Process Management

Background last update:6 Aug 2012

Garlic and cinnamon for a healthy working rumen

Optimal ruminal microbial activity is essential for the product ion of energy and high quality protein in ruminants. New studies have found plant extracts that have beneficial effects on this process.

By Chris Kamel and Henry Greathead

Plant extracts are complex mixtures of plant secondary metabolites that appear as one of the natural alternatives to antibiotic use in animal nutrition. Many of these plant extracts are able to affect metabolic pathways of the animal and its microbial flora and fauna alike. Their strengths lie at feeding levels well below the antimicrobial concentrations (Minimum Inhibitory Concentrations, MIC),providing a
selective advantage for desirable microorganisms. The structure of the phytogenic active compound(s) determines the compounds activity and therefore plays an important role, which has an effect not only on efficacy, but also on safety and milk quality issues.

A number of studies around the globe - centralised around a PhD programme at the University of Leeds, Faculty of Biological Sciences - have focused on the selection of phytogenic substances with benefits on protein and energy metabolism. Despite the vast number of different families of plant extracts and their associated active compounds, the astounding fact is that only a few (<10%) gave any kind of response. From there, only a handful met the objectives of improving rumen efficiency. Here we look at what has been learnt about the two compounds that have been found to be the most beneficial to protein and energy metabolism in the rumen.

Benefits of garlic oil

Garlic oil has been shown to modulate rumen dynamics in previous studies (Busquet et al., 2005; Busquet et al., 2005) and is represented by a mix of different organosulfur compounds with antimicrobial activity, such as

 thiosulfinates, allyl sufides, glutamylcysteinses and allicin occurring naturally, and as a result from the oil extraction and processing methods (Ankri and Mirelman, 1999).

Garlic oil

Garlic oil has been shown to modulate rumen dynamics in previous studies (Busquet et al., 2005; Busquet et al., 2006), and is represented by a mix of different organosulfur compounds with antimicrobial activity, such as thiosulfinates, allyl sufides, glutamylcysteinses and allicin, occurring naturally and resulting from the oil extraction and processing methods (Ankri and Mirelman, 1999). However, allicin is an intermediate volatile molecule that instantly decomposes to other compounds, including diallyl sulfide, diallyl disulfide and diallyl trisulfide, dithiins and ajoene (Amagase et al., 2001). This conversion has been shown to occur as early as one to six days (Brodnitz et al., 1971; Yu and Wu, 1989), accounting for the low levels (<1%) of allicin found in most commercial garlic oil preparations (Lawson et al., 1991). As such, most of the recent work has focused on the sulfhydryl end-products of allicin conversion, such as diallyl disulfide. Several investigators (Busquet et al., 2005, 2006; Kamel et al., 2007) have consistently shown in fermentation trials with rumen fluid that garlic oil and, in particular, one of its constituents, diallyl disulfide, reduced the proportions of acetate and increased the proportions of propionate and butyrate. This fermentation profile makes garlic oil different from that of monensin (reduces the acetate to propionate ration and butyrate concentrations) and is consistent with changes observed with methane inhibitors. In vitro studies demonstrated that garlic oil and diallyl disulfide reduce the methane-total volatile fatty acids (VFA) ratio and hydrogen recovery significantly (Busquet et al., 2005; Kamel et al., 2007). Methane is the main hydrogen sink in rumen fermentation, and the inhibition of its synthesis leads to other candidates, such as propionate and butyrate. The unique mode of action of diallyl disulfide relates to the action of its sulfhydryl groups to directly inhibit HMG-CoA Reductase, one of the major enzymes involved in the cell wall synthesis of methanogens from Archea microorganisms (Figure 1, Busquet et al., 2006). Follow-up studies by Ferme et al. (2007) looking at rumen microbiology fingerprinting have identified garlic oil (and diallyl disulfide in particular) as the first plant extract of its kind to selectively act on methanogens.


The second active ingredient that showed an effect on the rumen activity was cinnamaldehyde, found in different sources of cinnamon with antimicrobial activity against Gram-positive and Gram-negative bacteria (Davidson and Naidu, 2000). Cardozo et al., (2004) first suggested that low doses (<100mg/day) of cinnamon oil may affect N metabolism of rumen microorganisms by inhibiting peptidolysis, without effecting VFA concentrations. This was confirmed by Busquet et al., (2004), in an in vitro batch fermentation study, where ammonia N concentrations were reduced. In this study these trends closely followed the expected changes seen in selected microbial population profiles using molecular fingerprinting techniques where cinnamaldehyde reduced the numbers of the dominant Gram-negative populations, i.e. Prevotella spp – an important species in protein degradation.

Standardised mix

A commercial product is currently available with a standardised mix of garlic oil and cinnamaldehyde (G&C). Although the product was developed for dairy cattle purposes, data previously presented and preliminary animal feeding studies suggest that its application in beef cattle diets may also be appropriate. Trials with dairy cows in early lactation have shown the benefits of an encapsulated form of G&C, which eliminates off-taste of the ingredients and targets release to the rumen. Total VFA concentration was not affected by G&C, but the molar proportion of acetate decreased and the molar proportion of propionate tended to increase. The G&C resulted in the accumulation of small peptides and amino acids and the reduction of BCVFA (branched chain volatile fatty acids) and ammonia N concentrations, in line with the proposed mechanism of cinnamaldehyde. In terms of energy, methane was reduced by as much as 12%, as shown in previous in vitro trials with garlic oil and its main active substance, diallyl disulfide. Overall, the reduction in degradation coupled with the reduction in methane resulted in an increase of 1.2 litres of additional milk per day and a jump in milk protein from 3.45% to 3.62%.

In our experiences, this is the first combination of plant extracts that may act on both the energy and protein level bringing them into rumen equilibrium. Previous studies with other plant extract combinations have usually shown benefits of total and fat-corrected milk production, but at the detriment of lower milk fat and protein percentage (indicating a more diluted milk production). It is our believe that garlic oil standardised in diallyl disulfide acts purely on the energy side, allowing for a protein sparing action on the peptides and amino acids generated from cinnamaldehyde to be used directly for protein synthesis.

Novel rumen concepts

With information based on mode of action, strategies combining different products may bring benefits that are better than each one alone. Two concepts appear to be gaining ground in the beef and diary market: G&C with yucca extract and G&C with live yeasts. Several in vivo trials have shown the benefits of combining yucca extract with G&C. One of these trials with lactating cows in early lactation is shown in Table 1. In this trial performed with a 60:40 forage based diet, a commercial preparation of yucca extract was compared to G&C and a combination of the two. From the table, it can be seen that both individual additives yielded decreases of at least 8% in ruminal ammonia. However, the two together showed a significant effect over each alone, decreasing ruminal ammonia by over 20%! When fed in a protein concentrate to cannulated dairy cattle in early lactation, milk urea nitrogen dropped by 8% or more as early as the next monthly milk control.

The synergy with live yeasts

In vitro

and in vivo trials have shown that the combination of G&C with live yeasts also leads to benefits over the use of one or the other by itself. In a recent comparative trial in early lactating dairy cows, four treatments were compared based on a control diet of 60:40 forage: concentrate TMR (total mixed ration) versus the same TMR supplemented with either G&C, a live yeast preparation, and a combination of G&C plus live yeasts. As expected from the revelations on mode of action, the group fed the TMR with the combination of G&C and live yeasts showed better production performance (milk production, milk component percentage, and yields) compared to the other groups. While on paper this concept appears beneficial, it is not so easy when put into practice. Mixing plant extracts into a concentrate is complicated due to their aggressive nature to other additives, such as live yeast cultures. Laboratory trials have shown that G&C placed on a carrier without a protective coating significantly reduced numbers when mixed and plated in vitro with live Saccharomyces cerevisiae. This follows several studies which have shown that cinnamon and its active ingredient cinnamaldehyde is particularly lethal to yeast as it has been shown to inhibit cell wall formation. This brings the necessity to establish a barrier in order to assure maximum stability and efficacy of both additives administered in combination. The protection of G&C with a rumen-release protection system eliminates the reduction in numbers of Saccharomyces cerevisiae normally observed under the microscope when they are plated in vitro with non-encapsulated or poorly encapsulated plant extracts (Carotenoid Technologies, Spain, 2007). Other benefits, such as the residence time in the rumen, as well as the sustainability of rumen effects is currently under investigation.


The rumen is a dynamic fermentation system which coordinates the activities of bacteria, protozoa and fungi with the needs of the host animal. Research over the last six years has identified the benefits of the active ingredients from garlic and cinnamon on optimising the synchrony of protein and energy utilisation in the rumen. From the understanding of their precise mode of action, the application of G&C alone and in synergy with other additives, such as yucca and live yeasts, have shown proven benefits and are currently used on commercial farms. Finally, added-value applications, such as product encapsulation, play a role in improving aspects of dispensability, stability and controlled release in order to optimise and sustain the desired level of rumen effects and animal performance.

Further information on recommendations with other additives or cited publications may be obtained directly from the authors. Email:

Source: Feed Mix Vol 15 nr. 4

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