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United States Department of Agriculture

Agricultural Research Service

Research Project: Nutrition and Feed Development for Warm Water Aquaculture

Location: Aquatic Animal Health Research

Title: Effects of dietary levels of vitamin A on growth, hematology, immune response and resistance of Nile tilapia (Oreochromis niloticus) to Streptococcus iniae challenge

Authors
item Guimaraes, Igo -
item Lim, Chhorn
item Aksoy, Mediha -
item Li, Ming
item Klesius, Phillip

Submitted to: Animal Feed Science And Technology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 11, 2013
Publication Date: February 1, 2014
Citation: Guimaraes, I.G., Lim, C.E., Aksoy, M.Y., Li, M.D., Klesius, P.H. 2014. Effects of dietary levels of vitamin A on growth, hematology, immune response and resistance of Nile tilapia (Oreochromis niloticus) to Streptococcus iniae challenge. Animal Feed Science And Technology. 188:126-136.

Interpretive Summary: Vitamin A, is a fat-soluble vitamin, and plays a major role in a number of physiological processes including the maintenance of epithelial cells development, bone development, reproduction and vision. Vitamin A has also been identified to play an important role in the immune system function and therefore helps to protect against infections. Earlier research has shown that vitamin A is a dietary essential to all vertebrate, including fish. However, limited information is available with respect to dietary vitamin A on growth performance and health of tilapia. Thus, this study was conducted to evaluate the effect of dietary levels of vitamin A (0, 2,500, 5,000, 10,000, and 20,000 IU/kg diet) on the growth performance, hematology, immune response and resistance of Nile tilapia to a bacterium (Streptococcus iniae) infection. Each diet was fed to Nile tilapia (initial weight, 5.26 ± 0.10 g) in four replicate aquaria to apparent satiation twice daily for 10 weeks. The results indicate Nile tilapia are very sensitive to vitamin A deficiency. Reduced weight gain, feed intake and poor feed efficiency were observed after 2 week of feeding vitamin A unsupplemented diets. Survival was unaffected by dietary treatments. Other gross deficiency signs observed during the 10-week trial were hemorrhages, skeletal deformity, fin erosion, darker body coloration and lethargy. Significantly lower hepatosomatic index, anemia (low hematocrit, red blood cell count and hemoglobin) and decreased resistance of erythrocytes to hemolysis in hypotonic solutions were observed in fish fed the vitamin A unsupplemented diet. Supplementation of vitamin A at 3,910 IU/kg diet was sufficient to prevent the above indicated deficiency signs in juvenile Nile tilapia. Serum protein, lysozyme activity and superoxide anion production were enhanced by supplementation of vitamin A, but serum total immunoglobulin and spontaneous complement activity were not affected by dietary treatments. Dietary supplementation of vitamin A had no effect on the resistance of Nile tilapia to S. iniae infection challenge and antibody production against the same bacterium 21 days post challenge. Thus, based on the results of the present study, the potential of using high levels of supplemental vitamin A to improve the resistance of Nile tilapia to infectious disease is not warranted.

Technical Abstract: This study was conducted to evaluate the effect of supplemental levels of vitamin A (0, 2,500, 5,000, 10,000, and 20,000 IU/kg diet) on the growth performance, hematology, immune response and resistance of Nile tilapia, Oreochromis niloticus to Streptococcus iniae challenge. Each diet was fed to Nile tilapia (initial weight, 5.26 ± 0.10g) in quadruplicate aquaria to apparent satiation twice daily for 10 weeks. The results indicate that vitamin A is a dietary essential for Nile tilapia. After 2 weeks of feeding, fish fed the vitamin A unsupplemented diet exhibited significantly lowest weight gain, feed intake and feed efficiency ratio than those of other treatments. Dietary vitamin A levels had no effect on survival. Other gross deficiency signs observed during the 10-week trial were hemorrhages, operculum deformity, fin erosion, darker body coloration and lethargy. Significantly lower hepatosomatic index and hematological parameters (except white blood cell count) were also recorded in fish fed the vitamin A unsupplemented diet. The resistance of erythrocytes to hemolysis in hypotonic solutions was lowest in fish fed vitamin A unsupplemented diet and increased with increasing vitamin A supplementation. A supplemental level of vitamin A of 3,910 IU/kg diet was sufficient to prevent these deficiency signs in juvenile Nile tilapia. Serum protein, lysozyme activity and superoxide anion production were enhanced by supplementation of vitamin A, while serum total immunoglobulin and spontaneous complement activity were not affected by dietary treatments. Dietary supplementation of vitamin A had no effect on the resistance of Nile tilapia to S. iniae infection challenge and antibody production against the same bacterium.

Last Modified: 12/22/2014
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