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Vitamin A affects haematology, growth and immune response of N ile tilapia ( O reochromis niloticus , L.), but has no protective effect against bacterial challenge or cold‐induced stress
Author(s) -
Guimarães Igo G,
Pezzato Luiz E,
Santos Vivian G,
Orsi Ricardo O,
Barros Margarida M
Publication year - 2016
Publication title -
aquaculture research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.646
H-Index - 89
eISSN - 1365-2109
pISSN - 1355-557X
DOI - 10.1111/are.12656
Subject(s) - nile tilapia , biology , oreochromis , hematology , immune system , medicine , aeromonas hydrophila , physiology , immunology , fish <actinopterygii> , fishery
Abstract Vitamin A (vitA) is an essential nutrient that acts as an endocrine regulator of several metabolic pathways, modulating normal growth and health status of animals. Although the importance of vitA for normal haematology and immune response is well documented for higher vertebrates, there is limited information on the physiological effects of vitA on fish. Therefore, we designed a 130‐day feeding trial to evaluate the effect of vitA supplementation on growth, haematology, immune function and resistance to experimental infection with A eromonas hydrophila and cold‐induced stress. A group of 320 N ile tilapia fingerlings 7.49 ± 0.19 g weight (mean ± SD ) were randomly stocked into 40 250 L‐aquaria and fed practical diets containing graded levels of vitA (0, 0.06, 0.12, 0.24, 0.48, 0.96, 1.92, 3.84 mg retinol ( ROH ) kg −1 diet. Growth, haematology, plasma protein profile and immune response were significantly affected by vitA supplementation; however, no clear protective effect of vitA supplementation on disease and cold stress resistance were observed in this study. Clinical signs of vitA deficiency were: resting and abnormal swimming behaviour, exophthalmia, haemorrhages at the base of fins and on skin, serous fluids in abdominal cavity, neutropenia, reduction in red blood cell count, haematocrit and haemoglobin evolving to high mortality rates in a short period of time. A dietary level of vitA around 1.2 mg ROH kg −1 may be required to prevent gross deficiency signs and promote proper growth and health status of N ile tilapia. VitA does not seem to have a pronounced effect on leucocyte differentiation, but clearly plays an important role on maintaining normal erythropoiesis.