We compared the effects of using inorganic and organic forms of iron in plant-based diets on cat sh performance in a feeding trial with cat sh ngerlings (initial weight = 6.1 ± 0.2 g). Five diets supplemented with 0 (basal), 125, 250 mg Fe/kg of either FeSO 4 or iron methionine were formulated. Fish weight gain, feed conversion ratio, hepatosomatic index, and survival were similar among diets. Fish plasma and intestine iron concentration was similar among diets. Fish whole-body total lipid, protein, and dry matter were similar among diets. Ash content was higher in sh fed the basal diet than in other diets. Total liver iron concentration was higher in sh fed diets supplemented with 250 mg Fe/kg in both iron forms than other diets. Hematological parameters were similar among diets. Liver necrosis, in ammation, and vacuolization were highest in sh fed the diet supplemented with 250 mg Fe/kg from organic iron, followed by those fed diets with 250 mg Fe/kg from inorganic iron. Inorganic iron-supplemented diets caused more intestinal in ammation characterized by increased in ammatory cells, swelling of the villi, and thicker lamina propria than the organic iron-supplemented diets or the basal diet. Organic iron at 250 mg/kg resulted in a 0.143$/kg increase in feed cost. Latent iron de ciency and initial signs of anemia developed in cat sh fed the basal diet. Supplemental iron from either form prevented iron de ciency in sh. Organic iron at 125 mg/kg optimized sh performance at a cost comparable to that of sh fed other diets, but without overt negative effects.

We compared the effects of using inorganic and organic forms of iron in plant-based diets on catfish performance in a feeding trial with catfish fingerlings (initial weight = 6.1 ± 0.2 g). Five diets supplemented with 0 (basal), 125, 250 mg Fe/kg of either FeSO4 or iron methionine were formulated. Fish weight gain, feed conversion ratio, hepatosomatic index, and survival were similar among diets. Fish plasma and intestine iron concentration was similar among diets. Fish whole-body total lipid, protein, and dry matter were similar among diets. Ash content was higher in fish fed the basal diet than in other diets. Total liver iron concentration was higher in fish fed diets supplemented with 250 mg Fe/kg in both iron forms than other diets. Hematological parameters were similar among diets. Liver necrosis, inflammation, and vacuolization were highest in fish fed the diet supplemented with 250 mg Fe/kg from organic iron, followed by those fed diets with 250 mg Fe/kg from inorganic iron. Inorganic iron-supplemented diets caused more intestinal inflammation characterized by increased inflammatory cells, swelling of the villi, and thicker lamina propria than the organic iron-supplemented diets or the basal diet. Organic iron at 250 mg/kg resulted in a 0.143$/kg increase in feed cost. Latent iron deficiency and initial signs of anemia developed in catfish fed the basal diet. Supplemental iron from either form prevented iron deficiency in fish. Organic iron at 125 mg/kg optimized fish performance at a cost comparable to that of fish fed other diets, but without overt negative effects.

Channel catfish raised in the southern United States require two growing seasons to reach market size. Growing seasons are separated by a cool period of about 3 months when feed intake and growth are greatly reduced. A cool-weather feeding strategy to improve feed intake, growth or health of catfish might improve survival and reduce the time needed to achieve market size. We conducted a feeding trial with channel catfish at a suboptimal temperature (15°C) to determine the effects of supplementing diets with either a dairy/yeast prebiotic or flaxseed oil (high in 18:3n-3) compared with a control with soybean oil (high in 18:2n-6). The trial was conducted in recirculating systems with 1140-l tanks containing 100 fish each (mean initial weight 61.4 g ± 0.43 s.e.m.). A 28%-protein basal diet was supplemented with 20 g/kg cellulose and 20 g/kg soybean oil (SBO, control), 20 g/kg cellulose and 20 g/kg flaxseed oil (FLAX) or 20 g/kg of a dairy/yeast prebiotic and 20 g/kg soybean oil (PREB). Fish were fed once daily to satiation and weighed every 3 weeks to track growth. Hematology, non-specific immune responses, proximate and fatty acid composition of muscle were determined to assess diet effects. Catfish-fed FLAX or PREB had higher weight gain, feed consumption and lysozyme activity than fish fed SBO. Total n-3 fatty acids in muscle were higher in fish fed SBO or FLAX than those fed PREB. Total n-6 long-chain polyunsaturated acids were higher in muscle of fish fed PREB than those fed SBO. Fatty acids in the PREB and SBO diets were similar, so the PREB appeared to increase elongation and desaturation of n-6 fatty acids in muscle. Flaxseed oil and the dairy/yeast prebiotic both have potential to increase catfish performance at a low temperature.