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. 2019 May 20;14(5):e0217054.
doi: 10.1371/journal.pone.0217054. eCollection 2019.

Effects of oregano essential oil on the ruminal pH and microbial population of sheep

Rui Zhou  1 , Jianping Wu  1 , Liping Zhang  1 , Lishan Liu  2 , David P Casper  3 , Ting Jiao  4 , Ting Liu  1 , Jianfu Wang  1 , Xia Lang  2 , Shuzhen Song  2 , Xuyin Gong  2
Affiliations

Effects of oregano essential oil on the ruminal pH and microbial population of sheep

Rui Zhou et al. PLoS One. .

Abstract

Oregano essential oil (OEO), which has antimicrobial properties, may be used for altering the ruminal pH and microbial populations of sheep, as observed by the altered volatile fatty acid patterns. To further elucidate the effects of OEO on ruminal pH and microbial populations of sheep, 3 German merino sheep × local sheep crossbred rams with permanent ruminal fistulas were randomly assigned to a 3 × 3 Latin square design with 12-d periods. The treatments were as follows: control (CON); OEO4: OEO supplied at 4 g•d-1; and OEO7: OEO supplied at 7 g•d-1. Starting on day 11, rumen fluid was collected at 0 h, and at 4, 8, 12, 24 and 48 h after supplying OEO, and then pH values of rumen fluid were immediately measured. The abundance of microbial populations was determined by using qPCR. The ruminal pH values were similar among the sheep from all treatments. The abundance of ruminal fungi was higher for the sheep supplied OEO7 compared with the sheep supplied CON and OEO4, especially at 4 and 12 h. The abundance of ruminal protozoa decreased with supplied OEO, indicating that OEO could inhibit the protozoa. The abundance of the total ruminal bacteria was similar for the sheep from all treatments, but R. flavefaciens, R. albus and F. succinogenes increased in the sheep supplied OEO4 compared with those in the sheep supplied CON, however, the sheep supplied OEO7 had higher abundances of R. flavefaciens than the sheep supplied CON. These results demonstrated that supplying OEO to sheep did not affect the ruminal pH but could shift the rumen microbial population to one with less protozoa. Supplying OEO can preferentially enhance the growth of certain rumen microbial populations, but the shifts were influenced by the supply rate. Therefore, supplying low amount (i.e. 4 g•d-1) of OEO could have positive effects on ruminal microbial populations, whereas supplying elevated doses of OEO could be detrimental to those same ruminal microbial populations.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Ruminal pH for sheep fed oregano essential oil (OEO) at 0 (CON), 4 (OEO4), or 7 (OEO7) g•d-1.
a, b, c Means within the same collection time with unlike superscripts differ, (P < 0.05).
Fig 2
Fig 2. Abundance of ruminal Fungi for sheep fed oregano essential oil (OEO) at 0 (CON), 4 (OEO4), or 7 (OEO7) g•d-1.
a, b, c Means within the same collection time with unlike superscripts differ, (P < 0.05).
Fig 3
Fig 3. Abundance of ruminal Protozoa for sheep fed oregano essential oil (OEO) at 0 (CON), 4 (OEO4), or 7 (OEO7) g•d-1.
a, b, c Means within the same collection time with unlike superscripts differ, (P < 0.05).
Fig 4
Fig 4. Abundance of ruminal Bacteria for sheep fed oregano essential oil (OEO) at 0 (CON), 4 (OEO4), or 7 (OEO7) g•d-1.
a, b, c Means within the same collection time with unlike superscripts differ, (P < 0.05).
Fig 5
Fig 5. Abundance of ruminal R. flavefaciens for sheep fed oregano essential oil (OEO) at 0 (CON), 4 (OEO4), or 7 (OEO7) g•d-1.
a, b, c Means within the same collection time with unlike superscripts differ, (P < 0.05).
Fig 6
Fig 6. Abundance of ruminal R. albus for sheep fed oregano essential oil (OEO) at 0 (CON), 4 (OEO4), or 7 (OEO7) g•d-1.
a, b, c Means within the same collection time with unlike superscripts differ, (P < 0.05).
Fig 7
Fig 7. Abundance of ruminal F. succinogenes for sheep fed oregano essential oil (OEO) at 0 (CON), 4 (OEO4), or 7 (OEO7) g•d-1.
a, b, c Means within the same collection time with unlike superscripts differ, (P < 0.05).
See this image and copyright information in PMC

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