TABLE 1.

Antimicrobial agent exposure in 6 months of raise for each farm categories.

Purpose of use	Antimicrobial classes	Antimicrobial agents	Farm categories
			Extensive antimicrobial use	Limited antimicrobial use	No antimicrobial use
Feed additive	β-lactam	Amoxicillin	+	−	−
	Macrolides	Kitasamycin, tilmicosin, tylosin, tylvalosin	+	−	−
Treatmenta	β-lactam	Amoxicillin, ampicillin, penicillin, ceftiofur	+	+	−
	Fluoroquinolones	Enrofloxacin, marbofloxacin	+	+	−
	Aminoglycosides	Gentamicin, neomycin, streptomycin	+	+	−
	Polymyxins	Colistin	+	−	−

+ indicate use those antimicrobial classes, − indicate not use those antimicrobial classes. ^aNot all farms used the same antimicrobial agents and may not use all antimicrobial agents list, for instance farm A used β-lactam, fluoroquinolones, aminoglycosides, and polymyxins for treatment while farm B used only β-lactam and aminoglycosides.