Use of Carazolol at Pre-Synchronized Timed Artificial Insemination in Cows

Abstract

Efficacy of the β-adrenergic receptor blocker (carazolol) at Timed Artificial Insemination (TAI) was investigated. Cows (n = 73) were pre-synchronized with two PGF2α injections given 14 d apart to initiate the Ovsynch protocol at early and middle luteal stages 14 d later, and received injections of GnRH and PGF2α seven d apart followed by GnRH 48 h later, and TAI 16 - 18 h later. Corpus luteum (CL) was detected via rectal palpation at the beginning of the Ovsynch protocol. Carazolol (Treatment I; n = 41) or physiologic saline (Treatment II; n = 32) were administered via jugular vein five min before TAI. Uterine tone was determined prior to infusion and at TAI via rectal palpation. Pregnancies were diagnosed with transrectal ultrasonography 40 ± 7 d after TAI. Uterine tone was 2.8 (1.4 - 5.3) times higher (P < 0.01) in Treatment I than that in Treatment II at TAI. Increase in uterine tone was affected by treatment × CL × parity (P < 0.05), and 66.7%, 75%, 52.6%, 100% and 16.7%, 33.3%, 25%, 28.6% in primiparous cows with CL and without CL, and in multiparous cows with CL and without CL in Treatments I and II, respectively. Pregnancy rates did not differ between treatments I (34.2%) and II (40.6%). In conclusion, no beneficial effect of carazolol administration prior to TAI was found except for the increased uterine tone.