feed managemant as the 4th dimension in disease prevention

50

Introduc on

Ecological disturbances caused par cu-

larly by global warming have resulted in a

rise in surface water temperature. In-

creased shrimp farming ac vity, spurred

by more than two years of a rac ve

shrimp prices, have produced eutrophi-

ca on of many coastal waters. The result

of these two factors of warmer environ-

ment and availability of nutrients has

been the onset of many new viral, bacte-

rial and fungal shrimp diseases such as

IMNV, Early Mortality Syndrome, White

Feces Disease and the new comer micro-

sporidian Enterocytozoon heptopenaei.

Recurring shrimp diseases have resulted

in the loss of billions of dollars and thou-

sands of employment opportuni es in

many affected countries. FAO indicated

that global shrimp produc on reached

3.9 million tons in 2011. Due to just

AHPND alone, GAA in November 2013

es mated that produc on would be re-

duced by 23%. This translated into a

shor all of US$3.6 billion! Just for com-

parison, Fiji has a GDP of $4.2 billion,

Maldives $2.4 billion and Somalia $2.3

billion. It will not be surprising that to-

gether with all the other shrimp diseases,

the economic loss will be many magni-

tudes higher.

Main Causes of Diseases

In all instances, life will proliferate where

the environment is conducive and nutri-

ents are available. Thus warm water bod-

ies with high organic load, enriched pond

soil, fermen ng sludge are all breeding

grounds for pathogenic bacteria, viruses

and fungi. All these are made worst by

the desire to intensify farming in a small-

er area to maximize profit. In a small vol-

ume of water with a high number of

shrimp and fish, the ra o of feed amount

to the volume of water has vastly in-

creased. Analogous to a kitchen where

excess food wastes are le overnight

a rac ng and breeding large number of

cockroaches, an intensive pond with high

organic load a racts and breed high con-

centra on of pathogenic viruses, bacteria

and fungi.

Why is Feeding Shrimp a Big

Challenge?

Unlike feeding chicken or fish where

floa ng pellets are used, the shrimp feed

sinks and any uneaten feed cannot be

seen. It takes immense skill to master the

dispensa on of exact amount of feed to

a pond of shrimp. Too li le feed will

affect growth and health but too much

feed will result in high organic load in the

pond.

Uneaten feed and excessive excreta pro-

duced from excessive feeding will result

in high organic ma er in the pond, pro-

ducing not only harmful gases such as

ammonia an hydrogen sulphide which

deteriorates the water quality, but also

supplying food for the growth of patho-

genic bacteria and harmful algae.

AQUAFEED::ADVANCES IN PROCESSING & FORMULATION from Aquafeed.com Vol. 7 Issue 4

Feed Management as the 4th Dimension in shrimp Disease Preven on

Poh Yong Thong, Gold Coin Aquaculture Division, Assistant Director,

Nutri on and Technical Service, Selangor, Malaysia.

As I see it

Views from the aquafeed industry

A lot of cockroaches in the kitchen if there is a lot of le -over food

A lot of pathogenic bacteria in the pond if there is a high organic load

51

It is thus impera ve that the shrimp

farmer is able to dispense just sufficient

feed to the intensive shrimp pond by

me culous monitoring of feed trays. The

feed trays are ingenious tools invented

by the Taiwanese and are very useful in

fine tuning the daily feed distributed and

responding to the daily changes in

weather and water quality.

An Effec ve Remedy

Through experience, many farmers invar-

iably immediately reduce feeding

amount when pond water quality is

found to start deteriora ng or when dis-

eases are first discovered to have started

to infect the shrimp. This is evident in the

cases of AHPND (or EMS, Early Mortality

Syndrome), IMNV (Infec ous Myonecro-

sis Virus), vibrio bacterial infec ons and

WFD (White Feces Disease). In the major-

ity of cases this measure is highly effec-

ve. Excessive uneaten feed and excre-

on deteriorates water quality via the

produc on of ammonia and hydrogen

sulphide. The high organic load become

food for the pathogenic bacteria, fungi

and viruses. So the momentary reduc on

of feed serves as a pause in loading or-

ganic ma er to the pond ecosystem,

allowing the shrimp and fish to pick up

edible organic ma er s ll prevailing in

the pond, cleaning up the pond and also

allowing the growing beneficial bacteria a

breather to purify the ecosystem and in

the process improves water quality. Thus

occasional fas ng is highly remedial in

shrimp farming.


Feeding shrimp is a big challenge because the feed sinks into the water and cannot be seen.

Cannot see the shrimp,

cannot see the feed

Too li le feed?? Too much feed?

http://www.tysonanimalnutrition.com

52


Conclusion

Shrimp farmers have to realize that

shrimp farm management and technology

is constantly changing. What worked pre-

viously may not work anymore due to the

shi in weather and the coastal ecosys-

tem. Shrimp farmers who hold on to past

farming husbandry will find it hard to suc-

ceed. A cri cal aspect to this adapta on is

new perspec ves in feed management.

Shrimp farmers who learn and adapt will

stand a be er chance of success.

Snieszko had aptly illustrated the principle

of disease preven on by his epidemiologi-

cal triad. Due to the fact that shrimp feed

sinks in the pond and the feeding amount

cannot be accurately verified visually as in

floa ng fish feed, one more dimension has

to be added to Snieszko’s epidemiological

triad. Feed Management should be added

as the 4th dimension. The principle of dis-

ease preven on is the epidemiological

quadruplets, which is illustrated as below:

The ul mate aim in shrimp health man-

agement is to reduce or dwarf the growth

of the pathogen by reducing excessive

nutrient loading to the ecosystem through

stringent feed management while op miz-

ing the quality of the environment as well

as safeguarding the health status of the

stock via gene cs and nutri on.

Ideally we want to have a situa on pictori-

ally presented as below:

And ideally, with the applica on of strict

biosecurity segrega ng the pathogen from

the Shrimp and Environment.

AFΩ

More informa on

Poh Yong Thong E: [email protected] or [email protected]

Pathogen

Environment Stock

Feed