This study aimed to investigate the effects of different forage ratios of orchardgrass (Dactylis glomerata) and alfalfa (Medicago sativa) on in vitro rumen degradation and fermentation characteristics. Orchardgrass and alfalfa were harvested separately and prepared as hay and silage mixtures at ratios of 100:0, 75:25, 50:50, 25:75, and 0:100 (w/w on a dry matter basis) and anaerobically incubated for 48 h with rumen fluid obtained from lactating dairy cows. Fermented residues and cultured fluids were used to determine nutrient degradability, fermentation parameters, and associative effect indices. Increasing the proportion of alfalfa in hay and silage mixtures quadratically increased in vitro organic matter disappearance (IVOMD, up +5.14%) and marginally decreased in vitro neutral detergent fiber disappearance (NDFD, down −1.79%). Meanwhile, increasing the proportion of alfalfa accelerated the rumen fermentation process (e.g., gas production) and remarkably enhanced the growth of rumen microbes as indicated by microbial protein production (MCP, 13.4% increase). Increments of rumen degradability and methane production were more pronounced in silage mixtures than hay mixtures. In combination, a forage ratio of 50:50 for orchardgrass and alfalfa is recommended for both hay and silage in order to improve the feed use potential in ruminants.

Intercropping is a globally accepted method of forage production and its effect on silage quality depends not only on forage combination but also fertilization strategy. In the present study, field intercropping of orchardgrass (Dactylis glomerata) and alfalfa (Medicago sativa) at five seed ratios (100:0, 75:25: 50:50, 25:75, 0:100 in %, based on seed weight) was applied under three N fertilizing levels (0, 50, and 100 kg/ha), and harvested for silage making and in vitro rumen degradation. As a result of intercropping, the actual proportions (based on dry matter) of alfalfa in mixtures were much closer to seed proportion of alfalfa in field, except 75:25 orchardgrass-alfalfa intercrops with no fertilization. The actual proportions of alfalfa in mixtures decreased by 3–13% with the increase of N level. Increases of alfalfa proportion in mixtures increased silage quality, nutrients degradability and CH₄ emissions. Increasing N levels increased silage pH, concentration of butyric acid, and fiber fractions. In summary, inclusion of alfalfa at around 50% in orchardgrass-alfalfa silage mixtures were selected for favorable ensiling and higher forage use efficiency while also limiting CH₄ emissions, compared to monocultures. The silage quality and feeding values of mixtures were influenced more by forage ratios than by N levels.

The aim of this study was to investigate whether guanidine acetic acid (GAA) yields a response in rapid-growing lambs depending on forage type. In this study, seventy-two small-tailed Han lambs (initial body weights = 12 ± 1.6 kg) were used in a 120-d feeding experiment after a 7-d adaptation period. A 2 × 3 factorial experimental feeding design was applied to the lambs, which were fed a total mixed ration with two forage types (OH: oaten hay; OHWS: oaten hay plus wheat silage) and three forms of additional GAA (GAA: 0 g/kg; UGAA: Uncoated GAA, 1 g/kg; CGAA: Coated GAA, 1 g/kg). The OH diet had a greater dry matter intake, average daily gain, and hot carcass weight than the OHWS diet. The GAA supplementation increased the final body weight, hot carcass weight, dressing percentage, and ribeye area in the longissimus lumborum. Meanwhile, it decreased backfat thickness and serum triglycerides. Dietary GAA decreased the acidity of the meat and elevated the water-holding capacity in mutton. In addition, the crude protein content in mutton increased with GAA addition. Dietary GAA (UGAA or CGAA) might be an effective additive in lamb fed by different forage types, as it has potential to improve growth performance and meat quality.

A class of aliphatic short chain nitrocompounds have been reported as being capable of CH₄ reduction both in vitro and in vivo. However, the laboratory evidence associated with the metabolic fate of nitrocompounds in the rumen has not been well documented. The present study was conducted to compare in vitro degradation and metabolism of nitroethane (NE), 2-nitroethanol (NEOH), and 2-nitro-1-propanol (NPOH) incubated with mixed rumen microorganisms of dairy cows. After 10 mM supplementation of nitrocompounds, a serious of batch cultures were carried out for 120 h under the presence of two substrates differing in the ratio of maize meal to alfalfa hay (HF, 1:4; LF, 4:1). Compared to the control, methane production was reduced by 59% in NPOH and by >97% in both NE and NEOH, and such antimethanogenic effects were more pronounced in the LF than the HF group. Although NE, NEOH, and NPOH addition did not alter total VFA production, the rumen fermentation pattern shifted toward increasing propionate and butyrate and decreasing acetate production. The kinetic disappearance of each nitrocompound was well fitted to the one-compartment model, and the disappearance rate (k, %/h) of NE was 2.6 to 5.2 times greater than those of NEOH and NPOH. Higher intermediates of nitrite occurred in NEOH in comparison with NPOH and NE while ammonia N production was lowest in NEOH. Consequently, a stepwise accumulation of bacterial crude protein (BCP) in response to the nitrocompound addition was observed in both the HF and LF group. In brief, both NE and NEOH in comparison with NPOH presented greater antimethanogenic activity via the shift of rumen fermentation. In addition, the present study provided the first direct evidence that rumen microbes were able to cleave these nitrocompounds into nitrite, and the subsequent metabolism of nitrite into ammonia N may enhance the growth of rumen microbes or promote microbial activities.

This study was conducted to determine the dietary supplemental effects of nitroethanol (NEOH) in comparison with monensin on growth performance and estimated methane (CH₄) production in feedlotting lambs. Sixty male, small-tailed Chinese Han lambs were arranged at random into three dietary treatment groups: (1) a basal control diet (CTR), (2) the basal diet added with 40 mg/kg monensin (MON), (3) the basal diet added with 277 mg/kg nitroethanol (NEOH). During the 32-day lamb feeding, monensin and nitroethanol were added in period 1 (day 0–16) and then withdrawn in the subsequent period 2 (day 17–32) to determine their withdrawal effects. The average daily gain (ADG) and feed conversion rate in the whole period ranked: NEOH > MON > CTR (p < 0.01), suggesting that the dietary addition of NEOH in comparison with monensin presented a more lasting beneficial effect on feed efficiency. Methane emission was estimated with rumen VFA production and gross energy intake. Both monensin and NEOH addition in comparison with the control remarkably decreased CH₄ emission estimate (24.0% vs. 26.4% decrease; p < 0.01) as well as CH₄ emission per kg ADG (8.7% vs. 14.0% decrease; p < 0.01), but the NEOH group presented obvious lasting methanogenesis inhibition when they were withdrawn in period 2. Moreover, the in vitro methanogenic activity of rumen fluids was also decreased with monensin or NEOH addition (12.7% vs. 30.5% decrease; p < 0.01). In summary, the dietary addition of NEOH in comparison with monensin presented a greater promoting effect on growth performance in feedlotting lambs by inhibiting rumen methanogenesis more efficiently and persistently.

Nitroethane (NE), 2-nitroethanol (NEOH), and 2-nitro-1-propanol (NPOH) were comparatively examined to determine their inhibitory actions on rumen fermentation and methanogenesis in vitro. Fermentation characteristics, CH₄ and total gas production, and coenzyme contents were determined at 6, 12, 24, 48, and 72 h incubation time, and the populations of ruminal microbiota were analyzed by real-time PCR at 72 h incubation time. The addition of NE, NEOH, and NPOH slowed down in vitro rumen fermentation and reduced the proportion of molar CH₄ by 96.7%, 96.7%, and 41.7%, respectively (p < 0.01). The content of coenzymes F₄₂₀ and F₄₃₀ and the relative expression of the mcrA gene declined with the supplementation of NE, NEOH, and NPOH in comparison with the control (p < 0.01). The addition of NE, NEOH, and NPOH decreased total volatile fatty acids (VFAs) and acetate (p < 0.05), but had no effect on propionate concentration (p > 0.05). Real-time PCR results showed that the relative abundance of total methanogens, Methanobacteriales, Methanococcales, and Fibrobacter succinogenes were reduced by NE, NEOH, and NPOH (p < 0.05). In addition, the nitro-degradation rates in culture fluids were ranked as NEOH (−0.088) > NE (−0.069) > NPOH (−0.054). In brief, the results firstly provided evidence that NE, NEOH, and NPOH were able to decrease methanogen abundance and dramatically decrease mcrA gene expression and coenzyme F₄₂₀ and F₄₃₀ contents with different magnitudes to reduce ruminal CH₄ production.