Editor’s note: The following case study was handled by Wade Steen, dairy nutritionist in Roswell, N.M.

It was baffling: Two herds identical in many ways, owned by the same person, but different in how they handled the introduction of dried distillers grains into the ration.

Each of the herds was 2,500 cows, located in southeast New Mexico.

Last year, the herd managers and nutritionist tried including a moderate amount of dried distillers grains — 4.5 pounds on a dry-matter basis — into the ration.

In one herd, the butterfat remained constant following the inclusion of DDGs. But, in the other herd, butterfat dropped dramatically from 3.2 percent to 2.7 percent. This was puzzling, since both herds had the same rations, the same forage base — even the same feed mixer and feed truck.

Intuitively, most people would focus on the DDGs. But, could it be something with the grain? Or starch levels?

Nutritionist Wade Steen already had a good baseline to work from. For four months, he had been testing out a new forage diagnostic system known as Calibrate from Forage Genetics International.

"Calibrate not only allows me to monitor starch level in the ration, but gives me an accurate, predictable estimate of how degradable that starch is in the rumen," Steen says.

"I knew where the starch levels were (and they did not change following inclusion of DDGs), so I knew it wasn't starch," he adds.

He also knew that his forage and digestible NDF levels were adequate.

Digestibility of the forage is a difficult thing to stay on top of since the degradability of corn silage can change during the course of year, even among silage stored in the same pit or bunker silo. But Calibrate allowed Steen to monitor this before and after inclusion of the DDGs.

So, with those other things out of the way, Steen was quickly able to move on to the next rule-out, which was polyunsaturated fatty acid (PUFAs) from the distillers grains. In this case, one of the herds apparently did not react to the introduction of PUFAs as favorably as the other herd. Once the DDGs were removed, the herd’s butterfat came back up within a matter of three to four days. Within 10 days, butterfat was 3.2 percent, which was normal. Herds in New Mexico are generally around 3.2 percent butterfat for much of the year, Steen says.

More information about Calibrate technologies will be available in next month's Nutritionist e-Network newsletter.