A COMPREHENSIVE REVIEW ON GINGER (Zingiber officinale Roscoe) UTILISATION IN RUMINANT NUTRITION: PHYTOCHEMISTRY, RUMEN FERMENTATION, ANIMAL PERFORMANCE AND METHANE MITIGATION

Ginger (Zingiber officinale Roscoe) is an important supplement for incorporation into ruminant feed formulations. The rhizome contains bioactive phenolic compounds such as gingerols, shogaols, paradols and zingerone, which have antimicrobial, antioxidant, anti-inflammatory and potentially antiprotozoal properties that may modulate ruminal microbial ecology and fermentation dynamics. The present review carefully evaluates the existing evidences concerning ginger supplementation in ruminant diet, focusing on rumen fermentation characteristics, nutrient digestibility, microbial protein synthesis, methane production and general animal performance. Recent in vivo reports demonstrate that dietary ginger powder increases growth performance, feed conversion efficiency, nutrient digestibility, antioxidant status and selected rumen fermentation variables in sheep. In addition, ginger straw has been shown to partially replace conventional roughage in goat diets, resulting to higher dry matter intake, higher microbial protein synthesis, elevated butyrate concentrations, increased fibre digestibility and relatively positive growth responses. However, in vitro experiments using ginger essential oil (GEO) have inconsistent findings, with some reports indicating reduced total gas production, diminished organic matter digestibility and low volatile fatty acid concentrations, although methane output may decrease. These inconsistent findings indicated that ginger effects are influenced by product formulation, phytochemical profile, inclusion levels, basal diet composition, animal species, adaptation and experimental protocols. Ginger may influence ruminal fermentation through selective inhibition of specific microbial populations, alteration of hydrogen metabolism, protozoal modulation and changes in nitrogen utilisation pathways. While the anti-methanogenic potential of ginger is encouraging, current evidences remain predominantly from in vitro trials and it is insufficient to support definitive recommendations for methane mitigation under practical production conditions. Ginger should therefore be considered as a dose dependent phytogenic rumen modulator rather than conventional nutrient source. Future investigations should prioritise product standardisation, dose response characterisation, rumen microbiome analysis, long term in vivo trials and direct methane quantification.