A new study has revealed that mothers favour daughters more than boys when it comes to Holstein dairy cows and how much milk they produce for their offspring.
Researchers at Kansas State University and Harvard University studied 2.39 million lactation records from 1.49 million dairy cows and found that cows produce significantly more milk for daughters than for sons across lactation.
Barry Bradford, associate professor in K-State's Department of Animal Sciences and Industry, said the study provide the first direct evidence that the sex of a gestating fetus can influence milk production.
The researcher said that 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.
In addition, the researchers found that the sex of the fetus a cow is carrying can enhance or diminish the production of milk during an established lactation and that the sex of the fetus gestated in the first pregnancy has persistent consequences for milk production on the second lactation.
One of the researchers said that the study could have implications for humans.
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The team also found that the percent fat and protein in milk did not differ between cows that gestated a son or daughter, so the quality of milk was the same.
The study was published in the journal PLOS One.