Table 13.

Characteristics of 3 different papers quantifying antimicrobial use in North American feedyards.

	Brault et al.	Rutten-Ramos et al.	Apley et al.
Metrics reported	nADD of active antimicrobial ingredient/100,000 cattle	Milligrams of active antimicrobial ingredient/kg liveweight sold	Milligrams of active antimicrobial ingredient/kg of liveweight sold and Regimens/Animal Year, with regimens described by mg/Reg and Calendar Days of Administration (CDoA)/Reg
Populations and antimicrobial attribution	Defined as cattle lots received in the designated study period with all drugs administered (characterized by administration records) attributed to each lot during their entire feeding period.	Defined as cattle lots placed in the designated periods with all drugs administered (characterized by lot records of drug billing to each lot converted to active ingredient) attributed to each lot during their entire feeding period.	Defined as the cattle lots closed out (sold) in the study year with all drugs administered (characterized by administration records) and days on feed attributed to the study lots for the entire feeding period.
Assignment of nDDD to single injection antimicrobials	nDDD/administration and ADD (mg/kg per day) assigned values are included in supplemental information in the Brault, et al. article. An nDDD value of 3 DDD per administration was assigned to 8 injectable antimicrobials and one oral bolus antimicrobial. An nDDD value of 2 DDD per administration was assigned to two injectable products.	nDDD values per regimen or DDD values were not assigned. Analysis addressed mg of active product.	nDDD/administration and ADD (mg/kg per day) values are not assigned. Administered mg of active substance and regimens are reported along with descriptions of the regimens as CDoA/Reg and mg/Reg.
Assignment of nDDD to in-feed antimicrobials	ADD (mg/animal per day) assigned values are included in supplemental information for the Brault, et al. article. The DDD value for chlortetracycline in the feed is established by selecting a median dose from the mg/day regimens used for respiratory disease (5,500 mg/day). The administered daily dose is then divided by the DDD value to assign an nADD value to that administration. The DDD value for tylosin in the feed was established from the consideration of injectable doses (17.6 mg/kg for a 450 kg animal, 7,920 mg).	nDDD values per regimen or DDD values were not assigned. Analysis addressed mg of active product.	ADD (mg/animal per day) values are not assigned. Administered regimens and descriptions of the regimens as calendar days of administration (CDoA)/Reg and mg/Reg are reported. Mean mg/CDoA may be calculated from these values.

DDD, Defined Daily Dose; nDDD, number of Defined Daily Doses; ADD, Animal Daily Dose.