Tuesday, October 24, 2017

24/10/2017: Selenium-enriched yeast improves the antioxidant status and selenium body content of rainbow trout

by Nadège Richard, Otavio Serino Castro, Philippe Tacon, Brice Bouyssière, Stéphanie Fontagné-Dicharry
 


Aquaculture nutritionists have been experiencing multiple challenges to maintain formula costs and performance while facing significant fluctuations on the raw material market in the past years

The decreasing availability of some key traditional ingredients such as fishmeal and fish oil, the price volatility of protein sources and the pressure to increase production sustainability are the main factors driving these efforts.

As a result, the incorporation level of marine ingredients sources (fishmeal and fish oil) in aquaculture diets has dropped in almost all industry segments such as marine shrimp, salmon, etc. In this scenario, plant-based ingredients, terrestrial animal rendered by-products, among others, have emerged as alternative protein sources.

Despite being a cost effective alternative in terms of protein replacement, alternative ingredients can bring to the diet nutritional imbalances, anti-nutritional factors and mycotoxins.

Concerning micronutrients, fishmeal is an important source of selenium for fish and shrimp, and replacing it with ingredients of plant origin usually results in decreased selenium content in the feed (Table 1).

Importance of selenium in fish

Selenium is an essential micronutrient, required for normal development and growth, as well as for the maintenance of metabolic functions and good health status of animals.

Selenium participates in the antioxidant defense of cells, protecting cells against oxidative stress damages through its essential role in the activity of several antioxidant enzymes (e.g. most of the glutathion peroxidases, thioredoxin reductases).

It is also involved in thyroid hormone metabolism, DNA synthesis and fertility. Selenium deficiency generally reduces fish growth performance, increases mortality rates and, when combined with vitamin E deficiency, contributes to the appearance of muscular dystrophy and exudative diathesis (Watanabe et al. 1997).

Development of ataxia (abnormal swimming) as well as nerve cord and liver pathology have also been reported in trout fed a selenium-deficient diet (Bell et al. 1986).

Fish selenium requirement is difficult to determine because it varies according to the developmental stage of the fish, environmental factors and rearing conditions (e.g. water quality, stocking density, stress factors, immune-depression).

It also depends on the dietary content of other trace elements and vitamins (E and C), with which selenium can display synergistic interactions (Khan et al. 2017). Finally, selenium requirement also depends on the form in which the micro mineral is supplied, since selenium bioavailability can differ from its inorganic to organic form (higher bioavailability with organic forms).


Read the full article along with tables and references, HERE.

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