Table 16.

Possible measures with regard to feeding calves colostrum from cows treated with antimicrobials during the dry period

Measure	Evidence in support of the measure	Evidence against the measure	Advantages	Disadvantages
C1 Allow use of colostrum during the withdrawal period irrespective of antimicrobial used	Direct Colostrum from cows treated with penicillins and aminoglycosides did not increase faecal shedding of resistant Escherichia coli (Duse et al., 2015) (3.4.1) Indirect Residue levels in the colostrum are low and decrease with the length of dry period (3.2.3)	Direct No evidence from studies (3.4.1)	No interference with current routines on dairy farms. Sufficient colostrum for calves available	Increased shedding of AMR bacteria by calves cannot be ruled out
C2 Prohibit use of colostrum during the withdrawal period irrespective of antimicrobial used	Direct No evidence from studies (3.4.1) Indirect Possible presence of residues when cows calve earlier than the specified withdrawal period	Direct Colostrum from cows treated with penicillins and aminoglycosides did not increase the faecal shedding of resistant E. coli (Duse et al., 2015) (3.4.1) Indirect Residue levels in the colostrum are low and decrease with the length of dry period (3.2.3)	Reduced risk for shedding of AMR bacteria by calves	Shortage of colostrum on farms using antimicrobials at dry‐off Disposal of waste colostrum might increase residues in the environment Low compliance if not well founded and communicated
C3 Prohibit use of colostrum during the withdrawal period except from cows treated with β‐lactams and/or aminoglycosides Prohibition could be limited to highest priority CIAs	Direct Colostrum from cows treated with penicillins and aminoglycosides did not increase faecal shedding of resistant E. coli (Duse et al., 2015) (3.4.1)	Direct No studies supporting a distinction between antimicrobials (3.4.1) Indirect Residue levels in the colostrum is low and decrease with the length of dry period (3.2.3)	Reduced risk for shedding of AMR bacteria by calves No interference with current routines on farms using penicillin and/or aminoglycosides To focus on highest priority CIAs targets resistance of most public health significance and could also be a lever for reducing the use of these antimicrobials CIAs	Shortage of colostrum on farms using antimicrobials other than penicillin and/or aminoglycosides Separation of colostrum from cows by treatment includes practicalities that might interfere with compliance Disposal of waste colostrum might increase residues in the environment
C4 Prohibit use of colostrum if it is not treated to reduce bacterial load and/or residue levels	Direct Ensures that no or minimal residues and/or bacteria are present	Direct Colostrum from cows treated with penicillins and aminoglycosides did not increase faecal shedding of resistant E. coli (Duse et al., 2015) (3.4.1) Indirect Residue levels in the colostrum are low and decrease with the length of dry period (3.2.3)	Ameliorates some disadvantages of a complete ban (C2) Probably higher compliance than to a complete ban. Treatment methods are available (3.6.2 and 3.63)	Practicality at the farm level is not obvious and might interfere with compliance Potential impact on nutritional and immunological properties of the colostrum A need to adapt and evaluate methods for practical use

AMR: antimicrobial resistance.

CIA: critically important antimicrobial for human medicine, e.g. 3rd–4th generation cephalosporins and fluoroquinolones, according to the WHO definition (Collignon et al., 2016; WHO, 2016). See Appendix A.