The objective of this research was to evaluate the nonspecific immune responseÂ and resistance of Litopenaeus vannamei fed with nucleotide, Î²âglucan, and protagenÂ diets. Shrimp juveniles with an average weight of 5.39Â±0.56 g were reared in glassÂ aquaria at a density of 15 shrimps/aquarium. Shrimps were fed three times a day forÂ four weeks at a feeding rate of 3%/bw/day. Treatment diets consisted of A: basal dietÂ (without immunostimulant), B: Î²âglucan, C: protagen, and D: nucleotide, each withÂ three replicates. At the end of feeding period, the shrimps were intramuscularlyÂ injected with Vibrio harveyi 0.1 x 106 cfu.shrimp-1. Total haemocyte count (THC) ofÂ shrimp fed with nucleotide-diet was significantly different compared to that of controlÂ shrimp (p=0.01), but not different compared to shrimp fed with protagen-diet.Â PO activity also increased significantly in shrimp fed with nucleotide-diet (p=0.02).Â Î²âglucan diet could also increase THC and PO activity, but compared to the control,Â the increase was not significantly different. Overall, PO activity of shrimp fed withÂ nucleotide, Î²âglucan, and protagen diets was high (>0.35). Oral administration ofÂ nucleotide, Î²âglucan, and protagen for four consecutive weeks significantly increasedÂ resistance of shrimp to disease (<0.01) where the highest resistance rate was observedÂ on shrimp fed with nucleotide-diet. Growth of shrimp fed with nucleotide-diet wasÂ significantly different compared to that of control shrimp (p<0.01), as well as to Î²âglucan, and protagen-treated shrimp. As a conclusion, supplementation of nucleotideÂ into shrimp pellet enhanced nonspecific immune response and growth performanceÂ better than Î²-glucan, and protagen.
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