Garlic and cinnamon for a healthy working rumen

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.

Cinnamaldehyde

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.