Physiological Responses of Nile Tilapia, Oreochromis niloticus, Fed Vitamin C‐ and Lipid‐Supplemented Diets and Submitted to Low‐Temperature Stress*

Abstract

Abstract.— Water temperature alterations can determine harmful physiological modifications in fish, which should be prepared to cope with this, and nutrition strategies seem to be essential. This study evaluated the effects of different levels of vitamin C and lipids on physiological responses of Nile tilapia, Oreochromis niloticus, submitted to temperature stress. There were two phases: Phase I – preparing fish to store vitamin C and lipid at appropriate temperature, and Phase II – evaluating the contributions these reserves make to fish physiology under low‐temperature stress. The experiment used a 3 × 2 factorial design with three vitamin C levels (300, 600, and 1200 mg/kg diet) and two lipid levels (8.0 and 12.0%), plus absence of nutrient test and a diet of 6.0% lipids and 125.0 mg/kg vitamin C. In Phase I, 192 fish were kept at 26.0 ± 1.0 C for 112 d, and in Phase II, 48 fish were kept at 18.0 ± 0.5 C for 32 d and at 15.0 ± 0.5 C for 11 d. Fish fed C0L0 diet showed lower erythrocytes values in both phases; higher vitamin C supplement determined higher red blood cell (RBC) number and higher hematocrit (Htc) (Phase II); Htc was significantly lower in Phase II; after temperature stress, fish fed C0L0 diet had higher mean corpuscular volume, lower hemoglobin corpuscular concentration, and significantly lower vitamin C concentration in the liver; and higher supplementation determined a higher concentration in the liver (Phases I and II). Higher plasmatic cortisol concentration was seen in fish fed C0L0 diet. In conclusion, our results show that the absence of vitamin C in diets impairs RBC formation and does not enable fish to cope with stress; excess vitamin C is efficient in mitigating stress and 600 mg/kg diet is economic and physiologically sufficient to prepare fish for coping with low‐temperature stress. Lipid supplementation does not determine alterations in stress biochemical parameters.

Immunomodulatory Effects of Dietary β‐glucan and Vitamin C in Nile Tilapia, Oreochromis niloticus L., Subjected to Cold‐induced Stress or Bacterial Challenge

“…The vitamin C concentration in fish liver was related to the supplementation level. Similar results were also reported in channel catfish by El Naggar and Lovell () and in Nile tilapia by Falcon et al (). Vitamin C supplementation above the recommended levels provided a necessary reserve, which enabled the redistribution and use under CIS.…”

“…hydrophila (Andrade et al ). Although the stress influenced differences in the blood parameters, dietary β‐glucan and vitamin C supplementation could not maintain suitable erythropoiesis patterns in healthy animals even at different concentrations (Falcon et al ; Weiss and Wardrop ). In this study, supplementation with 0.8% of β‐glucan influenced the release of immature blood cells under CIS conditions.…”

Consequences of High-Density Fish Culture as Monitored By Growth, Behavior and Immune Responses of Nile Tilapia (Oreochromis niloticus)

“…Meanwhile, in previous studies, the increase in red blood cell numbers in fish reared at HD (Montero et al, 2001;Abdel-Tawwab, 2012) in which stress promote the numbers of erythrocytes. Stress increases the levels of cortisol that in turn lead to elevated erythropoietin level activating RBCs production (Falcon et al, 2007).…”

Feed training of giant trahira fingerlings fed diets containing different levels of vitamin C

“…During this process, the constant change of diet can be a stressor for fish (Barcellos et al, 2000). However, stress can be relieved by controlling the diet inasmuch as the physiological state of an animal is a reflection of the quality and quantity of available nutrients in the diet (Falcon et al, 2007a). Among the nutrients used in diets to reduce the effects of stress on fish, vitamin C acts as an antioxidant eliminating free radicals (Lall and Lewis-McCrea, 2007), reducing stress and promoting comfort for the animal (Li & Lovell, 1985;Sakakura et al, 1998;Petric et al, 2003;Moraes et al, 2003;Wang et al, 2006).…”

“…Unfavorable conditions increase demand for vitamins, especially vitamin C (Wedemeyer, 1969;Navarre & Halver, 1989, Falcon et al, 2007b. In carnivorous fish, stressful situations are common due to the high degree of cannibalism.…”