Most people aware that there is an amino acid loss in liquid feed due to fermentation of the feed residues in the feeding tubes. Especially the loss of the added synthetic amino acids lysine and threonine can be costly. If you have a problem with amino acid loss to such an extent that it affects feed quality and needs to be compensated, one of two methods are usually used. Either you can increase the content of the amino acids to compensate for the loss or you can use organic acids in liquid feed to limit fermentation and thus reduce the loss of the amino acids. But when do you choose one or the other strategy?
Is amino acid loss in liquid feed the only reason to use organic acids in liquid feed?
If you only focus on the loss of amino acids, it will often be cheaper to increase the level of artificial amino acids in the feed recipe than to add organic acids in liquid feed. This is because the addition of organic acids will most often exceed the cost of increasing amino acids.
However, this assumption is only correct if the direct costs of amino acid loss are your only concern, but as the authors point out, it may still pay off to use organic acids when other factors such as feed hygiene or the acid’s effect on pigs’ productivity are taken into account. The question is therefore when it would be wise to use organic acids anyway – like for reasons of hygiene or productivity. Here we look at several cases where that may matter more.
Beware of fermenting complete feed
The fact that fermentation takes place in an ordinary liquid feeding system cannot be avoided; the trick is being able to control this fermentation. The advantage of controlled fermentation are that you get lactic acid bacteria with their probiotic effects, as well as the lactic acid itself which helps to keep the unwanted microbes under control.
However, studies show that a fermenting complete feed or soya results in lower feed intake, feed conversion and growth. It is therefore recommended that you only ferment your feed grains. This is because when fermenting the complete feed, you have a higher loss of amino acids. This also applies to the residues of complete feed that may be left in the feeding tubes. For this reason, it is also recommended that there is no more than 50% residue in the feeding tubes after feeding.
Fermentation also adversely affects the feed in terms of taste, as the metabolites of the degraded amino acids result in undesirable flavours. Some of these substances smell like rotting meat for example cadaverin and putrescin whose names are derived from cadaver and putrefication respectively.
Make sure the pH is below 4 during fermentation
Even in a well-functioning liquid feed system, the pH should be monitored regularly, as a successful fermentation of grains takes place at a pH below 4. Temperature is crucial to keeping the pH low in that temperatures above 20 ° C lead to a lower pH value. Grains fermentation works best at 20 – 21 ° C. This also means that in winter, when the temperature drops below 20 ° C, fermentation problems with a pH that is too high are more likely to occur.
When pH gets too high formic acid can be include at 0.2% to help lower the pH and promote fermentation. At this level, the formic acid does not affect the growth of lactic acid. If you still cannot get the pH down low enough, an acid mixture with lactic acid and formic acid can help. This allows you to add more organic acid in liquid feed and achieves the same effect as with fermentation, without being dependent on the lactic acid bacteria’s production of lactic acid. Also, one avoids high levels of formic which the animals often find unpalatable.
Feed hygiene must be top notch
In general, feed hygiene must be top notch regardless of the type of liquid feed system used. As a first step, you should clean the liquid feed tank at least once a week, and you must be especially careful around lids and threads. Here, automatic acid spraying with formic acid can help reduce the need for washing, but of course not replace it.
Even if you keep the tank clean, you may still see signs of developing problems with feed hygiene. Loose stools, diarrhoea, poor feed intake in the animals or unwanted fermentation in the feed may all be signs of hygiene problems. In addition to isolating the root cause by having the feed analysed, a sensible first step is to start adding organic acid in liquid feed.
Reasons for use of acids in residue free feeding
Loss of amino acid is rarely a major problem when it comes to residue free feeding. This is because there are no feed residues in the feeding tubes which have added amino acid that stand still and ferment after the individual feeding. On the other hand, hygiene can be a big challenge with residue free feeding.
No matter how thorough you are in ensuring that the feeding tubes are emptied of feed, the water used to push feed through the system, the pushing media, will still contains some leftover feed. This ‘dirty’ water has a very low dry matter content (2-6%), but actually a better growth medium for harmful bacteria than complete feed in a regular liquid feeding system. This dirty water also carries an increased risk of mould, harmful gut bacteria and Cl. perfringens. This is because in a normal system, fermentation will produce more lactic acid, and the higher dry matter content will limit the growth of other microbes.
The general recommendation is therefore to use 0.2% formic acid or 0.5 – 1.0% benzoic acid in the pushing media to limit the growth of harmful bacteria. If you have special challenges with yeast and mould and other harmful microbes, an acid blend that contains propionic acid is preferable, as this will also have an effect against yeasts and moulds.
Pay attention to fermented pushing media
Some of the hygiene challenges in residue-free liquid feeding can be addressed by using an alternative pushing medium in the form of fermented grain or whey. Here, the principle is that, as in an ordinary liquid feed system, that lactic acid is produced by fermentation and harmful microbes are out competed by the lactic acid bacteria (competitive exclusion).
Our experience is that this can still cause increase the amino acid loss, as the residues of the pushing medium will inevitably be included in the feed and inoculate a fermentation process. The problem is best avoided by rapidly feeding out before the fermentation starts. In practice this can be a challenge, for example, in piglets which have a low feed intake and therefore require that your system has narrower feeding tubes to reduce the need for large volumes of pushing media. Likewise, feeding sows in the farrowing pen where feed consumption is also low can be problematic.
No matter what type of liquid feeding system you are using, it may be reasonable at times to use different acids to help you get the most out of your liquid feed. They should be used, not only to limit amino acid losses, but also for the benefits related to feed hygiene. Read in our next article where we will focus on animal health and production benefits of using organic acids in your liquid feed.