Enhancing Holstein steers growth performance: oregano essential oil's impact on rumen development, functionality and microorganism.

Abstract

Background: Dietary supplementation with oregano essential oil (OEO), a natural plant extracts, is an effective and acceptable method to improve growth, beef quantity and quality, but the undergoing mechanism in rumen has not yet been reported in Holstein steers. This study investigated the effects of oregano essential oil (OEO) on growth performance, fermentation parameters, digestive enzymes activity, rumen development and microbiota in Holstein steers. Eighteen steers were randomly divided into two groups (n = 9) and fed either a basal diet (CCK) or the same diet supplemented with 20 g/(d·head) OEO (CEO) for 270 days.

Results: OEO increased the rumen contents of volatile fatty acids (VFA, acetate (P = 0.011), propionate (P = 0.008), butyrate (P = 0.018)) and digestive enzymes activity (cellulase (P = 0.018), protease and β-glucosidase (P < 0.001)), and improved rumen development (papillae width (P = 0.008) and micropapillary density (P = 0.001)), which reasons contribute to increase body weight (BW, P = 0.022), average daily gain (ADG, P = 0.021), carcass weight (P = 0.001), dressing percentage (P < 0.001), and net meat production (P = 0.001) of steers. Meanwhile, metagenomic and metabolomic analysis revealed OEO significantly reduced abundance of rumen microorganisms, especially methanogenic archaea and viruses while beneficial bacteria (Bifidobacterium) and virulence factors were not affected. KEGG analysis revealed that OEO significantly reduces the host risk of disease, improves the digestive system, and reduces the energy basic metabolism level. A correlation analysis indicated fourteen kinds key microbiome and six downregulated metabolites interfere with each other and together influence the growth performance of steers.

Conclusion: These results suggest that feed with 20 g/(d·head) OEO in steers diets could improve growth performance, and reduces virus abundance and disease risk. And the findings provide fundamental insights into OEO, as an alternative source of natural bioactive compounds, how effect on rumen development, composition and function of microorganisms.