Genetic Accuracy – Can you trust the numbers?

Wednesday, May 7th, 2014

Dairy breeders are continually taking steps to be more exact about the way they farm and the products they buy, produce and sell. However when it comes to the genetic make-up of our animals there remains significant difference of thought, amongst breeders, about the actual accuracy of the genetic information. Breeders are presented with a wide range of facts. Gold Medal, Extra, Star Brood, DOM, proven, genomic, photos, Supreme Champion … no wonder many breeders are confused. The Bullvine feels that breeders need to be objective about the animal information they see and to think in terms of the accuracy of the information. Now we are not talking about whether or not an animal meets the ideal. We’re talking about how much we can rely on the facts we see in hard copy or from virtual communication sources.

In the Beginning

In the nineteenth century milk cows were mostly dual purpose and herd size was small. People wanting to get into dairying purchased a cow or bull based on what the seller said were the animal’s merits. In time breed societies were formed to document lineage. That was followed in the early twentieth century with third party authentication of both yield and conformation. The third party oversight of parentage and performance were the beginning steps to know the accuracy of the information. That was the start.

Many Steps Along The Way

Having a milk record or type classification authenticated for a single one cow in a herd was initially thought to be very useful information. The next move was to compare a cow to her dam to see if improvement had been made. But that did not help much as the cow and her dam were not simultaneously at the same age and, in some cases, not in the same herd. Of course, over time we have learned that we need to know the performance of the cow’s herdmates. That was the stage where breeders started to compare animals within a herd with the desire to know which animals were superior, or, conversely, inferior for a trait. The biggest breakthrough in accurately determining the relative genetic merit of an animal came when Dr Charles Henderson, Cornell University, developed the analysis technique that he called B.L.U.P. (Best Linear Unbiased Prediction). Forget about trying to understand the term, what it does is compare all animals within a herd and then compile the results across all herds to produce genetic rankings for males and females.

What About Accuracy?

From a genetic merit perspective it is important to know two things. Firstly where does the animal rank in the populations? And secondly, and also very important, how accurate is the prediction? How much trust can a breeder put in the animal’s genetic rating? If information is of limited accuracy, then it may be nice to know, but it does little for constructive breeding or to provide the opportunity to drive up on-farm profits. Accuracy produces confidence; confidence accelerates advancement, and negligence ruins the reputation which accuracy had raised. (Read more: Has Genomics Knocked Out Hot House Herds? And The Hot House Effect on Sire Sampling)

Let’s Compare Accuracy

The range in accuracy of genetic evaluation indexes goes from 0 to 99% and is called Reliability. The following chart is an approximation of the accuracy of predicting an animal’s total merit index (i.e TPI, NM$, LPI, or any other national total merit index) from the information that is known on the animal.

Reliability In Predicting An Animal Total Merit Index

As far as accuracy goes the winners, as a result of incorporating genomic information into our genetic evaluation systems, have been young bulls, young heifers and brood cows. Adding genomic information has resulted in a doubling of the accuracy of their indexes. For further information on accuracy an interesting read is Two Ways to Look at Accuracy for Genomic Young Bulls published by Canadian Dairy Network.

What’s Ahead?

As more and more animals are genomically tested and recorded for their performance, the accuracy of all genetic indexes will increase. Three other steps that will assist in increasing the accuracy of total merit indexing are needed:

Have every milk weight, fat %, protein% and SCC automatically captured at every milking;
Have information on new economically important traits collected; and
Have more economic information available on more traits.

Breeders will be the benefactors of having more and more accurate information so that they can make more and more accurate decisions.

The Bullvine Bottom Line

Having genomic information has been a significant step forward for increasing the accuracy of genetic indexes. But it will go beyond genetics and genomics in the future. Read past Bullvine articles for further details about genomics for health and management (Read more: Herd Health, Management, Genetics and Pilot Projects: A Closer Look at ZOETIS) and what lies beyond genomics (Read more: Forget Genomics – Epigenomics & Nutrigenomics are the Future). When buying genetics breeders need to check that the animals, semen or embryos they are considering will both follow their breeding plans (Read more: What’s the plan?) and that the information is accurate. Breeding dairy cattle is faster paced every year. The accuracy of the information used is an important consideration.