Antibiotic Use In Poultry
Fast-growing broiler chickens, which reach slaughter age in just 32-40 days, are widely used in intensive farming and have much greater need for antibiotics than the slower-growing breeds used in free-range and organic farming and increasingly in indoor farming in the Netherlands. Lower stocking densities in indoor flocks are linked to reduced disease incidence, as air quality is better, wet litter is less of a problem and disease spread is lessened.
The information below has been taken from a new report from the Alliance to Save Our Antibiotics. You can find the full report here.
The use of medically-important antibiotics has been cut very significantly in UK poultry in recent years. Since 2012, the British Poultry Council – which represents 90% of poultry meat produced in the UK, but does not include egg production – has been collecting data on
its antibiotic use and its latest report shows that use of medically important antibiotics has been reduced by 71% between 2012 and 2016 . The BPC’s welcome initiatives on antibiotic use include:
• an end to all routine preventative antibiotic use
• an end to all use of the last-resort antibiotic colistin
• an end to all use of the critically important fluoroquinolone antibiotics in chickens.
It is clear that part of the BPC’s reduction in use are down to targeting treatments more accurately when they are needed, rather than relying on relatively routine use of antibiotics. The BPC also says that it has been achieving its reductions through focusing on good husbandry, hygiene and stockmanship.
However, the BPC also says that it has replaced antibiotics “with alternatives where available” . Alternative treatments may refer in some cases to vaccination. However, another alternative, widely used in poultry are “coccidiostats”. These are antimicrobials, which are not used in human medicine due to toxicity concerns, that can be added to feed without the need for a veterinary prescription to control
the disease coccidiosis which occurs in intensively farmed poultry. The most widely used coccidiostats are the ionophore antibiotics.
Data we have obtained from the Veterinary Medicines Directorate via a Freedom of Information request shows that use of ionophores and other coccidiostats has increased very significantly in recent years and reached record levels in 2015, see Figure 3 (page 13 of report).
The increasing quantities of coccidiostats being used may be partly due to the ban on the growth promoters which was implemented in the EU in 2006, as well as recent reductions in preventative use of medically-important antibiotics. In addition to their growth-promoting effect, growth promoters helped control necrotic enteritis, an intestinal disease which is widespread in intensively farmed poultry . Ionophores are also known to control necrotic enteritis . Furthermore, like zinc oxide in pigs, several ionophores have a known growth-promoting effect and some used to be licensed as growth promoters in pigs and cattle in the EU. Several ionophores, used as coccidiostats in the UK, are used as growth promoters in non-EU countries .
The routine and widespread use of ionophores in poultry does not raise the same level of concern regarding antibiotic resistance as the overuse of medically important antibiotics does, due to the fact that these antibiotics are not used in human medicine. There are nevertheless some human-health concerns associated with their overuse. High levels of use can lead in some cases to Maximum Residue Levels being exceeded in food, which can be a concern due to the ionophores toxicity . There is also some evidence that the use of certain ionophores can ‘co-select’ for resistance to medically important antibiotics in certain bacteria .
So whilst the use of medically important antibiotics in poultry can clearly be cut without altering farming systems significantly, the heavy reliance on alternatives like coccidiostats does raise some concerns.
Antibiotic use is much lower in slower-growing chickens
Under standard intensive production, broilers are now slaughtered at between 32 and 40 days of age , . In free-range production, however, broilers cannot be slaughtered before 56 days of age, and in organic production this increases to 70 or 81 days , .
As the European Food Safety Authority (EFSA) Panel on Animal Health and Welfare explains, “Over the second half of the 20th century, the growth rate of commercially produced broiler chickens has been increased greatly, with standard broiler chickens now reaching 1.5 kg body weight in 30 days whereas 120 days were needed in the 1950s. Simultaneously, the feed conversion ratio (the amount of feed eaten per kg of chicken growth) has been reduced from 4.4 to 1.47” . As EFSA’s Panel on Animal Health and Welfare says, “It has been shown that this is largely the result of genetic selection and it is generally accepted that most of the welfare problems [in broilers] are caused by genetic factors”.
Rapid growth of broilers has been linked in various studies with welfare problems, including metabolic problems and leg problems, immobility and also with higher mortality56. There is also now clear evidence, from the Netherlands, that slower-growing breeds have a much lesser need for antibiotics.
In the Netherlands, a public campaign led since 2012 by an animal-welfare group, Wakker Dier, has highlighted the plight of fast-growing chickens, which they refer to as “plofkip” (exploding chicken) . By raising public awareness of the issue, the NGO managed to put pressure on supermarkets to move away from the fastest-growing breeds, and towards animals that have a “better life” with a minimum slaughter age of 56 days.
The public pressure has led many supermarkets to commit to selling more expensive, slower-growing birds, although the standard the supermarkets have mainly adopted has a minimum slaughter age of 45 to 49 days. By the end of 2016, 90% of retail poultry meat in the Netherlands was from these “slower-growing” birds, representing 27% of total production (most Dutch production is exported) .
Despite Dutch supermarket broilers often still being relatively fast growing, industry data shows they receive three to six times fewer antibiotics, with the exact number depending on the measurement used , . The Plofkip campaign provides a remarkable example of supermarkets and industry accepting consumer pressure to improve animal health and welfare by partly reversing a key aspect of modern intensive poultry production. The use of even more slow-growing broilers, as used in UK free-range or organic production, would likely lead to even greater reductions in antibiotic use.
Stocking density is a measure of the average amount of livestock per area of farm space. More cramped conditions can increase animal stress and the spread of disease, hence increase the need for veterinary interventions. The baseline maximum permitted EU stocking density for standard broilers is 33 kg of chicken per square metre, although under certain conditions, widely met by the poultry industry, derogations allow this to rise to a maximum of 42 kg/m2.
The UK only allows a maximum stocking density of 39 kg/m2 for farms that meet the conditions of the EU derogation, and the Red Tractor Standards place a limit of 38 kg/m2. So the standard maximum stocking density used by most intensive chicken farms in the UK is 38 kg/m2, which equates to 19 birds weighing 2 kg per square metre, or less than an A4 sheet of paper per bird.
Free-range and organic production not only have requirements for access to the outdoors, but the permitted stocking densities for fixed housing are also lower: for free-range it is 27.5 kg/m2 and for organic it is 21 kg/m2.
According to the EMA and EFSA, higher stocking densities have been associated with increased preventative use of antibiotics due to the expectation of increased disease risk . An earlier EFSA study found that the top-ranking “environmental” hazard for broiler welfare is stocking density .
Higher stocking densities promote stress, particularly thermal stress in the birds and are associated with wet litter, increased ammonia concentrations in the air, increased footpad dermatitis and lower welfare , , . Heat stress damages the immune system and is associated with intestinal injury , . Higher stocking densities also mean that there is a need to thin the flock (some birds are removed for early slaughter), which is a stressful event for the birds.
Ammonia concentrations in poultry houses can be very high. Ammonia is produced in the litter, particularly wet litter, by microbial decomposition. High levels of ammonia damage the immune system. Concentrations above 10 parts per million (ppm) can also damage the lung surface and increase the birds’ susceptibility to bacterial respiratory disease, especially E. coli infection. These high concentrations have been linked with air sacculitis, pneumonia and septicaemia caused by E. coli , . These infections are a major cause of antibiotic use in the poultry industry .
The maximum ammonia concentrations permitted under Red Tractor standards is 20 ppm , which is twice the concentration associated with increased susceptibility to respiratory infections.
Lowering stocking densities would be likely to reduce wet litter problems, lower ammonia concentrations and reduce respiratory and intestinal diseases which require antibiotic treatment.
The cost of reducing stocking densities would not be very significant. A report by an advisory committee to the European Commission calculated that reducing stocking densities from 38 kg/m2 to 30 kg/m2 would increase production costs by 5% and the cost to the consumer by just 2.5%. Similarly, reducing the stocking density to 20 kg/m2 would only increase production costs by 15% and the cost to the consumer by 7.5% .
Access to outdoors
According to EFSA and the EMA “The stress associated with intensive, indoor, large scale production may lead to an increased risk of livestock contracting disease” . Although there is very little publicly available data on antibiotic use in animals kept indoors and those with access to the outdoors, providing outdoor access is listed by EFSA and the EMA as one practice of free-range and organic farming systems that could be used in other farming systems to reduce antibiotic use4. A Defra study of seven organic poultry farms found that during the two years of the study, only one farm used any antibiotics at all, see Figure 1 (page 11 of report).
Advocates of intensive farming methods often point to worse “external biosecurity” when animals have access to the outdoors. This means that it is more difficult for animals kept outdoors to avoid exposure to wildlife and pests and to pathogens in the air, soil or insects. However, “internal biosecurity”, which is the risk of disease transmission between animals in a herd of flock can be much better because of decreased contact between animals and better air quality.
Poultry housed outdoors are also likely to be less susceptible to disease as more resilient breeds are chosen.
The range stocking density of free-range poultry cannot exceed one bird per square metre, and in organic farming it cannot exceed one bird per ten square metres.
This information has been taken from a new report from the Alliance to Save Our Antibiotics. You can find the full report here.
For references please see report.