The last two decades have seen a decline in fertility and an increase in milk production. This fertility
decline is associated with genetic progress, such as improvements in nutrition and management,
which have led to a continued increase in milk production. This increase has also been linked to the
incidence of twin calving, which is undesirable in dairy cattle, as it reduces livestock profitability and
animal longevity, and increases the use of antibiotics. One of the most effective ways to improve
dairy cow fertility, especially during warm seasons, or to reduce twin calving and therefore twin
pregnancies, is embryo transfer. This practice drastically reduces the negative effects of decreased
fertility and increased pregnancy losses.
Embryo transfer will allow farmers to focus nulliparous and primiparous cows on the production of
female offspring of high genetic value as replacements, and multiparous cows on milk production.
This will increase the farm’s average lactation number and the price of calves to be sold. Despite all
these benefits, this system is implemented neither in Spain nor Europe. A change in the mentality of
farmers and veterinarians is needed to make this technique routine practice in females that have
given birth more than twice on commercial dairy farms. This technique can only be used on well-
managed farms, where other factors that could affect the process, such as nutrition state or stress,
are controlled.