In vitro ruminal fermentation of a diet for lambs by varying origin and dose of oregano essential oil

Abstract

Background: Oregano essential oil (OEO) is a natural alternative to conventional additives. OEO can improve efficiency in ruminant diets, but the magnitude of the impact may vary according to the origin and dose applied. Objective: To analyze the in vitro ruminal fermentation pattern by changing the origin and dose of OEO. Methodology: The treatments had a 2*5+1 factorial arrangement, the factors were the origin: Mexican (MOEO) and European (EOEO), and the dose: at levels of 70, 140, 280, 560, and 1120 ppm of the wet base substrate plus a control without addition of OEO. Contrasts and orthogonal polynomials were used to compare means. The variables quantified were: fast (FRF), medium (FMF) and slow fermentation fractions, as well as their total fermentable fraction (FFT); in vitro degradability of dry matter at 24 h (IVDMD24) and 72 h (IVDMD72); the in vitro degradability of organic matter at 72 h (IVOMD72); lag phase (L); fermentation rate (S); maximum volume (mV); VFA and CH4 production; acetic/propionic ratio (A/P); global warming potential index (GWPI) and environmental impact indicator (EII). Results. MOEO linearly affects FMF FTF, and Vm as the dose increases, while AEOE is a quadratic trend hence, MOEO is different from the control. IVOMD72 tends to decrease as the dose of the two OEOs increases; increasing the inclusion of MOEO decreases A/P linearly; EOEO and MOEO are different from the control in VFA production. There were no effects on environmental impact variables. Implications. The components of MOEO have greater antimicrobial capacity against rumen bacteria than AEOE, MOEO could act similarly to the impact of feed additives such as ionophores in reducing A/P. Conclusion. MOEO can better modulate ruminal fermentation than EOEO but decreases digestion and total gas production more.