Riskfactors for antimicrobial resistance in enteric Escherichia coli from calves in dairy herds - Part II
In dairy calves, common intestinal bacteria are often resistant to antibiotics. This project investigated risk factors for such occurrence. Specifically the impact of feeding milk from cows treated with antibiotics was studied.
• Colostrum from cows treated at drying off was used as feed for calves on almost all farms but this did not increase the occurrence of resistance.
• Milk from cows treated in lactation was used as feed for calves on about half of the farms during treatment and on the majority of farms during the withdrawal period for dairy delivery. Use of such milk increased occurrence of resistance.
• Also calf age, housing, geographical localization of the farm and use of specific antibiotics influenced occurrence of resistance.
• On farms where calves carried quinolone resistant bacteria such bacteria were also carried by older animals and were found in the environment. Most likely such bacteria are spread between animals on a farm but also between farms.