Immunomodulation of Labeo rohita juveniles due to dietary gelatinized and non-gelatinized starch

A 60 days experiment was conducted to study the effect of dietary gelatinized (G) and non-gelatinized (NG) starch on immunomodulation of Labeo rohita juveniles. Two hundred and thirty four juveniles (av. wt. 2.53 ± 0.04) were randomly distributed in six treatment groups with each of three replicates. Six semi-purified diets containing NG and G corn starch, each at six levels of inclusion (0, 20, 40, 60, 80, 100) were prepared viz., T1 (100% NG, 0% G starch), T2 (80% NG, 20% G starch), T3 (60% NG, 40% G starch), T4 (40% NG, 60% G starch), T5 (20% NG, 80% G starch) and T6 (0% NG, 100% G starch). After a feeding period of 60 days, the juveniles were challenged with Aeromonas hydrophila to study their immunomodulation due to feeding of G and NG starch. RBC and haemoglobin content were significantly (P < 0.05) reduced due to bacterial challenge, but dietary starch (G/NG starch) had no effect on it. G:NG starch ratio in the feed had significant effect on total leukocyte count during pre- and post-challenge periods. The leukocyte count concomitantly increased with the increased level of G starch in the diet. Highest albumin/globulin (A/G) ratio was recorded in T6 group (100% G starch) and lowest in T1 group (100% NG starch) group followed by T2 group both in pre- and post-challenge periods. NBT, lysozyme activity, total protein and globulin content were highest in T2 group (80% NG, 20% G starch) both in pre- and post-challenge periods. After challenge with A. hydrophila, the highest survival was recorded in T2 group, whereas lowest survival was recorded in T6 group. Conclusively high level of G starch was found to be immunosuppressive in Labeo rohita juveniles and NG:G starch ratio of 80:20 seems to be optimum for promoting growth and protecting immunity in L. rohita juveniles.