Wednesday, March 22, 2017

22/03/2017: How to control moulds in aquaculture

by Dr Elisabeth Holl and Tilman Wilke, Dr Eckel Animal Nutrition GmbH & Co., Germany

One of the most critical factors in global feed and food production remains to be the prevention of post-harvest losses of raw materials

Efficient preservation methods for plant based components with organic acids are therefore of special interest also for the continually growing aquaculture sector and its requirement for industrially produced aquafeed.

Aquafeed traditionally relies on fishmeal as the predominant protein source. Limited volumes and high prices make it economically and environmentally necessary to look for other sustainable options for aquafeed formulation.

Therefore, plant components that are used as alternative protein sources in commercial fish feeds are soybean meal, rapeseed meal, sunflower meal and wheat.

However, these components are subject to deterioration caused by moulds and yeasts, especially in warm climates. There are multiple factors leading to spoilage in feed and food such as moisture content, temperature, storage conditions and the naturally occurring microbial contamination.

Nutrient losses
Moulds in feed are a serious economic problem because they consume the main nutrients and affect the palatability of the feed. Losses of nutrients caused by moulds can occur in magnitudes up to 10 percent.

Especially the crude fat content of grains is affected by mould growth during storage, even more so than proteins and carbohydrates. Losses in metabolisable energy from maize may even reach 25 percent.

The danger of mycotoxins
Apart from these nutrient losses, moulds also produce mycotoxins, threatening animal and human health. Aflatoxins for instance can be transferred into animal tissues and therefore pose a serious risk for the consumer (carry-through-effect).

The detrimental effects of mycotoxins, on animal health and performance, have been comprehensively studied in land animals but there are relatively few studies in aquaculture systems. There is however evidence, that fungi and mycotoxins have a negative impact on health and performance of fish.

The most important mycotoxicosis in fish and shrimp is caused by aflatoxins, primarily produced by aspergillus ssp. during storage of feed and raw materials.

For yellow catfish Gonçalves (2010) described growth depression and decreasing feed conversion ratio with increasing levels of Aflatoxins in the diet.

Trout, Tilapia and shrimp have also been shown to be susceptible to Aflatoxin contamination in the feed, reacting with weight loss, liver damage or increased mortalities (Tacon, 2002).

Read the full article HERE.

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