Proper milk sampling is an overlooked, yet important contributor to the accuracy of milk test results, especially when it comes to high-producing, early-lactation cows.

“Sometimes we forget about the sampling part and how important that is,” says Dave Barbano, food scientist and director of the Northeast Dairy Foods Research Center at Cornell University.

On-farm milk flow meters and proportionate samplers have replaced glass weigh jars as the sampling devices of choice on many of today’s dairy operations. However, getting a representative milk sample is a concern when using these devices.

For example, an early-lactation cow milked 2X can fill the sampling container three times in one milking.

“If you don’t take it off and empty it, you just got a sample of the first third of what that cow produces,” Barbano said at the 2012 Tri-State Dairy Nutrition Conference. “That first third is very different composition than the last (third).”

Collecting just the first third of milk is not only a poor representative of what a cow is producing in terms of milk composition, but it also can lead to “totally erroneous results” for that animal, Barbano said.