It is generally accepted that adequate supervision at calving has a significant positive effect on reducing calf mortality, which has been of increasing importance with the use of larger beef breeds and cattle with larger birth weights.

"On most ranching operations, supervision of first-calf heifers and more mature cows will be best accomplished in daylight hours, while the poorest observation typically will take place in the middle of the night," says Glenn Selk, Oklahoma State University Cooperative Extension emeritus cattle specialist.

The easiest and most practical method of inhibiting nighttime calving at present is by feeding the expectant mothers at night; the physiological mechanism is unknown, but some hormonal effect may be involved.

Selk says rumen motility studies indicate the frequency of rumen contractions falls a few hours before parturition. Intraruminal pressure begins to fall in the last two weeks of gestation, with a more rapid decline during calving.

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