Smart protein use is needed for piglet health
In the critical time around weaning, every step has to be as easy as possible for young piglets. Preparing the feed protein content, in the right quality and quantity, is one of the best possible ways to support healthy development.
Around the globe, awareness is growing to reduce antibiotic use in pig rearing. For instance, China recently banned colistin and the European Union forbade the use of zinc oxide in 2022 and is pushing for further reduction of antibiotics. In addition, Brazil’s Ministry of Agriculture, Livestock, and Supply (MAPA) recently decided to ban the use of 3 growth-promoting antibiotics. In order to deal with these new challenges, a multidisciplinary approach is necessary.
One of the key elements in creating excellent gut health is making the right nutrition choices. When making nutrition decisions to raise piglets in a healthy way with no or few antibiotics, attention to protein use and digestion is required.
Gut health is the result of a delicate relationship between the host, its microbiota, and the environment. A change in the sensitive relationship will lead to gut dysfunction and, subsequently, health problems. However, around weaning, changes and stress are inevitable. This is due to a new hierarchy, a new environment, and a transition from sow milk to a vegetal diet.
As the host is young, microbiota in the intestine is not yet established. Moreover, it is known that enzyme secretion before weaning is low. Therefore, when piglets are weaned at an early stage (21 days), the stress factors above will cause a disbalance to negatively impact gut health, and eventually trigger post-weaning diarrhea.
During this transition, protein is one of the most important players in keeping the microbiota stable, as undigested (vegetal) protein will rapidly result in bacterial fermentation and pathogen overgrowth.
Avoid undigested protein
Protein digestion can be influenced by many factors.
If the stomach is not sufficiently acidified, further protein digestion in the GIT will be more difficult, which may lead to bacterial fermentation. That is why it is important, at feed formulation, to consider the complete feed’s acid binding capacity. In the stomach, feed with a high acid-binding capacity will have the effect of buffering (increasing) its pH value (Table 1). This should be avoided because a pH that is too high makes the stomach less bacteriostatic or less bactericidal and will inhibit proper protein digestion. Adding the right organic acids through water and/or feed can help lower the stomach pH in the piglet.
In the small intestine, the protease enzymes trypsin and chymotrypsin are indispensable. Both compounds are only produced in a limited amount by piglets and any inhibition (e.g. due to badly processed raw materials) will lead to extra undigested proteins. Therefore, digestible protein is important after weaning so no undigested protein ends up in the large intestine.
In general, two things can happen with undigested proteins in a piglet’s gut. It can be built in as bacterial protein and then excreted through the feces. Commonly though, undigested proteins will be fermented for energy. The upside of this process is that it leads to branched and short-chain fatty acids, which have a positive effect by lowering the pH and supplying energy to the villi.
However, the downside of protein fermentation has far more impact. The fermentation leads to the production of toxic mono-amines, poly-amines, ammonia, hydrogen sulphide, phenols, and indoles. As the gut barrier is rapidly adapting the first 24 hours after weaning, these toxic metabolites threaten intestinal integrity and lead to inflammation.
Influence of (soy) protein quality
In short, choosing the right protein source is of great importance to avoid harmful protein fermentation. Potato protein, fish meal, rice protein, or whey protein concentrate are often used in piglet diets but the most important raw material for protein supplementation in animal husbandry is soybeans. This raw material is globally obtainable and has a good amino acid profile and is available in many different forms.
Expensive soy derivatives are soy protein concentrates, soy isolates, full-fat soybeans, fermented soybeans, and enzyme-treated soybeans but the most common form in pig diets is soybean meal.
Whatever soy source one is using, due to the presence of anti-nutritional factors (ANFs), it is generally accepted that it needs processing before use in animal feed. In soybeans, ANFs vary in presence, toxicity as well as heat stability. In relation to protein digestion, soybeans contain specific protease inhibitors with trypsin inhibitor activity level is used to measure the level of trypsin inhibitors present in soy.
|Anti-nutritional factors in soy products|
|– Anti-nutritional factors |
– Trypsin inhibitor
– Antigenic proteins
– Complex carbohydrates
Adequate heating step
By applying an adequate heating step during the production process, trypsin inhibitors can be reduced to acceptable levels as to not interfere with the protein digestion as stated above. An irreversible side- effect of heat treatment of soybean meal, however, is theat it can possible damage to the protein structure leading called the ‘Maillard reaction’ – a chemical reaction between reducing sugars and amino acids. This reaction leads to unavailable lysine for pigs. Measuring reactive lysine can be of use by determining how much of the lysine will be available for protein deposition.
Apart from trypsin inhibitors, soybeans also contain other anti-nutritional factors: lectins, antigenic proteins or complex carbohydrates (Table 1). Depending on the soy source, these can be reduced as well. The best way to reduce antigenic proteins and oligosaccharides is to utilize aqueous alcohol extraction. This process leads to a highly dense and digestible protein, low in ANFs, that is idea for use in piglet and young animal feed.
Standardized ileal digestibility
Standardized ileal digestibility (SID) values for crude protein and amino acids of soy products are usually published in feed ingredient databases. However, this digestibility data is used for all categories of pigs, which would suggest that a weaned piglet would have the same digestive capacity as adult pigs.
For most protein sources there is limited data available on SID for crude protein and amino acid values for piglets. However, soybean meal has been investigated in piglets and research confirms that, as they are often overestimated, the standard ileal digestibility values for grow-finisher pigs cannot be used for piglets.
Moreover, as soybean meal is produced on a large scale around the world, production parameters can vary. Although there is more standardization, German research in 2012 highlighted that different origins of soybean meal led to different SID values of crude protein and amino acids in early weaned piglets (17 days, on average 5.6 kg).
On average (out of 6 batched per origin) a significant variance in the SID level for crude protein between 77–80% was noted. As the SID of crude protein of soybean meal is generally around 85-93% in ingredient databases, this results in drastic change in protein quality within the category of soybean meal.
Influence of protein quantity
Offering the right quality of protein is key, and so is offering the right quantity. Several authors have related diets too high in protein levels to dysbiosis and diarrhea. Too much protein can possibly lead to a higher flux of undigested protein and dominant protein fermenters—such as E. coli and Clostridium—will get the upper hand and lead to post-weaning diarrhea. Hence why selection for good digestible protein sources is important.
For that reason, lowering protein content can be a solution to reduce fermentation levels and thus increase piglet health. Recent research by Dr. Martin Nyachoti et al. at the University of Manitoba, Canada, showed that low protein concentrations in feed for early weaned piglets reduced toxic microbial metabolites. This demonstrates why it is vital to not over feed protein but provide the proper level of protein; also be aware that performance should not be compromised by lowering protein levels too much.
To conclude, both soy protein quality as well as quantity are of great importance for piglets and is an important link in the total approach towards pig rearing without antibiotic growth promoters or zinc oxide. A more sustainable business can be achieved by correct processing of soy sources, performing a good digestibility evaluation, and a well-considered formulation.