In previous posts we covered some of the outcomes from research on biochar feeds in various livestock, touching on the measured increases in animal growth, feed efficiency and other factors (see Parts: 1, 2, and 3). This week’s post will overview the specific mechanisms by which biochar interacts in the gut to improve animal growth and health.
Schmidt et al. (2019) has provided a comprehensive overview of these mechanisms in their review paper, which covers the extensive body of knowledge and state of the art in biochar animal feed. Some of the findings of this review paper are summarised below.
Extensive research has shown that biochar as a feed for livestock can improve nutrient uptake and feed efficiency, controls gut pathogens and facilitates various metabolic mechanisms that promote health and the well-being in the animal, whilst improving the quality of the end product, whether it be dairy products, meat or eggs.
Adsorption properties of biochar
Biochar has a high adsorption capacity for a range of charged ions, molecules and even microbial cells. This is due to its high surface area and complex porosity. Additionally, on the surface of the biochar matrix is a variety of negatively charged organic functional groups, including carboxyl, hydroxyl and phenolic groups.
Detailed images of the pore structure of biochar taken with an electron microscope. The top image shows the macropores of biochar. The bottom image shows the clay particle sized micropore structure within a macropore. These pores host numerous sites to which ions, molecules and microbes in the gut attach.
Image source: Electron microscopic analysis of Green Man Char Biochar.
In the gut, biochar’s high adsorption capacity has been shown to selectively adsorb various plant, fungal (e.g. mycotoxins) and bacterial toxins, as well as pesticides, hormones, trace and heavy metals, and pathogens that are ubiquitous in livestock feeding systems. Biochar can also eliminate toxins that have already been absorbed into the bile, liver and blood circulation systems by adsorbing toxins across the permeable gut wall or by adsorbing toxins secreted into the gut.
Electron storage and transfer in the gut
Biochar is attributed to improving feed efficiency by also mediating the transfer of electrons in the gut. The degradation of feed to its constituent nutrients in the gut is facilitated almost entirely by the activity of microorganisms. During microbial decomposition of feed, a surplus of electrons accumulates in the cells of the feeding microbes. In high-energy diets common among livestock, this accumulation of surplus electrons is pronounced. Other biochemical decomposition and enzymatic processes require the presence of surplus electrons, but only in very close proximity to where these processes occur.
Without a sufficient number of electron acceptors in the gut or a method by which electrons can be shuttled between activity sites, the metabolic activity of microbes and the digestive process as a whole is greatly inhibited. As biochar has a high affinity for electrons, its acts as a battery, accepting and storing surplus electrons and exchanging those electrons to electron deficient decomposition processes elsewhere.
Increasing habitat in the gut
The microhabitats created by the complex surface area of biochar promote colonisation and diversity in beneficial microbes within its pore structure. Biochar in feed increases the surface area of the gut where beneficial biochemical processes of digestion occur.
In this way, Biochar acts as a hotspot of microbial activity in the gut. This mechanism is attributed to why ruminants fed with biochar have a higher diversity in their gut biome and a lower presence of methane producing microbes, which are deleterious to feed efficiency in livestock.
Animal health and vitality depends on a complex and intricate symbiosis with various gut microorganisms. High productivity livestock systems are inherently vulnerable to shifting the balance of these symbioses resulting in reduced animal growth, poor-quality products and compromised health, immunity, and animal welfare conditions. The substitution of even a small proportion 0.5-2% of regular feed with biochar is a low-cost, low-tech and non-invasive method to improve the care and quality of your livestock.
To read more on the review of biochar animal feed and the specific studies covered in the paper, see:
Schmidt, H.P., Hagemann, N., Draper, K. and Kammann, C., 2019. The use of biochar in animal feeding. PeerJ, 7, p.e7373.