Rainbow trout silage oil as immunity enhancing feed ingredient in formulated diets for South African abalone Haliotis midae

This study was conducted to evaluate the effects of rainbow trout silage oil on the immune function, growth performance and foot muscle fatty acid profile and proximate composition of South African abalone Haliotis midae. Rainbow trout silage oil was prepared from farmed rainbow trout processing waste, included at 25 g kg− 1 in a formulated diet and compared to a control diet in a 153 day growth trial. It was found that rainbow trout silage oil addition significantly improved abalone cellular immune function by increasing hemocyte phagocytic activity from 48.8% in the control diet to 65.2% in the silage oil diet. However, production performance was negatively impacted: specific growth rate (SGR) and final animal weight were decreased 17% and 5.6% respectively, and feed conversion ratio (FCR) increased by 25.1%. Foot muscle fatty acid profile and proximate composition were unaffected. It is concluded that dietary fish silage oil inclusion can improve cellular immune function in H. midae, but that the optimal inclusion level should be determined in order to negate the negative effects on production efficiency.