Low disease resistance due to rapid growth in farm animals

Farm animals are selected for fast growth, for economic reasons, but this is detrimental to their resistance to diseases according to researchers at the University of Groningen led by Prof. Simon Verhulst. By selecting for fast growth, the agricultural industry may thus inadvertently have contributed to the incidence of epidemics and the growing demand for antibiotics, so the ecophysiologists suggest in the scientific journal Functional Ecology.

Farm animal diseases and the resulting large-scale administering of antibiotics are increasingly considered a major problem in the intensive poultry and livestock industries. The calls to limit the use of antibiotics are growing louder, partly due to the undesirable consequences for public health. These undesirable consequences arise because the widespread use of antibiotics results in antibiotics resistance of pathogens, which makes it more difficult to treat an infection in humans.

Immune system

The Groningen researchers compiled for the first time the immune function measurements that were done in the context of experiments in which poultry were selected for fast growth over several generations. Meta-analysis of these experiments showed that, almost without exception, selection for faster growth resulted in decreased resistance to disease.

Epidemics

Animals held commercially for the production of meat grow extremely fast, which decreases their immunity. This has probably contributed to the increased incidence of epidemics and perhaps the farmers’ practice of administering more antibiotics.

Alternative breeding programme

However, the researchers also found that experimental selection for a more responsive immune system had, on average, no effect on growth. This suggests that with an alternative breeding programme, selecting simultaneously for growth and immune function, it should be possible to select fast-growing poultry that are also resistant to disease

Note for the reader

- Trade-off between growth and immunocompetence: a meta-analysis of selection experiments. Authors: Peter J. van der Most, Berber de Jong, Henk K. Parmentier and Simon Verhulst. Functional Ecology, on-line November 15th 2010.
– More information: Prof. Simon Verhulst, Professor of Behavioural Ecophysiology, Centre for Behaviour and Neurosciences of the University of Groningen, s.verhulst@rug.nl, tel. +31 (0)50 363 2059.