STEPHAN WESSELS, ANDREAS MÜLLER-BELECKE, GABRIELE HÖRSTGEN-SCHWARK
Georg-August-Universität Göttingen, Institute of Animal Husbandry and Genetics, Germany
To avoid the problem of stunting, production of all-male and triploid stocks are methods in Nile Tilapia (Oreochromis niloticus) aquaculture to increase the overall productivity. All-male populations are known to facilitate culture in a broad range of systems as they show better growth performance and homogenity if compared to mixed sex populations. Due to their functional sterility the use of triploid seed represents an effective approach to eliminate negative effects of uncontrolled reproduction. Although triploid fish show various advantages, especially females tend to produce large amounts of intestinal fat if subjected to ad libitum feeding regimes. Fodder could be saved if the energy, deposited in intestinal fat stores, would be utilised for somatic growth. Therefore an eight week feeding trial during the early growth period was conducted to investigate the effects of different feeding regimes on the body composition of three different genetic groups of tilapia (Lake Manzala strain, Egypt: mixed sex, triploid, all-male) with emphasis on intestinal fat deposition. Three month old tilapia of the different genetic groups, stocked in replicates of 26 fish in 80 l-aquaria in a recirculating system, were either fed ad libitum three times a day or subjected to food deprivation every second day. At five month of age all fish were slaughtered and carcass traits were measured. Males fed ad libitum had a 60% better growth compared to the restricted groups. The all"=male groups showed the best overall growth capacity. The growth of females in the restricted regime was 92% inferior to the growth of their daily fed counterparts. Food deprivation did not result in decreased amounts of intestinal fat in the triploids, neither in males nor in females, during the early fattening phase under the given feeding regimes. Only in the all"=male groups intestinal fat was significantly affected by food restriction.
Keywords: All-male, aquaculture, carcass composition, feeding regimes, Oreochromis niloticus, triploid