Last Saturday I wrote a blog about the rise of maize growing in this country including Devon and Dartmoor and the environmental problems associated with it. I also made reference to a Soil Association paper on the subject called ‘Runaway Maize’ – that document made reference to an anecdotal association between the incidence of TB in cattle and the growing of maize – there was no scientific reference detailing this so I didn’t mention it. However this week the University of Exeter (B Winkler and F Mathews) has published a detailed paper on the topic in a journal of the Royal Society “Environmental risk factors associated with bovine tuberculosis amongst cattle in high risk areas”. You can download the Royal Society paper here and you can read the University’s press office release here.
The paper details a mathematical model which has been produced based on data from over 1300 farms (some where TB was prevalent and some where it was not). The model predicts and I quote from the paper that “The risk of bTB breakdown increased on farms with greater areas of deciduous wood, maize, marsh and rough pasture, and in herds that were larger, fed silage and were dairy units. The risk decreased on farms that had a greater percentage of hedges in boundaries, that grazed cattle on fields that had been cut for silage or hay and had greater numbers of cattle moving off the holding”.
The discussion section states “Broadly, characteristics of higher intensity production, such as larger herd size, maize production, use of silage and reduced hedgerow abundance were linked with elevated infection risk”.
“The dairy industry is currently undergoing particularly marked alterations owing to market and regulatory changes. Average dairy herd sizes rose by 36% from 1990 to 2003 in England. In the same period, the area planted with maize in South West England increased fourfold. Badgers favour maize as a food source: in the south west of England 72% of land owners report badger damage to cereal crops (oats, maize, barley and wheat). Contamination of maize by badger faeces and urine may therefore present a possible route of infection. Maize may also play a role by altering badger population sizes and their nutritional status”.
This is a very important study produced by a highly reputable research unit and published in a world class journal. In essence the paper says that the way we manage the countryside directly impacts on the incidence of bTB and therefore by changing some of these practices we should be able to reduce outbreaks of TB in cattle.
For every 10ha of maize that is planted the risk of a TB outbreak increases by 20%. In dairy herd of over 150 animals in size they were 50% more likely to suffer a bovine TB outbreaks than herds with 50 cattle or less. The report suggests that by excluding cattle from marshland (by fencing them out) TB outbreaks would be substantially reduced – for every 10ha of marsh on a farm TB outbreaks increase by 70%. On farms with 50km of field boundaries each extra 1km of hedgerow was linked with a 37% reduction in risk.
There is much in here for us all to mull over but there is also a real message of hope. If we are prepared to heed this advice and take action there is a route forward in the battle against bTB. Many of the actions proposed would also lead to a countryside richer in wildlife. If we choose to ignore the findings or are unable to implement them for economic reasons then the incidence of TB in cattle will continue to rise. This approach offers a science based alternative to the current controversial and unproven policies being trialled to reduce TB in some parts of the south west.