Influence of Diet on Mitochondrial Complex Activity in Channel Catfish

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Abstract
A 2 × 2 factorial experiment was conducted to evaluate the effects of commercial diets (32% protein, 3% fat [32/3 diet] or 36% protein, 8% fat [36/8 diet]; Malick Aquafeed, Inc.) and the influence of strain (U.S. Department of Agriculture [USDA] 103 or Norris) on performance variables and mitochondrial respiratory chain enzyme activities in the liver, muscle, and intestine of channel catfish Ictalurus punctatus. Juvenile channel catfish (average weight = 29.71 and 38.79 g for USDA 103 and Norris strains, respectively) were stocked into sixteen 152‐L aquaria at a density of 10 fish/aquarium. Four aquaria were used for each dietary treatment. Fish were fed twice daily to apparent satiation for 16 weeks. Results indicated that diet and strain had significant (P < 0.05) main effects on weight gain, feed consumption, feed efficiency, and specific growth rate. Diet composition had a significant main effect on condition factor, regardless of strain. There was a significant (P < 0.0007) fish strain × diet composition interaction effect on feed efficiency. Regardless of strain, fish fed the 36/8 diet formula had higher activities for respiratory enzyme complexes I, II, III, and IV in the liver, intestine, and muscle than fish fed the 32/3 diet. The strain effect was significant but not consistent for complex I and IV activities in the liver and muscle and complex II activities in the liver and intestine. The fish strain × diet composition interaction effect was significant for complex I activity in the liver and for complex II and IV activities in the muscle. These data demonstrate that the USDA 103 strain of channel catfish appears to possess superior traits in growth performance compared with the Norris strain. Our data indicate that diet has an important effect on channel catfish production and that a commercial 36/8 diet produces enhanced growth performance and mitochondrial enzyme activities relative to a 32/3 diet.