Dairy herds that use genomic testing achieve increases in the reliabilities of genetic estimates for their heifers. Based on information presented at Michigan State University Extension workshops in February, the reliabilities of heifer genomic evaluations for production traits are approximately 30 percentage units higher than reliabilities of genetic estimates calculated from parent averages only.
Accessing genomic data in an easy-to-use format is important when making heifer management decisions. The Heifer Genomics Guide (DHI-428) is available to dairy producers that have genomic-tested heifers and whose DHIA (Dairy Herd Information Association) records are processed by Dairy Records Management Systems (DRMS). Genomic test results flow monthly from the Council on Dairy Cattle Breeding (CDCB) to DRMS.
The Heifer Genomics Guide provides lists for four groups of heifers. The report contains animal identification, birthdate, sire and maternal grandsire identification as well as parent averages or genomic PTAs (predicted transmitting abilities) for Merit $, milk, protein, somatic cell score, productive life, daughter pregnancy rate and type.
Criteria used to generate each list correspond to the types of management decisions relevant to the specific heifer cohort group.
- List 1: Heifers < 6 Months – Not Yet Genome Tested - Dairy producers can use the list to determine which heifers to collect samples for genomic testing. The heifers are sorted by parent average for Merit $ (typically the Net Merit or NM$ for Michigan herds). The Heifer Flag listed on the report is the percentile ranking for this cohort group based on the parent average Merit $.
- List 2: Heifers < 12 Months – Genome Tested – This list can be used to determine which top-ranking heifers would be good candidates for embryo production or which heifers might be removed from the herd if there are surplus replacement heifers. A percentile ranking within this heifer cohort group is designated for each heifer. Heifers in the top 20% nationally for NM$ are identified. In addition to the ranking within this heifer cohort group, each heifer’s NM$ is used to indicate her rank relative to cows with NM$ in the current milking herd (labeled Projected Heifer NM$ Rank).
- List 3: Heifers to Breed or Cull – 12+ Months and Not Pregnant – Service sire decisions may be made based on the genetic ranking of the heifers. The NM$ ranking specifies if heifers have been genomic tested. For older heifers that are not yet pregnant, culling decisions may depend on the heifer’s genomic NM$ and relative genetic ranking in this cohort group. The Projected Heifer NM$ Rank also is reported on this list.
- List 4: Pregnant Heifers – The genetic potential of future herd replacements is indicated by the NM$ of both the pregnant heifer and her service sire. In addition, pregnancies from gender-selected semen are listed which helps producers determine the number of heifer calves that can be expected.
The Heifer Genomics Guide (DHI-428) is available on a monthly or quarterly basis. More information about this report can be obtained from the herd’s DHI information specialist or technician.
Genomic testing increases the reliability of genetic rankings of dairy heifers. The Heifer Genomics Guide (DHI-428) from DRMS enables dairy producers to efficiently use genomics information to make heifer management decisions.