Reducing the effects of anti-nutritional factors

By Carsten Pedersen, application manager, Hamlet Protein, Denmark

In weaner diets, soya causes problems as it contains the less favourable anti-nutritional factors (ANF). But with the right bio-processing it is possible to reduce ANF activity.

For young piglets, anti-nutritional factors can be detrimental. Achieving a low level of anti-nutritional factors in feed can therefore improve animal health and growth. Identifying and reducing the main ANFs helps to overcome these negative effects.

We aning is considered as one of the most challenging and stressful period for piglets. They are separated from the sow, they are going from mainly liquid feed (milk) to solid feed, and they are often being moved and mixed with piglets from other litters. At the same time the piglets are ‘requested’ to achieve a high feed intake, ensuring their growth potential is met. A high intake of the necessary nutrients is needed for utilising the growth potential of modern pigs today.

An important aspect of weaning is also the development of their digestive tract, which needs to develop and at the same time often has to fight an invasion of pathogenic microbes. This has become even a greater challenge due to the ban of antibiotic growth promoters which have been introduced in the European Union and several other countries around the world. Nevertheless, often productivity has been maintained or even improved. One of the main tools is to focus on the right nutrition for weaned piglets.

Anti-nutritional factors

Soya is the most used protein source for feed, with its amino acid profile being very favourable for use in animal nutrition. In weaning diets, however, soya is not a favourable protein as it also contains less favourable anti-nutritional factors (ANFs).

These are:

Trypsin inhibitors

Trypsin inhibitors are native proteins in the feed, blocking the endogenous proteases trypsin and chymotrypsin. This is a natural defence mechanism of plants to avoid being eaten. Essentially, this ‘trypsin inhibitor activity’ (TIA) reduces protein digestibility and increases endogenous losses. Activity from trypsin inhibitors can be reduced by heat treatment, but overheating will have a negative impact on protein quality and be counterproductive. The effects of TIA are particularly strong in young animals, because older animals are capable of compensating for the loss of trypsin activity by increasing the size of their pancreas. The trypsin inhibitor activity is the best known anti-nutritional factor, but there are others too, not being inactivated by higher temperatures.

Oligosaccharides

Soyabeans contain approximately 6% oligosaccharides, particularly raffinose and stachyose. Soya oligosaccharides are indigestible but fermentable by mammal microflora. This fermentation is not beneficial as it is done by potential pathogenic bacteria, thus producing gas (flatulence), causing diarrhoea and lowering energy utilisation.

Antigens

About 65-80% of the raw soyabean protein is made up of β-conglycinin and glycinin which are the main storage proteins of the soyabean. One of the subunits of β -conglycinin causes an allergic response in the gut epithelia of most animals. Glycinin causes antibody formation only by intravenal administration. The antigens create an allergic response in the gut, which damages the gut, decreases digestive capacity and costs energy and protein.

Phytic acid

Phytic acid is a phosphorous-containing acid with the ability to complex vital minerals such as calcium, magnesium, iron and zinc, impairing their utilisation. As it is associated with protein as well, its breakdown will also increase protein digestibility. The degradation of phytate by phytase is well known, with the aim to increase phosphorous availability. Recently, phytase producers are increasing their dosage advices to reduce the other ANF effects of phytic acid. However, many studies have found a considerable variation in phosphorus digestibility. A study by Kerr and others, in 2010, showed this after having added exogenous phytates to a corn-soy based diet fed to pigs.

Lectins

Lectins are (tetrameric) glycoproteins that are resistant to proteolysis. They bind to the small intestine epithelium and cause severe disruption of the brush border and villi ulceration. This increases endogenic nitrogen losses. Using lectin-free soyabeans in pigs improves feed conversion by about 10% ( Table 1 ).

Undigested materials

The loss of the nutrients due to anti-nutritional factors is one of the problems related to soyabean use in weaned piglets. The undigested material also forms a substrate for bacterial fermentation in the gut. Variation in the amount of soya ANFs not only affects growth performance of piglets but also increases the risk of e.g. diarrhoea, due to growth of pathogenic bacteria. Therefore ensuring the lowest possible ANF activity in soyabean ingredients is a valuable tool to improve the performance, health and welfare of piglets.

A novel ingredient

Reduction of anti-nutritional factors can be done by heat treatment, solvent extraction or enzymatic degradation. As said, heat treatment only affects heat liable molecules, but does not affect not heat stable ANFs like oligosaccharides. Overheating is a realistic risk and will give a severe reduction in the availability of the protein for animals. Solvent extraction is also an option but it is a more crude process and cannot eliminate some ANFs like phytic acid and oligosaccharides. Hamlet Protein has developed a bioconversion process that reduces antinutritional factors using enzymes. The company’s product HP 800 Booster is a newly developed product, being the result of co-processing of soya and yeast. The product contains valuable components from the yeast cell walls, mannan sugars and mannan glucans. Bacterial attachment in the gut is known to be mediated by the binding of bacterial lectins to receptors containing D-mannose. Thus, the use of products containing mannose-based carbohydrate is useful to reduce colonisation by enteropathogenic bacteria, as the sugars attach to the gut and thereby prevent attachment of enteropathogenic bacteria.

Performance

Figure 1 shows the average daily feed intake (ADFI) from three tests with weaners, carried out on Danish pig farms. In common for all three tests, the co-processed soya and yeast product, HP 800 Booster, was tested against HP 300, a high-quality soya protein source, also manufactured by Hamlet Protein. In test 1 and 2 the test period was 21 days and the inclusion level of both protein sources was 10%. In test 3 the inclusion level of both protein sources was 15% and the test period was only ten days. On average, the ADFI was improved with 7% (5-11%). That even taking into account the ADFI for the piglets, the ADFI was already on a high level. The data show that the co-processed soya and yeast product can stimulate feed intake, even though the starting point is at an already high level. New trials are on-going and primarily data is confirming the findings, that this combination is stimulating feed intake in weaned piglets.

Carsten Pedersen, Hamlet Protein:
«Reduction of antinutritional factors can be done by heat treatment and solvent extraction or enzymatic degradation.»

Table 1 — Performance of piglets fed conventional soyabean meal and lectin-free soyabean meal (SBM). 

 Source: Palacios and others, 2004.

Table 2 — ANF reduction by enzymatic degradation.

* HP 800 Booster, Hamlet Protein

Figure 1 — Comparison of average daily feed intake (ADFI) in three feeding tests with weaned piglets, conducted on commercial farms in Denmark.