Effect of a Guar Meal Protein Concentrate in Replacement of Conventional Feedstuffs on Productive Performances and Gut Health of Rainbow Trout (Oncorhynchus mykiss)

A trial was performed to investigate the effect of a proprietary guar protein concentrate, as a partial replacement of conventional protein sources, on the productive performances of rainbow trout through the growing phase. A total of 2700 rainbow trout were reared in 3 m3, 12 concrete tanks for 90 days. Three diets were formulated to contain a protein level of 43% and a lipid content of 25.3% by replacing 0% (CD), 5% (D5), and 15% (D15) of conventional protein sources with guar protein concentrate. The final mean weight was similar between D5 and CD, significantly higher than D15. The same trend was observed in weight gain and specific growth rate. The feed conversion rate had the most favourable performances in D5 and CD. Feed palatability was higher in CD and D5 than in D15. Histological intestinal score showed significant differences (p < 0.05) between the groups with the highest values in CD and the lowest in D15. Significant differences were observed for goblet cell hyperplasia with higher values in the CD group. Based on this trial, the 5% guar protein concentrate inclusion gave the best zootechnical results.