Dear Bert,

The answer is that yes, clay might buffer the rumen environment. It will prevent CO2 holdup which is the cause of pH decline and ruminal acidosis. The effect of clay might be related to increasing CO2 bubbles coalescence and formation. However, it might be that the effect of rumen buffering by clay on methane emissions is inverse. Methanogens are hydrogen scavenger, thus hydrogen accumulation is not a driver for growth. A high CO2 environment, on the other hand, is not beneficial for methanogens and competition against carbophilic bacteria, i.e. propionate producers, might lead to the decline in CH4 production. Hence, the close negative relationship between both ruminal CH4 and propionate concentrations.

There is not much work done on this field. However, Zeolites had shown a good performance regarding buffering capacity. But all comes to the right type of minerals composition of the clay and the porosity of the material to improve CO2 release.

I must suggest caution, though, the effect might not be constant, because the physicochemical properties of the rumen fluid are not constant and without monitoring CO2 holdup, we might never be able to optimise ruminal fermentation.

Hi Jose

Thanks for your really informative answer! Do you know of any published studies regarding the effects of different clays on CH4 emissions? For example, I think allophane has a much stronger pH buffering capacity than zeolite. It also has a very high a very high anionic absorption capacity because of its high Al/Si ratio.

As you will have picked up, I have no expertise in ruminant physiochemistry at all, but I am very intrigued that published studies cattle (and sheep) of the same breed and feed input vary considerably in their rumen microflora composition and associated methane production. As a layperson in the field, it seems to me that the rumen microflora composition in any one cow will be a function of that of the mother's and of the environment in the weeks after birth, as with us humans. It perplexes me that a given animal's rumen would favour CH4 production to get rid of excess H, when CH4 emissions reduce the energy recovered by the cow by 2-15% in a range of studies, compared to other biochemical processes that can operate.

So I am wondering if it is predominantly something to do with the physical rather than the biochemical side. I read somewhere where the smaller Jersey cows were found to emit less CH4 per kg milk, thought to be associated with their smaller rumen, relative to dietary intake, leasing to faster passage through the rumen. Do you think there is anything in this?

Kind regards

Bert

Hi Bert,

Many thanks, I don't know of (old) articles that looked into the effect of clay on methane production. Most of the work on clay is related to mineral supplementation. The work on the rumen environment is collateral, because the rumen is the main place of absorption of many minerals.

https://www.journalofdairyscience.org/article/S0022-0302(18)30061-4/fulltext

You are right, there is a genetic and environmental component for ruminal microorganism composition, for instance gnotobiotic calves develop their ruminal flora once expose to other ruminants. In other words, the ruminal microflora is acquired after birth, hence the importance of calf-mother interaction.

Article Repeated Inoculation of Young Calves With Rumen Microbiota D...

The set NH4/NH3 does not play a role in rumen buffering because the pKa of this set is 9.6, therefore at average ruminal pH ~6.1, effectively all NH4/NH3 is in NH4 form (>90%).

The way that the cattle get rid of most of the H+ (H3O+) is water formation. i.e. by combining HCO3- and H3O+ due the the extensive presence of Carbonic Anhydrase in the rumen fluid (along the whole GIT and within the body, i.e. ruminal cells). Bicarbonate (and H+) is extensively secreted as a way to absorb nutrients by the ruminal epithelia, and added by saliva. CO2 formed in this way is released via eructation (or respiration) and H2O is retained and reabsorb to complete the cycle. Many of my colleagues overlooked the fact that it is H2O/CO2 cycling the key aspect on nutrient absorption in the rumen.

CH4 inhibitors reduce sharply CH4 production, but there is no effect on ruminal function. CH4 production is collateral for H+ buffering and effective only for methanogens. Thus, indeed CH4 is a waist of energy. However, work with inhibitor also showed that the lost of energy is not easily compensated by CH4 reductions. i.e. no increase in milk yield or growth rate.

https://www.publish.csiro.au/an/an20295

Regarding your question, CH4 emissions are a function of the DMI, therefore small cattle will have less emissions. i.e. Fasting cattle reduce CH4 emissions by the 3- 4 day of starvation from 200l/day to less than 2l. (The energy metabolism of ruminants, Blaxter, 1962)

You are also not wrong, the physico-chemical composition of the rumen plays an important role on how efficiently ruminal fermentation can proceed (how much methane a cow might emit). For instance, the ruminal osmotic pressure, viscosity and surface tension has been identified as key component on disease/health on ruminants (see research on bloat and acidosis). These physical components are strongly related to CO2 holdup and throughout this effect to optimising ruminal fermentation. If you can modulate and control CO2 holdup with clays, you will optimise the rumen environment. But first, you have to monitor CO2 holdup, because those physical components vary widely, thus the effect of clays will not always be the same, as with many ruminal additives.

Cheers,

José

Thanks again Jose for an extraordinarily detailed, highly -quality answer. Truly fascinating reading. It may be totally irrelevant, but allophane clay in soils is widely known for its ability to adsorb phosphate in plant-available form, and also to increase and stabilise the level of organic matter in soils, making the soil more productive and also improving its water-holding capacity and therefore tolerance to drought. This is why allophanic soils in the Taranaki, Waikato and BOP were the favourite soils for dairying in NZ (at least before the advent of irrigation, anyway!). It would be fantastic to find out if allophane helped to control CO2 holdup in the rumen. Is this something that MPI or the NZ Greenhouse Gas Research Institute in Palmerston North might fund you to do? Just as good a shot as seaweed maybe? I know Harry quite well.

Thanks Bert,

I believe that you are right on the effect of clays. As I say before, the effect will be associated to the mineral composition of the clay. See the following document as an example.

https://www.sciencedirect.com/science/article/abs/pii/S0263876211002966

The problem with my line of thoughts is that it goes against the idea of pH as the controlling mechanism in rumen function.

I will try to explain. Always that CO2 holdup develops the pH of the rumen is low. Not always that the pH is low CO2 holdup develops. This is the reason that pH cannot be used to monitor ruminal acidosis.

In mathematical terms pH cannot measure CO2 holdups because, under pH ~5.4, HCO3- does not exist in solutions and all CO2 is in dissolved carbon dioxide form.

The HH equation is:

pH = pKa' + log Base/Acid, hence pH = pKa’ + log HCO3-/dCO2,

under ~5.4 (acidosis threshold),

pH = pKa' + log 0/1000 mM and pH = pKa' + ?

thus, under the threshold for acidosis, pH cannot measure CO2 concentrations and CO2 poisoning is the cause of ruminal acidosis.

If my colleagues acknowledge this fact, they might believe that all their research on ruminal pH as the cause of disease is wrong. But, for me, this is the way forward on understanding rumen function.

A way that will allow us to reduce methane emissions and to improve conversion efficiency in ruminants.

Cheers and many thanks for the great conversation

José

Dr Josë; I have not heard about that. But what I know is that cattle, together with camel do lick soil deposit in certain areas; perhaps with high mineral content. Worth investigating.

Hi Othusitse Ricky Madibela, yes absolutely.

Ions have different effect on the coalescence of bubbles. ie.,

Article The Effect of Electrolytes on Bubble Coalescence in Water

Therefore, it is not only the type of clay but also the composition that will determine the effect on rumen function.

Patent Apparatus for monitoring nutrition, especially fermentation ...

Please see the figure 3 in my patent. I know is not that clear, sorry I could not disclose this information. However, the information comes from a experimental work at Wageningen University. Increasing ruminal dCO2 concentrations leads to greater VFA absorption, as discussed by Ash and Dobson in 1963.

Article The effect of absorption on the acidity of rumen contents

Thus, cattle with high ruminal dCO2 concentrations produce more milk and have better feed conversion efficiency (FCE) or less CH4/kg feed. Nevertheless, An excess of dCO2 will increase the osmotic pressure of the rumen fluid and trigger of subacute ruminal acidosis.

Therefore, finding the right mixture of clay and adding it to the feed that cattle consume might control and prevent CO2 holdup and nutritional diseases. However, promoting high dCO2 concentrations will optimise ruminal fermentation and improve FCE.

Because the complexity of the relationships in the rumen you need a sensor similar to the one that I described above to be able to warrant the effect of your clay mix on rumen function in standard commercial operations, there is no other way.

Hello,

Here someone interested on conducting that type of research. Find below a couple of links to the 2 articles I've been able to find so far looking at clays and CH4.

10.1016/j.smallrumres.2006.11.003

https://www.researchgate.net/publication/291831352

Best,

Ainhoa