How to Support Swine Production and Reduce the Use of Antimicrobials
Growth promoters added to swine diets offer several benefits including improvements in many performance parameters, but at what cost? Using antimicrobial products in animal production may be linked to bacterial resistance which raises concerns for human health. Here are strategies to reduce or eliminate antimicrobial use while maintaining high herd performance levels.
24.09.2020In Brief
+ Growth promoters were previously used to boost production performance, but in modern swine facilities and with increasing levels of awareness of the importance of biosecurity, the beneficial effects of growth promoters are greatly diminished.
+ A strong correlation between levels of antimicrobial use and levels of resistant bacteria has been found in studies conducted in seven countries in the European Economic Community, raising concerns for human health.
+ Stringent external and internal biosecurity measures, along with prudent use of antimicrobials, will ensure high levels of herd performance while reducing the risk of antimicrobial resistance developing.
Growth promoters used for decades
Growth promoters were discovered several decades ago and have provided a positive stimulus for agricultural activities such as pig farming, owing to the animal husbandry benefits they have generated as well as improvements in weight gain, feed conversion ratio and even mortality levels.
Most growth promoter products contain antimicrobial activity and some of them could even be classified as antibiotics for therapeutic use simply by increasing their dose. More recently, the scientific community has reflected on whether, besides use in human medicine, such extreme use in animal production might be causing the occurrence of bacterial resistance to antimicrobials, particularly those used in both humans and swine.
Performance benefits linked to growth promoters
There is consistent evidence that the use of performance enhancers leads to improvements in daily weight gain and feed conversion ratio between 4 and 10%. In meta-analytical studies conducted in Brazil seeking to quantify the impact of withdrawing growth promoters on pig performance, 67 articles covering 90 experiments involving 40,592 pigs were assessed. The conclusion was that feed conversion ratio got worse in 73% of cases. There was also a reduction in weight gain of 4.5% even though it did not impact feed intake. Overall, feed conversion was negatively impacted by 4%.
Improving hygiene standards
Growth promoters are far more effective in sick animals or in those housed at high stocking densities with poor standards of hygiene. Many of the studies investigating the benefits of growth promoter additives were conducted decades ago when hygiene and management standards were much lower. As such, the benefits of using these products in current housing conditions are diminishing and may no longer even exist.
Growth promoters are far more effective in sick animals: the benefits of using these products in today’s improved housing conditions are diminishing and may no longer even exist.
Improvements only in nursery stage
Many experiments have been conducted in the United States to assess the effect of different growth promoter regimes on weight gain and feed conversion in multiple-site production units. In those papers, covering many animals in different production systems, there was no difference between the treatments and the negative control. There was only a difference in daily weight gain in the experiments involving the nursery stage. No difference was found in weight gain in the finishing stage, nor in feed conversion ratio during the nursery or finishing stages. The authors concluded that the use of in-feed antimicrobials in finishing pigs in multiple-site systems must be limited to treatment for bacterial infections only.
The use of in-feed antimicrobials must be limited to treatment for bacterial infections only.
Resistant bacteria
The use of antimicrobials in animal production and the possible appearance of resistant bacteria have given rise to concern for human health for several reasons.
- The bacteria associated with animals are also pathogenic to humans.
- Bacteria may be easily transmitted to humans via contaminated animal products in the food chain.
- The feces of infected animals may spread bacteria into the environment more widely.
- Resistant bacteria associated with animals may have the capacity to transmit that resistance to human pathogens.
Several papers have shown that the routine use of antimicrobials in production animals leads to the development of resistance in commensal bacteria. Studies involving seven countries of the European Economic Community found a strong correlation between the levels of antimicrobials used and the resistance of commensal Escherichia coli isolated from swine, chickens and cattle. The use of subtherapeutic doses of antimicrobials in production animals results in the selection and colonization of resistant bacteria in the intestines and other breeding environments.
Association between treatment and resistance found
Investigations suggest a strong correlation between the use of antibiotics in production animals and the development of resistance of the associated bacteria. An association was made between treatment and resistance in E. coli in swine feces on 34 full-cycle production farms in Ontario, Canada.
The introduction of antibiotics as growth promoters or for the treatment of specific infections through the feed may lead to changes in the gut microbiota of the production unit staff resulting in the emergence of resistant bacterial strains. Both production animals and workers in contact with the antibiotics on farms using growth promoters host more resistant bacteria than those on farms not using those substances.
Superbacteria
Antibiotic-resistant bacteria associated with production animals have been spread into the environment including to the workers in those establishments who then become the last microorganism carriers. This is critical as the agents include Staphylococcus aureus which is resistant to methicillin. It is associated with infectious processes in hospital environments and may result in death, earning it the title of a ‘superbacteria’.
Biosecurity is key
In any production unit, livestock health must take priority. Reactive, curative treatment is being reduced by implementing proactive preventative measures. This preventive culture may be attained with the use of biosecurity on farms.
In any production unit, livestock health must take priority, but proactive, preventative measures can reduce reactive, curative treatments.
Biosecurity comprises a series of factors which aims to prevent the onset, proliferation and dissemination of disease among livestock, preserving and/or restoring the health of the animals.
Biosecurity may be said to be external when it focuses on preventing the entry of disease agents or internal when it seeks to control the proliferation and dissemination of those agents among the livestock in question (Figure 1).
External biosecurity measures
- A green belt: rows of non-fruit-bearing trees that form a physical barrier to the prevailing winds. Trees should be adapted to the local climate with perennial leaves.
- A separating fence: to prevent access by animals, vehicles and people without first passing through the biosecurity procedures of the site.
- Disinfection arch: a set of jets with the capacity for external washing, including the underside of lorries, paying special attention to the wheels.
- A platform: close to the perimeter fence of the facility, for the entry and removal of animals from the site.
- Feed silos: close to the perimeter fence of the facility, with external access, subject to periodic dry sanitization.
- Composter: close to the perimeter fence of the facility or outside the farm, covered in netting, with a water supply and large enough to store the unused substrate depending on the capacity and type of farm.
- Waste treatment system: outside the perimeter fence, paying attention to the distance of application at times of fertigation.
- Water supply: periodic washing of water tanks and supply pipes, annual microbiological analysis and chlorination equipment for use in the event of contamination by coliforms.
In addition, the following factors should be considered:
- Office/changing room: should be close to the separating fence and used to separate the dirty area (outside the farm) from the clean area (internal part of the farm).
- Clothing and footwear: only for use on the farm, items should be washable or disposable and preferably with a shower in the changing room. Before entering the clean area, all personnel should wash their hair, blow their nose and brush their nails.
- Bathroom: one outside and one inside the separating fence, with sink and toilet facilities for use outside and inside the site, respectively.
- Vector control: baiting points for flies and rodents, physical control by cleaning and clearing, and chemical control with products based on the type of infestation, keeping records of application.
- Origin of animals: always give priority to the same supply source of the animals, whether replacement sows, weaned piglets or piglets removed from the nurseries, with a knowledge of their health status in relation to relevant production diseases.
Biosecurity on the inside
In terms of internal biosecurity, it is important to consider the following points (Figure 3):
- Footbath: wash boots or change shoes between sections for easy and effective sanitization and decontamination of footwear.
- Wash hands after any handling of animals, considering the use of alcohol gel as an antiseptic as well as soap and disposable paper towels.
- Cleaning equipment should be kept solely for the room, including shovels, brooms and scrapers.
To ensure the health of the animals, these further internal biosecurity precautions must be taken:
- Taking a sanitary break between batches to clean and disinfect using detergent, a high-pressure and low-flow pump, hot water and disinfectants based on the sanitary requirement. Facilities should be completely dry before the subsequent housing of animals.
- Adequate availability and use of hospital bays with differentiated feeding and drinking infrastructure, availability of feed and water, systems for the thermal insulation of animals and a euthanasia policy for terminally sick animals.
- An adequate vaccination program should be in place based on a health assessment carried out by a veterinary surgeon, with schedules, categories and doses declared, sanitized applicators and needles of adequate quantity and size.
Prudent use of antimicrobials
The prudent use of antimicrobials is being used to rationalize therapeutic treatment in veterinary medicine, particularly for production animals. This approach organizes and standardizes the consistent use of antimicrobials in veterinary medicine, in order to mitigate the possibility of bacterial resistance developing, maximizing the efficacy of medicinal products and avoiding the occurrence of residue above the safe and legal limits in products of animal origin intended for human consumption.
14 recommendations on microbial use
The use of antimicrobials must be supervised by a veterinary surgeon.
Antimicrobials must be used in cases where the agent is suspected to be bacterial, with consideration for the medication selected.
The etiological agent must preferably be identified by isolation and the choice of medication must take into consideration the sensitivity results produced by antibiograms.
The choice of antimicrobial must consider the cost-benefit ratio of both human and animal health.
The recommendations on use must be strictly followed, taking into consideration the dose, route of administration, number of applications, interval between applications, waiting period and form of storage.
The period of antimicrobial use must be as short as possible considering the minimum time required for total remission of the bacterial agent.
A record must be kept of the animals treated, medicinal products used, recommendations on use, time of treatment, who prescribed the antimicrobial and who supplied it.
The use of antimicrobials as performance-enhancing animal husbandry additives must be reduced and avoided wherever possible.
The choice of products and doses must consider the pharmacokinetics and degree of toxicity, taking into account which type of infections must be avoided or controlled.
Avoid the use of antimicrobials used both in veterinary medicine and in human medicine or that may generate resistance in those for human use.
Antimicrobials must be used in a rational rotation.
When antimicrobials are combined, synergies must be sought, and antagonisms avoided.
Preventive measures must be implemented regarding environmental pollution with antimicrobial residues.
Preventive measures must be implemented regarding the occurrence of residues in products of animal origin intended for human consumption.
Growth promoters no longer produce significant performance benefits
The use of performance-enhancing additives in animal production is a sensitive and complex subject owing to its interdependence with human medicine. The use of this type of substance today, under appropriate breeding conditions, does not produce significant benefits as it did in the early stages of its use.
Scientific evidence shows that the use of both growth promoters and antimicrobials without any appropriate technical criterion may promote bacterial resistance. Regulation is needed on the use of antimicrobials in veterinary medicine and, in particular, the use of active ingredients that have a shared use with human medicine should be avoided.
The culture of preventing the occurrence of diseases must be fundamental in the actions of all those involved in swine production.
Prevention rather than cure
The culture of preventing the occurrence of diseases must be fundamental in the actions of all those involved in swine production. When antimicrobial substances have to be used in production systems, obtaining advice from professionals duly trained in the subject area is key.