When we talk about sustainable practices that protect the environment and preserve our natural resources, we often focus on reducing emissions and managing nutrients. For livestock farmers, sustainability also includes how they raise animals and make changes to improve efficiency of the herd or flock.

At the California Dairy Sustainability Summit, two producers shared insights on a genetic tool that has made a big difference for their herds: genomic testing.

Genomic testing analyzes an animal’s DNA to predict its genetic merit for various traits, including milk production, fertility, and health. Since genomic technology was made available to the industry in 2009, more than 10 million dairy cattle have been genomically tested.

Making informed decisions

Simon Vander Woude was one of the early adopters and has been genomic testing his herd since 2012. He and his wife, Chris, started their farming career with 150 cows on a farm near San Diego, Calif. Today, they milk 6,000 cows at three locations in Merced County and are working to bring some of their children into the operation.

“Genomics is a tool in our tool bag,” he said of the technology.

Vander Woude used genomic testing first to help them determine which animals they wanted to produce more heifers from. After growing their herd size aggressively for years, they got to a point where they did not need to raise as many heifers as replacements. They were then able to use genetic data to determine which animals to breed to beef.

“It was very common for us to raise one heifer per cow when we were growing our herd,” he explained. “Now we are raising 0.6 to 0.7 heifers per cow, and that is the most efficient way to run our operations.”

Marketing dairy-beef calves has also been a valuable aspect of their business. “We’ve become an integral part of the beef chain by raising Holstein-Angus crosses for more than a decade,” he added. Vander Woude explained that the carbon footprint of a dairy-beef calf is 20% that of a beef calf, since the beef cow is just growing a calf while the dairy cow is also producing milk. “We have a good story to tell there as well.”

Better from top to bottom

Wiebren Jonkman is a first-generation farmer milking 1,100 Jerseys in Merced, Calif. He credits genomic testing for part of their success.

“I am passionate about farming practices that ensure the health of the herd and the environment,” he noted.

Jonkman said his herd is healthier and more productive today, top to bottom, than it was when they bought the cows nearly a decade ago. When he and his wife, Luciana, took over the dairy, Jonkman said there were no records on the cows. They decided to breed 100% to sexed semen and use genomic testing to find their top-tier cows. After a few years, they established those top-level cows to breed from, and then they started incorporating beef-on-dairy genetics.

“It never stops. You will always have a top and a bottom in the herd,” he said. “With genomic testing, you try to boost the top and take out the bottom.”

As they got farther along on their genetic journey, they focused more on health traits. Their animals today are stronger and stay in the herd longer.

“It takes a while to see it, but it’s a fun journey once you see the results,” Jonkman shared. Underscoring the progress Jonkman has made, his herd achieved an impressive feat: In the same year, it was recognized for its reproductive efficiency by the Dairy Cattle Reproductive Council and for milk quality by the National Mastitis Council.

Wisdom from experience

The dairymen offered advice to others looking to use genomic testing. Vander Woude emphasized the importance of having a strategy for genomic testing.

“Have a plan for what you are going to do with your genomic data,” he said. “You have to think about the fact that every breeding decision you make today is three years away from being realized.” This includes the time it takes to order the semen and breed the cow to when the calf is born and then raised.

“You have to have a long-range plan,” he said. “Either you are in or out — don’t dabble.”

Jonkman agreed about the importance of consistency. “Find a protocol that works for you and stick to it. Don’t defer from it.”

For both of these dairies, genomic testing has advanced the animals and the overall efficiency of the operation.

“We are doing more with less, and genomic data has allowed us to do that,” Vander Woude explained. “We are getting more milk from fewer cows, and more components with fewer cows. We have fewer heifers in inventory, so we are feeding fewer mouths those maintenance calories.”

Vander Woude continued, “A lot of things in our business are about efficiency. As a business owner and a data manager, efficiency is what we strive for. It is what we enjoy.” For Vander Woude and Jonkman, genomic testing has elevated the efficiency and quality of the cows milked on their dairies each and every day.

This article appeared in the August 2025 issue of Journal of Nutrient Management on page 22-23.

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