A study to determine whether growth of weaner red deer stags ( Cervus elaphus) in winter can be stimulated by a split night photoperiod: A dissertation submitted in partial fulfilment of the requirements for the degree of Bachelor of Agricultural Science with Honours at Lincoln University

Abstract

This study tested the hypothesis that a split night photoperiod would induce spring-like growth rates during winter like that seen in sheep. The study was run from 6 May until 18 September, 2002, where weaner red deer stags were housed inside up until the last 2 weeks of this period when they were returned to pasture. Whilst inside the stags (n=10) were subjected to either a long day photoperiod (16L:8D, where L = h of light, D = h of darkness), natural daily photoperiods (short days experiencing the normal seasonal pattern of daylight) or natural daily photoperiods with a 1 h period of light during the dark phase (split night). During the first 12 weeks of the study live weight gain was comparable in all groups (approx 150g/day). However growth of long day treated animals began to surpass that of the other treatments so that by 6 August mean live weight of the long-day treated group was significantly (P<0.01) greater than that of the other groups. From 6 August to 3 September mean live weight was gain was 374, 266 and 290 g/day for long day, natural and split night groups, respectively. The long day group had the highest voluntary feed intake and initiated antler pedicle growth and testicular enlargement earlier than other groups. Plasma prolactin concentration was elevated (P<0.01) in the long day treatment (mean at 9 July: 33 ± 4.09) in comparison to the split night and short day groups (2.9 ± 0.99 and 6.9 ± 3.75, ng/ml respectively). These results clearly illustrate that weaner red deer stags do not respond to a split night photoperiod 16-17 h after the subjective dawn and force me to reject the hypothesis that was under test here. It is concluded that some of the periodic signals that evoke responses in sheep are not effective in deer and, hence there are differences in the underlying mechanisms of photoperiodisin between these two species.