Artificial long days and daily contact with bucks induce ovarian but not oestrous activity during the non-breeding season in Mediterranean goat females

Abstract

The aim of the present study was to determine whether a treatment of 3 mo of artificial long days and daily contact with bucks can stimulate reproductive activity during the normal seasonal anoestrous in female goats, and whether such treatment modifies the onset of the normal breeding season. Thirty-nine adult, open does were assigned to two treatments of similar mean body weight (BW) and body condition score (BCS). One treatment (LD; n = 18) was housed in a light-proof building and exposed to long days (16 h of light/d) from 17 November to 5 February, and then exposed to the natural photoperiod in an open shed. The remaining females were housed in an open shed under natural photoperiod conditions throughout the experiment (control [C]; n = 21). Plasma samples for progesterone, BW and BCS were recorded every wk. Oestrous activity was checked daily using aproned bucks. Bucks were housed close to females in a separate barn from the onset of the experiment. Ovulation rate was determined by laparoscopy 7 d after positive identification of oestrus. The interaction of treatment by time for temporal concentrations patterns of progesterone concentrations indicated that luteal activity in LD does were greater ( P < 0.001) than those of C does during the natural seasonal anoestrous season. None of the C does exhibited oestrous or luteal activity during the non-breeding season; whereas, 72% of LD does exhibited luteal activity only 33% of them showed oestrous activity and during this season ( P < 0.01). Differences in resumption of the oestrous or luteal activity were not observed ( P > 0.05) in the subsequent breeding season between treatments. In conclusion, 3 mo of exposing does to long days and daily contact with bucks during the breeding season appears to stimulate reproductive processes that normal would not occur during the anoestrous season. However, this treatment does not induce oestrus is adequate numbers of does to be of practical value. Finally, this treatment does not modify the onset of the subsequent natural breeding season.