The complex biological and mechanical hurdles a calf faces during its first hours of life.

Nature · Published 3 October 2026 Swipe more like this →

In short: Birth in cattle is a high-stakes, hormonal, and often mechanical process. From the precise chemical signals that trigger labor to the physical challenges of passing through the pelvic canal, the transition from fetus to calf is a critical event that has required human assistance since the time of Ancient Egypt.

The journey of a calf begins with a sophisticated hormonal cascade. As the fetus nears full term, its hypothalamus produces ACTH, stimulating the adrenal glands to release corticosteroids. These hormones prompt the placenta to shift production from progesterone to estrogen, which in turn triggers the release of relaxin. This hormone softens the cow's ligaments and cervix, preparing the birth canal for the calf's arrival. This process is so finely tuned that farmers often use a sudden 0.5 °C drop in the cow's body temperature, occurring roughly 24 hours before birth, as a reliable predictor of calving.

Despite these preparations, birth is not always straightforward. Dystocia, or difficult calving, occurs when the calf's progression is obstructed. In 60% of cases, the difficulty is attributed to the calf itself, often due to its size relative to the mother's pelvic canal. Certain breeds, such as the Belgian Blue, are particularly prone to these issues due to genetic traits like double-muscling. When natural contractions—which can exert 70 kg of force—are insufficient, human intervention becomes necessary. This may involve manual traction using ropes or, in extreme cases, mechanical devices capable of exerting up to 450 kg of force.

The survival of the calf depends heavily on the speed and success of this transition. If the delivery is prolonged, the placenta may detach prematurely, cutting off the calf's oxygen supply and leading to anoxia. Even after a successful birth, the newborn remains vulnerable to environmental and infectious threats. Conditions such as omphalitis, an inflammation of the umbilicus, or respiratory diseases are common in the first few weeks. Because calves are not initially able to keep up with the herd, mothers often hide them for the first few days, returning periodically to suckle them until they are strong enough to follow the group at about one week old.

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