Essential Oils as Stress-Reducing Agents for Fish Aquaculture: A Review

In fish, stressful events initiate a hormone cascade along the hypothalamus-pituitaryinterrenal and hypothalamus-sympathetic-chromaffin (HSC) axis to evoke several physiological reactions in order to orchestrate and maintain homeostasis. Several biotic and abiotic factors, as well as aquaculture procedures (handling, transport, or stocking density), activated stress system inducing negative effects on different physiological processes in fish (growth, reproduction, and immunity). In order to reduce these consequences, the use of essential oils (EOs) derived from plants has been the focus of aquaculture studies due to their diverse properties (e.g., anesthetic, antioxidant, and antimicrobial), which have been shown to reduce biochemical and endocrine alterations and, consequently, to improve the welfare status. Recently, several studies have shown that biogenic compounds isolated from different EOs present excellent biological activities, as well as the nanoencapsulated form of these EOs may potentiate their effects. Overall, EOs presented less side effects than synthetic compounds, but their stress-reducing efficacy is related to their chemical composition, concentration or chemotype used. In addition, their species-specific actions must be clearly established since they can act as stressors by themselves if their concentrations and chemotypes used are not suitable. For this reason, it is necessary to assess the effect of these natural compound mixtures in different fish species, from marine to freshwater, in order to find the ideal concentration range and the way for their administration to obtain the desired biological activity, without any undesired side effects. In this review, the main findings regarding the use of different EOs as stress reducers will be presented to highlight the most important issues related to their use to improve fish welfare in aquaculture

Adapted Bailenger method improves the rate of Ascaris suum eggs recovery from liquid pig manure compost

ABSTRACT: Liquid pig manure (LPM) is widely used as a compost fertilizer for vegetable crops destined for human consumption. However, these wastes may contain parasites eggs, such as the nematode Ascaris suum, that pose serious health risks to humans. We attempted to determine the most appropriate technique for recovering A. suum eggs from LPM compost. Samples were collected from two waste sources during composting, including 23 samples containing LPM, sawdust, and wood shavings, and 14 samples of LPM alone-both in triplicate. Samples were analyzed using several different recovery methods. Recovery of eggs by the modified Bailenger method with adaptations was significantly more effective and recovered 57% more eggs than by the modified Bailenger method alone. Willis-Mollay method, modified Faust method, and the simple sedimentation technique only recovered 4.4%, 13.9%, and 26% of eggs, respectively, compared with the modified Bailenger method with adaptations, indicating that the adjustments made to the Bailenger method were key to improving the recovery of A. suum eggs from compost and LPM