High immune responder cows: What does it mean for calf health?

By ACER Consulting Ltd. for Veal Farmers of Ontario

The immune system protects dairy cattle against a wide variety of bacteria, viruses, or parasites in early life, through the transition period, and through lactation. Recently, researchers at the University of Guelph created a technology that tests the immune responsiveness of dairy cattle and identified a tremendous variation in immune response. They identified three groups of cattle (1. High immune responders; 2. Average immune responders; and 3. Low immune responders) based on their cell-mediated and antibody-mediated immune responses. Several research studies have been conducted, predominantly focusing on dairy cows, that highlight that immune response has an important influence on disease risk and that the trait of high immune response can be transmitted from the dam or sire to their offspring.

What has been shown in cows?

Tremendous benefit has been identified in high immune responder cows with lower levels of disease identified in this group. Specifically, it has been found that high immune responder cows have a lower occurrence of mastitis, metritis, ketosis, and retained placenta compared to cows that have average and low immune response. Higher immune responders also have been shown to have a better response to vaccination with fewer adverse effects. It is also important to note, as highlighted previously, that immune responsiveness has a large genetic component which means the high level of immune response can be passed from the cow to calf.

What does this mean for calves?

Although this is a new field of research, there is some evidence to suggest that there are benefits to the calf when born from a high immune responder cow or sired by a high immune responder bull. First off, high immune responder cows will produce a higher quality of colostrum. Specifically, high immune responders had 25 and 16 g/L higher Immunoglobulin G (IgG) in their colostrum compared to average and low immune responder cows, respectively. Given that colostrum quality plays such an important role in preventing failed transfer of passive immunity, the higher levels of IgG in colostrum of high immune responder cows could lead to improved passive immunity, contributing to lower levels of disease in calves.

Another study also identified positive results, with calves that were sired by a high immune responder bull having lower levels of mortality. In a study that evaluated records from 24 farms and 33,320 cows, it was found that calves sired by high immune responder bulls had 16 per cent lower mortality than those sired by non-high immune responders. In addition, although not a statistically significant finding, calves sired by high immune responder cows had lower levels of diarrhea.

Where to next?

Selecting for high immune response is becoming more mainstream with some genetic companies incorporating it into their breeding programs. The positive effect of using high immune responders in your herd can be seen through lower occurrence of disease in lactating cows, improved colostrum quality, and lower levels of mortality in dairy calves sired by high immune responders. A clearer understanding of the impact of high immune responders on calf disease and growth is required; however, there is some evidence in pigs highlighting that immune responsiveness may also influence those parameters as pigs that had high immune response grow faster and have lower levels of disease.

Take home messages

The immune system is tremendously important in protecting dairy cattle against disease. High immune responders are cattle that have an improved immune responsiveness and have been shown to have lower levels of disease in dairy cows and lower mortality in calves. Work with your genetics advisor and other advisors to determine if you can incorporate high immune response into your breeding program.

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