylobacter are good examples in this context, but streptococcal infections can also form a threat to human health and sooner or later these will be included in the guarantees that buyers will want from breeding material.

Healthy pigs have a positive effect on the cost price of pork

Healthy pigs have a positive effect on the cost price of pork

A completely different matter is the value of health in relation to the costs of the production of pork. For a large number of farms a simple calculation has already proven that if they can work with a defined higher level of health, the cost price can be reduced on a number of points. Saving in veterinary costs can amount to 30 to 60%. An improvement of 10 to 15% in growth rate and feed conversion is possible and will obviously lead to less mortality. These improvements depend of course on the population used to compare results.

Health not easy to control

High health levels help create smooth breeding structures worldwide. After all, if guarantees can be provided that particular germs are absent, guarantees can also be provided that genes packed in whatever form can be transported across borders without too many risks and barriers.

An article elsewhere in this Veterinary Journal (Spring 2007 edition of Diergeneeskundig Memorandum Periodical Magazine). describes the importance of such exchanges for the breeding sector.

Besides, this "borderless" genes transport is necessary to provide, within the framework of continuity, guarantees to buyers in the various countries and to provide new countries with breeding material. This will facilitate the supply of the desired quantities of pigs, embryos or semen of the highest genetic quality without any problems.

Methods to achieve a higher health status

Although not exhaustive, here follows a brief overview of methods with the help of which TOPIGS has been able - in a number of cases - to achieve a higher health status in its top breeding farms. Each time, the starting point was a normally functioning production process whereby the clinical problems caused by infections are for the most part under control. This can be achieved by the implementation of an adapted vaccination programme in combination with proper farm management.

  1. Eradication and certification

    The breeding structure as it is known in the Netherlands includes a number of modular certificates. A number of infection detection and eradication programmes have been developed for this certification scheme which are subsequently monitored regularly. Conditions to implement such programmes are:

    • A thorough knowledge of the epidemiology and the pathogenesis of a particular infectious disease.
    • A programme developed on the basis of the above that takes care of the elimination of the relevant germ.
    • A monitoring programme that rules out the presence of infection.
    • And a structure that prevents reinfection.

    Certificates have been developed for various infections occurring in the Dutch pig breeding sector. In all instances these certificates have been applied in the sector in order to provide the buyers with guarantees for the breeding animals. The following diseases have been minimised in the Netherlands with the help of these certificates.

    • Aujeszky's disease (pseudorabies).
      Although this disease requires official notification, it used to be a voluntary programme at the start. In view of the nature of the infection, the knowledge of the pathogenesis and the availability of a marker vaccine, a strict vaccination programme was started in the 1980s. Only approved vaccines could be used, in order to decrease the infection pressure on the breeding farms. After having carried out such a vaccination programme for some time, it became possible to remove the germ carriers from the farms with a test and removal strategy.

      Subsequently it became necessary to keep the doors of the farms locked to keep new pseudorabies germs out. In addition to the continuation of the vaccination strategy, certification was being prepared in order to avoid farms that were free of germs would be reinfected. Strict inspections regarding both vaccination and the continued absence of the germ have guaranteed the success of the method.

    • Atrophic rhinitis.
      When it became clear that this disease was primarily caused by a particular type of pasteurella, efforts were made to find ways to detect this germ at the breeding farms potentially at risk. It was found that a sufficient number of breeding farms in the Netherlands were free of the infection.

      With a protocol on how to test such farms (animal category, number, frequency) and a vaccination and medication prohibition, certainty as to the absence of the germ was better guaranteed.

      This approach has proved to be successful in the Dutch structure. All Dutch pig breeding farms now fulfil the so-called Pm+ free certificate requirements.

      Initially it was assumed that the approach of a strict vaccination programme and the eradication of positive animals would be enough to make a farm free of the pasteurella pathogen. However, this approach has only led to certification in one single case.

    • Scabies.
      The sarcoptes-mite cycle is relatively simple and there are effective instruments to break through this cycle. This is one reason why an eradication programme could be developed. Even more so when a serological test became available that could show whether an eradication programme had indeed killed the parasites on a farm, and the process of certification could be started successfully.

    The abovementioned programmes have in the meantime proved their value within the breeding pyramid in the Netherlands. Programmes for other diseases must now be developed. So far the earlier-mentioned criteria cannot be fulfilled: a thorough knowledge of the infection pattern, adequate germ detection, in particular of the carriers, and an effective way to rid the population of the germ. Until such time as this has been realised, we will have to be content with a clinically healthy stock of animals and farms. The fact that animals will transport germs to a farm should be considered at all times.

  2. Breaking through the infection chain

    In the case of a number of diseases it is possible to remove pigs from a possibly infected population before they are infected. A quarantine stage between the farm of origin and the final farm of destination is in such cases essential in order to exclude the possible introduction of infection. Germ fighting can be more successful if the infection risk on both the farm of origin and the farm of destination has been clearly defined, so that the transfer process can be harmonised.

    Accepted methods for breaking through the infection chain have been worked out in Han Smits' article. Methods that are successful and are being applied within TOPIGS breeding farms worldwide include medicated early weaning and piglet snatching. Under the present regulations, neither method can be used in the Netherlands.

  3. Depopulation and repopulation with animals with a high health status to raise the health level of breeding farms.

    Depopulating and repopulating a farm with SPF animals is a simple way of creating a higher health status

    When animals are born by Caesarean section – under sterile conditions – the chance that they are infected is very small. Consequently, a number of populations have been produced by this method in different parts of the world; they are free of a number of defined germs. Such a population is then given the SPF status. SPF is the abbreviation for "Specified Pathogen Free".

    When SPF is mentioned, it is always important to determine the definition of the SPF status, for "Specified" can also relate to one single germ. Moreover, it is also important to verify in which way the "Pathogen Free" status is tested. Size of sample, choice of animals to be sampled, methods of examination and the quality of the laboratories that carry out the analyses all give insight into the value that can be attached to a particular SPF status.

    It is also important to get insight into the way in which SPF populations are genetically improved. In other words, which securities and guarantees apply when genetics is introduced in the form of semen or embryos, for example. Working with frozen AI and embryo transplantations can provide such guarantees (see elsewhere in this journal). It is possible to repopulate new SPF populations elsewhere in the world from one primary SPF farm.

    The method of depopulation/repopulation is successfully being adopted in an increasing number of countries. The payback time of such operations can vary enormously and depends on the costs of health management that were incurred before depopulation and, naturally, on economic circumstances too. Experience throughout the world, however, shows that a payback time between 9 and 18 months must be regarded as feasible. Fears of reinfection after such an operation are, of course, justified. One should not forget, however, that if infection with a particular germ takes place, there will not normally be a large number of secondary germs present in this type of repopulated farms, as a result of which reinfection will be many times lower than in conventional circumstances. If, in addition, appropriate measures are taken to minimise the possibility of reinfection, this method can also be used successfully in intensive pig husbandry countries like the Netherlands to achieve better results. Conditions to guarantee better health Irrespective of the actual health status, it stands to reason that a farm should endeavour to maintain that status. Basically, it is not important what sort of status a pig farm has. Each status must seek to avoid entry of infections into the population. One word that is used in this context is "biosecurity". Biosecurity comprises all that must be done to prevent germs from settling on a farm. It concerns not only the prevention of infections (by applications of a technical nature such as clean and dirty roads, hygiene sluice, fence, etc.), but farm management also plays a crucial role. It goes beyond the scope of this article to go into all the aspects of biosecurity.

Conditions to guarantee better health

Irrespective of the actual health status, it stands to reason that a farm should endeavour to maintain that status. Basically, it is not important what sort of status a pig farm has. Each status must seek to avoid entry of infections into the population. One word that is used in this context is "biosecurity". Biosecurity comprises all that must be done to prevent germs from settling on a farm. It concerns not only the prevention of infections (by applications of a technical nature such as clean and dirty roads, hygiene sluice, fence, etc.), but farm management also plays a crucial role. It goes beyond the scope of this article to go into all the aspects of biosecurity.

From top to bottom

Precautions when working with a high health status within a breeding pyramid One of the challenges of working with good health is the introduction of breeding material with a high health status in populations of which the health is at a lower level. If adequate precautions are not taken, there is a risk that the new animal material will become infected and possibly fall ill.

Adaptation procedures can result in a problem-free introduction of pigs into populations with a different or a lower health status. Adaptation means that animals are gradually exposed to germs for which they have no resistance.

For a number of infections this means that the pigs should be vaccinated. This protects them against possible infections. However, there are no effective vaccines available for a large number of diseases. In such cases, pigs must be gradually exposed to the animals and/or the material already present in a controlled way. This form of adaptation does not allow for an explicit protocol. This means that a plan must be drawn up per farm, so as to take into account the prevailing circumstances of the receiving farm and the status of that farm.

Incidentally, some form of adaptation is not only to be recommended for farms with a high health status. It can be applied to each introduction of animal material on a farm, irrespective of its status. If it is possible to receive new animals in a separate section, this will act as a quarantine stage that prevents infections that may be introduced with the new animal, and therefore threaten the farm. If this quarantine period is also used for adaptation, the pigs can take as long as necessary to adjust to the farm circumstances. Adaptation is best practised if materials (manure) and animal contact (removal of healthy cull sows) is provided. By monitoring them carefully, and treating them immediately if they fall ill because of germs with which they have come into contact, the animals will be able to build up resistance to the farm micro flora and suffer the least possible damage. Doing this under isolated circumstances lowers the risk that the health balance of the farm will be disturbed. A normal adaptation procedure lasts approximately 6 weeks, but if germs spread slowly or if the secretion period of germs after infection is longer, it is advisable to extend the adaptation period to 10 to 12 weeks.



This article was originally published in the Spring 2007 edition of Diergeneeskundig Memorandum Periodical Magazine.

June 2007