Say no to antibiotics with glycerides - part 1: 'monoglycerides'

Thursday, June 10, 2021

Say no to antibiotics with glycerides – part 1: 'monoglycerides'

Sustainable Nutrition


Worldwide, nutritionists and researchers are working on the development of high quality animal feed without growth-promoting antibiotics (AMGPs). Despite the fact that this effort has clearly paid off, still there is a long way to go in terms of gut health. Only with a healthy and fully grown gastrointestinal tract production animals are able to reach their full genetic potential. A big step forward can be made with feed additives based on glycerides. Find out why.

Monoglycerides in a nutshell

Conventional short chain fatty acids (SCFAs), like acetic acid, propionic acid and butyric acid, play a fundamental role in modulating the intestinal microbial population and in promoting the digestion phase (Guevarra et al., 2019). Also medium-chain fatty acids (MCFAs), with a chain length of 6 to 12 carbon atoms, have demonstrated positive benefits as feed additives by improving animal health, production and feed digestibility (Jackman et al., 2020). These well-documented feed additives have long been used in diets without AMGPs to maintain animal performance, especially under suboptimal circumstances.

Over the past few years however, the so-called 'alpha-monoglycerides' of these SCFAs and MCFAs are gaining popularity. Alpha-monoglycerides are newly formed molecules based on a technology of esterifying one SCFA- or MCFA-chain with a glycerol molecule, specifically positioned at the first (or alpha) position. Various scientists all over the world studied the beneficial effects of these covalently bonded molecules in both animals and humans since the seventies. They have made progress in evaluating the performance of specific monoglycerides as well as in understanding mechanistic aspects of how these compounds function (Jackman et al., 2020). Interestingly, both from practice and from literature it became clear that alpha-monoglycerides of SCFAs and MCFAs are more effective as antibacterial agent compared to their free counterparts (Kabara et al., 1972, Nihei et al., 2004, Batovska et al., 2008, Skřivanová et al., 2006). Moreover, in contrast to the more conventional organic acids, monoglycerides have a neutral taste and smell.

Why are monoglycerides so effective?

The secret of the effectiveness of monoglycerides lies in their molecular structure. With the fatty acid chain attached to the first position of the glycerol molecule, alpha-monoglyceride has special properties. In contrast to conventional organic acids monoglycerides have very high pKa values of almost 14, thereby remaining undissociated across physiologically relevant pH conditions and hence is stable throughout the entire gastrointestinal tract. In addition, it is not susceptible to enzymatic breakdown by lipases in the mouth, stomach, and small intestine of broilers and piglets (Mu and Høy, 2004). In undissociated form monoglycerides are able to disrupt the cell membrane of pathogenic bacteria. By doing so they inhibit bacterial growth and even kill the affected pathogens, thereby restoring the balance between good and bad bacteria in the gut.

Monoglycerides of MCFAs and more particularly alpha-monolaurin, also possess antiviral properties against fat-enveloped viruses. They are found to affect the viral fat-envelope, causing leakage and at higher concentrations a complete disintegration of viral particles (Thomar et al., 1987). They may therefore be helpful to suppress the negative impact of viral challenges in pigs and poultry farming, for instance PRRS and Newcastle disease. In addition to their antibacterial and antiviral properties, some monoglycerides also reduce the expression of pro-inflammatory cytokines (Bedford and Gong, 2017) and help to avoid an overreaction of the immune system when small challenges occur. In this way piglets and broilers can save more energy for growth. Moreover, De Gussem et al. (2021) recently found that alpha-monolaurin has the potency to stimulate the immune response that is elicit upon vaccination against infectious bronchitis (IB) in broilers. This further supports the use of alpha-monolaurin as a feed additive. 

A powerful combination

Monoglycerides of SCFAs are mainly active against Gram-negative bacteria, like E. Coli and Salmonella, while monoglycerides of MCFAs exhibit more potent inhibitory activity against Gram-positive bacteria, like Clostridium perfringens and Streptococcus. As they inhibit different spectrums of pathogens with varying potencies, appropriate selection is required depending on the pathogens being targeted (Jackman et al., 2020). Mixing them in the right combination would give ultimate synergistic effects and a broad-spectrum antibacterial action (Batovska et al., 2009; Hanczakowska et al., 2013). SN® Monomix consists of a powerful combination of monoglycerides made after a long term study with the efficacy of single products, i.e. glycerides of propionic, butyric, caprylic and capric acid, in the field. It is especially designed to improve overall gut health, stimulate a more favourable microbiota composition and improve general performance results in monogastric species. Several European field studies suggest SN® Monomix can elicit beneficial effect in pigs and poultry.

From a recent study with about 3500 weaned piglets it can be concluded that the addition of SN® Monomix improves performance and health status of young pigs during the stressful weaning period. As shown in table 1, daily growth rate increased with 29 gram resulting in a higher end weight of 1 kilogram. This higher end weight in the nursery may result in a shorter fattening period of one week, which is economically very relevant. Feed conversion ratio was improved with 8 points (5 percent), which means the feed intake of piglets in the control and treatment group was comparable. This confirms the practical experience that monoglycerides do not cause problems with palatability and feed intake. Also a better health status and gut health were obtained as the mortality was reduced by as much as 41 percent. In addition, the uniformity among the pigs receiving SN® Monomix was observed to be better compared to the control group.

Table 1. Piglet performance of the control and treatment group (SN® Monomix).


Solution for antibiotic free diets


Monoglycerides of SCFAs and MCFAs, have proven to be innovative feed additives. They exhibit strong antimicrobial activities, especially when applied in AMGP-free diets for piglets and broilers. Sophisticated combinations, like SN® Monomix, improve overall gut health and general performance results.



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