on gas production from 200 mg of vetch-oat hay after 24h fermentation
on methane content of the gas after 24h incubation of 200 mg of vetch-oat hay
| Livestock Research for Rural Development 30 (6) 2018 | Guide for preparation of papers | LRRD Newsletter | Citation of this paper |
This study was conducted to evaluate the effect of essential oils of Lavandula dentata and Mentha piperita plants on gas and methane production in an in vitro rumen incubation using rumen liquor obtained from three slaughtered sheep. The mixture of rumen fluid with buffer 1:2 v/v, was placed in 100ml syringes containing 200mg of the substrate. The incubation procedure was repeated three times. The gas production and concentration of methane were recorded after 24h of incubation.
Gas production after 24 h incubation declined with a linear trend as the concentration of the essential oils in the substrate was increased in the range zero to 95µl/g of the vetch-oat hay, the rate of decrease apparently being greater for Mentha piperita than for Lavandula dentata.
The concentration of methane in the gas declined with curvilinear trends, the effect appearing to be more marked in the case of Metha piperita. However, there were no overall differences between the two sources of essential oil. The pH in the in vitro system was increased by addition of essential oils but the magnitude of the increase was very small. The pH did not differ between the two sources of oil. The potential for reducing methane production by adding the two sources of essential oils tested in this experiment must be viewed against the associated reduction in gas production, and the overall effects in the intact ruminant animal.
Key words: methane, ruminants, greenhouse, essential oil, Lavandula dentate, Mentha piperita, digestibility
Methane production in ruminants has received global attention in relation to its contribution to the greenhouse gas effect and global warming. Many researchers have explored a variety of approaches as a means of decreasing methane production in ruminants. Some approaches, such as feeding of antibiotics (bacteriophages, bacteriocins) and chemical inhibitors, directly target methanogens but the public concern over use of antibiotics in livestock production has increased in recent years because of their possible contribution to emergence of antibiotic resistant bacteria and their transmission from livestock to humans. Other approaches, such as defaunation and promotion of acetogenic populations, seek to lower the supply of metabolic hydrogen to methanogens. Most additives of this type tend to be eliminated due to safety concerns in animal-derived food (Castillijos et al 2006).
Characterization of microbial activity and methane production in the rumen may provide insights for development of effective strategies for reducing methane emissions from ruminants. Essential oils are naturally occurring volatile extracts of plants responsible for giving spices their characteristic essence and color; they also have antimicrobial properties (Newbold et al 2004) that make them potential alternatives to antibiotics to manipulate the microbial activity in the rumen (Spanghero et al 2008).
This study focuses on exploring the capacity of two essential oils (EO), extracted from lavender (Lavandula dentata) and menthe (Mentha piperita)) to reduce methane production and enhance degradability of vetch-oat hay in an in vitro fermentation.
The aerial parts of the two plants (Lavandula dentata and Mentha piperita) were collected during May 2007 by hand cutting. Extraction of the essential oil was made by the hydro-distillation process (100 g of the plant was mixed with 700ml of distilled water). The oils were collected by condensing and then separating the oil by settling. The oils were stored in dark bottles at 4°C.
The in vitro system was prepared following the procedure of (Menke et al 1979). Rumen liquor taken at random from 3 slaughtered sheep was mixed with artificial saliva (1: 2 v/v). The latter was prepared as described by Menke et al (1979). The syringes (100ml), prewarmed at 39°C, contained 200 mg (DM basis) of substrate (vetch-oat hay). They were inoculated with 30 ml of rumen fluid under continuous CO2 reflux and incubated at 39°C for 24 h. The oils were injected into the syringes just before the incubation. The levels were 10, 14 and 19 µl. In each test, three syringes with control substrate (blank) were also incubated but without additive (syringes incubated with the inoculum alone).
Cumulative gas production was assessed after 24h. The content of methane in the gas was measured by injection in each syringe of 4 ml of sodium hydroxide (NaOH, 10N) (Bouchiha et al 2015). The gas production in the blanks (syringes incubated with the inoculum alone) was subtracted from the gas production in syringes incubated with the inoculum and substrate, to get net gas production values.
The data were analyzed by ANOVA employing the SAS (1990) software. Polynomial regression equations were fitted to the data relating gas production and methane content in the gas (Y) with the level of oil level added to the substrate (X).
The pH in the in vitro system was increased by addition of the essential oils in the range zero to 95µl/g of the vetch-oat hay but the differences were very small (Table 1). There were no differences in pH due to the source of oil.
Gas production after 24 h incubation declined with a linear trend as the level of oil was increased (Figure 1). The rate of decrease was greater for Mentha piperita than for Lavandula dentata.
The concentration of methane in the gas declined with curvilinear trends with increasing level of oil in the substrate, the effect appearing to be more marked in the case of Metha piperita (Figure 2). However, over the range of oil concentrations that were studied there were no overall differences between the two oils (Table 1).
|
Table 1. Mean values for pH, gas production at 24h and content of methane in the gas according to addition of essential oils (Lavandula dentata and Mentha piperita) |
|||
|
Gas, ml |
Methane, % |
pH |
|
|
Oil, µl/200mg substrate |
|||
|
0 |
34.7 |
17.3 |
6.623 |
|
10 |
31.2 |
16.3 |
6.678 |
|
14 |
29.7 |
14.7 |
6.703 |
|
19 |
28.8 |
13.2 |
6.705 |
|
SEM |
0.056 |
0.25 |
0.013 |
|
p |
<0.001 |
<0.001 |
<0.001 |
|
Source of oil |
|||
|
Lavendula |
32.3 |
15.3 |
6.68 |
|
Mentha |
29.8 |
15.5 |
6.68 |
|
SEM |
0.4 |
0.25 |
0.0091 |
|
p |
<0.001 |
0.4 |
0.70 |
|
|
| Figure 1.
Effect of addition of essential oils from Lavandula dentata and
Mentha piperita on gas production from 200 mg of vetch-oat hay after 24h fermentation |
Figure 2.
Effect of addition of essential oils from Lavandula dentata and
Mentha piperita on methane content of the gas after 24h incubation of 200 mg of vetch-oat hay |
The potential for reducing rumen methane production by adding essential oils must be viewed against the associated reduction in rumen gas production (a relationship which has been shown in other in vitro rumen studies (eg: Ataly et al 2018). However, gas production in the rumen only measures the events in that part of the digestive tract. Feed biomass that is not fermented in the rumen has the potential to contribute amino acids to the animal if it is rich in “bypass” protein, while the “energy-rich” component can yield volatile fatty acids when fermented in the cecum-colon – a process which yields metabolizable energy excluding methane production and without carbon dioxide (Demeyer 1991; Immig 1996; Popova et al 2013; Leng 2018, in press). It is essential that corollary experiments are done to relate effects in the rumen with those in the intact animal.
Atalay A I, Ozkan C O, Kaya E, Kamalak A and Canbolat O 2018 Chemical composition, nutritive value and rumen methane potential of some legume tree pods. Livestock Research for Rural Development. Volume 30, Article #92. http://www.lrrd.org/lrrd30/5/akam30092.html
Bouchiha H, Rouabhi R, Bouchama K, Berrebbah H and Djebar M R 2015 Effects of pastoral plants essential oil redirecting rumen fermentation to reduce methanogenesis using in vitro gas production method. International Journal of Biosciences 7: 2222-5234. http://www.innspub.net/wp-content/uploads/2015/10/IJB-V7No4-p150-156.pdf
Castillejos L, Calsamiglia S, Ferret A and Losa R 2006 Effects of dose and adaptation time of a specific blend of essential oil compounds on rumen fermentation. Animal Feed Science and Technology132: 186–201
Demeyer D 1991 Differences in stoichiometry between rumen and hindgut fermentation. Adv. 1023 Animal Physiology and Animal Nutrition 22:50-66
Immig I 1996 The rumen and hindgut as source of ruminant methanogenesis. Environmental Monitoring and Assessment Volume 42, Issue 1-2, pp 57-72
Leng R A 2018 Unravelling methanogenesis in kangaroos, horses and ruminants: the links between gut anatomy, microbial biofilms and host immunity. Animal Production Science In press
Menke K H, Raab L, Salewski A, Steingass H, Fritz D and Schneider W 1979 The estimation of the digestibility and metabolizable energy content of ruminant feedingstuffs from the gas production when they are incubated with rumen liquor in vitro. Journal of Agricultural Science Cambridge 97: 217-222.
Newbold C J, McIntosh F M, Williams P, Losa R and Wallace R J 2004 Effects of a specific blend of essential oil compounds on rumen fermentation. Animal Feed Science and Technology 114 : 105-112.
Phonethep P, Preston T R and Leng R A 2016 Effect on feed intake, digestibility, N retention and methane emissions in goats of supplementing foliages of cassava (Manihot esculenta Crantz) and Tithonia diversifolia with water spinach (Ipomoea aquatica). Livestock Research for Rural Development. Volume 28, Article #72. http://www.lrrd.org/lrrd28/5/phon28072.html
Popova M, Morgavi D P and Martin C 2013 Methanogens and methanogenesis in the rumen and cecum of lambs fed two different high concentrate diets Applied Environmental .Microbiology doi:10.1128/AE
Spanghero M, Zanfi C, Fabbro E, Scicutella N and Camellini C 2008 Effects of a blend of essential oils on some end products of in vitro rumen fermentation. Animal Feed Science and Technology. 145: 364-374.
Received 31 December 2017; Accepted 6 May 2018; Published 1 June 2018