EFFECTS OF SUBSTITUTING PALM OIL FOR FISH OIL AND SOY OIL IN FEED ON THE GROWTH PERFORMANCE AND MUSCULAR FATTY ACID COMPOSITION OF PELTEOBAGRUS VACHELLI

To investigate the effects of dietary replacement of fish-soy oil mixtures by palm oil on growth performance, feed utilization, muscular fatty acid composition, morphological index and liver tissue structure of yellow catfish (Pelteobagrus vachelli Richardson), five iso-proteic (400 g/kg), iso-lipidic (100 g/kg) and iso-energetic (15.70 MJ/kg) diets were formulated, in which the control group was supplemented with 1鲶2 fish-soy oil mixtures, and trial groups adopted different palm oil level (10 g/kg, 25 g/kg, 40 g/kg and 55 g/kg) to replace the mixture oil, respectively. For a 8-week trial. The results showed that dietary palm oil replacement had no significant effect on the feed intake, body weight, growth rate, feed efficiency, and protein retention efficiency (P>0.05). All the above parameters were increased with increasing dietary palm oil replacement level up to 25 g/kg, and then decreased. LA and n-3 HUFA concentrations in dorsal muscle significantly decreased with increasing dietary palm oil replacement level (P<0.05), while muscular n-3/n-6 significantly increased with increasing dietary palm oil replacement level (P<0.05). Furthermore, there were no significant difference in condition factor and viscerosomatic index among different groups (P>0.05). However, hepatosomatic index of 55 g/kg palm oil group was significantly higher than that of 25 g/kg palm oil group (P<0.05). The swelling hepatocytes with nuclei displacement and the increasing number of hepatic sinusoid and lipid cells were observed in 55 g/kg palm oil group. In conclusion, palm oil that replace 1鲶2 fish-soy oil mixtures up to 25 g/kg had no significant effect on the growth performance but improved the fatty acid profile of dorsal muscle.