Effect of some medicinal herbs and spices from Enugu and Kaduna States, Nigeria, on in-vitro rumen fermentation and methanogenesis

A study was carried out to determine the effect of medicinal plants from Enugu (En) and Kaduna (Kd) States on in-vitro rumen fermentation and methanogenesis. Twelve medicinal plants comprising herbs and spices were collected from En and Kd States, respectively. The chemical composition and cell wall component (NDF, ADF and hemicellulose) of the plants were determined. The samples were evaluated in an in-vitro study at an inclusion level of 10 mg/ 200 mg substrate. The experiment was laid out in a factorial arrangement and executed as a randomized complete block design with incubation done in batches. At the completion of the 24-hour incubation period, total gas volume (GV), dry matter digestibility (DMD), fermentation efficiency (FE) and CH were determined while organic matter digestibility 4 (OMD), short chain fatty acids (SCFA) and metabolisable energy (ME) were estimated from established equations. The chemical composition indicated range values of 72.82 (Allium sativum, En) - 95.73% (Aloe barbadense, Kd) for DM, 7.01 (Aframomum  elegueta, En) – 30.59% (Allium sativum, En) for CP, 8.94 (Allium sativum, Kd) – 81.41% (Cymbopogon citratus, En) for NDF, 3.58 (Allium sativum, En) – 63.64% (Xylopia aethiopica, En) for ADF, 1.79 (Allium cepa, Kd) - 48.77 % (Aframomum melegueta, En) for hemicellulose, 2.64 (Aframomum melegueta, En) – 22.51% (Ageratum conyzoides, Kd) and 77.49 (Ageratum conyzoides, Kd) – 97.36% (Aframomum melegueta, En) for ash and OM, respectively. The effect of location on chemical composition varied among the plant types with significantly higher (P < 0.05) levels of CP in most of the Kd plants. The range for GV, DMD, CH 4 percentage, CH reduction, FE, OMD, SCFA and ME were 85.00 (Ageratum conyzoides, Kd) 4 - 149.49 mL/g DM (Aloe barbadense, Kd), 525.50 (Sida acuta, Kd) - 764.50 g/Kg DM (Aframomum melegueta, En), 45.75 (Allium sativum, En) - 72.59% (Aframomum melegueta, Kd), 2.36 (Allium cepa, Kd) - 32.86% (Zingiber officinale, Kd), 4.23 (Sida acuta, Kd) - 8.12 (Ageratum conyzoides, Kd), 45.83 (Ageratum conyzoides, Kd) – 57.18% (Cymbopogon citratus, Enugu; Aloe barbadense, Kd), 0.35 (Ageratum conyzoides, Kd) - 0.66 mmol/200 mg DM (Cymbopogon citratus, En) and 5.18 (Ageratum conyzoides, Kd) – 6.93 MJ/Kg DM (Cymbopogon citratus, En; Aloe barbadense, Kd) respectively. Allium sativum bulbs, Zingiber officinale rhizomes, Cymbopogon citratus and Sida acuta (both locations) reduced CH production without adversely affecting the desired fermentation parameters indicating 4 that the medicinal plants have methane reducing potential.