A new study shines new light on milk production, and the findings could have major economic implications for dairy producers.

The study, published in a recent issue of PLos One, examined 2.4 million lactations by nearly 1.5 million dairy cows across the country. The result: that cows that gestated back-to-back daughters produced as much as 1,000 pounds more milk than those that give birth to sons.

“Nobody knew if the fetus could possibly be affecting the mammary glands,” Katie Hinde, an assistant professor of human evolutionary biology, who co-authored the study with Barry Bradford, an associate professor at Kansas State University, told The New York Times.

She notes, “It might just be that the developmental needs for sons and daughters are different.”

According to the Harvard Gazette, the new discovery opens the door for the dairy industry.

“If this were adopted by the dairy industry today, not counting the cost of the technology for sperm selection, the growth in terms of wholesale milk value is in the ballpark of $200 million gross — just by manipulating the conception of a daughter on the first pregnancy,” said Hinde, adding the importance of the story goes far beyond the economics of dairy farms.

The researchers were surprised to find that a son-daughter sequence also led to an increase in milk production, though one less pronounced than the increase found with back-to-daughters.

Among the answers to explain the difference in production could be an evolutionary adaption cows use to help female calves develop earlier, thereby increasing their reproductive potential.  Click here to read more.