VAN CLEEFF, J.*; BLACHE, D.; MARTIN, G.: Early castration of male emus (Dromaius novaehollandiae) reduces their feed efficiency and attenuates vernal fattening without impairing appetite

The emu responds to increasing photoperiod with an increase in appetite and fat deposition. This response is normally delayed until breeding season hormones, stimulated by short days, have been cleared from the system, about 6 weeks after the Winter Solstice in the case of non-incubating males. We investigated the interactions between testosterone, feed intake and vernal fatttening in male emus fed ad libitum and maintained outdoors in a Mediterranean type environment (Perth, Australia). Emus castrated as 8-week-old chicks grew normally but in adulthood failed to undergo vernal fattening to the same extent as intact contemporaries, and lost less weight in Winter. Thus, live weight change was significantly attenuated in Castrated emus. Maximum summer weight was 43.1 � 1.4 kg for Castrated emus, and 49.2 � 1.6 kg for Intact emus. In Winter, Castrated emus lost 9% from the maximum live weight of the previous summer, compared to 18% for Intact emus. Annual feed intake was similar between Intact and Castrated emus, but intake was highest in Winter for Castrated emus and highest in Spring for Intact emus. Castrated emus can respond to increasing photoperiod very soon after the Winter Solstice with increased intake and fat deposition, but their ability to deposit fat is severely impaired. Testosterone appears to be necessary for normal feed efficiency and conversion of consumed feed to fat deposits in Spring and Summer in the emu.