Clinical study of the use of clenbuterol for postponing parturition in cows.

A clinical study was conducted to test the usefulness of clenbuterol for postponing parturition in cows. One hundred cows at various stages of labour were treated and there where 55 controls. The animals were classified into four groups according to the degree of cervical dilation when examined. Cows treated when in first stage of labour calved between 5.2 and 9.7 hours later than control animals. Calving was postponed two hours when cows were treated during early second stage of labour. Clenbuterol was used in a separate field trial to prevent calvings between midnight and 07.00; 127 cows were treated and only one calved earlier than seven hours after treatment.