While the standard of external biosecurity is very high on Irish pig farms, internal biosecurity i.e. the ability to break the circulation of pathogens that are already present on the unit, usually requires improvement.
This is according to Dr. Allison Kirwan, a veterinary practitioner with Highfield Veterinary Group, who specialises in pig health.
Better internal biosecurity on pig farms
Animal Health Ireland (AHI)-funded biosecurity assessments, carried out by specially trained vets, have helped verify that high external biosecurity standards are usually present on Irish pig farms.
However, internal biosecurity measures, especially on those pig farms that use in-feed medication, need to be more closely analysed with “all potential shortcomings identified and addressed as practically as possible”.
According to Dr. Kirwan, this is a key issue for pig farmers who are preparing for life after January 2022, when new laws governing the prescribing and dispensing of veterinary medicines come into effect.
“Most antimicrobials administered to pigs are given via the oral route, achieved by inclusion directly, or indirectly, into the final dry or liquid feed mix, or by adding to the drinking water,” she said.
“Around three quarters of the medicated feed used on pig farms in Ireland is given in the post-weaning phase, at a time when pigs are stressed as they leave their mother, enter new accommodation, are introduced to new pen mates and switch to solid feed.
“They also become more vulnerable to infections around this time, due to losing the bulk of the maternal antibodies that they ingested from mother’s colostrum, within the first hours of life.”
Antimicrobial reduction on pig farms
Implications of the new Veterinary Medicines Regulations include a reduction in the total use of antimicrobials on pig farms, since group prophylactic (preventative) treatments will be prohibited.
Prophylactic treatment of pigs has tended to take place at critical points in the pig’s lifecycle, when disease would be most likely to occur, such as after weaning or following movement and mixing into new accommodation, said Dr. Kirwan.
On most commercial pig units, pigs are born every week, so each farmer must learn how to best control the unique circumstances on their farm, whether multi-site or single-site, depending on:
- The quality and suitability of the accommodation for each stage of production (thermal comfort, stocking density, hygiene, feed and water accessibility);
- Physical separation of different age groups;
- The quality and consistency of the feed and water;
- The diseases present in their pig population.
“This experience allows them to more accurately predict what diseases and clinical signs are likely to arise, at which point in the pigs’ life.
“Historically, antimicrobials have been used at these strategic points in production, to reduce the likelihood of disease occurring and to avoid unnecessary suffering and loss.”
But this will change and that is why internal biosecurity is crucial.
Internal biosecurity
“As its most basic, emphasis should be placed on strict batch production, including physical separation of different age groups, with thorough cleaning, disinfection, and down time in between each batch,” said Dr. Kirwan.
“This is essential for reducing the spread of bacteria, viruses and parasites from batch to batch and from pig to pig.
“In particular, the spread of gastrointestinal pathogens, arising due to direct contact with faeces, can be greatly curtailed when hygiene and batch flow are improved.”
Because of their immunosuppressive modes of action, certain viruses will allow other pathogens, including bacteria, to become more problematic.
Dr. Kirwan explained:
“When immunosuppressive viruses are present on a unit, such as porcine reproductive and respiratory syndrome virus (PRRSv) or flu viruses, an appropriate and complete vaccination programme must be in place to maximise the immunity of the whole herd, to reduce the existence of sub-populations of naive animals and to reduce shedding after infection.
“Suboptimal vaccination programmes will allow the recirculation of viruses and bacteria, contributing directly and indirectly to the need for antimicrobials,” she added.
“In the case of PRRS, if only the breeding herd is vaccinated, then piglets become susceptible to disease once mother’s antibodies wane, around late first stage or second stage.
“Virus can then successfully replicate in the grow/finisher population, with direct negative implications for their growth rate, feed conversion efficiency and with increased susceptibility to other respiratory diseases, mortality, and the likelihood for antimicrobial treatment,” said Dr. Kirwan.
She added:
“Increased viral shedding from the progeny also bounces back to the adult herd, continuously adding to the infection pressure in the breeding herd, potentially resulting in disease, or in transplacental infection back to piglets.”
Administered at strategic points in life, antimicrobials will continue to play an important role in controlling endemic bacterial diseases on pig farms, with important economic and welfare implications, according to Dr. Kirwan.
“However, farmers are becoming more aware of the importance of the other factors that must be fully implemented to prevent diseases from becoming clinically significant.”
New veterinary medicine regulation changes mean that pig farmers will be obliged to more closely scrutinise all the fundamental factors that constitute good internal biosecurity and management.
“A ‘one size fits all’ solution does not exist, and it will take time to learn what approach works best for each unit.
“More inclusive and meaningful veterinary participation at farm level is required to give pig farmers the confidence they need to farm sustainably and consistently, with minimal future reliance on antimicrobials,” said Dr. Kirwan.