Chemical composition, ruminal degradation kinetics, and methane production (in vitro) of winter grass species

BACKGROUND: Information about the nutritive value, dry matter (DM) digestibility, and methane (CH₄) emission potential of grass species is required for their optimal utilization in ruminant rations. The present study was designed: (i) to quantify the nutrient profile, mineral composition and in vitro dry matter digestibility (IVDMD) of winter grass species commonly available in northern Pakistan; and (ii) to measure the in vitro gas production (IVGP) and CH₄ emission of the grass species during 72 h in vitro ruminal fermentation. Seven grass species, namely, Cenchrus ciliaris, Setaria anceps, Panicum antidotale, P. maximum, Pennisetum purpureum, Pennisetum orientale, and Atriplex lentiformis were assessed. RESULTS: A high level of variability (P < 0.001) was observed among grass species for the content of all measured nutrients, IVDMD, IVGP, and CH₄-production. Notably, the content (g kg⁻¹ DM) of crude protein varied from 59.8 to 143.3, neutral detergent fiber from 560.3 to 717.9, IVDMD from 375.1 to 576.2, and 72 h cumulative IVGP from 97.6 to 227.4 mL g⁻¹ organic matter (OM) and CH₄ from 48 to 67 mL g⁻¹ OM. Among the grasses, P. antidotale had greater content (g kg⁻¹ DM) of crude protein (CP) (143.3), IVDMD (576.2), and 72 h cumulative IVGP (227.4 mL g⁻¹ OM), and produced the smallest amount of total CH₄ (48 mL g⁻¹ OM) during 72 h fermentation. In contrast, A. lentiformis had the lowest content (g kg⁻¹ DM) of CP (59.8), IVDMD (375.1), 72 h cumulative IVGP (97.6 mL g⁻¹ OM), and produced a greater amount of total CH₄ (67 mL g⁻¹ OM) during 72 h fermentation. CONCLUSION: The findings of the current study highlight that it is possible to select and further develop grass species with high nutritional value and lower CH₄-production, which can improve livestock productivity, farm profitability, and long-term environment sustainability.