Mating Behavior Increases in Workload of Heart in Thoroughbred Stallions

Abstract

To evaluate an influence of mating behavior on cardiac function, changes in heart rate (HR), electrocardiogram (ECG), hematocrit (Hct), and serum concentration of alpha-atrial natriuretic peptide (ANP) were evaluated in 10 clinically sound Thoroughbred stallions before and after mating behavior. The stallions were submitted twice to experimental pseudo-mating in same month of 2009 and 2010. Measurements and blood samples were collected at a stable before the mating (baseline), at a covering yard before and after the mating. ECG was recorded by a Holter-ECG system. Arrhythmias were detected in 5 stallions before or after the mating behavior. Minimum HR (HRmin), maximum HR (HRmax) and HR recorded when the stallions entered into the yard (HRent) and ejaculated (HRejc) were 34.2 ± 3.7, 168.9 ± 14.2, 141.8 ± 35.3, and 142.6 ± 27.3 beats/min, respectively. Time from the entrance into the yard to ejaculation (mating time; MT) was ranged from 30 to 2,103 sec and highly correlated to HRent (r=－0.82) and the time required for attaining HRmax after the entrance into the yard (dT HRmax) (r=0.87). Hct and serum alpha-ANP concentration significantly increased after ejaculation (60.0 ± 3.2%, P<0.0001 and 1.54 ± 0.61 ng/ml, P=0.0353), comparing to the baseline values (46.9 ± 4.4%, 1.40 ± 0.60 ng/ml). HRent and Hct was significantly higher in the stallions with MT less than 5 min (n=5), comparing to those (n=5) with MT more than 5 min (P=0.0324 and P=0.0082). The mating behavior increases a workload of heart in Thoroughbred stallions.