Special Edition: Protein Alternatives

How low can you go? Amino acid balance key to low protein poultry diets

By Jane Byrne contact

- Last updated on GMT

© istock/Zerbor
© istock/Zerbor

Related tags: Amino acids, Protein, Amino acid

In the second of our two articles on his work into protein alternatives, Marinus van Krimpen, animal nutrition researcher, Wageningen Livestock Research, tells us about insights gleaned in a study evaluating the potential of free amino acids as partial soybean meal replacers. 

He also reported on the institution’s investigations into the nutritional value of protein from grass and algae sources.

Grass protein

There is potential to extrude protein for pig feed from common, low quality grass, he said.

crude protein reduction study broilers van Krimpen et al
Results of Wageningen Livestock Research and ForFarmers study looking at CP reduction in broiler diets through higher AA inclusion levels © Wageningen Livestock Research

“But using high quality organic grass might generate protein that can be used in organic feed applications – a sector that urgently requires more protein sources,”​ he stressed. 

The digestibility value of grass-derived protein, though, can be low, and this fact could render it less interesting for take-up in monogastric production.

However, van Krimpen said he and his colleagues have been studying alkaline protein extraction methods to improve that. “We looked to find out what was the ideal temperature, in the range of 40 degrees C to 95 degrees C​, and what was the optimum concentration of alkaline required to generate a high yield of protein of good quality, where the digestibility value was not compromised.”

They concluded that alkaline protein extraction at a moderate temperature considerably increased the protein digestibility of grass.

Peas and beans

The researchers had also attempted to look into the benefits of protein from pulses like peas and lupines.

Information in the literature supports their candidature for use in animal diets, even if breeding and yields could be improved, said van Krimpen. 

Furthermore, crops like faba beans contribute nitrogen to subsequent crops in rotations such as rapeseed. However, until now, their efforts at getting funding for this have come to nothing, he said.

They are, instead, actively exploring other strategies, including diet formulation based on lower crude protein content - soybean meal (SBM) - backed up by supplementation with free amino acids (AA).

Some European feed manufacturers, he noted, are heavily promoting cultivation of soy within the bloc, but van Krimpen believes lowering the CP level of broiler diets could be a more efficient way of reducing dependence on soybean imports.

“In Europe, the rate of self-sufficiency for SBM is only 5% (EC, 2017), indicating the extreme dependency for this protein source from regions outside the EU, mainly South America. Politicians are increasingly concerned that such a massive dependency on imports makes the EU livestock sector extremely vulnerable to price volatility and trade distortions.

“It is, therefore, important to find alternatives for imported SBM.”

SBM substitution with amino acids

He recently carried out a study in collaboration with another Wageningen colleague and a researcher from Dutch feed manufacturer, ForFarmers, examining the effect of lower crude protein content in male broiler diets through a partial replacement of SBM by free AA, on growth performance, slaughter yields, litter quality and footpad lesions.

They found that giving the birds diets with up to 3% lower CP content but similar digestible AA resulted in similar or even better growth performance results compared to broilers fed a diet program with a standard CP content.

They obtained the best overall performance results with the 2% lower CP diet program, he said.

“Broilers fed the low protein diet programs had a lower water intake, which resulted in a better litter quality and less footpad lesions, a critical animal welfare issue.”

The breast meat yield of broilers fed the diet with 3% lower CP content was lower, but the breast meat weight did not differ, they said.

There was an increase in costs, for sure, arising out of using a higher amount of amino acids, together with a slight reduction in profitability per bird – €0.45 versus €0.51 per broiler on a standard diet.

chlorella wageningen study
Results of Wageningen Livestock Research study on use of algae - chlorella - in poultry diets © Wageningen Livestock Research

“Meanwhile, carbon footprint also increased by 3 to 6%. Threonine production requires a lot of sulphate, so there are environmental implications, acidification, as a result of that.”

However, overall, the European feed sector is very interested in partial substitution of SBM by free AAs in that it allows a reduction in the reliance on soybean imports from South America, and elsewhere, he said. The thinking is that economies of scale will kick in on the cost front: “With the increased use of free amino acids as CP replacers, their cost will eventually come down, making this strategy, long term, more profitable.”


Our earlier article​ on van Krimpen’s work on protein alternatives focused on seaweed, but the Wageningen researcher and his colleagues have also been looking at microalgae as a novel feed protein.

A paper​ that they published in October last year concluded that the cost-price of algae must fall, so that it is able to compete with SBM as protein source, with fish oil as an omega-3 source, and with other livestock feed additives. “Development of innovative, more productive algae cultivation systems, with limited costs for equipment and energy use should enable this.”

Though it will not be easy to reduce the high production costs of algae in short term, they said.

On a dry matter base, algae contain comparable or even higher levels of crude protein, carbohydrates and fats than conventional resources, said the authors.

There is quite a lot of variation in nutrient composition among the different algae, but most have a high protein level, they added.

A study (Becker 2013) concluded that compared to the amino acid profile of soybeans, the amounts of the essential amino acids lysine, cysteine and tryptophan in algae are relatively low, while the amounts of the essential amino acids methionine, threonine and isoleucine are comparable or higher.

“As shown in literature, algae can be supplemented to diets of growing finishing pigs at levels up to 14%, and possibly even up to 33% without having negative effects on performance. In laying hens and broilers the addition of 12% and 17% algae, respectively, proved to be quite feasible without influencing performance in a negative way,”​ said the Wageningen team.

For the production of the same amount of protein, land use is substantial lower compared to traditional protein crops, they argued. “Algae production does not compete with agricultural land so no replacement of current crop cultivation is needed.”

There are also indications from literature that microalgae have health promoting properties, they said.

Our coverage of van Krimpen's research into the potential of seaweed as a novel protein source for feed can be read here​.

Related topics: R&D

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