Take time to review the latest Net Merit percentile rankings for the August 2015 genetic evaluations and update your sire selection goals.
By: Kathy Lee, Michigan State University Extension
Genetic improvement is a key factor in managing a profitable dairy herd. Genetic improvement in dairy herds is dependent on the availability of genetically superior replacement heifers. Consequently, selection criteria for service sires should be updated routinely.
Net Merit (NM$) is a tool that can be used on dairy farms when making sire selection decisions. NM$ is a selection index which estimates lifetime profit based on incomes and expenses relevant for today’s dairy producers.
Traits currently included in NM$ are:
NM$ and other genetic evaluations for production and health/fitness traits are updated three times each year in April, August and December by the Council on Dairy Cattle Breeding (CDCB) .Yield traits receive 43 percent of the overall emphasis and health/fitness traits are at 41 percent. The type indexes are indicators of health/fitness and have a combined relative weighting of 16 percent.
The genetic merit of bulls marketed through AI organizations continues to improve with each release of updated genetic evaluations. Consequently, sire selection goals set by dairy producers a year ago may be outdated today.
The following table lists the August 2015 NM$ values for various percentile ranking levels for each breed. Knowing where service sires rank among active AI bulls is helpful in determining if the sires meet the herd’s genetic goals.
To maximize genetic improvement using NM$ as your selection index, Michigan State University Extension recommends that a herd’s service sires have an average at or above the 80th percentile. For example using the table below, the service sires in a Jersey herd would need to average $407 NM or greater to achieve the 80th percentile goal.
NM$ levels of top percentiles for AI sires by breed. August 2015 USDA-CDCB Sire Summary:
To ensure that a herd’s replacement heifers will be genetically superior, sire selection criteria should be reviewed and updated periodically. It is important to communicate these goals with semen sales representatives also.
Net Merit can be used as a key selection tool to identify high ranking service sires. Use the percentile ranking information to determine the level of superiority of your current group of service sires.