Effect of melatonin during the seasonal anoestrous on the reactivation of the sexual activity and semen production at the normal breeding season on mediterranean bucks

Abstract

One experiment was conducted to determine if the onset of the reproductive activity and semen production could be modified by a previous treatment with exogenous melatonin, used to enhance reproductive activity during the seasonal anoestrous in Mediterranean bucks. Two balanced groups of bucks were used. The 18th march 2005, one group (M group) received 3 s.c. implants of melatonin (N=7) and other group (N=4) was used like control (C group). From June to September, body weight and testosterone was measured weekly and testicular weight every 15 days. The reproductive activity of each buck was assessed using characteristics of the testosterone profile. During the first 8 days of each month, volume of ejaculate and sperm concentration was assessed. Each of these 8-d periods was divided into 3-d periods of daily sperm collection separated by 2 d of rest. The semen was collected using an artificial vagina. The effect of treatment and month was studied on each variable. An interaction, month-treatment was observed on ejaculate volume, July was the month with higher volume (0.62 ± 0.06 mL vs 1.07 ± 0.15 mL for M and C group respectively, P < 0.05). Sperm concentration was influenced by treatment (6.13 x109 ± 2.49 x108 vs 4.26 x109 ± 3.12 x108 sperm/mL, for M and C, respectively, P < 0.05). The onset of the reproductive activity, after the study of the testosterone concentrations was similar for both groups (31st August ± 7.89 days and 4th September ± 25.66 days for M and C group, respectively). Results demonstrate that melatonin treatment during the seasonal anoestrous does not influence the onset of the normal breeding season or ejaculate volume but it seems that could increases the sperm concentration at the normal breeding season in Mediterranean goat males.