Does Genomics Really Work? - The Jersey Edition

Genomics has received its fair share of attention in the Holstein breed. Since Holstein genomic evaluations became official in January 2009, the science has proven to be an effective breeding tool. Jersey genomic evaluations became official shortly after Holstein evaluations, in January 2010.

Proof stability from genomic to 1st crop

The Jersey breed’s much smaller population means it doesn’t benefit from near the number of bulls, the amount of performance data, or the size of the reference population that the Holstein breed enjoys. All of these factors contribute to the accuracy and subsequent stability of a genomic proof. However, one thing about Jersey breeders – no matter where you meet them in the world – they are a motivated group! They have taken great strides to increase the size of their reference population, and have always had a very high percentage of animals on milk recording programs. Still, Jersey genomic proofs aren’t estimating future proofs as accurately as Holstein genomic proofs are, however the gains in genetic progress are still very impressive. These gains warrant usage of genomic Jersey sires in groups in order to maximize genetic progress while minimizing risk.

Table 1. All bulls (n=30) that were genomic tested in August 2010 and have producing daughters in December 2011

In the early phases of Jersey genomic proofs, several model adjustments occurred so August 2010 was chosen as a reference point for this analysis. 30 Alta Jersey bulls received their first daughter proof between August 2010 and December 2011. The average change in JPI from genomic to 1st crop proof, during this time, is +22 JPI points (Table 1). It appears that to date, genomics are actually underestimating Jersey proofs. It is uncertain whether this will continue as the reference population grows and further model adjustments are made.

Table 2. Change in JPI and rank for the top 5 JPI ranked genomic bulls in August 2010

While the amount an individual bull changes often causes a lot of conversation, the change in rank is actually the more important factor. Table 2 shows the changes in JPI as well as rank for the top 5 JPI ranked genomic bulls in Aug’10. It is noteworthy that all top 5 genomic sires from Aug ’10 remained ranked in the top 8 for JPI once they received their first daughter proof. This confirms that you can be fairly certain that high JPI genomic bulls will remain high JPI after becoming daughter proven. Although each of the top ranked sires from Aug’10 below increased in their JPI with the addition of daughters, this should not always be the expectation.

The following graphs illustrate individual trait changes that can be expected from a genomic proof to a 1st crop proof. This time we look at all industry JE bulls, with the value of the proof change from August 2010 to December 2011 is indicated on the horizontal axis and the number of bulls with a certain change is indicated on the vertical axis. For example, the first graph shows that of the 132 Jersey sires included in the analysis, 5 of them had exactly zero change in their JPI from genomic to 1st crop proof. Meanwhile, the largest positive change was 105 points (2 bulls) and the largest drop was -60 points (2 bulls). You can therefore infer that the change of a genomic Jersey bull dropping by 60 JPI points is 1.5% (2/132), which is about the same probability of a bull increasing by that amount.

** To see these graphs clearer, please scroll to the bottom of the article and select the PDF version under 'DOWNLOADS'

These graphs show that the proof changes are normally distributed and that a large number of bulls change in the positive direction for all traits. Remember that the Jersey breed doesn’t have near the number of bulls being proven, nor the size of the reference population and amount performance data that the Holstein breed benefits from. These factors, combined with the fact that the reliability for Jersey genomic proofs is around 65% for production traits, 60% for type traits, and a bit lower for health traits, result in the kind of variation we see in the graphs above.

August 2010 Selection Decisions vs. Today’s Selection Decisions

Prior to genomics, Alta sampled approximately 20 Jersey bulls each year. This means that the 20 bulls sampled in 2010 were selected for sampling the ‘traditional way’ – a method of selection that did not take genomics into consideration for they were only released that year.

Whether you had chosen to breed to the top 5 daughter proven or top 5 genomic proven Jersey sires in August 2010, you would have very similar daughter groups today in terms of JPI. In fact, the average JPI of August 2010’s top 5 daughter proven bulls slightly exceeds the average JPI of August 2010’s top 5 genomic proven bulls (Tables 3 and 4).

Today, Alta genomic tests over 300 Jersey bulls and purchases only 30 of the most genetically superior from that group. The selection intensity that accompanies genomic testing has caused the selection decisions table to turn in favor of genomic sires (Tables 5 and 6).

If you decide to breed to today’s top 5 genomic proven sires, in three years, you will be milking daughters of the highest new daughter proven bull and effectively get a 1-generation jump on genomic progress. This group of 5 bulls averages 70 JPI points higher than today’s top 5 daughter proven bulls! While the proven bulls receive a lot of publicity and have made some great daughters, the predictions of the genomic group far exceed those of the daughter proven group – showing the extreme amount of progress made because of genomics.

Recall the first graph above, which illustrated the distribution of change in JPI from genomic to 1st crop proof. Based on this graph, and using the information that historically 95% of bulls change between +92 JPI and -48 points, the top 2 bulls (COLIN & CRITIC-P) have less than 2% chance to end up with a lower JPI than our current top rated daughter proven sire. Even more powerful is the fact that there is almost no chance that the AVERAGE JPI of the group of genomic-proven sires will end up lower than the AVERAGE JPI of the group of their older, daughter-proven counterparts.

If you want to maximize the genetic gain in your herd and reach your breeding goal at a faster pace, genomic sires are certainly the way to achieve your goals. As with Holstein genomic sires, we recommend using Jersey genomic bulls in groups of 4-5 in order to mitigate risk. Alta’s JerseyDRIVEN program was developed to provide priority access to such a group of genomic sires according to a herd specific genetic plan. Popular in its early stages, there are already 53 JerseyDRIVEN herds in the US, now well on their way to maximizing genetic progress.

Article by: Nate Zwald, Tara Bohnert, Gerbrand van Burgsteden and Lynsay Henderson