Cows

domesticated bovine raised primarily for its milk

thumb|A plate showing a "Free Martin" from the collected works of John Hunter. A freemartin or free-martin (sometimes martin heifer) is an infertile cow with masculinized behavior and non-functioning ovaries. Such a cow is born as one of a pair of twins, with a male calf as the other twin. Phenotypically, the animal appears female, but various aspects of her female reproductive development were altered due to acquisition of anti-Müllerian hormone from the male twin. Genetically, the animal is chimeric: karyotypy as a sample of cells shows XX/XY chromosomes. The animal originates as a female (X

Cow surgically fitted with a cannula

Dairy cow lactation stage