effect of c:n ratios on
probiotics
From: sunil verma sunil_aqua2003@yahoo.co.in
To: shrimp@yahoogroups.com
Sent: 2 Oct 2004
question:
effect on water probiotics in shrimp culture (P. monodon)?
(MFSc,Pantnagar)
e-mail: sunil_aqua2003@yahoo.co.in
***************
COMMENTS
1:
Probiotic bacterial cultures added to shrimp ponds
typically are composed primarily of heterotrophic bacteria, or a mixture of
heterotrophic bacteria and autotrophic nitrifiers. Heterotrophic
bacteria are those bacteria that primarily obtain their nutrition from
organic sources. The primary source of carbon for these bacteria is in
the form of carbohydrates. Nitrogen is typically obtained from the proteins
in the organic material consumed by the bacteria. Just like the shrimp,
heterotrophic bacteria excrete ammonia as a by-product of the metabolism of
the proteins they consume. However, some heterotrophic bacteria
are able to utilize ammonia directly as an alternative source of nitrogen.
Well what does this all have to do with C:N ratios? Shrimp feeds used
in intensive shrimp ponds typically have at least 35% protein. These
feeds do not contain a lot of carbohydrate. C:N ratios in these feeds
typically run around 9:1. However, the bacteria require about 20 units
of carbon per unit of nitrogen assimilated. With such a low C:N ratio
in the feed, carbon is the limiting nutrient for heterotrophic bacteria
populations. The bacterial population will not expand beyond a certain
point due the limited availability of carbon. The protein in the
organic detritus supplies most of the nitrogen requirement for the
heterotrophic bacteria under these circumstances, and inorganic ammonia is
not utilized as a nitrogen source to any great extent. However,
if the C:N ratio is increased, either by feeding lower protein feeds with a
higher percentage of carbohydrate, or by adding a carbohydrate source such
as molasses in addition to the regular feed, the increased availability of
carbon allows the heterotrophic bacterial population to consume a higher
percentage of the protein in the organic material. This results in
more complete digestion of the organic material in the pond by the
heterotrophic bacteria. As the C:N ratio increases, the heterotrophic
bacteria resort increasingly to ammonia metabolism to meet their nitrogen
requirements. As C:N ratios are increased even further, a point is
reached where nitrogen, rather than carbon, becomes the limiting nutrient.
At this point ammonia concentrations should be
close to 0 mg/L in the pond.
It should be pointed out, that holding the feed protein constant and
supplementing with pure carbohydrate will result in much higher bacterial
counts in the pond. The oxygen required to support this additional
bacterial biomass will increase proportionally with the increase in
bacterial population. Likewise, CO2 production will also increase,
driving pH down. If you are contemplating carbohydrate supplementation
to increase C:N ratios, make sure that your pond is well-aerated and
circulated to keep the organic detritus suspended in the water column where
there is sufficient oxygen for the heterotrophs. Also, once you have
developed a dense population of heterotrophs through carbohydrate
supplementation, don't discontinue the carbohydrate supplementation
suddenly. This will starve the bacteria of carbon, and a die-off will
occur. This will be followed
shortly by an ammonia spike.
Another point that should be considered before enhancing C:N ratios in P.
monodon ponds. P. monodon do not utilize the organic detritus and
associated bacterial protein as effectively as a food source as do L.
vannamei. With vannamei, C:N ratios can be enhanced by lowering
the overall feed protein levels and utilizing feeds that are high in
carbohydrate. Because vannamei feeds on the organic flocs and utilizes
bacterial protein efficiently, growth rates don't suffer, and protein
utilization efficiencies improve dramatically. With monodon, feeding
low protein, high carb diets will likely result in lower growth rates.
Therefore it might be necessary to rely more on supplementation with pure
carbohydrates to boost C:N ratios. But this will result in more bacterial
biomass, more BOD, and higher CO2. This makes it somewhat questionable in my
mind whether it is worth the risk to manage a monodon pond with high C:N
ratios.
Aquaculture Project Planning Specialist
Harbor Branch Oceanographic Institution
5600 Hwy. US 1N
Fort Pierce, FL 34946, USA
Phone: 772-465-2400 x384
email: vanwyk@hboi.edu
***************
COMMENTS 2:
Do you know some genus or species of heterotrophic
bacteria that work in a heterotrophic system in shrimp ponds ?
Claudio Paredes
e-mail: crparedes@cantv.net
***************
COMMENTS 3:
With respect to your question about which species of
heterotrophic bacteria are already present in shrimp ponds, I can only say
that is a very long list. To say that a bacteria is
"heterotrophic" only says that it derives its nutrition primarily
from organic sources. Common heterotrophic bacteria in shrimp ponds
include both beneficial genera (e.g. Bacillus, Lactobacillus) and pathogenic
genera (e.g. Vibrio.) Bacillus is often a dominant species. The
bacteria in probiotic preparations do occur naturally in ponds.
Measurement of C:N ratios in a pond is not a simple task because the carbon
and nitrogen end up in a lot of different "compartments": in
the shrimp, in the faeces and other organic flock, in the bacteria, and
dissolved in the water column. Usually when C:N budgets are studied in
a pond, researchers use labelled isotopes of carbon and nitrogen in the
feed. Of course this isn't practical in a production pond.
Managing the C:N ratio in a pond is handled more easily by managing the C:N
ratio of your feed inputs. I estimate the C:N composition of the feed
rather than measure it. (I don't have access to laboratory equipment to
measure TOC and TKN, nor have the budget to send out samples to a laboratory
for analysis.) Carbon accounts for roughly 50% of the dry weight of
most feeds. This is a crude estimate, but carbon content is remarkably
constant even for feeds with widely varying compositions. The nitrogen
content of the feed is calculated from the protein content. Protein is
approximately 16% nitrogen. Although this method for calculating C:N
ratios is admittedly crude, it provides a reasonably close estimate of
actual C:N ratios.
Peter Van Wyk
email: vanwyk@hboi.edu
***************
This has been an interesting discussion on C:N
ratios, and thanks to Peter for the time he's taken to provide these clear
explanations.
I'm in agreement with pretty much all he's stated, in particular the
usefulness of molasses in promoting a heterotrophic bacteria bloom
in ponds, and the value of using probiotics in hatcheries.
However, I would like to put the case for using probiotics in ponds,
especially where carbon addition is practised; these enclosed water
bodies will develop a bacterial bloom whose growth is largely
dependent on the main carbon sources of uneaten feed and faeces.
Often this is aided at fill-time by the use of manure to initiate
the pond bloom. As Peter has explained, you can enhance the
heterotrophic bacterial component of the bloom further through
addition of more carbon. However the characteristics of the bacteria
that dominate these blooms can be bit of a lottery; for example,
some of our customers have high levels of luminescent Vibrio in the
sea water they bring in to fill their ponds. David Moriarty has done
plenty of work to show that Bacillus probiotics can be easily used
to improve pond health, even when they aren't the
dominant bacterial species present; and they will accelerate
breakdown of organic matter (especially the particulate matter that
settles to create black sludge) and actively suppress
luminescent Vibrio. Yes, you will need to make weekly application of
the probiotics.
Peter mentioned that sometimes probiotics in ponds have failed to
deliver on their promises. They keys to successful use in ponds
include:
- choosing products with a proven track record.
- understanding that much of the work that probiotics do in
aquaculture is about providing a low stress environment for the
stock to grow in. This means that the microbes used must be active
in the water column as well as in the animals' gut.
- knowing that probiotics are not a "magic cure" for any and all
problems. Rather, they are a powerful tool to be used as part of an
overall program of management, which will deliver the results you
want provided the entire program is followed with diligence.
Kevin Healey
e-mail: khealey@iahp.com.au
www.iahp.com.au
***************
comments 5:
As we all know, organic matter starts building up
very slowly and gradually right from 1st day of culture during which period
there shall be enough good number of vibrios available in the water. While
applying probiotics, although we try our best to incorporate 1,000 cfu/ml of
bacillus probacteria, it may not be sufficient to get rid of, or to compete
with the vibrios existing in the water as well as the guts of the animal.
David Moriarty has done excellent work to balance vibrios both by their
elimination through competitive exclusion as well as by direct killing. He
also proved that apart from improving pond health by degrading the organic
matter probacteria also clear the animal guts out of vibrios to a
greater extent especially in hatcheries. We could see very clearly that the
vibrio counts including green and luminous vibrio have started reducing
every day with double dosage of application used in larval feeds.
The pond dynamic is so complex that we should keep track of all individual
parameters and to ascertain their individual as well as cumulative actions
of all of them together while using Probiotics if you want to make a real
study.
I fully agree with Keven and Peter on all the comments made out of their
expertise.
I think, ultimately we should admit that vibrios cannot be totally
eliminated but we can balance them keeping them under low numbers to prevent
disease virulence.
For the information of Antonin, we have been using probiotic in shrimp ponds
with and without aeration since a long time. In semi-intensive ponds with
high stocking, a minimum of 1,000 cfu bacillus per ml is required.
Dr.S.Vasudevan
e-mail: hiline@xlweb.com
***************
comments 6:
Several replicated pond studies conducted over the
past 20 years at Auburn University and Mississippi State University in the
United States did not demonstrate improvements in sediment and water quality
in ponds treated with bacterial inocula and enzymes.
Even at doses several times the treatments suggested...the amendments did
not cause positive changes in water quality in lab systems.
Source: The Global Aquaculture Advocate (www.gaalliance.org).
Probiotics enhancement of soil, water quality examined. Claude Boyd
(Ph.D., Professor, Department of Fisheries and Allied Aquacultures, Auburn
University Auburn, Alabama 36849, USA, email boydcel@auburn.edu).
Volume 7, Issue 2, P-32,
April 2004.
Bob Rosenberry
Editor/Publisher
Shrimp News International
10845 Scripps Ranch Boulevard, #4
San Diego, CA 92131 USA
Phone 858-271-6354
Fax 858-271-0324
Email bob@shrimpnews.com
Webpage http://www.shrimpnews.com
***************
Bob Rosenberry correctly quotes the statement made by
Claude Boyd in the article; however his article doesn't actually give any of
the trial details, and his conclusion is simply that the products he tried
didn't work. In fact he also refers to published trials where probiotics
were successful, and goes on to encourage people to try probiotics in their
ponds, and makes positive statements regarding their safety to the animals,
workers and the environment.
The keys to success in using probiotics in ponds are:
- choosing products with a proven track record of success
- understanding that much of the work that probiotics do in
aquaculture ponds is about providing a low stress environment for
the stock to grow in. This means that the microbes used must be
active in the water column as well as in the animal's gut
- knowing that probiotics are not a "magic cure" for any and
all problems. Rather, they are a powerful tool to be used as part of an
overall program of management, which will deliver the promised
results provided the entire program is carried out with diligence.
Kevin Healey
e-mail: khealey@iahp.com.au
www.iahp.com.au
***************
comments 8:
Does
anyone of you tried probiotics in semi-intensive ponds (large and without
aeration)?
What
do you think about “chaining” the bottom during the application? Can
this help the settlement of the probiotics? If probiotics have to be used
once in a week, what’s the basic treatment (kg/ha)?
I
fully agree with David about the importance of choosing the good product.
Without any advertisement do you know an effective probiotic for
semi-intensive pond?
Antonin
Jamois
e-mail: antosiomaj@yahoo.com
***************
COMMENTS
9:
You
can find out more about probiotics for your application by visiting www.iahp.com.au;
when the home page opens select “Overseas” and then “Aquaculture”,
where you’ll find links to the product data sheet and application
bulletins. For information about adapting the probiotic application to your
specific farm, please contact me offline and I’d be happy to go through it
with you.
Kevin
Healey
e-mail: khealey@iahp.com.au
www.iahp.com.au
***************
comments 10:
Well, we all know that
probiotic bacteria is useful to decompose organic matter. But how fast the
bacteria can do that? 1st day application? Or six months? I
believe this probiotic bacteria works if application of the bacteria is in a
long time period, let’s say 6 months or 1 year. Since culturing Penaeus
shrimp needs 3 months only, application
of probiotic is not so much useful. It takes 2-3 times of culturing to know
these bacteria worked. I agree to Claude Boyd statement.
Mohamad
Nasir
(no email address available)
***************
COMMENTS
11:
The
best way to use probiotics is to start right at the beginning, when the pond
is filled and before it is stocked. Then provide a regular weekly top-up
application and there should be sufficient probiotic activity to meet your
needs.
Kevin
Healey
e-mail: khealey@iahp.com.au
www.iahp.com.au
***************
Comments 12:
You can look at the microbiological ecology of one of
these shrimp
system from the point of view of relative biomass and metabolisms.
When you add shrimp feed to the pond, only a fraction of that feed is
converted into shrimp biomass -- on the order of 10% (dry wt basis)
with another 20% or so being metabolized by the shrimp with the
balance being handled by the rest of the pond ecology or flushed with
water changes. The yield coefficient of some of the decomposing
bacteria can be in the 0.50 range (feed/biomass dry wts). That
means that we may grow several times as much bacterial biomass as
shrimp biomass. However, that bacterial biomass can then be consumed
by other bacteria, protozoans, etc. With each transfer in that
microbiological food chain, biomass is lost. Algae get in the
game
by using the nutrients from the shrimp and the stages of the
microbiological food chain. However, the algae intern enter the
decomposition food chain or if we are cleaver enter a flock that the
shrimp consume before going back into the decomposition food chain.
What this means is that the relative size and metabolism of this
microbiological decomposition food chain is greater than the shrimp
biomass in the pond and its food consumption is comparable to the
feed rate of the pond + algae productivity. This relative size makes
me question the impact of a few kg of bacteria per week on a system
that is getting 50-100 kg of feed/ha per day.
Unless you are near an ecological instability, a few kg's of
non-optimized bacteria is irrelevant (which is why replicated studies
don't show anything). Perhaps a better solution is to take some
sludge from the pond that is working best and add it as seed culture
to the ponds that are not performing. As you are just using this
sludge for microbiological decomposer seed, you may want to let it
sit for many months with aeration and let any potential shrimp
pathogens go without a host long enough to die or dump some of their
virulence genes they need to attack shrimp.
We are all in the business of growing bacteria with a secondary crop
that we sell to pay the bills.
Dallas
PS: It takes a lot more than one species of bacteria to decompose
mixed waste, it usually takes thousands. We don't have waste that
consists of one group of chemicals that can be handled with one
bacteria species. For example, my MTBE eating bacteria can handle
MTBE, TBA, formaldehyde, ethanol, methanol, and a few other things
including ether bonds, but it doesn't do well on BTEX (benzene,
toluene,...).
Dallas E. Weaver, Ph.D.
Scientific Hatcheries
5542 Engineer Dr.
Huntington Beach, Ca 92649, USA
714-890-0138
Fax 714-890-3778
deweaver@surfcity.net
http://www.ScientificHatcheries.com