Preliminary in vitro screening of some spices and medicinal plants from Edo and Rivers States, Nigeria for reducing enteric methane production in ruminants

Abstract

Methane gas produced by ruminants during feed fermentation contributed to global warming as well as poor efficiency of food utilization. Mitigating ruminal methane production through anti-microbial feed additive has serious health implications. A preliminary study of the potential of medicinal plants and spices from Edo and Rivers State, as possible replacement to antibiotic feed additives was carried out. Medicinal plants and spices were purposefully sampled, dried at 40^oC, milled and 10 mg was added with 190 mg of substrate in a preweighed nylon incubation bags. Bags and their contents were incubated using 30 mL of buffered rumen liquor in 100 mL syringes following the standard procedure of in vitro fermentation. Variables monitored were 24h total gas volume, short chain fatty acids (SCFA) methane (CH₄ ) gas, dry matter degradability (DMD) as well as some chemical, cell wall and anti-nutritive components. Results revealed that adding the medicinal plants and spices as feed additives did not depress gas production in most cases (19.5 – 29.50 mL, 17.75 – 30.00 mL and 12.00 – 29.00 mL for Edo medicinal plants, Edo spices and Rivers medicinal plants respectively) and also did not depress DMD (> 50%). Azadirachta indica stem reduced CH₄ production mostly by 53.56% while Dennttia tripetala did by 47.69% among the Edo medicinal plants and spices, respectively. In Rivers State, Amaranthus spinosus gave the highest value of 60.33% CH₄ reduction. In the same bracket of similar and good CH₄ reduction potentials were Alstonia boonei leaves (49.06%), Newbouldia laevis root (41.50%), Euphorbia heterophyla (37.97%), Allium crispum (47.31%), Allium cepa (46.80%), Aframomum mueguata (46.54%), Capsicum annum (47.32%), Ageratum conyzoides (56.52%), Lagenaria breviflora (48.03%) and Centrosema molle (45.08%). All the medicinal plant and spices with potential for CH₄ reduction had corresponding high SCFA values (0.46 – 0.65 Mmol) with tannin (%) and saponin (%) contents of 0.011 – 17.50 and 0.01 – 2.40 respectively. Conclusively, the medicinal plants and spices demonstrated good potentials for reducing rumen methane production in vitro and may be subjected to further in vivo studies.