January 23, 2014

Science Daily/Kansas State University Research and Extension

Sorry, boys. In the end, mothers favor daughters –- at least when it comes to Holstein dairy cows and how much milk they produce for their offspring, according to a new study. The research may have implications for humans.

A study of 2.39 million lactation records from 1.49 million dairy cows showed that cows produce significantly more milk for daughters than for sons across lactation, said Barry Bradford, associate professor in K-State’s Department of Animal Sciences and Industry. He, along with Katie Hinde in Harvard’s Department of Human Evolutionary Biology, Abigail Carpenter, K-State graduate student and John Clay, with Dairy Records Management Systems collaborated on the study.

“Our results provide the first direct evidence that the sex of a gestating fetus can influence milk production,” Bradford said. “One possible explanation is that a daughter is able to let her mom know, in advance, that she expects to receive more milk than her brothers.”

Implications for humans

“Well no study has yet systematically addressed differences in milk for sons and daughters in terms of both composition and yield,” said Hinde. “But in the last couple years there have been a handful of studies among humans reporting differences in milk composition between sons and daughters.

Humans have a very invasive placenta that would allow fetal hormones to pass into maternal circulation and possibly influence mammary gland development. But it hasn’t yet been systematically studied.”

“This research in cows demonstrates that the fetus can influence the milk the mother produces during lactation and limited evidence suggests that similar processes may be operating in humans,” she added.

“Such a finding has potential implications for nutrition management of babies in neonatal intensive care units and selection of donor milks. And such research can inform infant formulas tailored more specifically to the physiological needs of sons and daughters.”

http://www.sciencedaily.com/releases/2014/01/140123221910.htm