The study's findings call for initiatives to preserve antibiotic effectiveness while simultaneously ensuring food security in low- and lower-middle-income countries, say Simon Levin of Princeton University and and co-authors from a number of international institutions.

In a paper published early in Proceedings of the National Academy of Sciences of the United States of America (PNAS), they explain that demand for animal protein for human consumption is rising globally at an unprecedented rate, and that modern animal production practices are associated with regular use of antimicrobials, potentially increasing selection pressure on bacteria to become resistant.

Despite the significant potential consequences for antimicrobial resistance, the researchers say, there has been no quantitative measurement of global antimicrobial consumption by livestock.

They have addressed this gap by using Bayesian statistical models combining maps of livestock densities, economic projections of demand for meat products, and current estimates of antimicrobial consumption in high-income countries to map antimicrobial use in food animals for 2010 and 2030.

They estimate that the global average annual consumption of antimicrobials per kilogram of animal produced was 45mg per kg for cattle, 148mg per kg for chickens and 172mg per kg for pigs, respectively.

Using these figures as a baseline, they estimate that between 2010 and 2030, the global consumption of antimicrobials will increase by 67 per cent from 63,151 to 105,596 tons.

They attribute up to one-third of the increase in consumption in livestock between 2010 and 2030 to shifting production practices in middle-income countries where extensive farming systems will be replaced by large-scale intensive farming operations that routinely use antimicrobials in sub-therapeutic doses.

For Brazil, Russia, India, China and South Africa, Levin and co-authors have calculated that the increase in antimicrobial consumption will be 99 per cent - up to seven times the projected population growth in this group of countries.

The researchers call for better understanding of the consequences of the uninhibited growth in veterinary antimicrobial consumption is needed to assess its potential effects on animal and human health.

'Global trends in antimicrobial use in food animals' by Thomas P. Van Boeckel, Charles Brower, Marius Gilbert, Bryan T. Grenfell, Simon A. Levin, Timothy P. Robinson, Aude Teillant and Ramanan Laxminarayan is published in Proceedings of the National Academy of Sciences of the United States of America. An abstract of the paper is available by clicking here.