Sow Farms
Data were available for 63 different sow farms, of which 17 participated in 1 yr of the study period; the remaining farms participated in 2 or more years. Number of farms per year were 45 in 2004, 44 in 2005, 31 in 2006, and 35 in 2007. The total data set consisted of 155 sow farm-year combinations, including 62 farrow-to-finish farm-years (only piglets were considered) and 93 specialized sow farm-years. Table 2 presents the average NDD per average piglet year at the sow farms (NDD2). The overall average was 129.7, varying from the smallest average of 108.5 in 2004 to the greatest average in 2006 of 138.2. The average number of daily dosages per average piglet year varied between the sow farms, from zero at some farms to a maximum of around 400. Figure 2 presents the Lorentz curve for NDD2 and shows that at 10% of the farms about 25% of the antibiotic dosages were administered. The study sample of sow farms was representative for the entire LEI FADN sample of sow farms (data not shown).