[Electronic quantification of traction force during use of a mechanical calving aid in bovine parturition].

In this study, a specially developed computer-controlled system was used to obtain a continuous measurement of the forces that arise when using a mechanical calving aid. By this means, potentiograms for twenty-four births in cows using a tractive device were obtained (fourteen primiparae with an average age of twenty-eight months; ten pluriparae with an average age of fifty-four months; breeds: thirteen RB, eleven SB). A modern mechanical calving device with a locking mechanism was used as an aid in the extraction process. In births with use of light tractive force (approx. 50 kp), extraction took between 41 and +/- 21 seconds. Moderately heavy tractive force (approx. 80-100 kp) was applied in extractions taking 86 to +/- 22 seconds, whereas heavy tractive force (etwa 100-120 kp) was used in extractions lasting between 268 and +/- 117 seconds. The highest levels measured for brief applications of force were between 130 and 140 kp. Single strains of up to 150 kp were reached. Injuries in the soft birth canal were ascertained in 29.2% of the births. Such injuries were discerned more often in primiparae than in the pluriparae. The lacerations were merely superficial and caused no further after-effects. There were no limb injuries in the calves. For the use of mechanical calving aids the use of chains with exact markings should ensure that the limbs are fixated at equal lengths. Furthermore, every device should be equipped with a locking mechanism (150 kp) to prevent the use of too much force. This also prevents misjudgment of the birth situation concerning fetus size and the dimensions of the mother cow's pelvis.