The use of antibiotics in the Dutch livestock sector has stabilised after an earlier drop of approximately 70 per cent. Has the usage of antibiotics been cut back by enough? The answer is not a straightforward one, say WUR's Kees Veldman and Hetty Schreurs and Dick Heederik of the Dutch veterinary medicine authority foundation (Stichting Diergeneesmiddelen Autoriteit, SDa). They refer to structural high-volume users.
For over a quarter century, Wageningen Bioveterinary Research (WBVR) in Lelystad has been measuring the effects of the use of antibiotics in the Dutch livestock sector on the resistance to antibiotics in domestic farm animals and food. To this end, WBVR, which tests samples taken from the slaughter line, partners with the Netherlands Food and Safety Authority (Dutch acronym NVWA), which takes samples from animals and meat products, and Wageningen Food Safety Research (WFSR), which tests fresh meat products for resistant bacteria.
Furthermore, the SDa releases an annual report on the use of antibiotics in the livestock sector. This report shows antibiotics use in daily doses per annum for different animal sectors (bovine, poultry and hogs) and different husbandry systems (porkers and piglets, broilers and laying hens). The annual MARAN report combines the data from WVBR and the SDa.
According to the latest edition of the MARAN report, a significant drop in the use of antibiotics has caused the resistance to antibiotics in domesticated farm animals to be substantially reduced since 2009. However, over the last five years, both the usage and resistance in most livestock sectors have stabilised.
When can we say there has been sufficient reduction in the use of antibiotics? That is the topic we discussed with Dick Heederik, chair of the SDa expert panel and professor of Health Risk Analysis at Utrecht University and Hetty Schreurs, SDa director and her colleague Kees Veldman, a WBVR researcher.
Veldman, head of the National Resistance Laboratory for antibiotics resistance, studies how resistance develops in domesticated farm animals. His message is two-fold. 'The drop in resistance in the E. coli bacterium has reduced the risk of propagation among humans and animals. Moreover, there is a considerable drop in the incidence of ESBL-E. Coli in broiler chickens and chicken meat, which is positive news, as this bacterium is resistant to a key group of antibiotics used in humans and must, therefore, be prevented from entering the food chain as much as possible.
However, some other types of bacteria show no positive response to the reduced usage of antibiotics in domestic farm animals in terms of their level of resistance, Veldman says. 'Further research on the effect of antibiotics on the resistance against them is needed.' Moreover, what the effect of prolonged usage on resistance against antibiotics is, is not known. That makes long-term monitoring essential, says Veldman.
Dick Heederik works for the Veterinary Medicine Authority to determine the total annual usage of antibiotics per livestock sector. Heederik: 'But we also monitor the usage on individual farms over multiple years. This reveals that some businesses structurally use very few antibiotics while others structurally exceed the benchmark. We call the latter structural high-volume users. We aim to reduce the number of such high-volume users.'
Does this imply that there has been a sufficient reduction in the use of antibiotics, with the exception of these high-volume users?
Heederik: 'The data per sector must be viewed in perspective. Consider, for example, the poultry sector. When we started registering antibiotics use in 2010, some poultry farmers used as much as 200 or even 250 daily doses per year. In other words, high-volume users gave their animals antibiotics almost daily. Poultry farmers have significantly reduced their use in recent years, with high-volume users now dispensing 25-35 daily doses per year. The benchmark, however, is set at 10. So, the current high-volume users must still cut back on their usage.'
Heederik: 'In addition to a drop in the number of kilos of antibiotics, there has also been a reduction in the number of different medicines against infectious diseases. The substances available have been divided into three categories. We aim to eradicate the use of substances in the third category from the livestock sector, as these substances are needed for human health care, and we do not wish to create resistance against them. On the positive side, the substances in this third category are barely used anymore.'
Are high-volume users called out on their practices?
Schreurs: 'The SDa report signals trends in the use of substances. If there are concerns, these are highlighted in the letter accompanying the report. It is then up to the government or the livestock sector to address the issue. All sectors have quality assurance systems and regulations that livestock farmers must meet. They, too, see which farmers are high-volume users. These farmers receive a letter explaining their relatively high usage. If their usage does not decline, an advisor comes by to provide free advice. If that fails to spark change, an advisor is deployed, for which the farmer pays. This shows they are called out by the sector.'
Are there problematic sectors?
Heederik: 'Antibiotics use in the dairy sector has always been low and dropped even further in recent years. In the pig farming sector, it dropped significantly at first, followed by a continuous decline, which is really positive. Poultry has already been discussed; it is doing quite well. This is currently the second year in which we are monitoring the goat sector, where the use of antibiotics is low, comparable to the bovine sector. The veal sector, however, is more problematic.'
What is the issue with the veal sector?
Schreurs: 'The number of daily doses in this sector is not only high but changing that practice is challenging because the sector works with imported calves that originate in different countries with a variety of husbandry systems. That results in the "day-care effect": the claves carry different infectious diseases that are transmitted in the barn. As a result, many veal farmers are not in control. The same applies to the smaller turkey and rabbit sectors, where the usage of antibiotics is not stable. Coaches are now being deployed to help reduce the use of antibiotics. There are only forty rabbit farmers in the Netherlands, which does not justify writing a separate recommendation. They will be given tailored advice from a coach.'
So, barring a few exceptions, has the use of antibiotics been reduced sufficiently?
Heederik: 'All sectors could do with a further reduction, although we realise that zero usage is impossible. We aim to keep everyone on their toes. We must continue this policy because of the issues with resistance to antibiotics. Although the issues have abated somewhat in recent years, pathogenic bacteria still develop resistance against antibiotics. So, if there is a way to further reduce the use of these substances, we should do so.'
Schreurs: 'The pig sector is doing quite well in general, but the use of antibiotics in suckling piglets is still relatively high because they face quite a lot of diseases. A new barn with a proper climate system could solve this issue, but the nitrogen problems prevent new barns from being constructed. So, sometimes farmers are willing to reduce their antibiotics use but unable to do so.'
What is the Netherlands' position internationally?
Heederik: 'We may have reduced by 70%, but we still match the European average.'
Schreurs: 'It's worth pointing out that there are many intensive businesses in the Netherlands, which makes it difficult to compare it to countries with mostly extensive livestock farms. The higher the concentration of animals, the higher the likelihood of disease. My former colleague Dik Mevius, the SDa's founder, put it as follows: we will never be the best in Europe, but in view of the high number of production animals in the Netherlands, we are doing fine.'
