Managing disease to reduce antibiotic use in calves

By Dr. Dave Renaud
ACER Consulting Ltd.

Antibiotics are medications used to kill infection-causing bacteria and are important tools for farmers to treat disease. Unfortunately, the widespread use of these drugs has led to antimicrobial resistance, where certain bacteria are able to survive even in the presence of antibiotics given to kill or limit their growth.

Antimicrobial resistance is threatening to become one of the most common causes of death in humans and is growing at a rapid pace in pathogens responsible for causing disease in dairy cattle and calves. To combat resistance, we, including those involved in human and veterinary medicine, need to responsibly reduce our use to ensure antibiotics are effective for future generations of humans and animals.

Where to start?

The biggest thing we can do to reduce antibiotic use is to prevent disease from occurring in the first place. In calves, this starts by ensuring respiratory disease and diarrhea are recognized early and managed appropriately, as they are responsible for the majority of use.

Preventing diarrhea

Diarrhea is a costly disease and is better prevented than treated, as it is responsible for causing reduced growth, increased mortality, and reduced milk production. Prevention starts with ensuring excellent colostrum management, as those with failed transfer of passive immunity are at a 1.5 times higher risk of diarrhea.

Besides colostrum, pre-weaning milk nutrition is almost as important. Calves provided with eight to 12 litres (L) of milk per day will have improved immunity and capacity to fight disease, leading to a reduced level of diarrhea and improved recovery if it does occur. Additional benefits include improved growth and feed efficiency, as well as increased milk production. Specifically, for every 100 grams (g) per day increase in growth in the pre-weaning period, an additional 150 kilograms (kg) of milk are produced in the first lactation. Clearly, nutrition is extremely important for ensuring health and preventing disease.

Additional considerations include ensuring cleanliness and sanitation in housing areas and feeding equipment. Vaccination can also play a role, however, when vaccinating pregnant cows, excellent colostrum management is still best practice to get protective antibodies into the calf and establish immunity.

Preventing respiratory disease

Similar to diarrhea, colostrum management and pre-weaning milk nutrition are equally important in preventing respiratory disease. Specifically, calves with failed transfer of passive immunity have a 1.75 times greater risk of developing respiratory disease. In addition, when calves are fed four litres of milk per day or less, they are also at a much greater risk of developing respiratory disease.

Beyond these critical factors, the housing environment also plays a significant role in disease prevention and/or development. Air quality is a key factor, so delivering fresh air in draft-free indoor housing with a positive pressure tube at an appropriate rate, will prevent respiratory disease. When calves are housed in groups, ensuring they have at least 35 square feet per animal in the pre-weaning period will also help to reduce airborne bacteria and humidity. Another important factor to consider in colder temperatures is to ensure that calves are able to nest in their bedding, or have long, dry straw that is deep enough to cover their legs, as it prevents calves from becoming chilled. Vaccines, especially intranasal vaccines, will also add to provide immunity to prevent infections with pathogens from occurring.     

What about disease treatment?

No matter how good our preventative strategies are, the risk of disease is never zero. When it occurs, early identification and treatment is critical. Where antibiotic use can be most improved is with the treatment of diarrhea. Research suggests that approximately 75 per cent of calves with diarrhea are treated with antibiotics, however, those studies have identified that antibiotics are only needed in approximately 30 per cent of cases.

So, when are they really needed?

Antibiotics should be restricted to calves that are showing systemic signs of illness, such as those with a dull or depressed attitude, elevated rectal temperature, or those with fresh blood in their manure. When calves show these signs, there is a higher chance that bacteria is responsible. It is important to note, this is an important discussion to have with your veterinarian as they will understand the pathogens responsible and can help guide discussion. 

Take home messages

We all need to work together to reduce antibiotic use to prevent antibiotic resistance from occurring. When working with your calves, preventing disease can lead to meaningful reductions in antibiotic use. This can also have a positive economic impact on your farm operation.

Prevention starts with excellent colostrum management and providing calves with a high plane of milk nutrition. With respect to diarrhea treatment, antibiotics are only necessary in calves that exhibit systemic signs of illness. Work together with your veterinarian to reduce antibiotic use in your calves. 

This project was funded by the Canadian Agricultural Partnership, a five-year federal-provincial-territorial initiative.