Addition of activated carbon in a cattle diet to mitigate GHG emissions and ameliorate ingested toxins

Addition of activated carbon in a cattle diet to mitigate GHG emissions and ameliorate ingested toxins

Emissions from dairy and beef productions represent around 40% of methane emissions worldwide. In this study both in-vitro and in-vivo approaches are used to study the effect of Powdered Activated Carbon (PAC) on reducing Greenhouse gas (GHG) emissions from dairy cattle. Since ancient times various forms of carbon have been used as a remedy for ingestion of toxins and digestive ailments in animals and humans. We chose to study surface area effects as a focus, with commercially available quality assured products readily available i.e. PAC. Just prior to in-vivo PAC addition trials the dairy herd suffered from an incident with Lantana poisoning of 50 heifers on agistment, as a result additional work on the amelioration of toxins was included in this study.

The first in-vitro study (Chapter 3) added three concentrations of PAC (0%, 0.5% and 2%) to a dairy cattle pellet diet and two types of rumen liquid (grain and grassfed) were used in this study. The reduction of methane (CH4) emissions were from 61% to 69% for all of the PAC concentrations in both grain and grass-fed cattle. The reduction of GHG emissions from grain and grass-fed dairy cattle was between 25% and 20% for 2% and 0.5% of PAC respectively. Production precursors of volatile fatty acids (VFAs), of acetic, butyric and propionic acids were slightly positive, influenced by adding PAC concentrations to both feeds.

The second in-vitro study (Chapter 4) investigated the inclusion of powdered activated carbon (PAC) at (0.5% and 2%) dry matter (DM) on GHG emissions and key rumen health pre-cursors for a dairy cattle forage diet. Four types of forage diet were used. The 2% PAC concentration reported the highest GHG reduction (30 - 42%) and CH4 emissions reductions were (54% - 69%), slightly outperforming the 0.5% PAC concentration. While emissions were substantially abated, production was not greatly affected, with concentrations of volatile fatty acids (acetate, propionate and butyrate) not differing significantly (P<0.001) when it was added to forage sorghum silage diets.

The third in-vitro study (Chapter 5) tested the effect of PAC on decreasing Lantana toxins in the diet of dairy cattle, reducing GHG emissions and improving rumen fermentation. Initially four concentrations of PAC (0, 0.1, 0.4 and 1g) were added to a Lantana extract i.e. berry, leaf or flower, to determine their base Lantadene adsorption rates for a nominally lethal Lantana dose (1% weight by weight (w/w) of diet). PAC addition achieved Lantadene reductions of (0.5 to 0.58 mM/g) with a combined Lantadene A and B concentration of 2.19mM/g. Three PAC concentrations (0%, 0.5% and 2 %) DM were then added to a dairy cattle diet, with and without Lantana extract (leaf) to evaluate the effects on greenhouse gas emissions and rumen fermentation, with VFAs measured as productivity indicators. GHG and CH4 emission reductions were between (36% - 37%) and (40% - 47%) respectively for all PAC concentrations compared to control. In summary, a 0.5% PAC modified dairy cattle diet appears sufficient to ameliorate a typical lethal Lantana dose (1% W/W), with production levels unchanged (P<0.05). PAC‘s high surface area appears to be responsible for reducing Methanogenic flora species, resulting in GHG and CH4 reductions of 36 - 37% and 40 - 47% respectively.

The fourth study was an in-vivo study (Chapter 6) to determine the effect of Powder Activated Carbon (PAC) at 0.5% by dry matter (DM) of diet on the enteric methane emissions and performance of dairy cattle when incorporated into a concentrated pellet. These results were obtained from 180 dairy cattle located in Brymaroo, Queensland (Qld), Australia. The addition of PAC improved daily milk production by 3.43% on average for the herd. PAC supplementation significantly increased the (P<0.05) milk protein by 2.63% and milk fat was significantly increased (P<0.001) by an average of 6.32%.

PAC concentration contributed to reducing CH4 emissions observed (P<0.001) before, during and after milking. The PAC also slightly reduced the amount of CO2 before, during and after milking. It can also be concluded from flux meter tests that the PAC did not significantly reduce CH4 from the manure emissions of dairy cattle, although these emissions are small by contrast with those eructated from the rumen. The presence of 0.5% PAC in the diet significantly reduced (P<0.001) the CO2 emissions from 1631 ppm to 1464 ppm from the manure of dairy cattle.

In addition, 16S rRNA Gene Sequencing was performed to determine the collective population of prokaryotic bacteria and Archaea as well as to characterize the specific Methanogenic communities between dairy cattle manure fed one of two pelleted diets; either a basic diet or supplemented with 0.5% PAC. There was a significant decrease (P<0.001) in the proportion of Proteobacteria (57% to 23%). There was a significant decrease in the proportion of members of the genera Methanobrevibacter from (83% to 51%) with a concurrent significant increase in the genera of the family Methanocorpuscuralceae (from 12% to 42%). The percentages of the other two minor genera also showed a minor increase, although their proportion remained low (Methanosphaera an observed increase from (3% to 4%) and members of the Methanomassiliicoccacea increasing (from 2% to 3%).