RESUMO
The uterotonic characteristics and effectiveness of a single treatment with either oxytocin or carbetocin were quantified in early postpartum dairy cows after normal, uncomplicated calvings. Both the short-term (within 4 h), and the long-term effects (between 12 and 36 h) of the two treatments were compared. Between 14 and 16 h after parturition, 27 multiparous Holstein-Friesian dairy cows, without fetal membrane retention, were selected and divided into three groups. The first group (n = 9) was administered 50 IU oxytocin intramuscularly, the second group (n = 10) received 0.35 mg carbetocin, while animals of the third group (n = 8), serving as a control, were administered 5 mL saline solution. A transcervically introduced open tip catheter system was used for the non-invasive acquisition of the intrauterine pressure (IUP) recording. After digitalization, the signals were analyzed, using a specially adapted graphical software program. A significant short-term effect was found both in the oxytocin and carbetocin treated groups from the analysis of the contraction frequencies (FREQ) and of the total area under the curve (TAUC). After significant peaking during the first post-treatment hour, the values of the parameters for these two groups remained higher during the second hour, returning to the initial levels again during the third hour and reaching the level of the control group by the 12th hour. Mean amplitude (AMP), duration (DUR) and area under the curve (AUC) of pressure cycles were not significantly affected by any of the treatments. Although mean FREQ and TAUC significantly declined from the initial values to 12, 24 and 36 h in all groups, mean AMP and AUC in the oxytocin and carbetocin treated groups, and mean DUR only in the carbetocin treated group to 12 and 36 h, the long-term analysis revealed no significant treatment differences for any IUP parameters. Because treatment with either oxytocin, or carbetocin elicited similar uterotonic effects in healthy, early postpartum cows, it cannot be expected, that using carbetocin in preference to oxytocin, will result in a more beneficial clinical effect on uterine involution during this period.
