Apparent digestibility coefficients of various feed ingredients for juvenile and grower rockfish ( Sebastes schlegeli)

Abstract

Apparent digestibility coefficients of dry matter, crude protein, energy, and amino acids in white fish meal, anchovy meal, meat meal, feather meal, blood meal, soybean meal, corn gluten meal, cottonseed meal, wheat flour, and brewer's yeast were determined for juvenile and grower rockfish. Apparent digestibility coefficients were determined using a reference diet with chromic oxide indicator and test diets that contained 70% reference diet, by weight, and 30% of the feed ingredient being evaluated. The juvenile and grower fish averaging 30 and 300 g were held in 200 l tanks at a density of 50 and 8 fish per tank, respectively. Feces were collected from three replicate groups of fish using a fecal collection column attached to fish rearing tank. Apparent dry matter digestibility of ingredients decreased as nitrogen-free extract or fiber contents of ingredients increased, ranging from 73–95% for animal products and corn gluten meal to 32–54% for soybean meal, cottonseed meal, wheat flour and brewer's yeast. Apparent energy digestibility of ingredients followed similar trends to differences in dry matter digestibility. Apparent protein digestibilities of animal and plant products ranged 63–95% and 73–92%, respectively. White fish meal, anchovy meal, meat meal, and corn gluten meal showed the higher protein digestibility among ingredients tested ( P<0.01), regardless of fish size. Apparent digestibilities of protein and energy were not affected by fish size ( P>0.05), except for feather meal. These data provide more precise information concerning nutrient and energy utilization of rockfish and will allow ingredient substitutions in practical feed based on levels of available nutrients.