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.
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