Photoperiodic control of the time of parturition in alpacas (Lama pacos)

Twenty-three mature female alpacas in late gestation in October (spring group) and in January (summer group), were randomly allocated to two treatments. In each season, one group was placed indoors under natural light and the other group was placed in a treatment room which could be totally blacked out to external light and had artificial lights controlled by an automatic time switch. Lights in the treatment room were switched on at 12:00 h and switched off at 02:30 h. Video cameras were used to record the times of parturition. The mean time of parturition for alpaces in the treatment room (16:43 h ± 69 min) was 6 h 23 min later (P < 0.001) than the alpacas in the control room (10:20 h ± 67 min). The mean intervals from sunrise or lights-on to parturition and from sunset or lights-off to parturition were similar for both treatment groups, and there were no effects of treatments on gestation length. The mean interval from the start of the treatments to parturition was shorter (P < 0.001) in the spring group(18 ± 2 days) than in the summer group (36 ± 2 days). In conclusion, the results showed that the time of parturition in alpacas is under photoperiodic control.