In humans as in chickens, certain bacteria such as Lactobacilli and Bifidobacteria are absolutely essential for intestinal development. These microbes are normally taken up from the environment. The most important factors for microbe uptake by chickens are the hatcheries, the henhouses, and the feed and water taken up.
The increasing efforts in the field of production hygiene are restricting the pathways to uptake of important bacteria ever further. Hatcheries are almost sterile, henhouses are disinfected before the chicks are installed, and the feed is being treated ever more in order to avoid pathogenic germs as far as possible. However, parallel with this the microbes necessary for development of the birds are being increasingly killed off. This now leads to a situation in which poultry is restricted in its growth potential as certain stimuli necessary for development can no longer be provided. This can be observed in particular among parents for broilers, as contrary to their genetics these animals are fed restrictively in order to increase their fertility. All this is done with very high hygiene measures, which leads to a particularly difficult situation regarding the development status of the fowl. Non-specific clinical pictures among the parents are frequent, and in many cases then also lead to losses in the rearing of the parents.
lt has been proved that essential microbes can be added to the feed in order to allow normal growth of the poultry. Recently, however, there has been increasing discussion on whether the bacteria necessary for the development of the poultry have to be fed live, or whether it is possible to administer them in killed form in order to achieve the same or even better effect. In this connection the following factors should be considered: many stimuli in the development of the chicken are structural, in other words the surface of the probiotic bacteria leads to an influence on the immune system. The bacterium need not necessarily be alive for this. On the other hand the colonisation resistance is often cited - this concerns which bacterium first colonises a certain niche in the digestive tract and thus forestalls colonisation by other bacteria, even if the microbes essential for development possibly do not directly prevent pathogenic bacteria. Despite this colonisation by pathogenic germs is thus prevented, provided that the essential microbes can colonise the intestinal wall first. lf the probiotic added in the feed is inactivated, this effect is limited. Receptors in the intestinal wall can admittedly be occupied, but permanent colonisation by live pathogenic germs cannot be prevented to the same extent, as these can move around. Only live Lactobacilli produce lactic acid, which in turn is available as nutrition to other essential microbes, such as Bifidobacteria, and at the same time leads to local acidification. Counterpart opponents such as Escherichia coli, which can occupy the same receptors as the colonising Lactobacilli, prefer to grow in neutral or alkaline surroundings. On the other hand, living organisms have maintenance needs. Consequently ifwe provide probiotic bacteria necessary for development specifically via the feed, they will also use a part of the feed energy for their own growth. Naturally there are also quite practical advantages and disadvantages in the use of bacteria in feeds. Essential microorganisms that have already been killed are more durable as a product and in feedstuffs and can be pelletized without problems. This is naturally a benefit for the producers of additives as weil, as no live detection is possible. Probiotic Lactobacilli and Bifidobacteria are specialists in the digestive tract, but generally not very stable in storage and cannot be pelletized without sufficient encapsulation.
The right strategy in poultry production
What benefits me most as a poultry producer? In two scientific experiments with broilers conducted over 40 and 42 days, either 500 g/kg or 1000 g/kg PoultryStar® was tested in the feed, with the probiotic bacteria being administered once live and once inactivated. In the case of 500 g/kg administration of the live product, increased early growth was observed in the first week of life, which was not the case with the inactivated product. In contrast, feed conversion was improved by comparison with the control animals in both treatments with live and killed product. In the trial with a dose of 1000 g/t feed PoultryStar®, the effect of the killed product was more uniform throughout the entire duration of the study. On the other hand, the effects of the live and killed product were improved over a control without supplements (see Figures 1 and 2).
Figure 1. Growth and feed uptake in broilers, a comparison between a control group, broilers fed feed supplemented with 1000 g/t PoultryStar® with active bacteria, and a group fed with the same quantity of PoultryStar® with inactivated strains.
Figure 2. Feed conversion in broilers, a comparison between a control group, broilers fed feed supplemented with 1000 g/t PoultryStar® with active bacteria, and a group fed with the same quantity of PoultryStar® with inactivated strains.
lnterestingly enough, in the case of administration of the inactivated product, however, improved digestibility of the dry matter and the crude protein fed to the birds was observed by comparison with the trial groups with the live probiotic and the control group. Here it can be suspected that a part of the dry matter and the protein in the live probiotic group was transformed into bacterial biomass, which was not the case with the inactivated bacteria administered or the control group. As there was no significant difference in growth performance between the birds with live bacteria in the feed by comparison with those with killed bacteria in the feed, it can be shown that the live bacteria supplemented do not compete with the broilers for nutrients in the intestine, as otherwise there would have been differences in growth. In the cecal tonsils, the largest accumulation of lymph cells in the hen gut, the expression of the inducible nitric oxide synthase (iNOS) gene was lowered in both cases (see Figure 3), which confirms the immunomodulating effect of the bacteria, both live and inactivated. Macrophages produce nitric oxides with iNOS to kill off bacterial cells. Lower secretion could indicate improved selectivity of these immune cells in both cases.
Figure 3. Secretion of the iNOS gene in ceca/ tonsils in broilers, in a comparison between a control group, broilers fed feed supplemented with 1000 g/t PoultryStar® with active bacteria, and a group fed with the same quantity of PoultryStar® with inactivated strains.
Based on these studies, it was possible to show an effect of inactivated bacteria essential for poultry development which leads to the same production results in a controlled feeding experiment. This also represents advantages for practical use, as it documents that inactivated bacterial strains too have positive effects that may be comparable with those of live strains. However, it should be considered that both experiments were tested under optimal trial conditions -under field conditions the pathogenic germ pressure is much higher in the course of production than in the trial. Here it is questionable whether the inactivated form of the bacterial strains can have the same effect at the same concentration.
This article was first published in FeedMagazine/Kraftfutter (Issue 1-2/2017).