by Dr. Iris Kröger, Dr. Eckel Animal Nutrition GmbH & Co. KG, Germany

Endotoxins derive from gram-negative bacteria replicating and dying in the digestive tract of the animals.

In livestock, the mechanisms are clear: better genetics and intensive feeding have resulted in more productive livestock over the last years; especially with a specialised diet of high protein and starch contents which meets the requirements of high-performing animals.

However, one problem is becoming more acute, endotoxin contamination. Why? Because diets low in fibre result in a shift towards gram-negative bacteria in the microflora of the gastro-intestinal tract and ultimately, to the accumulation of endotoxins.

Furthermore, these intensive diets damage the intestinal wall of the animals. Subsequently, endotoxins are absorbed through the intestinal wall and transported to the liver. If the level of endotoxins exceeds the liver's capacity to detoxify them, endotoxins trigger heavy immune reactions in the animals. Consequently, feed efficiency declines significantly, by up to 27 percent. This is because these immune reactions cost a lot of energy—energy that is no longer available for growth and performance.

In livestock, awareness for the topic of the detrimental effects of endotoxins has already increased in recent years. In aquaculture however, the topic of endotoxins is discussed in a more diverse manner.

Some authors still claim that aquatic species are not as susceptible to endotoxins as higher vertebrates, although recent research has been able to show that endotoxins in aquatic species exert immunological and pathological effects just like in livestock.

It has even been demonstrated repeatedly that additives which are capable of reducing detrimental effects of endotoxins can also unfold performance enhancing effects. Yet, despite the sufficiently well-known harmful effects of endotoxins on health, welfare and performance of livestock, cell envelopes of micro-organisms containing endotoxins are still used as immuno-stimulants in aquaculture.

These are supposed to boost the immunological capacities of aquatic species. A risky procedure because after all, the continuous use of immunostimulants can easily lead to over-stimulation of the immune defense system.

In order to help farmers and producers to better understand the effects of endotoxins in aquaculture, the multidisciplinary R&D team of Dr. Eckel Animal Nutrition has spent more than two years on intensive research in this topic, followed by the careful development of an innovative solution supporting livestock and aquatic animals against the negative effects of endotoxins.

This new product is called Anta®Catch and it reduces the quantity of free endotoxins in the gastrointestinal tract, supports the gut barrier by its prebiotic components and supports the liver with phytogenic compounds (fig.1).

During the extensive research and product development process of Anta®Catch, one main area of focus was aquaculture. Here, the team aimed to determine the effects of endotoxins on survival rate and performance and to reveal if Anta®Catch could reduce performance limiting effects of endotoxins.

For this purpose, two trials were performed in collaboration with the Faculty of Fisheries at Kasetsart University, Thailand.

Trial results reveal: Great potential of inhibiting endotoxins in shrimp and fish

In trial 1, a total of 1,000 Nile tilapia (initial size 2—2.5 cm) were kept for 30 days. Fish in the control groups were challenged with either no endotoxins (AC; 0 µg/L) or high (LPSAC; 100 µg/L) endotoxin dosage. Diets of treatment groups were fed 0, 0.1 or 1 kg/t Anta®Catch (AC0, 100 or 1000).

Survival rate was determined every 10 days. Fish were weighed at day 30. At the end of trial 1, data on survival rate and average daily gain (ADG) were statistically compared using t-test.

In trial 2, a total of 1,000 Pacific white shrimp (initial size 3—5g) were kept for 30 days. Shrimp in the control groups were challenged with either no endotoxins (AC; 0 µg/L) or high (LPSAC; 100 µg/L) endotoxin dosage. Diets of treatment groups were fed 0.1 or 1 kg/t Anta®Catch (AC100 or 1000).

Survival rate was determined every 10 days. Shrimp were weighed at day 30. At the end of trial 2, data on survival rate and FCR was statistically compared using t-test.

Results showed that endotoxins decreased survival rate of shrimp by up to 28 and survival rate of tilapia by up to 22 percent (p<0.05; fig 2a, b). Furthermore, the feed conversion rate (FCR) in shrimp challenged with high level of endotoxins was up to 11 points higher than with natural endotoxin concentration (p < 0.05; fig 3a).

Correspondingly, endotoxin challenge in tilapia reduced ADG by up to 0,24 g/d (p < 0.05; fig 3b). This shows that endotoxins have detrimental effects on survival rate and performance in aquatic species.

However, Anta®Catch increased the survival rate, in relation to the dosage. Thus, 1,000 ppm of Anta®Catch increased the survival rate during endotoxin challenge in shrimp by 6.66% compared to feeding 100 ppm of Anta®Catch (p<0.05; fig 2a). In tilapia, the survival rate during endotoxin challenge increased by 13.33% in the group fed 1,000 ppm Anta®Catch compared to the control group (p<0.05; fig 2b).

Furthermore, Anta®Catch at a dosage of 1,000 ppm improved survival rate of tilapia by 6.77 percent even under natural endotoxin contamination (p<0.05 fig 2b). This underlines the potential of Anta®Catch to protect shrimp and fish from endotoxin related mortality.

The results also indicated that Anta®Catch improved FCR in shrimp and ADG in tilapia. Thus, increasing the dosage of Anta®Catch improved FCR both under natural conditions and under artificial endotoxin exposure in shrimp (p<0.05; fig 3a).

In tilapia, the ADG of the Anta®Catch group was increased by up to 0.09 g/d under natural conditions and by up to 0.03 g/d during artificial endotoxin challenge (p<0.05; fig 3b).

This shows that Anta®Catch can visibly improve the performance of shrimp and fish under natural conditions and in environments contaminated with endotoxins.

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