Say no to antibiotics with glycerides - part 2: 'mono- and tributyrin'
The article 'Say no to antibiotics with glycerides - part 1' discussed the opportunities and benefits of monoglycerides of short and medium chain fatty acids in AMGP-free diets. In part 2 a specific class of glycerides will be addressed, i.e. 'monobutyrin' and 'tributyrin'. Their role in replacing in-feed antibiotics and promoting animal health and performance will be in the spotlight.
Butyric acid in a nutshell
It has long been recognized that dietary short chain fatty acids (SCFAs), when added to poultry and pig diets, are able to control a broad range of pathogenic bacteria. But there's more. Butyric acid, a 4-carbon SCFA, is not only known for its ability to avoid colonization of pathogenic bacteria - especially Salmonellaand E. Coli (Namkung et al., 2011)- it also is an important energy source for intestinal epithelial cells, mainly colonocytes. By improving epithelial cell proliferation and stimulating villi height, butyric acid favours the absorption of valuable nutrients. In addition, butyric acid promotes a healthy gut microbiome and helps to maintain proper tight junctions to prevent the so-called 'leaky gut syndrome', which frequently occurs in stressful periods like weaning in piglets and the starter phase of broilers. Thus, butyric acid not only possesses antibacterial properties, it can also lead to improved performance due to enhanced gut integrity (see figure 1).
Figure 1 Multiple effects of butyrate in the intestines (Guilloteau et al. 2010)
Handling the bad smell
It is not a secret that butyric acid is associated with a strong and persistent smell. It is difficult to handle and apply in practice. In addition, free butyric acid is known to quickly disappear in the upper gastrointestinal tract of monogastrics while its favourable effects on intestinal health as well as on pathogenic bacteria only are possible when it arrives in the lower parts of the gut. These are the main reasons why butyric acid - or its salt (sodium or calcium butyrate) - usually are encapsulated with a fat matrix coating. The fat coating can be up to 70% of the total product weight. Dilution of the active component can be seen as a disadvantage of these coated products, as relatively high dose level often results in higher cost price.
To overcome the problems with smell and dosing,Sustainable Nutrition intensively explored the possibilities of glycerides of butyric acid: SN® Monobutyrin and SN® Tributyrin, in which one ('mono') or three ('tri') butyric acid molecules are chemically attached to a glycerol molecule. In contrast to the smelly butyric acid, these glycerides are odourless and taste-neutral, easy to handle for farmers and in feed mills and will not negatively affect feed intake. Moreover, butyrate glycerides would deliver relatively high amounts of butyric acid in the small intestine, owing to their molecular structure (Bedford and Gong, 2017; Yang et al., 2018).
Strong antibacterial effect
Based on the available literature, monobutyrin, the active compound of SN® Monobutyrin, has proven to be a valid and cost-effective alternative to butyric acid or its salts. Not in the last place because it is even more biological potent compared to its free counterpart. As with any SCFAs, bactericidal activity of butyric acid is greatest when the acid is in its undissociated form. Unlike butyric acid, monobutyrin stays undissociated along the entire gastrointestinal tract. This is due to its specific molecular structure (Skřivanová et al., 2006) as described in part 1. So, next to the neutral taste and smell, a major advantage of monobutyrin is its stronger antibacterial effect compared to free butyric acid or its salts. Moreover, dietary butyrate glycerides stimulate gut health in general and positively modulate intestinal microbiota composition. In particular the abundance and species diversity of Bifidobacteriumincreases (in broilers; Yang et al.(2018).
Improving gut integrity
Another effective strategy to deliver a highly concentrated, user-friendly and taste-neutral butyric acid into the lower intestines is tributyrin, the main component of SN® Tributyrin. The concentration of active compound in tributyrin is high as three butyric acid molecules are attached to one glycerol molecule. In addition, butyric acid chains are protected from rapid absorption in the stomach while the active compounds can be gradually be released by pancreatic lipase (Jackman et al., 2020). Supplementation to piglet diets showed positive effects on growth performance and gut health, like villi length and crypt depth and mucosa thickness, even under suboptimal circumstances (Sotira et al., 2020). Recently, Sotira and co-workers concluded from their study that weaned piglets fed tributyrin showed a significantly higher daily gain and feed efficiency compared to the negative control. In addition, tributyrin showed the ability to promote gut health, to modulate gut microflora and to improve protein digestibility. Dong et al.(2016) confirmed the fact that supplementation of tributyrin improves the growth and intestinal digestive and barrier functions, especially in small and under-developed piglets. Also in broilers a mix of mono-, di- and tributyrin helped to maintain the performance and carcass quality, especially in vaccinated birds challenged with coccidiosis (Leeson et al., 2005).
Solution for antibiotic free diets
Butyric acid shows various beneficial effects in diets for production animals, such as antimicrobial and anti-inflammatory activities and a stimulating effect on gut tissue development and favourable intestinal microbiota, thereby enhancing growth performance and general health. Butyrate glycerides, like monobutyrin and tributyrin however, offer a novel and effective delivery system of butyric acid to the small intestine (Namkung et al., 2011). They are free of the stringent smell and easy to handle and serve as a valuable alternative for in-feed antibiotics, especially in young animals.
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Article made possible through the contribution of Sustainable Nutrition