Epsilon Archive for Student Projects

Abstract

As the global food demand continues to rise and projected to reach 9.7 billion by 2050. The adoption of sustainable livestock practices becomes vital, particularly in regions like the Nordic countries that are heavily dependent on dairy production. Ruminants play a crucial role in converting fibrous plant material into high-quality protein, but they also contribute significantly to methane (CH₄) emissions, a potent greenhouse gas and an energy loss source in cattle.
This research explored the impact of varying forage-to-concentrate (F:C) ratios by using in vitro methodology to estimate total gas and CH₄ production from diets containing grass silage as the forage source and a concentrate mixture of barley and rapeseed meal. The experiment involved two incubation runs with five dietary treatments (100:0, 80:20, 60:40, 40:60 and 20:80) and four replicates per treatment. Rumen fluid was collected from two cannulated dairy cows and incubated with feed samples in anaerobic serum bottles. The samples were incubated at 39°C, with automatic gas production measurements taken every 12 minutes. Methane concentration was analyzed at 2, 4, 8, 24, and 48 hours using gas chromatography. The pH and volatile fatty acids (VFA) were measured at the end of the incubation from each replicate. To determine total dry matter digestibility (TDMD) and total organic matter digestibility (TOMD), samples were randomly selected. Data were analyzed using a MIXED procedure of SAS® 9.4, with treatment and run as fixed effects and bottle as a random effect. The results indicated that increasing concentrate levels led to a significant linear rise in total gas (P < 0.001), and CH₄ production (P < 0.001), along with a tendency for a decrease in pH (P = 0.09). Acetic acid concentrations decreased linearly (P < 0.001), while butyric acid increased (P = 0.002), indicating a shift in fermentation patterns. Although total VFA concentrations and propionate proportion remained stable. TDMD and TOMD peaked at intermediate F:C levels (60F and 40F), suggesting optimal nutrient utilization at these ratios. In addition, the observed increase in CH4 production at higher concentrate levels may be partially attributed to the nature of the in vitro system itself. Unlike the rumen environment in vivo, where there is continuous absorption of end products and passage of feed particles, the in vitro batch fermentation setup functions as a closed system.
These findings suggest that diet composition significantly influences fermentation dynamics and CH₄ output, underscoring the potential for manipulating F:C ratios to enhance feed efficiency and reducing CH₄ emissions in ruminant systems. However, the limitations of in vitro models, including the lack of absorption and microbial adaptation, require cautious extrapolation to in vivo scenarios.