Effects of air quality on pig health and welfare : Towards improved decision making regarding this open norm in animal-welfare legislation, with special attention to the effects of aerial ammonia

Summary

European and Dutch pig-welfare legislation prescribes that the air quality, esp. pollutant gases, dust, and ambient temperature, should not be harmful to the pigs. This is a so -called open norm (principle-based standard), which is subject to interpretation, and as a consequence potentially failing to effectively protect animal welfare. An attempt has been made to close (i.e. implement or enforce) this norm in the Netherlands, but the Dutch Food Safety Authority (NVWA) seems to encounter very few if any cases of harmful air quality despite the prevalence of animal-based indicators such as lung lesions/pleuritis, conjunctivitis, pen soiling and tail biting, and despite fairly high concentrations of esp. ammonia ( NH3), esp. in winter.
An inventory was made of publications reporting effects of air quality, esp. NH3, on pig health and welfare (Appendix 1) and a number of questions regarding likely harm done to Dutch pigs have been answered tentatively.
The effects of NH3 on the farmer and other persons who may be in the barn were also examined, the idea being that where pigs can be a model for human health, humans, and other species, can be a model for pigs too.
In practice, it is difficult to change the open norm for air quality into a well substantiated “closed” quantitative norm on the basis of scientific findings. It is clear that the lower the concentrations of air pollutants, the lower the risks that animal wellbeing is being harmed, or that animals experience discomfort.
Some studies indicate that the maximum allowable NH3 should not be higher than 15 or 20 ppm. However, there are some indications in literature that levels below 15 or 20 ppm can still cause a certain level of harm, discomfort, or production loss in pigs. With a strict interpretation of the law, this would indicate that the maximum level should be lower than 15 or 20 ppm. Furthermore, findings in literature indicate that maximum levels NH3 should probably be lower for weaners than for growing and finishing pigs. It is recommended to further explore if key performance indicators (KPI’s) can be implemented which enable a pig farmer to monitor and control if air quality is harming the animals. Relevant elements in such an approach can be for example antibiotics use, condition of (intact) tails (with hair plume), level of tail biting, production performance, lung-lesion scores at the slaughterhouse, level of pen soiling, tear staining, conjunctivitis, etc.