Demonstrating the problem of farm-specific cattle weights vs standard weights when comparing antimicrobial use (AMU) in total mg/kg across (hypothetical) farms

FarmTotal mgTotal number of adult milking cattleMean cattle weight (kg)AMU
Total mg/kg using mean cattle weight specific for that farmTotal mg/kg using ESVAC 425 kg mean weight at time of treatment
31 000 00010075013.323.5
41 000 00010045022.223.5
  • Both farms have the same number of cattle and use the same total mg of medicine, but cattle on farm 3 are heavier than those on farm 4 (eg, Holstein-Friesian vs Jersey). Total mg/kg using a cattle weight specific to that farm gives more accurate figures than using a standard weight (in this case, the standard weight chosen is 425 kg, the estimated mean weight at time of treatment for dairy cattle defined by the European Surveillance of Veterinary Consumption group (ESVAC))