PRACTICAL EVALUATION of HANDHELD GAS
DETECTOR for MEASURING SHEEP METHANE EMISSION
Jinan Nova NS400 Handheld Multi Gas (CO2 and CH4) Detector
NZ$1000 landed direct from China.
I first posted this in 2020, but as AgResearch's PAC offering was being floated, I thought it better to pull my head in.
Since then I've shifted my approach to looking at emitted CH4 relative to liveweight on day of measurement, which includes fleece weight, yielding production per emission, or as I assume, a form of feed conversion efficiency around kg's production per unit emission.
The index so derived has good correlation with growth+meat (DPG+DPM), wool (DPW), and dag-score (DPG). To a lesser extent FE (DPX) and FEC (DPF) may be involved, but mainly I think through their association with health and well-being, emission being worse in animals with health problems. High DPF dosen't necessarily mean poorer health in my experience, and DPX only counts in a bad challenge year.
My position is; if you combine DPG+DPM+DPW+DPG into a single aggregated index, you've got the best animal for low emission.
I've got a definite type of sheep evolving, muscled bigger frame, finer woolled (for Coopworth 48/50 while retaining HFW), and bare triangle bum. I think Perendale, and to a lesser extent, Texel breeders should be rejoicing at this comment.
One other observation; these sheep invariably are the progeny of ewes with a long productive lambing career, 5 years or more at 150%.
To my critics... if this is a questionable process, why are my results consistent with previously researched and documented waypoints.
More to come in future posts... meantime read the background following...
“Read
some instructions first”… is always a good idea…
A wise
man once told me, “there’s nothing new under the sun, whatever you’re doing,
there’ll be someone, somewhere…..”
This
isn’t a scientific discourse, so I’m allowed to put my citations, and resultant
comment up front, which I hope will go some way to explaining the course/s of
action I took in setting about this evaluation.
If you
want to delve deeper, Google “pubmed.gov” then in the search box, type in the
citation code. There’s a little box to the right of the paper subject header
that says “PMC Full Text” which in some instances you might need to click on to
get the full paper.
A Review of Enteric Methane Emission Measurement Techniques in Ruminants
Zhao et al
RC (Respiration Chamber) – Animal in container
full-time, regarded as ultimate because it collects total flux, (dung, farts, urine
etc as well as respired), disadvantage said to be, its un-natural, not reliably
reflecting animals emitting differently to what they might when outside.
Green Feed – Similar to above but outdoors with a bait station to lure the animal
in, has high between day and animal variations, depending how long the cow
stays in station.
Sniffer – Utilised on dairy cows feeding while milking, when they put their head
into the feed-bin. Same infra-red CH4 detection as above two systems, but dosent
measure total flux, only respiration, and is less accurate between animals because
no control where cows head is relative to sensor. However, authors mention,
respiration does provide PREDICTION values, so keep that in mind for
NS400 implementation.
Ventilation hood or Face Mask – Both have a
time/logistics problem as do RC and GF, either a hood/mask for every animal, or
one you have to change from animal to animal, which would carry an additional problem
of vacating the hood of gas residue from the previous subject.
LMD (Laser Methane Detector) – State of art laser
beam from hand-held instrument measuring CH4 concentration via infra-red
spectroscopy, again only measuring respired/eructed concentration.
Cheapest one I’ve seen, cost
approx. $6000 USD, quote here in NZ, $10,000.
PAC (Portable Accumulation Chamber) – What we’re being
offered locally by AgResearch for 84 animal x 3 week repeat survey service. PAC
has advantage over RC in that animal confined for shorter time, up to one hour,
but for the still not inconsiderable logistics involved, dosen’t include flux
as comprehensively. Zhao et al further say the results don’t correlate at all
well with RC, possibly due they say, “different aspects of genetic traits”.
IPCC, for GHG ruminant
emission mitigation considerations, prefers the RC method, maintaining CH4
measurements are of little value without knowledge of feed intake, which can be
best controlled in the RC system.
The authors conclude LMD
and PAC have low cost simplicity, short term measurement in individuals under
practical production conditions, offering potential opportunity for breeding
lower emitting animals.
Genetic parameters of methane emissions determined
using portable accumulation chambers in lambs and ewes grazing pasture and
genetic correlations with emissions determined in respiration chambers
Included here for
interest, Jonkers et al, including among the et al, Shackell, Dodds, Knowler,
McEwan, this work likely contributing to the MO of the methane testing service
currently offered local breeding industry. They put h2 at around 0.16 for PAC
and 0.20 for RC.
NS400- type handhelds offering a “breathalyser” approach, not included in the above survey, but following points pertain:
- Utilises the same
infra-red technology, passing an inducted air stream via suction pump, past an
infra-red sensor.
- Same tech as used by Transport authorities here in NZ in the 6000 odd roadside tests done each year.
- Same small size utility
as LMD, but better directional capability, intake nozzle can be held within
30mm of nostrils easily enough, with less background intrusion.
- Faster animal throughput
at lower time and capital cost.
- With animals fresh off
natural environment/pasture, given the above Sniffer comment, I've assumed the
predictive snapshot. This comment also supported in the following citation:
PMC7191252/
Assessment of
methane emission traits in ewes using a laser methane detector: genetic
parameters and impact on lamb weaning performance
Reintke et al
Authors maintain a factor
derived from either (respired or eructed), correlated well with ewe body wt
(EBW), back fat thickness (BFT), body condition score (BCS), and lamb body wt (LBW).
Interestingly, this paper
was not about GHG emissions, but focussed on feed conversion efficiency.
High levels of ewe CH4
emissions (representing energy losses) were significantly associated with lower
LBW, EBW and BFT.
They say h2’s were small,
(0.1), and not sure, but I think established via LBW on one generation of
progeny. However, they say breeding on reduced CH4 emissions, (especially
eructated), contributes to genetic improvement in that trait.
They used mini-peaks of respired and eructed CH4, and maintain such
separation is reasonable physiologically.
Ewes with low CH4 during
respiration reared heavier lambs, and simultaneously, were associated with
higher EBW.
CH4 eructation represents
larger CH4 emission than does respiration, but respired CH4 influences LBW and
EBW significantly enough.
NS400- I read this stuff after we’d done the first trial runs with the
detector, carried out on our 200 ram hgts.
The NS400 allows setting
for recording interval and I had elected for average CH4 over 10 and 20 second intervals,
instead of the 3 minutes as in the above trial, and assuming that an average of
ppm values might suffice.
As the Reintke Fig1 graph
shows, respiration CH4 levels are quite constant, and I found this to be so also,
even given the shorter time interval I used.
Importantly, I did find
significant difference in average respired CH4 levels between sheep with these
shorter intervals, and such difference would be emphasised if the peak values
as indicated by Reintke were used instead of average.
We struck a frequency of
somewhere around 5% of the ram hgts where eructation occurred during the 20
seconds, which shot CH4 well over 1000 ppm, at times up to 3000 ppm.
Switch-off and re-boot of
the detector was needed to clear the residual CH4, the 60 second boot-up
process includes a 45 second pump activation while holding the instrument in
“fresh” air.
- faster throughput
- the longer the read
time the greater risk of an eructation interruption
- the NS400 attains a
steady “read” within the first few seconds
- WYS in a 10 second respiration
pattern is fairly indicative of WYG subsequent
- sufficient between
sheep difference achievable within this time
- shorter restraint time,
better all round for both sheep and handler.
Incidentally, the 2 hour
200 sheep session only used 1/5 of battery life indicator.
Pictured here an NS400 sample
60 second CH4 graph, the 10 second peak to the left of the 15 sec vertical approx
127 ppm, and closing ppm 105.
We thought we might
encounter some taper off in CH4 with standing time in the yard, higher CH4
values were obtained in first hour.
So here are the scatters
for the pasture and clover sessions: ppm CH4 up the side, and time across the
bottom, in number of sheep, corresponding to 100=1 hour.
I suppose unsurprisingly,
the CH4 settled fairly quickly for the clover, consistent with it being a
better quality, more highly utilisable fodder, while off the rye pasture there
was a longer tail.
The trend lines were more
consistent than I thought they were going to be, but looking at both scatters,
a half hour stand-time (=50) might be appropriate.
Couple more citations
worth a read:
/25149329/
Genetic and
environmental variation in methane emissions of sheep at pasture
/26055577/
Animal board invited review: genetic possibilities
to reduce enteric methane emissions from ruminants
RESULTS USING THE NS400
200 ram hgts run through
the Racewell squeeze, 100 per hour.
Holding sheep head with
left hand, detector in right, assistant punching data to XR5000 indicator.
NS400 interface has 3
selectable modes,
Dual - showing both CO2
and CH4
Single – showing either
or as pic below
Graph – as Page3. tracks
readings over whatever gas and time period set.
I tried 5, 10, and 20
second timing periods, and used the final ppm indicated at period end. After
some long-hand calculation I established this number was the ppm read at close
of scan, not an average over the time period.
Any reading over 500ppm regarded
as an eructation, and excluded from the summary. Readings I felt were
influenced by an eructation in the previous sheep also excluded. While taking
readings it is easy enough to tell if this is happening, and in future, will shut
down/re-boot to clear the pump, if necessary.
However, would expect in
future to avoid this with a short 10 sec read time.
Update, late 2022, now have an Excel spreadsheet calculating a moving average from which to deviate each animal's recording, as CH4 declines with time off feed.
I then compared CH4:
between the top 25% LWT and HFW, and the bottom 25%.
|
LWT |
LWT CH4: |
HFW |
HFW CH4: |
Top 25% |
53.7 |
.96 |
2.7 |
.99 |
Bottom 25% |
37.9 |
1.02 |
1.6 |
1.03 |
Difference |
15.8 |
6% |
1.1 |
4% |
There’s no adjustment in
here for birth rank which might show lower emitters in better light, but I
think the best I can say at this stage is, higher performing sheep are kinder
on the environment. High production,
lower emission is a useful association, but limited by how big do we want our
sheep to ultimately be. Efficiency at a fixed weight is a more ‘noble’
aspiration. My own genetic trend graphs, approx. 5kg LW12 and 0.2 kg FW12 in
the last 8-year generation turn-over, equate a 1-2% per generation improvement
in CH4 emission, based on production gain alone.
ie. approx. 50% worse
emitters/inefficient feed utilisers.
1 |
.73 |
44.1 |
2.1 |
.17 |
2 |
.76 |
50.2 |
2.7 |
.00 |
3 |
.99 |
42.6 |
1.7 |
.15 |
4 |
1.01 |
48.7 |
2.1 |
.03 |
5 |
1.01 |
46.6 |
2.1 |
.16 |
6 |
1.04 |
50.0 |
2.5 |
.04 |
7 |
1.06 |
44.6 |
2.1 |
.48 |
8 |
1.13 |
44.5 |
2.1 |
.15 |
This applicable also when
considering the effect of different feed species illustrated here with the
difference in emission profile between rye mix pasture and clover, and which could,
by extrapolation, exist with feed crops like chickory, plantain, and brassicas, 10-20% lower emissions.
Incorporation of methane measurement into a breeding program would demonstrate a will to positively engage in GHG mitigation, and the contribution should ultimately be measurable. However, given the positive relationship between higher production and lower CH4 emission, performance driven flocks and herds have indirectly been doing the “right thing” by livestock GHG mitigation for at least 50 years, (here in NZ).
For myself I’ll implement
a worst CH4 performing 10% cull to my sale ram and replacement ewe hgts, in
line with what I apply to all traits, and will be looking for the best male to
retain as a stud keeper. I’ll be basing emission performance on two or more
observations in the first 18 months of age.