The Role of Genetics in BRD – Part I

There is no doubt genetic science has brought significant benefits to the cattle industry. Unfortunately, the genetic roots of disease hardiness, including incidence of bovine respiratory disease (BRD), have proven particularly difficult to analyze. Here is what we know.

While evaluation of certain physical traits, such as hip height, is relatively straightforward, BRD can be triggered by stress, pathogen load or environment as easily as genetics. Even in research conditions, it’s difficult to isolate the variables. On top of that, a major discovery often means sorting out the interactions of multiple chromosomes scattered across three million base pairs in the bovine genome. When a correlation is discovered in one breed, it is not easily transferred to another.

At the breed level, research has begun to help us understand the function of certain chromosomes and glimpse the complexity of their interactions with each other, but there is a genetic puzzle for each individual animal. Some research has shown that before entering the feedlot, the incidence of BRD in weaned calves varies from 10 percent in Angus cattle to a high of 35 percent in Pinzgauer Cattle. Even then, animals with identical DNA can express different genetic traits.

Heritability is especially difficult to determine for BRD resistance. The variability of risk factors and our limited understanding of multi-chromosome interactions limit our knowledge of what made the parent animals perform or get sick in the first place. Only more research will allow us to better evaluate the factors that contribute to BRD.

What do you think? Have animal genetics changed the way you manage your operation? Have you ever consulted with a geneticist? The good news is our understanding of BRD susceptibility is growing. Eventually, it may be one of the most valuable advancements in the history of the cattle business. We will talk more about that in part two.

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