Effects of Essential Oil Blends on In Vitro Apparent and Truly Degradable Dry Matter, Efficiency of Microbial Production, Total Short-Chain Fatty Acids and Greenhouse Gas Emissions of Two Dairy Cow Diets

Abstract

The current study evaluated nine essential oil blends (EOBs) for their effects on ruminal in vitro dry matter digestibility (IVDMD), efficiency of microbial production, total short-chain fatty acid concentration (SCFA), total gas, and greenhouse gas (GHG) emissions using two dietary substrates (high forage and high concentrate). The study was arranged as a 2 × 2 × 9 + 1 factorial design to evaluate the effects of the nine EOBs on the two dietary substrates at two time points (6 and 24 h). The inclusion levels of the EOBs were 0 µL (control) and 100 µL with three laboratory replicates. Substrate × EOBs × time interactions were not significant (p > 0.05) for total gas and greenhouse gas emissions. The inclusion of EOBs in the diets resulted in a reduction (p < 0.001) in GHG emissions, except for EOB1 and EOB8 in the high concentrate diet at 6 h and for EOB8 in the high forage diet at 24 h of incubation. Diet type had no effect on apparent IVDMD (IVADMD) whereas the inclusion of EOBs reduced (p < 0.05) IVADMD with higher values noted for the control treatment. The efficiency of microbial production was greater (p < 0.001) for EOB treatments except for EOB1 inclusion in the high forage diet. The inclusion of EOBs affected (p < 0.001) the total and molar proportion of volatile fatty acid concentrations. Overall, the inclusion of the EOBs modified the rumen function resulting in improved efficiency of microbial production. Both the apparent and truly degraded DM was reduced in the EOB treatments. The inclusion of EOBs also resulted in reduced GHG emissions in both diets, except for EOB8 in the high forage diet which was slightly higher than the control treatment.

Pleurotus ostreatus Can Significantly Improve the Nutritive Value of Lignocellulosic Crop Residues

“…A significant (p < 0.001) decrease in partitioning factor (PF) in the treated samples after 48 h of in vitro batch culture fermentation could be a result of its higher gas production (187 mL) compared with the lowest gas volume (3.56 mL) noted for untreated samples at 6 h. Lower PF in the current study due to higher gas production is expected as total gas volume is one of the variables used in calculating PF. This is in contrast with [59,70] who reported higher values for both PF and microbial mass. The use of essential oil blends in [59] which is known to depress gas production could be responsible for the higher PF values.…”

“…This is in contrast with [59,70] who reported higher values for both PF and microbial mass. The use of essential oil blends in [59] which is known to depress gas production could be responsible for the higher PF values. In [18], the authors reported that a decrease in gas production for P. ostreatus treated corn stover could be related to the proportion of lignin in the original substrate.…”

“…The decrease could have resulted from biologically active phenolic compounds from P. ostreatus (e.g., lovastatin) which are known to have strong depressing effects on lipids [57,58]. This could likely favor DM digestibility and microbial growth which are negatively affected by EE [59,60]. The decrease in EE for treated samples is consistent with [51] but [50] reported an increase in EE when rice straw was treated with P. ostreatus.…”

Effects of the Incubation Period of Pleurotus ostreatus on the Chemical Composition and Nutrient Availability of Solid-State-Fermented Corn Stover

“…Additionally, the lower EE content noted in the corn stover fermented for 2 wk tends to favor the activities of rumen microbes [ 41 , 42 ] as a higher EE concentration is known to have negative effect on the digestibility of DM. Thus, the 2 wk treated corn stover demonstrated a better nutrient profile in terms of DM, CP, ash and EE.…”

Global Warming and Dairy Cattle: How to Control and Reduce Methane Emission

“…Manh et al show that eucalyptus leaf meal addition at 100 g/d for grazing animals could be an alternative feed booster: it reduces the development of rumen methane gas in cattle while preserving mineral digestion [ 117 ]. Oregano and white thyme essential oils can modulate ruminal fermentation and decrease rumen methanogenesis without affecting feed digestibility, showing promise as alternatives to ionophores for methane reduction in beef cattle [ 119 , 135 ]. Moreover, it was studied that cinnamon and cloves have a phenolic monoterpene that demonstrated antimicrobial activity against both Gram-positive and Gram-negative [ 136 ].…”