Porcine plasma proteins for feed intake and health

Since September 2005 porcine plasma has been re-allowed as a feed ingredient for pigs and poultry in the European Union. Coincidentally this fitted in perfectly with the ban on Antimicrobial Growth Promoters (AMGP), which was imposed on the 1st January 2006, because plasma also improves piglets’ growth performance and health without developing antibiotic resistance.

By Geert van der Velden, MSc, product manager, Sonac

The ban on Antimicrobial Growth Promoters (AMGP) and the reallowance of porcine blood plasma as a feed ingredient for pigs and poultry stimulated the question whether plasma could be a good alternative for AMGP’s. In a recently published experiment it was concluded that plasma has more effect on growth and feed intake when using feed without AMGP than it has with feed containing AMGP (Figure 1). Various research groups proved as well that besides the growth promoting potency, plasma also improves piglet’s health. This suggests that also from a health point of view plasma can be seen as an alternative for antimicrobial agents. The latter is a very important finding for EU pig producers, because the EU authorities are demanding a reduction in the use of therapeutic antibiotics in order to diminish the problem of so called ‘cross resistance’ to antibiotics for human use.

Porcine plasma use in the EU
The reduction in the use of therapeutic antibiotics in piglet feeds is not yet ‘common practice’ in Europe, but it is very likely that all the European member states will soon have to move in this direction. The feed industry should be prepared for these changes. Whether plasma will then be the alternative is still questioned, since some EU countries, like United Kingdom and France, are still reluctant about the reintroduction of porcine plasma proteins. This mind-set is predominantly based on (BSE) emotions and unfortunately not on science. Nevertheless we can state that in piglet feeds, plasma proteins are the best performing and documented alternative to antibiotics. Even when antibiotics or ZnO are being used in weaning diets, the addition of plasma proteins still improve the performance because they stimulate the feed intake of the piglets while antibiotics and ZnO mostly have a negative effect on palatability. The reintroduction of porcine plasma was not an easy step to take, because it went with strict regulations regarding the production and usage of these proteins. First of all, plasma proteins can only be produced at dedicated processing plants (no ruminant by-products allowed). Secondly the feed mills that use porcine plasma can only produce non ruminant feeds. Finally, transport of feed may NOT be combined with feed for ruminants. When plasma proteins are used in feeds it should be clearly mentioned on the feed label: ‘contains blood products, shall not be fed to ruminants’. In practise it means that plasma proteins can only be used by specialised feed mills, which are registered by the national food safety authority.

Summary of challenge experiments in piglets studying the effects of plasma against diarrhoea.Improving intestinal health
Trials have shown that one of the main properties of plasma proteins is a substantial stimulation of feed intake after weaning (>25%). These experiments also demonstrated that a high feed intake after weaning prevents intestinal damage (villus atrophy) and improves the intestinal integrity. This is demonstrated by less leakage of undesired substances like toxins or pathogens through the intestinal wall. There are also indications that a high feed intake reduces intestinal inflammation. Finally latest research shows that plasma directs the normally occurring immune response after weaning towards an anti-inflammatory one by influencing cytokines involved in this.

Post-weaning diarrhoea
The schematic making of porcine plasma proteins.In the recent years, several research groups have performed challenge experiments in which the effect of dietary plasma on post weaning diarrhoea was studied. In most experiments it was found that plasma reduces diarrhoea (Table 1). In some cases, also the faecal excretion of E. coli was reduced. To better understand this effect a Dutch research team demonstrated that the prevention of diarrhoea is mediated by blocking the adherence of E. coli bacteria to the intestinal wall (Figure 2). This blocking effect is initiated by the immunoglobulin fraction of plasma, which prevents the bacteria to colonise, grow and produce their toxins.

By banning AMGP’s piglets will become more susceptible to E. coli problems. In that respect the outcome of these recent experiments, which prove that plasma plays a major role in preventing post-weaning diarrhoea in piglets, comes right on time for the EU pig producers.

Plasma protein quality
As of now European piglet feed producers can choose from a range of locally produced and commercially available porcine plasma proteins. However, they have to be aware that there are some key (quality) parameters to be taken into account when evaluating plasma proteins for piglet f eed applications:

  • Is the porcine plasma protein approved for EU feed applications?;
  • Is it produced according to an appropriate QA system (e.g. HACCP, QS or GMP+)?;
  • Good solubility of the plasma powder - no denaturation of the protein Ig’s - should be intact and remain bioactive;
  • Low Total Bacteria Count (TBC) of the plasma powder;
  • Constant quality;
  • Low sodium and thus high protein and IGG content.

How are porcine plasma proteins produced?
Only blood of healthy pigs is collected daily at dedicated EU approved slaughterhouses. This means that all blood processed has passed ante- and post-mortem veterinary control. The collection system includes automatic anti-coagulant (sodium citrate) dosage, blood identification tanks, chilled (4ºC.) storage tank and a cleaning system (Figure 3). As soon as the blood arrives at the processing plant a sample is taken and evaluated before unloading the truck.
1. The first step in processing the blood is centrifugation. Blood cells are separated from plasma by means of the difference in specific weight of the two fractions. Fully automatic and self cleaning centrifuges are used. After centrifugation, the liquid plasma protein with 7% crude protein is stored in an intermediate tank.
2. The second step in processing the plasma protein is evaporation or nano filtration or ultra filtration. Ultra filtration of the liquid plasma removes water, salts and other small molecules. This process step increases the crude protein level of the liquid plasma to 20% – 25% before spray drying. The advantage of removing salts before spray drying is that the protein level of the spray dried porcine plasma protein can reach a level of at least 80%.
3. The third major step in processing the plasma protein is the spray drying of the concentrated plasma.
4. Finally, the plasma is standardised and packed in 20 or 25 kg bags. Samples of each batch are taken and analysed both chemically and microbially. Within 24 hours after reception all blood 0 has been processed.

Difference between proteins
Plasma proteins are ideal proteins for replacement of any type of dairy protein. High quality dairy protein products like skimmed milk powder or whey protein concentrates can be replaced by plasma proteins. Technical performance of the piglet feed will improve and the feed costs will be reduced when these dairy proteins are being replaced by plasma proteins. Historically plasma proteins were more expensive than dairy proteins, but in recent years market conditions have changed dramatically. There is less competition with human food applications for plasma proteins as compared to dairy proteins. In case, for example, whey powder is replaced by plasma proteins it is how ever important to maintain a similar level of lactose in the diet (e.g. by supplementing pure lactose or permeate). It is obvious that plasma proteins will outperform any type of vegetable protein. Therefore the synergy approach is much more interesting. Extensive research work and practice from the United States, where weaning diets with 5% to 10% soybean meal are not uncommon, shows that piglet weaning diets with plasma proteins can contain a limited amount of soy bean meal without reducing the performance.