The Feed Additive that is Reducing Phosphorus Emissions

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Article | 25.03.2020

How the addition of OptiPhos®, a phytase enzyme, to extruded feed can significantly reduce emissions of phosphorus from the aquaculture sector.

Phosphorus is essential for all life and is required for optimum growth, feed efficiency and bone development. Whilst an essential nutrient in aquaculture feed, it also has an environmental impact and is responsible for algal growth and oxygen depletion in many lakes and rivers.

Global salmon and trout production in 2019 was estimated to be 3.25 million tonnes per annum. This production is dominated by Atlantic salmon at 2.6 million tonnes, of which approximately 50% is produced in Norway. Salmonid production historically, like most farmed animal species, does not have a great track record in terms of environmental impact, although huge improvements have been made by the industry. The salmon industry in Norway produces ~1.3 million tonnes of salmon and ~1.7 million tonnes of salmon feed. This industry is also the third largest importer of inorganic phosphorus (P, 16,500 tonnes), even surpassing domestic P fertiliser usage. 

The salmon aquaculture industry in Norway is estimated to discharge ~9,000 tonnes of P into the environment. This is deposited into the ocean causing eutrophication, which contributes to coastal algal blooms. These can have crippling environmental effects and cause self-inflicted financial hardship to the farms through loss of stock as the algae can also be responsible for salmon production losses.

The goal of sustainable aquaculture production is still far from being achieved, with fish retaining only ~40% of the P content of modern commercial fish feeds. Reduction of P levels in feed without impacting growth, feed efficiency or health is key to the development of low pollution diets. This is currently being achieved by the use of low-ash fishmeal and highly available P supplementation. But there are other, more cost-effective strategies. Phytase enzymes that efficiently release unavailable P from vegetable ingredients in fish diets have a very important role to play.

Figure 1. Atlantic salmon P retention, excretion and reduction vs control using OptiPhos® at 500 and 750 OTU/kg

Large amounts of organic P bound in phytic acid are present in modern day salmon and trout diets, but these are poorly utilised. This represents an opportunity to supplement the diet with OptiPhos®, a globally recognized phytase enzyme, to help reduce the environmental impact of the salmonid industry.

Recently conducted Atlantic salmon (Salmo salar) and Rainbow trout (Onchorhynchus mykiss) trials demonstrated that P levels in the feed can be reduced significantly (2.5 - 3.5 g/kg) and that in some cases, added inorganic P sources could be eliminated completely (Figures 1 and 2). This not only has the potential to reduce the environmental discharge of P by ~3,200 tonnes in Norway alone, but there are also financial benefits of implementing an OptiPhos® strategy. 

Figure 2. Rainbow trout P retention, excretion and reduction vs control using OptiPhos® at 500 and 750 OTU/kg

Increasing digestible energy (DE) levels in salmonid feeds has a significant impact on space in formulations. Competition for space in diets is high so any opportunity to create space will provide a significant cost benefit. By reducing the necessity for P supplementation, OptiPhos® can offer formulation cost savings of up to €15 per metric tonne, a win for both economic and environmental sustainability. This excludes any opportunity the farmer may have to increase production volumes and make better use of production biomass consents, which could be significant.

Key facts

  • OptiPhos® at 500 - 750 OTU/kg significantly reduces P discharge in trout and salmon. 
  • OptiPhos® can significantly reduce usage of monoammonium phosphate (MAP) and monocalcium phosphate (MCP) in salmonid feeds.
  • OptiPhos® helps minimize the environmental impact of salmonid aquaculture in water courses and significantly reduces carbon footprint of inorganic P production and transportation. 

Feed application of OptiPhos®

The application of OptiPhos® to extruded feed is an important consideration to ensure optimum performance and to avoid losing phytase activity due to high extrusion temperatures. OptiPhos® is therefore supplied in liquid form in 1,000 litre IBC's to allow for post-extrusion application during the fat coating phase of production.

As well as IBC's, Huvepharma® has developed a new and fully automated enzyme application system called Huvematic®. The Huvematic® machine uses highly concentrated water-soluble powder enzymes (WSP) to produce liquid enzymes onsite and on-demand, operating fully automatically. It can be incorporated into the oil addition system of feed mills, allowing feed production to be truly optimised. 

The Huvematic® enzyme dosing system

Producing liquid enzymes on-site replaces the need for shipping, storage and receiving liquid enzymes in IBC containers, resulting in cost savings, releasing labour and warehouse space, and a drastically reducing carbon footprints.

The Huvematic®, fully-automatic enzyme dosing system

For more information on OptiPhos® or other Huvepharma® products and applications, please contact us.


This article originally appeared on The Fish Site, 23.03.2020 

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