A study in the Journal of Dairy Science by J. Vattulainen, A. R. Bayat, and a team from the Natural Resources Institute Finland evaluated two feed additives—calcium peroxide (CaPe) and a combination of biocharBiochar is a carbon-rich material created from biomass decomposition in low-oxygen conditions. It has important applications in environmental remediation, soil improvement, agriculture, carbon sequestration, energy storage, and sustainable materials, promoting efficiency and reducing waste in various contexts while addressing climate change challenges. More with fibrolytic enzymes and live yeast (BFE)—for their potential to mitigate enteric methane (CH4​) emissions in Nordic Red dairy cows. Reducing CH4​ emissions from livestock is a key goal for strengthening the sustainability of the agricultural sector. Four multiparous cows were used in a 4×4 Latin square experiment across four 28-day periods, including a control diet (CON) and three experimental diets: BFE (CON with 0.2% BFE), CaPe1 (CON with 0.75% Ca O2​), and CaPe2 (CON with 1.5% Ca O2​). The BFE was added to the total mixed ration (TMR), while the Ca O2​ was included in the concentrate pellet. The study hypothesized that Ca O2​ would linearly reduce CH4​ production and that BFE would reduce CH4​ or positively affect milk production by improving nutrient digestibility.

The addition of CaPe resulted in a dose-dependent linear reduction in feed intake, milk yield, and nutrient digestibility. The dry matter intake (DMI) and organic matter intake (OMI) decreased linearly by 16.6% and 18.6%, respectively, compared with the CON diet. This reduced intake was accompanied by linear decreases in the yields of milk, energy-corrected milk (ECM), fat, protein, lactose, and total solids. Apparent total-tract digestibilities of nutrients like DM, OM, crude protein (CP), ether extract (EE), neutral detergent fiber (NDF), and gross energy (GE) also decreased linearly with increasing CaPe concentration. Critically, the conversion of feed into milk, expressed as ECM yield divided by DMI or OMI, remained similar to the CON group. This confirms that the observed drop in milk production was directly proportional to the decrease in feed intake, indicating no improvement in feed efficiency.

Dietary CaPe inclusion linearly decreased daily CH4​ production (g/d) by 15.0%. However, CH4​ yield (g/kg DM or OM intake) and CH4​ intensity (g/kg milk or ECM) were not affected by the CaPe treatments. This outcome indicates that the reduction in daily CH4​ was a reflection of the reduced feed intake, not a true CH4​-mitigating effect per unit of feed or product. The study also noted that hydrogen production ( g/d) decreased at the CaPe1 level but plateaued at CaPe2, showing a significant quadratic effect. This decrease in hydrogen production suggests CaPe alters hydrogen pathways in the rumen differently from other CH4​ inhibitors. The CH4​ reduction observed in this trial contrasts with a previous study in beef cattle, which reported a 20% to 27% reduction in CH4​ yield, primarily because feed intake was not negatively affected in that experiment. The lack of efficacy for CH4​ mitigation confirms that under the conditions of this experiment, CaPe was not an effective additive.

Feeding the BFE additive had a minor or non-significant effect on all parameters evaluated in the experiment. It did not affect feed intake, milk yield, CH4​ emissions, or gut microbiota composition. The lack of effect, possibly due to the high-quality basal diet used, suggests that conditions were not suitable for BFE to improve diet digestion. Regarding rumen fermentation, CaPe addition tended to decrease the molar proportion of acetate and increased that of propionate and butyrate, resulting in a significant quadratic effect in the lipogenic to glucogenic volatile fatty acid (VFA) ratios. The addition of CaPe significantly influenced the rumen bacterial and ciliate protozoa communities but had no such effect on archaea (methanogens) or anaerobic fungi. Notably, CaPe linearly increased the relative abundance of Entodinium sp. (a ciliate protozoa genus) and several bacterial groups (e.g., Bacteroidales BS11, Prevotellaceae sp.) while decreasing others (e.g., Gastranaerophilales, Butyrivibrio). This microbial shift, particularly the increase in Entodinium (which can tolerate oxygen) , suggests the microbes were responding to the oxidative stress induced by CaPe.

The primary issue identified with CaPe was reduced palatability leading to marginal sorting against the concentrate pellets, which resulted in reduced intake. It is hypothesized that the continuous supply of CaPe in the TMR elevated the rumen’s oxidation-reduction potential (ORP), negatively affecting appetite. The study suggests future research with dairy cows should test feeding CaPe pellets separately from silage and allowing a break of several hours between offerings to overcome palatability issues and prevent continuous oxidative stress in the rumen.

Source: Vattulainen, J., Bayat, A. R., Stefański, T., Rinne, M., & Tapio, I. (2025). Effects of calcium peroxide or biochar-enzyme feed additives on milk production, enteric methane emissions, and ruminal microbiota in Nordic Red dairy cows. Journal of Dairy Science, TBC.