Mon, 27 Jan 2014
US – Holstein dairy cows produce significantly more milk for daughters than sons, a joint study between Kansas State and Harvard Universities has found.
The study also found evidence to suggest that first pregnancy foetus gender had persistent consequences for milk production in the second lactation.
Simply put, if a cow had two daughters concurrently, it would produce 445 kilos (980 pounds) more milk than a cow with two sons.
Milk quality was not affected by this, infact, the team explained that when accounting for greater quantities, the amount of milk fat and protein was greater after a daughter than a son.
The figures arose from an analysis of 2.39 million lactation records from 1995-1999 of 1.49 million Holstein cows. The database was managed by Dairy Records Management Systems.
The team, led by Professor Barry Bradford from K-State and Katie Hinde from Harvard’s Department of Human Evolutionary Biology, calculated the economic impact of the phenomena.
“According to our rough calculations, taking into account the wholesale value of milk, the number of two-year-old heifers added to U.S. dairy herds annually, the production advantage across the first two lactations of conceiving a daughter on the first pregnancy, and the increased probability of conceiving a daughter from sex-selected semen, suggests a gross value in the neighborhood of $200 million in milk production across the first two lactations alone,” the team reported.
As for why this is occurring, the team suggested that hormonal differences between female and male foetuses could trigger a response in the mammary gland. This would alter the milk-producing cells.
Professor Bradford said: “After finding the programming effect of fetal sex on subsequent lactations, our team discussed the possibility that daughters were releasing hormones into the maternal circulation that could directly influence the mammary gland.”
“It occurred to us that if this was true, becoming pregnant with a daughter might influence milk production even in an ongoing lactation. I was floored when we tested that effect and found it to be significant as well.”
“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.”
Katie Hinde explained the study could have implications for humans and nutritional management during neonatal care.
She said that humans have a very invasive placenta, able to allow foetal hormones to pass into maternal circulation and possibly influence mammary gland development.
“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 said. “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.”