Accuracy of bull proofs has been one of the biggest challenges for dairy cattle improvement for many years. It has been well known that top index cows have always received some level of “preferential treatment” and as a result their indexes have been inflated. Usually this didn’t affect their sire’s proof since they were usually already proven sires and when weighted with many other daughters this had little to no effect on the sires proofs. Enter genomics and large portions of young sire daughters receiving preferential treatment and this could have huge effects on the proofs of these genomic index bulls. There is no question that the current systems around the world cannot account for this preferential treatment and as a result many genomic sires’ first proofs will be inflated.
In the past when young sires were sampled they were used across many different herd environments and regions. I remember when regionally proven sire (California, etc) or breeder proven sires were released. Many breeders where hesitant to use them because they were not confident that these sires proofs would hold up. Young sire programs in the past offered semen at low cost or pretty much free (when you factor in incentives) to many different breeders in order to ensure that the sire got enough daughters and that they would be able to achieve a reliable proof.
Does random sampling still exist?
Young sires are no longer randomly sampled. In today’s genomic age, a lot of the systems and controls are gone. Yes, many of the sires are still offered to all breeders, but these high-ranking young sires are sold at a much higher price, and marketed much heavier. In addition often the first release semen is only used on contract matings on extremely high index, carefully selected mates. This results in anything but random sampling and in reality is almost the perfect method for receiving an inflated proof. It isn’t just because of the actual mates they are being used on but also because of the care the resulting calves will receive.
Why do daughters receive preferential treatment?
Think about it, if you have paid upward of $750 for a dose of semen (Read more – $750 Dollar Semen! Are you crazy?) to be used on your most valuable animals, wouldn’t you make sure you protected your investment by giving them the best care possible? It is well known that top index cattle around the world have received over inflated indexes as a result of preferential treatment. The problem is ‘how do we account for the biases?
Does the current system account for preferential treatment?
Genetic evaluation systems assume that all animals in the herd are treated equally. Yet while there is nothing wrong with a breeder wanting to ensure their return on their investment in these top genetic animals, it certainly causes many problems when accounting for it in the genetic evaluations of these animals. (Read more – The Hot House Effect on Sire Sampling).
Most “animal-model” genetic evaluations in the world account for the genetic merit of a sire’s mates. However, when the US first added females to their genomic reference set they actually got lower reliabilities as a result of inaccuracies in female’s proofs due to preferential treatment. That is why some countries actually leave female genomic data out of their reference sets, as a large portion of the females are these high index animals that, in many cases, have received preferential treatment. In the US they actually implemented a scaling-effect adjustment to bring those top females down. The US has also implemented a new single-step model that includes genomic and traditional data together designed to account for this in bull proofs. Other countries are also looking for potential solutions. This includes potentially withholding early data from evaluations as well as other options. The challenge is that no one has found a real solution to the actual problem, and steps so far just mask the issue with scale downs and other band-aids.
How to identify preferential treatment?
I recently attended a GEB session put on by CDN (Canadian Dairy Network) where they gave a presentation on accounting for herd bias. Brian Van Doormaal presented a few different ways he theorized would identify bulls’ daughters who might have received this preferential treatment. One indicator he presented of possible preferential treatment was if a high percentage of a bull’s early offering were the result of ET. Another indicator he looked at was the percentage of daughters that have been genotyped. However, neither delivered conclusive results. Another suggestion that was presented was increasing the number of daughters a sire needs in order to receive an official proof. The challenge with that is that A.I. companies and most high profile breeders are wanting sires to get a proof as quickly as possible and increasing the requirements will cause delay. In addition, analysis of semen price so far does not show it to be a great predictor either. Currently there are simply no answers.
In Brian’s presentation he equated this problem to the challenges we have seen with second-country proofs. In Canada bulls like Shottle, Planet and more recently Man-O-Man (Read more – Man-O-Man will he turn platinum? and Is Man-O-Man really going to be a sire of sons?) that come through with initial Canadian proofs over 3500 LPI, which everyone knows to be unrealistic, in time saw their proofs drop 300+ points with the addition of more daughters. Van Doormaal also comments that you could expect bulls like Snowman, and genomic sires to do the same.
The Bullvine Bottom Line
Currently there are no definitive answers only growing concerns. This preferential treatment problem is going to get greater attention, as more high profile genomic sires, priced high and highly marketed will start to receive proofs in 2013. The industry must be proactive about this issue. If not we are going to see breeder confidence in proofs decrease, instead of increase, because of genomics. That would be a killer!
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