This cross-sectional survey research study examined the role moral beliefs play in predicting behavioural beliefs and attitudes and the role that subjective norms play in predicting moral beliefs. Using a self-administered questionnaire, one hundred and three feedlot veterinarians completed measures of behavioural beliefs, referent others, perceived constraints and moral beliefs regarding recommendations to use antimicrobials in four situations (i.e. acutely sick cattle, chronically sick cattle, at-risk cattle and high-risk cattle). Regression analysis and F-tests indicate moral beliefs as contributing significant increases in R² to models predicting behavioural beliefs regarding anti-microbial use in each situation. In addition, subjective norms contribute a significant increase in R² in models predicting moral beliefs in each of the four situations. The results indicate the effects of moral beliefs on behavioural beliefs are somewhat contingent on the condition; that is the level of risk associated with treating cattle with antimicrobials, the level of risk of not doing so, and the effectiveness of the antimicrobial in situations such as acute illness or being at-risk of illness.