Using diagnostic tools to identify high-risk calves at arrival

By Dr. Dave Renaud, Assistant Professor, University of Guelph

New and innovative strategies need to be discovered and implemented in order to curb antimicrobial use and the subsequent development of antimicrobial resistance in food animals, including the veal industry. Several studies completed at the University of Guelph highlight the period following arrival as an area to implement these strategies as the first 21 days following arrival are the areas of greatest mortality. There are certain traits, such as an inflamed navel, a rectal temperature of greater than 40°C, dehydration, body weight less than 47 kg (103.6 lbs.), diarrhea, and a sunken flank, that when present at arrival are associated with a higher risk of mortality occurring in the first 21 days following arrival. What remains unclear from these findings is which calves require antibiotic treatment or just supportive therapy.

The use of precision agricultural technologies has begun to show promise in the identification of animals at risk for disease. There has been widespread implementation in the monitoring of health status in dairy cows (rumination monitors and pedometers), however, few validated technologies are available for dairy calves. These on-farm tools could be used to identify high-risk calves at arrival and improve therapeutic decision-making, ultimately reducing antimicrobial use while increasing animal health and welfare.

Based on this, we tried to validate several parameters and tools to identify calves that are at high-risk of developing disease at a veal facility. Through the project, which was funded by Veal Farmers of Ontario and the Ontario Ministry of Agriculture Food and Rural Affairs, we found several important findings that could influence how you think about purchasing calves. Specifically, we found that calves with low levels of Immunoglobulin G (IgG), a marker of colostrum intake, heavily influences the risk of calves getting disease. This highlights the importance of excellent colostrum management for male dairy calves and working with dairy farms that are able to ensure transfer of passive immunity.

We also found that the levels of certain white blood cells influenced the risk of disease. Specifically, we found that calves with high levels of neutrophils 72 hours following arrival to a veal facility had a greater risk for disease. Low levels of cholesterol at arrival, which is primarily influenced by nutrition prior to transportation, age at transit, and colostrum management, was associated with a greater risk of mortality. Therefore, as technology becomes available allowing us to test for these parameters on-farm, we can use them to generate a risk profile where we could separate high- and low-risk calves and manage them differently.  

It is really important to note that despite evaluating many different parameters, body weight at arrival is the parameter that most accurately and consistently predicts mortality. Purchasing calves that are greater than 47 kg (103.6 lbs.) will go a long way to reducing mortality and disease, as highlighted in Figure 1, but also improving growth. Body weight at arrival is mostly influenced by the age that calves leave the dairy farm but also the length of time calves are in transit. Therefore, purchase calves that are nine days of age or older and transport calves for less than six to 12 hours from the time they leave the dairy farm of origin until they arrive at your veal farm.