Effects of Citrus sinensis Pulp Essential Oil on In Vitro Digestibility Parameters and Methane Production in Small Ruminant

For a better use of Citrus sinensis essential as phytobiotics in small ruminants, an experiment was conducted in the Research Unit of Production and Animal Nutrition (RUPROAN) of the University of Dschang between June 2023 and February 2024. Four (4) rations were formulated using Trypsacum laxum hay (FTl+HECs0) to which 100, 200 or 300 mg/ Kg DM of Citrus sinensis essential oil was added. A non-pregnant adult Djallonke sheep and a Guinea dwarf goat aged of 18 months and 2 years respectively were used as ruminal fluid donors. Results of this study shows that, regardless of the ruminal fluid used, gas production (GP), volatile fatty acid (VFA), metabolizable energy (ME), in vitro dry matter digestibility (IVDDM) and in vitro organic matter digestibility (IVDOM) significantly (p<0. 05) decreased with the addition of 100, 200 or 300mg/Kg DM of essential oil compared to the control ration, with the lowest level at 300mg/Kg DM. A contrary trend was observed with microbial weight (MW) and residual nitrogen (NDF-N), whose values increased following the addition of the essential oil. Furthermore, pH, methane percentage and protozoa population values were different (p<0.05) between the two species apart from methane percentage for the T0 ration; pH and protozoa population for the T1 ration which were comparable (p>0.05). The highest pH and protozoa population values (6.98±0.07and 5.17±0.00 respectively) were obtained with goat ruminal fluid, in contrast to methane percentage, whose highest value (35.88±0.83) was obtained with sheep ruminal fluid. The lowest values for pH, methane percentage and protozoa population (6.77±0.00; 16.11±0.19 and 3.35±0.13 respectively) were obtained with ovine ruminal fluid. Overall, incorporation of Citrus sinensis essential oil reduced protozoa population and methane production, and increased residual nitrogen despite adverse effects observed on volatile fatty acids which proportions turned to decrease with essential oil addition.

Keywords: Digestibility, Essential Oil, Methane, Protozoa, Hay.