For both young birds and piglets, anti-nutritional factors can be detrimental. Reduced anti-nutritional factors in feed can improve animal health and growth. This article discusses the main anti-nutritional factors and how to overcome the negative effects.
Weaning is a challenging and stressful period for piglets. Having been separated from the sow and going from mainly milk to solid feed, piglets require a high feed intake for optimal growth potential. At the same time, the piglets’ digestive tract needs to be developed. One of the main issues in this respect is to fight off pathogen microbes – in a world where antibiotic growth promoters are increasingly being discussed. In poultry production, a somewhat similar problem occurs. Chicks grow at an incredible speed in the first week after hatching. The hatchling quadruples in weight and develops the ‘infrastructure’, such as heart, liver and digestive tract, essential to building muscles and bones. However, due to the undeveloped digestive tract, the absorption capacity is impaired. Chicks tend to draw on the immunoglobulins and unsaturated fatty acids in the yolk sack for energy rather than for development and immunity.
To overcome these problems in both swine and poultry production, a special feed is essential, improving nutrient uptake in initial periods and also enhancing overall performance. They need different nutrients, such as amino acids, vitamins and minerals besides energy.
Soya is the most abundantly available protein source for feed with a favourable amino acid profile. However, it also contains ANFs – materials that cannot be digested and can potentially even be harmful for animals, e.g. by forming a substrate for bacterial fermentation in the gut. Unevenness of soya ANFs therefore not only affects growth performance but also increases the risk of pathogenic bacteria. Therefore ensuring the lowest possible ANF activity in soya bean ingredients is key to improve the performance, health and welfare of animals. Which ANFs exist exactly? See below for a short overview.
The trypsin inhibitor activity (TIA) comes from native proteins that block the endogenous proteases; trypsin and chymotrypsin. It reduces protein digestibility and increases endogenous losses. Although TIA is reduced by heat treatment, overheating has a negative impact on protein quality. The effects of TIA are particularly strong in young animals, whereas mature animals are capable of compensation for the loss of trypsin activity by enlarging pancreas.
Soya beans contain approximately 6% oligosaccharides, particularly raffinose and stachyose. These molecules are based on sucrose with one and two extra galactose units. Galacto-oligosaccharides are indigestible but fermentable by the micro-flora in mammals and poultry. This fermentation is not beneficial as it causes diarrhoea and lowers energy utilisation. It is reported that stachyose added to a stachyose-free diet reduced digestibility and performance of piglets and chicks.
In total, 65-80% of the raw soya bean protein is made up of ß–conglycinin and glycinin which are the main storage proteins of soya bean. A subunit of ß-conglycinin causes allergic response in the gut epithelia of animals. Glycinin causes antibody formation only by IV administration. The antigens create an allergic response in the gut and decreases digestive capacity protein.
Phytic acid is a phosphorous-containing acid which chelates vital minerals such as calcium, magnesium, iron and zinc, impairing their utilisation. As it is also associated with protein, its breakdown increases protein digestibility. Phytic acid is considered as ANF, however, the degradation of phytate by enzyme phytase increases phosphorous availability. Therefore phytase producers are increasing the dosage advices to reduce the ANF of phytic acid. However, the condition in animals’ guts is not always ideal and variation in digestibility of phosphorous has been found when phytase was added, especially for young animals.
Lectins are 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 soya beans improved true metabolisable energy, protein digestibility and feed conversion by about 10%.
Reduction of ANFs can be realised in various ways, by heat treatment, solvent extraction and enzymatic degradation. Heat treatment only affects heat-sensitive molecules like TIA, but not heat stable ANFs like oligosaccharides. Next to it, risk of overheating remains which can reduce available protein. Solvent extraction is also an option but cannot eliminate some ANFs e.g. phytic acid and oligosaccharides.
As supplementation to the current Hamlet Protein products - HP 100, HP 200 and HP 300 - Hamlet Protein has developed products that are not only soya protein concentrates with a low content of ANF, but also contain app. 10% yeast at the same time. The addition of yeast to the substrate release mannan-sugars and ß-glucans from the yeast cell walls. Mannan sugars block to the molecular structure for gut attachment of invading bacteria eg E. coli and Salmonella. The bacteria attached in gut are mediated by binding bacterial lectins to receptors containing D-mannose; thus, mannose-based carbohydrate is useful to reduce colonisation by enteropathogenic bacteria. For more information, see Table 1.
Performance of piglets
At Danish pig farms, three tests were carried out in an attempt to measure the average daily feed intake (ADFI) of weaned piglets, using the new soya-yeast supplement.
In all three tests, a diet based on this soya-yeast supplement was compared with soya protein concentrate (HP 300), see Figure 1. The feed intake improved by 7% on average when piglets were fed the soya-yeast supplement when compared to soya protein concentrate. In absolute terms, the feed intake in these tests were higher than found in many scientific studies, where ADFI about 250g during the first 21 days post weaning is found.
Performance of chicks
Trials into the efficacy of the soya-yeast supplement in poultry production has also been carried out. Researchers at Catholic University of Leuven in Belgium evaluated the performance of the starter feed based on soya and yeast in young birds.
The trial group which were fed the diet (5% soya bean meal replaced) during seven days post-hatch showed an improved gut viscosity, growth and feed conversion rate compared to the control group (Table 2). This paid off about 11 times based on meat and feed prices in Europe and nine times in USA.
Another trial was carried out at the Kalmbach Feeds trial farm in Ohio, USA. The test diet was fed during ten days post-hatching. Broilers fed with the reduced ANFs in twhe feed experienced an improved daily gain, mortality and FCR (Table 3). This paid off approximately seven times based on US pricing and ten times on European pricing.
References available on request.