When a cow gives birth to her first female, she makes about 1.6 per cent more milk than she would have for a son. This is according to research conducted by Katie Hinde and colleagues. This fact came from a study of the dairy records of 1.5 million cows. Hinde has put some of the facts onto her blog, amusingly titled ‘Mammals Suck…Milk!
Another fact to emerge from the study is that the first pregnancy has a big influence on the cow’s future milk production. Cows that had sons first saw a slight bump in production when they got pregnant with a daughter, but not to the level shown by cows that had a daughter followed by a son.
It has also been found that:
Breast milk produced during the night is different from breast milk in the day.
Breast milk for a 2-week-old baby is different from milk for a 1-year old.
Breast milk produced when mom and baby are fighting a cold probably has specially formulated antibodies.
So, what about humans? According to Laura Sanders, writing for Science News
, some small studies have hinted that lactating women produce different milk for sons than daughters. In some cases, sons seem to get milk that contains more protein and fat than daughters.
Hinde’s work has been published in
the journal PLOS One
, in a paper titled “Holsteins Favor Heifers, Not Bulls: Biased Milk Production Programmed during Pregnancy as a Function of Fetal Sex.”