Photoperiod-treated bucks are equal to melatonin-treated bucks for inducing reproductive behaviour and physiological functions via the “male effect” in Mediterranean goats

Abstract

The aim of this study was to examine whether photoperiod-treated bucks have the same capacity as melatonin-treated bucks to induce reproductive responses in female goats during the spring. On 10 April, 38 anoestrous does were placed with: 1) photoperiod-treated bucks (additional light hours for 83 days from the end of the previous November; PHOTO; n=12); 2) bucks treated with exogenous melatonin at the beginning of March (MEL; n = 13); and 3) bucks that received no treatments (CONTROL; n = 13). The bucks' sexual behaviour was assessed for 10 days, and doe oestrous behaviour was recorded for the next 32 days by checking for harness marks. Ovulation was confirmed from plasma progesterone concentration (measured twice per week) and ovulation rate was assessed by transrectal ultrasonography. Fecundity, fertility, prolificacy and productivity were also determined. The percentage of does in the PHOTO, MEL and CONTROL group: 1) having ovulations was 92%, 100% and 38% respectively; 2) expressing behavioural oestrous associated with ovulation was 92%, 100% and 31%; and 3) that became pregnant was 75%, 69% and 23%, respectively. The kids produced per doe were 1.08 ± 0.23, 1.15 ± 0.25 and 0.31 ± 0.17 for the PHOTO, MEL, and CONTROL groups, respectively with there being no differences between the PHOTO and MEL groups, however, there was a difference (P < 0.05) between PHOTO/MEL and CONTROL groups. Thus, imposing a stimulatory lighting regimen during the preceding winter period is as efficient as using subcutaneous melatonin implants in stimulating reproductive behaviours and physiological functions of bucks.