When genomic testing became commercially available a few years ago, it was almost immediately incorporated into genetic evaluation systems for dairy cattle. Today, genomic data is used to select young bulls that enter A.I. companies, and many cows, heifers, calves and embryos sold at auction are marketed based on genomic information.
Genomic testing can also be a great tool on the farm level, noted Kent Weigel, University of Wisconsin-Madison, in his presentation at the Dairy Cattle Reproductive Council annual meeting last month.
Culling rates tend to be low on today’s modern dairy farms, and the use of gender-enhanced (sexed) semen has produced a surplus of replacement heifers. Producers now have the opportunity to improve the genetic potential of their herd by culling inferior females at a young age. The added benefit is reducing feed costs associated with rearing heifers that are unlikely to perform at a profitable level once they reach lactating age, he explained.
Should you use genetic testing? First, ask yourself a few questions. Do you have an excess of heifers? If so, what percent of extra heifers do you have? If you have enough heifers to maintain current herd size based on culling rate, you may consider genomic testing as a form of herd size management.
If the price is paid to do genomic testing, have a plan in place to use the results. Weigel suggested three strategies for testing females:
- Test the whole herd and rank accordingly
- Test potentially elite animals for marketing
- Test potentially inferior animals for culling
Genomic testing can also be used as a herd diagnostic tool, Weigel said. If a group of animals are underperforming, can something be changed to improve their productivity?
Recent data validated that genomic testing of heifer calves at a young age can provide farmers with useful information for making selection and culling decisions. A study at the UW-Madison Integrated Dairy Facility in Arlington, Wis., took a look at the performance of first lactation cows in comparison to their genomic predictions derived at 12 months of age (see chart below). Heifers were grouped according to their genomic predictions for milk yield, in categories labeled as Q1 (high), Q2 (high-medium), Q3 (medium-low) and Q4 (low).
An impressive 83 percent of the heifers in Q1 exceeded herd average for actual daily milk yield, compared with 61 percent of heifers in Q2, 39 percent in Q3 and less than 17 percent in Q4. Moreover, no heifers from Q4 ranked near the top for daily milk yield in their first lactation, and only one heifer from Q1 produced significantly less than the herd average.
The author is an associate editor and covers animal health, dairy housing and equipment, and nutrient management. She grew up on a dairy farm near Plymouth, Wis., and previously served as a University of Wisconsin agricultural extension agent. She received a master’s degree from North Carolina State University and a bachelor’s from University of Wisconsin-Madison.
