Bit by bit, it becomes clear that sows might have stomach problems without becoming apparent. The only way that is confirmed to positively
influence stomach health is by
providing pelleted and
home-mixed feed with large particles.
By Jacob Dall, MSc, technical manager,
pig nutrition, Vitfoss, Denmark
For decades gastric ulcers have been known as a feeding-related problem in pig production. Danish research from the mid-1980s found no correlation between low crude fibre content and gastric ulcers in trials on cereal based feeds with low crude fibre and no bedding material. During the 1990s, there was increased focus on finding the cause of too many sows showing poor feed intake or milk production. Looking at gastric health, it soon became clear that some sows had gastric lesions, limiting feed intake and productivity.
Gastric ulcers in pigs
Unlike human stomachs, pig stomachs are not fully covered by a protective mucus, preventing acid burns within the stomach. Where the esophagus enters the stomach, an extension esophagus is located, also known as the ‘white area’. This area has no such protection, making it especially susceptible to acid burns, should it happen to be exposed to the acidic stomach content.
When unprotected tissue is exposed to acidic stomach content, acid burns will happen. As with other ulcers, these acid burns will heal over time, but will also leave scar tissue, which is not nearly as flexible as the original tissue. For a sow that has repeatedly experienced developed and healed ulcers in the region, eventually the diameter of the opening from the esophagus into the stomach will be restricted, letting only very little amounts of feed pass through.
Gastric ulcers located in the glandular part of the stomach in pigs are extremely rare; most ulcers are found in the white area. New research assumes a role in bacterial infections by Helicobacter suis, a pig variant of the micro-organism Helicobacter pylori, which is associated with gastric ulcers in humans. This bacteria, however, appears not to be of the same importance for the development of gastric ulcers as its ‘relative’ in humans.
Instead, the viscosity of the stomach content appears to play a very important role. When the stomach content has a very low viscosity (i.e. being not very thick), the risk increases of the white area being exposed to the stomach’s acidic content.
Bloating is another issue when dealing with the impact of feed on gastric health. As large particles of feed leads to increased viscosity and decreased passage rate, this is often combined with fibrous components, that furthermore makes the gestating sows feel full, thus reducing stress.
Other causes for more severe bloating, usually visible after death, can be due to:
- an imbalance in the gut microflora, where certain types of clostridia produce endotoxins, or;
- poor feed hygiene leading to growth of fungi in silos or;
- a feeding system with faults that stimulate the production of
Recent work in Denmark showed that gastric ulcers are more prevalent amongst sows than previously was assumed. The results of trials on 1,023 stomachs have been shown in the below diagram. In late 2014, a Danish national action plan will be introduced that requires all Danish sow herds to have a number of stomachs investigated per year at the slaughterhouse, and to act accordingly, if the prevalence and/or severity is found to be too high.
Symptoms of early gastric ulcers often are not visible in the live pig. Animals with severe gastric ulcers show clinical symptoms like stomach ache, vomiting (after feed intake), paleness (anaemia), or overall reduced productivity. On a scale from 0-10 (with 0 being no ulceration), only animals with grades above 7 seem to show clinical symptoms. It has been shown that investigating the stomachs of culled sows is a good indicator of the general level of gastric ulcers in a herd.
Handling gut health
With increasing focus on gastric health, a lot of effort has been put into identifying factors that affect gut health and especially gastric ulcers positively or negatively, but with only limited success. It seems that crude fibre content of the diet is not the key factor, as high fibre components do not seem to be able to reduce the prevalence of these ulcers. Until now, the only factor that seems to be able to significantly change gastric ulcer prevalence in a herd, is the feed’s particle size. This conflicts with the wish for as low a feed consumption as possible. Very fine milling, through an increase in the total available surface area for the digestion process, leads to high feed conversion, but with a risk of increasing gastric ulcers. Large particles on the other hand, improve viscosity of the gut content, improving the physical properties, leading to a healthier environment in the entire gut.
In Danish herds, compound feed is pelleted, which decreases particle size beyond milling. Adding rolled/flaked or shredded/graded barley or wheat has shown to improve gastric health. For home mixers that usually don’t have this option, focus should be on optimising the milling to the point of high feed conversion, without helping gastric ulcerations get to unacceptable levels.
This can be done by systematically checking the milling by sieving and comparing to investigations on gastric health of culled sows. The ability to work with different milling, letting one component or a part of the cereals being milled coarsely, with the rest being fine, can lead to an optimised feed conversion and gastric health relation.
It is not well documented what exactly is the mode of action of how larger particles reduce gastric ulcers. Large particles, however, do lead to a higher viscosity and maybe even form a high viscosity layer at the top of the stomach content, acting as a barrier preventing the white area to be exposed to the stomach’s acidic contents.
As shown in the box, other factors also influence the level of gut problems. The possible causes shown should be considered at any feed intake and performance problems in a herd. A combination of the above causes is not uncommon, but the only factor that has yet been identified as being able to significantly change the prevalence of gastric ulcers is, as mentioned above, the feed’s particle size. Bloating also can be handled by improving feed hygiene or, if the cause is microbial imbalance, by adding probiotics to the feed.
Factors influencing gut problems
High stocking density
Pig shifting and mixing
Limited acces to water
Mycotoxins in feed
Pelleting of feed
Particle size in feed
PCV2 or PRRS infection
High room temperature
[Source: Pig Progress magazine Vol 30 nr 9, 2014}
References available on request.