Effects of Dietary Lipid Concentration and a Dairy–Yeast Prebiotic on Growth, Body Composition, and Survival of Stressed Goldfish Challenged with Flavobacterium columnare

Abstract

Preliminary feeding trials with goldfish Carassius auratus were conducted by using four practical diets with 4% or 10% supplemental poultry fat (PF) and 0% or 2% dairy–yeast prebiotic. Total lipid in the diets ranged from 9.7% to 16.4%, which is higher than the lipid level in most commercial baitfish diets. Aquarium and pool trials were conducted to compare diet effects in the presence or absence of natural foods. In aquaria, weight gain, survival, and feed conversion were similar among diets, but whole-body lipid and dry matter percentages were higher in goldfish that were fed 10% PF diets than in fish receiving 4% PF diets. In pools, weight gain was higher in goldfish that received the 10% PF diets or the 4% PF diet with prebiotic than in fish that were fed the 4% PF diet without prebiotic. Lipid and dry matter were higher in goldfish that were given 10% PF diets than in fish that were given 4% PF diets. The presence of natural foods in pools may partly explain the differences in results between aquaria and pools. Subsequent bacterial challenges with Flavobacterium columnare were conducted separately for fish in pools that received the 4% PF and 10% PF diets. Some groups of fish were stressed prior to exposure. Stressed goldfish that were fed the 4% PF diet with prebiotic had a survival rate similar to that of unstressed fish that were fed the basal or prebiotic diets, but stressed fish that were given the 4% PF diet without prebiotic had lower survival. Unstressed goldfish that received the 10% PF diets had higher survival than stressed fish, but there was no prebiotic effect. Preliminary results indicate that the dairy–yeast prebiotic has some potential to protect stressed goldfish against F. columnare infection, but more studies are needed to determine whether dietary lipid concentration influences the results.

Received February 16, 2010; accepted January 20, 2011

ACKNOWLEDGMENTS

We thank ARKAT and Omega Protein for donating the feed ingredients used in this study. We thank Pool's Goldfish Farm for donating the fish and International Ingredient Corp. for donating the GroBiotic-A. Felicia Bearden and Ruguang Chen provided technical assistance. We thank Nathan Stone, Peter Perschbacher, and Hugh Thomforde for reviewing this manuscript. The work reported in this publication was supported in part by the Southern Regional Aquaculture Center through Grant Numbers 2003-38500-12997 and 2004-38500-14387 from the U.S. Department of Agriculture's Cooperative State Research, Education, and Extension Service.

Notes

^aVitamin premix contains (per kg of premix): ascorbic acid, 50.0 g; D-calcium pantothenate, 5.0 g; choline chloride, 100.0 g; inositol, 5.0 g; menadione, 2.0 g; niacin, 5.0 g; pyridoxine HCl, 1.0 g; riboflavin, 3.0 g; thiamine HCl, 0.5 g; DL-α-tocopherol acetate (at 250 international units [IU]/g), 8.0 g; vitamin A acetate (20,000 IU/g), 5.0 g; vitamin micro-mix, 10.0 g; and cellulose, 805.5 g. Vitamin micro-mix contains (per kg of micro-mix): biotin, 0.5 g; cholecalciferol (at 40 IU/g), 0.02 g; folic acid, 1.8 g; vitamin B12, 0.02 g; and cellulose, 97.66 g.

^bMineral premix contains (per kg of premix): calcium phosphate (monobasic) monohydrate, 136.0 g; calcium lactate pentahydrate, 348.49 g; ferrous sulfate heptahydrate, 5.0 g; magnesium sulfate heptahydrate, 132.0 g; potassium phosphate (dibasic), 240 g; sodium phosphate (monobasic) monohydrate, 88.0 g; sodium chloride, 45.0 g; aluminium chloride hexahydrate, 0.15 g; potassium iodide, 0.15 g; cupric sulfate pentahydrate, 0.50 g; manganous sulfate monohydrate, 0.70 g; cobalt chloride hexahydrate, 1.0 g; zinc sulfate heptahydrate, 3.0 g; and sodium selenite, 0.011 g.

^cGroBiotic-A was donated by International Ingredient Corp., St. Louis, Missouri.

^dAnalyzed composition (%, dry basis).

^eKilojoules of gross energy per gram of protein. Estimated energy content of the diets was based on values of 16.7, 16.7, and 37.7 kJ/g for carbohydrate, protein, and lipid, respectively (Serrano et al. 1992).

^aCalculated as final mean individual weight—initial mean individual weight. Mean ± SE of total initial weight for 30 fish was 17.2 ± 0.1 g. Calculated initial weight per fish was 0.57 g.

^bCalculated as dry feed weight/fish weight gain.

^cNot defined.

^aCalculated as final mean individual weight—initial mean individual weight. Final mean individual weight was calculated from bulk weights of 100 fish/sample. Mean ± SE of total initial weight for 400 fish was 145.4 ± 1.0 g. Calculated initial weight per fish was 0.36 g.

^bCalculated as feed weight/fish weight gain.

^cFulton's condition factor, calculated as 100 × [(weight, g)/(standard length, cm)³] (Stone et al. 2003) from individual weights and lengths of randomly selected fish (50 fish/pool).

^aData from controls are presented for qualitative comparison but were not included in statistical analysis.

^aData from controls are presented for qualitative comparison but were not included in statistical analysis.