Fuente: WIPO "milk" The method comprises taking a milk sample from the cow on day 4, 5 or 6 post-insemination and determining the milk progesterone level by RIA or ELISA, a milk progesterone concentration of >3 ng ml-1 being indicative that the animal is pregnant. The success of pregnancy may be improved by timely supply of progesterone or a functional equivalent thereof (such as progestagen). Methods of assessing the suitability of a cow for progesterone replacement therapy and of embryo transfer are also disclosed.