Effects of dietary fish silage and fish fat on growth performance and sensory quality of growing-finishing pigs

Thirty-six growing-finishing pigs, with an average initial weight of 24.8 kg ± 2.6 SD, were allocated to six groups to determine the effect of fish silage and fish fat in the diet on performance, carcass characteristics and sensory quality. The treatments were either a control diet, or one of three diets containing 50 g kg−1 fish silage and different levels of fish fat (2.5, 5.5 or 9.5 g kg−1). The diets were either fed until the time of slaughter (treatments CO, FSA1, FSB1 and FSC1), or until 60 kg liveweight followed by the control diet (the diets with 5.5 [treatment FSB2] and 9.5 g kg−1 fish fat [treatment FSC2]). Pigs were slaughtered at 98.7 kg ± 4.5 SD. No significant differences in growth performance or carcass quality were found among diets. The contents of the fatty acids C20:1 and C22:6 in the subcutaneous fat was increased by the dietary inclusion of fish silage. The total level of omega-3 fatty acids were highest for the 9.5 and the 5.5 g kg−1 fish fat diets when they were fed until slaughter. High blood plasma levels of vitamin E in pigs fed diets containing fish silage and 5.5 g kg−1 fish fat may explain these differences, and thus indicate the importance of vitamin E status when feeding diets containing fish silage and fish fat. The diets containing 2.5 and 9.5 g kg−1 fish fat until slaughter caused off-flavour of bacon after both 1 and 6 mo of frozen storage, and of loin muscle after 6 mo frozen storage. Curiously, the diet with fish silage and 5.5 g kg−1 fish fat could be used in diets for growing-finishing pigs without adverse effects. Key words: Fish silage, fish fat, growing-finishing pigs, growth performance, carcass characteristics, sensory quality