Dietary vegetable choline improves hepatic health of Nile tilapia (Oreochromis niloticus) fed aflatoxin-contaminated diet.

Aflatoxin B1 (AFB1) is one of the most important mycotoxins due to its hepatotoxic and carcinogenic effects on animals. The effect of dietary supplementation with vegetable choline (VC) at 400, 800, and 1200 mg/kg against the deleterious effects of AFB1 (2 ppm/kg diet) in the liver of Nile tilapia (Oreochromis niloticus) was studied. The experimental period was 81 days, and the diet with VC was offered to the fish for 60 days prior to challenge with AFB1. Diets with AFB1 were tested in three replications and animals were analyzed at days 14 and 21 of dietary intake. The addition of VC to tilapia diet increased body weight (days 30 and 60 pre-challenge and day 21 post-challenge). The group fed aflatoxin-contaminated diet presented significantly reduced antioxidant enzymes and increased reactive oxygen species (ROS) levels, thiobarbituric acid reactive species (TBARS) levels, and protein carbonyl (PC) content in the liver. Dietary supplementation with VC at 800 and 1200 mg/kg demonstrated a significant protective effect, avoiding the increase of ROS, TBARS, and PC levels in the liver of tilapia from the aflatoxin contaminated groups. Thus, dietary VC supplementation may be used in tilapia to increase antioxidant status and reduce the negative effects caused by AFB1 toxicity. Based on the findings, it is recommended to use VC as a food supplement for Nile tilapia in order to avoid AFB1 toxication. In addition, decreased aflatoxin toxicity can be attributed to the VC antioxidant property.

Melaleuca alternifolia essential oil abrogates hepatic oxidative damage in silver catfish (Rhamdia quelen) fed with an aflatoxin-contaminated diet.

Mycotoxins are secondary metabolites produced by varieties of fungi that contaminate food and feed resources and are capable of inducing a wide range of toxicity. This problem is extensively aggravated due to the increasing replacement of fish meal by plant-derived proteins. Among the mycotoxins, aflatoxins have received a great deal of attention owing to their great prevalence in plant feedstuffs and to the detrimental effects on animals. The objective of this study was to evaluate whether dietary supplementation with tea tree (Melaleuca alternifolia) oil (TTO) would avoid or minimize the negative impacts on silver catfish (Rhamdia quelen) fed with aflatoxins-contaminated diets. Four treatments were tested: control (fish fed with a control diet); AFB (fish fed with a mycotoxin-contaminated diet - 1893 µg kg-1 of AFB1 and 52.2 µg kg-1 AFB2); TTO (fish fed with a control diet + 1 mL kg-1 of TTO), and TTO + AFB (fish fed with a mycotoxin contaminated diet - 2324 µg kg-1 of AFB1 and 43.5 µg kg-1 AFB2 + 1 mL kg-1 of TTO). Diets were tested in three replications and analyzed at days 5 and 10 of dietary intake. Significantly reduced antioxidant enzymes (SOD, GPx, and GST) and increased lipid peroxidation (LOOH) and protein carbonyl (PC) content in plasma and liver, with 16.6% mortality occurrence, were observed in the group fed aflatoxin-contaminated diet. Furthermore, aflatoxins also significantly increased plasmatic and hepatic ROS levels and decreased hepatic antioxidant capacity against peroxyl radical (ACAP) levels. Plasma cortisol levels were not altered by aflatoxicosis, but the intoxication induced hepatose. Notwithstanding, addition of TTO to the groups receiving aflatoxins showed a protective effect, avoiding the increase of ROS, LOOH, and PC levels in plasma and liver. Moreover, TTO treatment ameliorated the aflatoxin-associated liver damage. Thus, TTO supplementation at concentration of 1 mL kg-1 in feed may be used in fish to increase antioxidant status and reduce the negative effects caused by aflatoxins toxicity.

Involvement of HPI-axis in anesthesia with Lippia alba essential oil citral and linalool chemotypes: gene expression in the secondary responses in silver catfish.

In teleost fish, stress initiates a hormone cascade along the hypothalamus-pituitary-interrenal (HPI) axis to provoke several physiological reactions in order to maintain homeostasis. In aquaculture, a number of factors induce stress in fish, such as handling and transport, and in order to reduce the consequences of this, the use of anesthetics has been an interesting alternative. Essential oil (EO) of Lippia alba is considered to be a good anesthetic; however, its distinct chemotypes have different side effects. Therefore, the present study aimed to investigate, in detail, the expression of genes involved with the HPI axis and the effects of anesthesia with the EOs of two chemotypes of L. alba (citral EO-C and linalool EO-L) on this expression in silver catfish, Rhamdia quelen. Anesthesia with the EO-C is stressful for silver catfish because there was an upregulation of the genes directly related to stress: slc6a2, crh, hsd20b, hspa12a, and hsp90. In this study, it was also possible to observe the importance of the hsd11b2 gene in the response to stress by handling. The use of EO-C as anesthetics for fish is not recommended, but, the use of OE-L is indicated for silver catfish as it does not cause major changes in the HPI axis.

Citral and linalool chemotypes of Lippia alba essential oil as anesthetics for fish: a detailed physiological analysis of side effects during anesthetic recovery in silver catfish (Rhamdia quelen).

The viability using Lippia alba essential oil as an anesthetic for fish was studied, particularly with respect to physiological effects during recovery. Anesthesia of silver catfish (Rhamdia quelen) using 100 and 300 µL L-1 of two different chemotypes of L. alba essential oil (citral EO-C and linalool EO-L) prevented the increase of plasma cortisol levels caused by handling, but did not avoid alterations in energetic metabolism. Silver catfish did not have increased the levels of thiobarbituric acid reactive species in the kidney and liver during recovery after anesthesia with either EO, avoiding lipid damage. On the other hand, fish anesthetized with EO-C showed higher protein carbonylation levels, superoxide dismutase, catalase, and glutathione S-transferase activities and non-protein thiol group levels in both tissues compared to controls. Our results suggest that both oils show antioxidant capacity, but anesthesia with EO-L does not cause damage to lipids or proteins, only temporary changes, typical of physiological adjustments during recovery from anesthesia. Therefore, EO-L is an effective anesthetic for silver catfish with fewer side effects than EO-C.