Effectively Using Jersey Young Sires in Your Herd

The September 2024 Breed Improvement article in the Jersey Journal explored the idea that breeds improvement and the profitability of your operation will be accomplished by heavily using proven bulls whose daughters have been found to be high-producing cows. The second article in this series will explore the best use of young sires in your breeding program.

In 2009, genomic Predicted Transmitting Abilities (GPTAs) became available for young bulls. This increased the reliability of predicting their genetic merit compared to using Parent Averages (PAs), because it could account for the differences in DNA inherited from parents. Many bulls selected using genomic PTAs are now old enough to have many milking daughters. Therefore, we can look back and see how much more accurate genomic PTAs were than PAs when selecting young sires to use in our herds.

The chart above compares the accuracy of using PAs and GPTAs for bulls when they were 12 to 18 months of age to predict their PTAs based on the performance of their daughters. The values were calculated from 239 Jersey bulls born from 2010 to 2017 and now have over 500 milking daughters in their genetic evaluations.

In all cases, genomic PTAs were more accurate in prediction than PAs. However, the increase in accuracy doesn’t appear high enough to justify the heavy use of an individual young sire.

To accurately determine the genetic merit of a bull, the performance of his milking daughters must be known. Furthermore, the young sires in this data set were over-evaluated by 35 JPI points as young sires compared to where they ended up as proven bulls.
When using young sires in your herd, it may be more appropriate to consider GPTAs as DNA-adjusted PAs rather than as PTAs. A limited number of daughters of individual young sires should be produced in your herd to avoid the risk of a young bull not maintaining his high rank as a proven sire when his daughters come into production.

Progeny testing young sires to identify the next generation of great, proven bulls is critical for breed improvement. However, using individual young sires much more heavily than when we had only PAs is not likely to drive breed improvement.

So, how does the Jersey breed use young sires and proven bulls?

Of the 83,373 Registered Jersey heifers born in 2023, 64,818 (77%) of them were sired by young sires, bulls who were less than five years of age, at the time their daughters were conceived. Only 18,898 (23%) of the registered heifers born in 2023 were conceived when their sire was a proven bull. In addition, the average number of daughters per proven bull was 17 and per young sire was 39. This is the opposite of how proven bulls and young sires should be used. Individual proven bulls should sire many more daughters than individual young sires because we don’t know the true genetic merit of a young sire until he has become a proven bull. With half as many daughters per proven bull compared to young sires, it is doubtful we are effectively using high-ranking proven bulls to improve the Jersey breed.

The table of bulls above shows the 16 bulls with at least 1,000 registered daughters born in 2023. The three proven bulls on the list are highlighted in gray.

Summary
Breed improvement results from the heavy use of high-ranking proven bulls and the random light use of young sires to identify the next great proven bulls. This is not what has been happening. Individual young sires are being used too heavily, low-ranking proven bulls are being used too heavily, and high-ranking proven bulls are not being used heavily enough. Only 3,596 (13%) of the 26,478 Jersey heifers represented in the above table were sired by high-ranking proven bulls (“Chief” and “Kestrel-P”).

In conclusion, let’s get back to doing what moved the Jersey breed into a competitive position in the early 2000s. Use proven bulls that sire high producing daughters very heavily in your herd and use a group of young sires to produce a limited number of daughters per sire so that the next group of proven bulls to be used heavily can be identified.

For more information, contact John Metzger, Research and Genetic Program Consultant, at jmetzger@usjersey.com.