A low nitrogen utilization efficiency (NUE, the ratio of retained N to N intake) and high methane (CH₄) emissions of ruminants can lead to potentially high diet protein wastage and directly contribute to global warming. Diet manipulation is the most effective way to improve NUE or reduce CH₄ emissions. This study investigated how replacing oat hay with alfalfa hay (AH) or common vetch hay (CVH) with different proportions (20% (20) and 40% (40) of the total dry matter (DM) allowance) affects the body weight gain (BWG), NUE, and CH₄ emissions of crossbred Simmental cattle. The forage dry matter intake (DMI) and the total DMI of cattle fed on a CVH40 diet were significantly higher than the values for those fed on AH20 or AH40 diets (p < 0.05). There were no differences in the BWG for the four treatments observed, however, nutrient digestibility significantly decreased in the AH40 diet as compared with the AH20 diet (p < 0.05). The NUE was significantly lower in AH40 than in CVH20. The CH₄ emissions were significantly lower for the CVH40 diet than with the AH20 diet (p < 0.05). Our findings suggest that a 20% AH and 40% CVH substitution for oat hay are the optimal proportions to maintain the BWG, NUE, nutrient digestibility, and reduce the CH₄ emissions of crossbred Simmental cattle. Overall, CVH has a greater potential to reduce CH₄ emissions than AH.

Mowing, Mowing, which affects the nutritional levels of grasslands, is the main utilization of sown pasture. We sowed alfalfa monoculture grassland, tall fescue monoculture grassland and tall fescue + alfalfa mixed grassland in typical steppe of the Loess Plateau to investigate the nutrient compositions and in vitro degradability of those three grasslands under different mowing stubble times and to provide reference for nutrient management of sown pastures. The results showed that the stubble time significantly affected (p < 0.05) the nutrient compositions and mineral elements of forages in alfalfa monoculture grassland, whereas had no effects on the nutrient compositions and dry matter digestibility of forages in tall fescue monoculture grassland and alfalfa + tall fescue mixed grassland. The relative feeding value of mixed grassland of alfalfa and tall fescue was increased by 2.6–22.4% as compared to monoculture grasslands. The model constructed based on forage nutrient content could accurately predict the forage dry matter degradability of alfalfa monoculture, tall fescue monoculture and mixed alfalfa and tall fescue, respectively.

Lycium barbarum is a potential high-quality woody forage whose crude protein concentration is up to 30% and it is rich in numerous secondary metabolites. This study aimed to investigate the effects of L. barbarum included in alfalfa-tall fescue mixture on in vitro dry matter digestibility (IVDMD), total gas production (TGP), fermentation characteristics, productions of carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O), and global warming potential (GWP). Three cultivars of L. barbarum, ‘Ningqicai (NQC) No.1’, ‘Ningqi (NQ) No.9’, ‘Qixin (QX) No.2’, were included at 4%, 8%, and 12% levels of substrate with 7 replicates. After 72 h of incubation, the highest IVDMD of 3 cultivars were observed at 4% compared to the control. Although TGP and GWP of 3 cultivars at 4% were similar to the control (P > 0.05), they increased quadratically (P < 0.05) with increasing substitution levels for ‘NQC No.1’ and reduced quadratically (P < 0.05) for ‘NQ No.9’, corresponding with the productions of CO2 and CH4, and ammonia nitrogen (AN) and violate fatty acids (VFA). The productions of CO2 and CH4, acetate to propionate ratio, and GWP of ‘QX No.2’ were significantly lower than the control at 12% level (P < 0.05). L. barbarum inclusion accelerated N2O production for all treatments (P < 0.05). Overall, 4%, 8% and 12% were recommended for ‘NQC No.1’, ‘NQ No.9’ and ‘QX No.2’, respectively, which increased IVDMD and fermentation characteristics, and reduced CO2, CH4 and N2O productions. These findings suggest that L. barbarum can be a kind of new potential woody forage for ruminant production with high degradability and low GWP at optimal inclusion levels.