GPS-derived foraging behaviour of red deer and liveweight gain of red deer and wapiti crossbred sire lines on contrasting winter forage types

Context: It is common practice to manage red deer on highly digestible easily harvested forage during winter on New Zealand deer farms, particularly in areas that experience low or no pasture growth during this period. However, not all individuals within these production systems perform equally.

Aims: To investigate foraging behaviour of young red deer and liveweight gain of young red deer and wapiti crossbred sire lines when offered two contrasting winter forage diets.

Methods: One hundred and sixty-three rising 1-year-old female red deer and red deer wapiti crossbreds representing five red deer and two wapiti sires, were split into two management groups balanced by sire and liveweight and managed on either an easily harvested highly digestible diet (forage kale) or a harder-to-harvest more poorly digestible diet (pasture) for a 6-week period during winter. Foraging behaviour was monitored on 95 red deer yearlings by using GPS collars over a 2-week period. Liveweights were recorded at the start and end of the 6-week period.

Key results: Progeny managed on the kale treatment exhibited an extended activity period during the dawn period and a suppressed activity period during the middle of the day. Progeny managed on the pasture treatment exhibited frequent shorter activity periods from dawn to dusk. Time spent foraging and the number of foraging bouts greater than 5 min in duration were different among progeny of different sires. These differences in behaviour did not affect liveweight gain. Liveweight gain over the 6-week trial period was significantly higher for progeny from one wapiti sire than for all red deer sire progeny while being managed on the kale diet (P < 0.001), but there were no differences among progeny on the pasture diet.

Conclusion: Foraging behaviour varied considerably between sire lines and appeared to vary between forage type, but there were no correlations between behaviour and liveweight gain in this trial.

Implications: Forage type offered to young red deer may alter their foraging behaviour. Offering an easier to harvest high digestible forage diet may increase liveweight gain of progeny that have a higher genetic potential to grow during the winter period.