Clenbuterol (planipart(trade mark)) for the postponement of parturition in cattle.

Department of Surgery and Medicine, School of Veterinary Medicine, Auburn University, AL 36849 USA.
Theriogenology (Impact Factor: 2.08). 10/1985; 24(4):385-93. DOI: 10.1016/0093-691X(85)90045-7
Source: PubMed

ABSTRACT Clenbuterol is a highly specific, long-acting (four to eight hours) beta-two sympathomimetic which causes bronchodilation and tocolysis (myometrial paralysis). The tocolytic effect was explored as a means to control parturition and reduce dystocia. Forty-six heifers were injected i.m. with either Clenbuterol or saline placebo in a randomly controlled experiment. Animals were treated when a cervical dilation of five centimeters or more was detected by vaginal examination. Length of first, second and third stages of parturition, ease of parturition, maternal pelvic area and calf viability were compared between treatment groups. Treatment with Clenbuterol increased (P<0.025; 119 vs 468 mins) the time heifers were in Stage I. However, the lengths of Stages II and III, pelvic area at birth and calf viability were not influenced by treatment. Diameter of the cervix at treatment was negatively related to the length of Stage I delay. Pelvic area also significantly affected the length of Stage II. Clenbuterol effectively delays Stage I of parturition with no adverse effects on the fetus or dam.

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    ABSTRACT: External as well as internal stressors prolong parturition in different species. At parturition, sympathoadrenal activation should be avoided because an increased sympathetic tone may cause uterine atonia via β2-receptors. We hypothesized that at physiological parturition horses are under parasympathetic dominance and stress-response mechanisms are not activated during delivery of the foal. To evaluate stress responses, heart rate (HR), heart rate variability (HRV), catecholamines and cortisol were analyzed in mares (n=17) throughout foaling. Heart rate decreased from 2 hours before (51 ± 1 beats/min) to 2 hours after delivery (41 ± 2 beats/min; P < 0.05). Heart rate variability variables standard deviation of the beat-to-beat (RR) interval (SDRR) and root mean square of successive RR differences (RMSSD) changed over time (P < 0.05) with highest values within 15 min after delivery. The number of mares with atrioventricular (AV) blocks and the number of AV blocks per mare increased over time (P < 0.01) and were significantly elevated from 15 min before to 45 min after birth of the foal. Salivary cortisol concentrations increased to a maximum at 30 min after delivery (25.0 ± 3.4 ng/mL; P < 0.01). Plasma epinephrine and norepinephrine concentrations showed significant fluctuations from rupture of the allantochorion to expulsion of the fetal membranes (P < 0.01) but were not markedly elevated at any time. In conclusion, mares give birth under high parasympathetic tone. Cortisol release during and after foaling is most likely part of the endocrine pathways regulating parturition and not a labour- associated stress response.
    Theriogenology 07/2014; · 2.08 Impact Factor