The effect of myrtle leaves and essential oil on the fermentation characteristics and digestibility in Arabi sheep

Medicinal herbs such myrtle leave are used in animals, and secondary metabolites of them alter rumen fermentation in livestock. Essential oils of myrtle leaf are containing terpinolene, cineole, linalool, terpineol and linalyl acetate. Also there are phenolic acids such as gallic acid, vanillic acid and ferulic acid; tannins such as galotannin and flavonoids such as myrcetin, catechin and quercetin in myrtle oil. Myrtle leave was used traditionally in the treatment of bronchitis, sinusitis, diarrhea and hemorrhoids. The studies showed that myrtle essential oils are used greatly as a food preservative. Also researchers reported that secondary metabolites of medicinal plants have hypoglycemic properties and reduce cholesterol and other blood lipids. There is rare information about using of myrtle leaf in livestock nutrition. Therefore, purpose of this experiment was to evaluate the effect feeding of myrtle leave on the gas production characteristics and fiber digestion and protein in Arabi sheep and effect of myrtle essential oils on gas production parameters. Material and In this trial, 8 Arabi sheep (about 9 months’ age and average weight 23±1.5 kg) were used and fed with diet without myrtle leave and diet containing 0.4 percent myrtle leave in diet 70:30 concentrate to forage for 30 days (4 replicates per treatment). In the end of experiment, fermentation parameters, gas production and in vitro digestibility of wheat straw and soybean meal with rumen fluid of sheep’s fed with experimental diets were measured. Rumen fluid was collected from animals before the morning feeding. About 200 mg sample (1.0 mm screen) incubated in 100 ml vials with 35 mL buffered rumen fluid under continuous CO2 reflux for 2, 4, 6, 8, 10, 12, 16, 24, 48, 72 and 96 h, in a water bath maintained at 39°C. Cumulative gas production data were fitted to the exponential equation Y=B (1−e−ct), where B is the gas production (mL) from the fermentable fraction, C is the rate constant of gas production (mL/h), t is the incubation time (h) and Y is the volume of gas produced at time t. Partitioning factor (PF), microbial biomass and truly digested organic matter was calculated by Makkar and Becker. For determination of partitioning factor at the end of each incubation period, the content of vials was transferred into an Erlenmeyer flask, mixed with 20 mL neutral detergent fiber solution, boiled for 1 hour, filtered, dried (in oven at 60 °C for 48 h) and ashed. In the second trial, the effect of different levels of myrtle essential oils (0, 0.05, 0.1 and 0.15 mL) in diet 30% forage and 70% concentrate on gas production parameters was measured by gas production method. Essential oils of myrtle leaf were taken by clevenger. Digestibility of dry matter and NDF of samples (wheat straw and soybean meal) were determined using tilly and terry method. Rumen fluid was collected from animals, and were mixed with McDougall buffer in a ratio 1:4. After gasifying with CO2, tubes were incubated at 39 ˚C. After 48 h of fermentation, 6 mL of 20% HCl solution and 5 mL pepsin solution were added and the incubated for 48 h, simulating post-ruminal degradation. After incubation, the residual substrates of each tube were filtered and used to determine digestibility of DM and NDF. The obtained data were analyzed in a completely randomized design using the General Linear Model (GLM) procedure of SAS software, version 9.1. The Duncan multiple range test was used to compare means at P< 0.05. Result and The results showed that no significant difference between treatments was observed in gas production potential of wheat straw, but gas production potential of soybean meal with rumen fluid of animals fed with myrtle leave after 96 hours’ incubation (158.13 mL/hour) increased (P<0.05). The gas production rate of wheat straw and soybean meal increased by myrtle leave (P<0.05). Fermentation characteristics (partitioning factor, truly digested organic matter and microbial biomass) of wheat straw were not affected by experimental treatments, but the partitioning factor, truly digested organic matter and microbial biomass of the soybean meal in animals fed with myrtle leave was higher in compared with control treatment (P<0.05). On the base of second experiment, using different levels of myrtle essential oils in diet significantly reduced gas production potential and rate and truly digested organic matter in comparison to the control treatment but PF significantly increased (P<0.05). Other parameters did not affect by levels of myrtle essential oils. It seems the inhibitory effect of essential oils on rumen microbial fermentation and decrease of digestion and gas production because of high content of active matters of essential oil in compared with myrtle leave, but increasing of gas production by inclusion of leave in diet refer nutrient availability of myrtle leave for microorganisms. The researchers reported cineole, alfa-pinen and tannins of myrtle essential oils caused to inhibition of microbial enzymes and decrease fermentation. Tannins can reduce microorganism adhesion to nutrients, inhibit microbial activity which have negative effects on fermentation and methane production. According to the result, it appears that inclusion 0.4 % myrtle leave in diet increased gas production and digestibility of NDF in Arabi sheep. But, myrtle essential oils levels significantly reduced gas production, fermentation and digested organic matter.