Electrocardiographic, endocrine and biochemical stress indices of electroejaculated Egyptian Baladi goat bucks

Abstract

This study aimed to evaluate the stress response to electroejaculation (EE) through electrocardiogram (ECG) indices alongside hormonal and biochemical indices. Lead II base-apex ECG was recorded at rest (control, T0) and immediately after EE (T1), repeated in four consecutive weeks. The collected ejaculates were evaluated for standard semen characteristics (ejaculate volume, mass motility, individual motility, sperm cell concentration and total sperm count per ejaculate). Blood samples were collected at rest (T0), 10 (T2) and 120 min (T3) after EE for determination of biochemical and hormonal stress indices. EE induced sinus tachycardia with simultaneous marked increase in P waves amplitude and decrease in all waves and intervals durations (except for QRS complex and PR interval). Similarly, significant variation between the first and the last EE sessions were observed in heart rate (HR) indices (mean RR, mean, maximum and minimum HR), some wave amplitudes and segment durations. While the stress index significantly increased in the 3rd week only. This was associated with significant short term increases in serum level of cortisol and progesterone (P4) with significant decrease of glucose and globulins at T2. Furthermore, at T3 there was significant increase in cardiac troponin I (CTnI) concentration, while free triiodothyronine (FT3), potassium (K+), calcium (Ca2+) and glucose levels decreased significantly. There were significant increases between the first and the last EE sessions in cortisol, FT3 and significant decrease in Lactate dehydrogenase (LDH) concentrations. On contrary, there were no significant changes in time related to EE and weekly repetitions in the corrected QT interval (QTc), root mean square of sum of squares of normal to normal difference (RMSSD), standard deviation of the normal to normal (SDNN) vasovagal tonus index (VVTI) and semen characteristics. In conclusion, although repeated EE causes acute stress response which increases with repetition, the response appeared transient and not deleterious to the cardiac activity and semen characteristics evidenced by non-persistent significant increases in CTnI and absence of significant changes in the standard semen characteristics of the bucks. Additionally, ECG might be beneficial in assessing the welfare of electroejaculated bucks. Further assessment of heart rate variability (HRV) indices of bucks after EE using frequency and non-linear indices in a larger animal population is recommended.