are very intensive antibiotic users [e.g., the maximum
value of NDD2 in 2007 exceeded 365 implying that the
piglets received even more than 1 dosage per day (1.09
doses) over the entire period they were on the farm].
Consistently, the Lorentz curves also show that some
farms are “heavy users” as 20% of the farms use about
45% of the antibiotics, both on the fattening pig and
sow farms. The large between-farm variation in the use
of antibiotics in the Netherlands corresponds to values
reported from other countries, including Belgium (Timmerman
et al., 2006) and France (Chauvin et al., 2002).
Variations may be due to differences in hygiene status,
prophylactic use, and treatment decisions made by the
farmer or the veterinarian or both (Timmerman et al.,
2006). This study showed that both on the sow and
fattening pig farms the use of antibiotics on individual
farms is relatively stable over the 4 yr of the study period
(variation due to year relative to variation due to
farm is very low). In other words, farms that use greater
amounts of antibiotics in 1 yr will also do so in the
next year, whereas farms that use decreased amounts
in a particular year may also use less in the other years.