Cows birthing daughters produce much more milk

The amount of milk a cow produces is affected by the sex of her fetus, a new study reports.

Cows that gave birth to a daughter produced considerably more milk than those that had sons. And back-to-back daughters led to a bonanza of milk from their mothers – over two 305-day lactation periods, nearly 1,000 pounds more milk than from cows that had given birth to sons, an increase of 3 percent.

The study, described in the journal PLoS ONE, could have implications for dairy farmers and for new discoveries about human breast milk.

“Nobody knew if the fetus could possibly be affecting the mammary glands,” said the first author, Katie Hinde, an evolutionary biologist at Harvard. “It might just be that the developmental needs for sons and daughters are different.”

The study examined 2.4 million lactations by nearly 1.5 million Holstein dairy cows in the United States. The data was drawn from numbers recorded from 1995 to 1999. Though there were striking differences in quantity between the mothers of sons and of daughters, the milk did not differ in terms of fat or protein content.

Whether human mothers produce different milk for sons and daughters deserves more research, Hinde said, adding that closer study could lead to more customized infant milk formulas and to better matches in neonatal units for babies who need donor breast milk.

Turning sense of smell against the mosquito

Mosquito sperm has a sense of smell, researchers report, in a finding that could suggest ways to help control the spread of disease-carrying insects. The sperm carries a set of chemical sensors identical to the olfactory receptors on the mosquitoes’ antennas, according to a study in Proceedings of the National Academy of Sciences.

Mosquitoes mate just once in their lifetime, and the female stores the male’s sperm in an organ called a spermatheca. Before the eggs mature, the female seeks out blood using the receptors on her antennas. Soon after, chemical signals cause the sperm tails to beat rapidly and start the fertilization process.

“The sperm may need a chemical signal to become ready for fertilization,” said Jason Pitts, a researcher at Vanderbilt University and an author of the study, which was supported by the Gates Foundation as part of its efforts to improve global health.

Another author, Laurence Zwiebel, also a Vanderbilt researcher, called the dual use of the olfactory receptors a clear and clever example of convergent evolution: The mosquitoes “found something that works and use it in multiple ways.”

The scientists are developing chemical compounds that can be applied to breeding grounds to block the receptors.

“You can effectively confuse the sperm or make them inactive,” Zwiebel said.

– New York Times