On a dairy farm, where efficiency is critical to business success, waste not want not is a phrase that hits home with many dairy producers. That is especially true with the most precious commodity produced on the dairy, milk. One of the least favorite things to do on a dairy is watch milk being poured down the drain, even if it does come from cows treated with antibiotics.

Over the last several years a conscious effort has been in place on dairy farms to reduce the use of antibiotics. In the past, antibiotics have been used to treat bacterial infections in calves and cows, with the significant majority of this use applied toward mastitis treatment. The other use, which falls under the category of mastitis prevention, is during dry off to avoid mastitis from building up prior to the next lactation.

Advances in technology and the understanding of mastitis causing mechanisms has helped dairy producers be more selective in the use of antibiotics to treat mastitis which has reduced the use of antibiotic therapy. Likewise, selective dry cow therapy has reduced the use of antibiotics at the end of lactation in cows that only fit a certain risk criteria.

While the use of antibiotics has declined as part of milk quality programs, treatment therapies that include antibiotics are still in use. This causes the production of unsalable milk that includes antibiotic residues in one of two forms:

A recent survey conducted by Hoard’s Dairyman reported that 55% of dairy farms feed waste milk to calves. Of these farms, 28% use a pasteurizer to reduce pathogen loads. This process, while beneficial toward reducing pathogen levels as well as some antibiotic residues, cannot completely degrade all antibiotic residues present in waste milk fed to calves.

Antimicrobial resistance (AMR) is a serious, global issue affecting all classes of livestock and humans alike, especially 3rd and 4th generation cephalosporins which are listed as “Highest Priority Critically Important Antibiotics”. In a study conducted at the University of Reading (UK), the presence of E. coli resistant to cefquinome, a 4th cephalosporin antibiotic, in the feces of dairy calves was examined.  

A group of calves were fed waste milk from the University dairy herd and fecal samples were analyzed. The results of the study demonstrated that almost half of the E. coli present in fecal samples from calves fed waste milk were resistant to the cephalosporin antibiotic. In lactating cows this category of antibiotic is effective in the treatment of metritis, bovine respiratory disease and foot rot and are popular due to the zero-day milk withdrawal times.

It would seem logical that the best way to prevent the development of antimicrobial resistant bacteria in calves would be to avoid feeding waste milk that contained antibiotic residues. Certainly the more judicious use of antibiotic therapies in dry cows and during lactation will help to reduce this incidence.

The other opportunity would be to switch from feeding waste milk to feeding a milk replacer. While there are several advantages and disadvantages to feeding milk replacer, this management change doesn’t reduce the volume of waste milk produced by the lactating herd and may not reduce the potential for development of antimicrobial resistant bacteria in the environment.

Waste milk not fed to calves will be disposed in the waste system of the dairy, which generally ends up as normal waste affluent that gets spread on crop ground as part of regular manure applications. This perpetuates the cycle as antimicrobial resistant bacteria can enter ground water and be taken up by crops that can eventually be consumed through feed rations.

Feeding waste milk to calves can cause a dilemma for dairy producers. On one hand it creates a use for an otherwise useless product. On the other, it can create health challenges in the calves to which it is being fed. Further insights will need to be developed with regard to opportunities to feeding waste milk to young calves.

Maury Ore is VP of Sales North America and David McRobbie, Business Development Director for Anpario