One of the latest developments in reducing diarrhoea among piglets is the use of organic trace minerals. This could provide the swine industry with new tools to reduce the use of antibiotics. A reduction is important because of an increasing development of resistant bacteria, which may cause consumer health and safety issues.
By Hans Aae, head of nutrition, Vitfoss, Denmark
Over the past 10-15 years there has been a lot of work done to find solutions for minimising diarrhoea problems in piglets by means of feeding. It is well-known that protein digestibility (protein sources), acids and probiotics have a positive impact on the gastro intestinal health. As a result they are widely used in the industry, however at a cost and because of running a business we need to find an economic balance.
Zinc is important
It is a well-known fact that high dosages of zinc oxide can reduce diarrhoea; 2,500 ppm inorganic zinc (3 kg ZnO per tonnes feed) works very well. However within the EU feed legislation this level exceeds the maximum content in feed several times. In some countries zinc oxide is registered as medicine and may consequently be used at a high dose by prescription for a short period (normally two weeks after weaning). There are discussions as to the exact mode of action of high dosages of zinc in the pig’s gastrointestinal tract. One theory is that a high dosage of zinc binds E. coli bacteria, whereas another suggests it can increase cellular immunity towards the E. coli bacteria. Anyway, research in Denmark showed that the main effect of a high dosage of zinc oxide is due to an increased absorption of zinc by the cells. Another interesting piece of research demonstrated that zinc in sow milk is the best available source of zinc for piglets. Zinc in sow milk is bound in milk protein (casein-phospho-peptides).
This research supports trials to compare high dosages of zinc (2,500 ppm) with different levels of zinc from organic bound zinc (Availa-Zn; Zinpro). From these trials it was concluded that, as illustrated in Table 1
, it is possible to replace 2,500 ppm inorganic zinc with 250 ppm zinc from organic bound zinc, whereas a lower level of organic bound zinc is not sufficient to control weaning diarrhoea. Unfortunately EU legislations allows only a total of 150 ppm zinc in feed, so we need to look at other minerals as well.
A Polish study compared iso-level of iron from inorganic (FeSO4) and organic (Availa-Fe) sources and showed a reduced level of diarrhoea as well as mortality in the group fed organic iron (see Table 2
). This trial as well as a similar trial also demonstrated that the inclusion of organic iron in pig feed showed a tendency to improve daily gain and feed conversion. Based on these and various other trials comparing inorganic and organic micro minerals for piglets, a mixture of zinc, copper and iron was created (Pig-Omic), in which inorganic sources are partly replaced by organic sources. The combination makes it possible to have the same effect on diarrhoea and performance as with a high dosage of zinc oxide without exceeding the maximum level given in the EU feed legislation. A test which compared this mixture with a high dosage of zinc oxide showed good results when fed to weaners. There was no significant difference in the level of diarrhoea and
mortality (see Table 3), although there was a numerical advantage for the mixture. Also performance figures in the two groups showed no difference.
The immunological gap
Weaning is a very stressful event in the life of young piglets. It causes a dramatic reduction in maternal immunity (passive immunity), while the piglet still has to build up it own immune system (active immunity). This means that up to 10-20 days post-weaning, the immunity of the piglets is very low. Meanwhile, they have to adjust their digestive system to deal with (often) cheaper feed, which frequently results in diarrhoea problems, and sometimes with oedema disease. Field tests conducted clearly showed that to avoid these problems, the mixture can be used to build a bridge over the immunological gap.
Reduction in diarrhoea and mortality In France, an on-farm trial was carried out using a mixture of Zn, Cu and Fe, see Table 4
. The feeding strategy here was to use a starter diet the first six days; then the feed was changed to ‘first age feed’ for three weeks and finally it was changed to ‘second age feed’ until the pigs reached a weight of 30 kg.
For this trial, the mixture of Zn, Cu and Fe was included in the ‘first age feed’ for two batches of piglets and the results were compared to the previous three batches.
The trial showed several interesting things:
1. Mortality was significantly lower after inclusion of mixture.
2. Daily gain was the same even though starting weight was lower. Normally a lower weight gain would have been observed, at a level of 30 g/day (normally, 50 g/day per kg less weaning weight is observed).
3. Less diarrhoea was clearly seen.
After the end of the trial, mortality was registered in the following batch. It went back to 3% - i.e. the original level.
It is just one of the tests that indicate that besides all classical ways to improve the piglet’s gastro-intestinal health, it seems very interesting to focus on the use of organic trace minerals.