Dairy cows produce more milk for heifers than for baby bulls, according to new research from Kansas State University and Harvard University.
Researchers studied lactation records for more than 1 million dairy cattle across the country.
Their findings contradicted evolutionary biology theories that predicted bias was in favor of sons. The cows actually produced more milk for their female offspring.
“Daughters seemed to have the most dramatic effect on the initial development of the mammary gland, because the bias against sons was greatest in the first lactation,” said K-State Department of Animal Sciences and Industry associate professor Barry Bradford.
The study also found that the sex of the first baby might determine the amount of milk produced for the following children.
The results were available in the scientific journal PLOS One.