Feed and Feeding
Cost of feed constitutes a major part of the production cost and accounts for 50%
to 70% of the total variable cost. The use of feeds will improve shrimp production
and increase profits. The availability of nutrients from feeds depends on the type
and quality of the raw material used, the formulation, the feed processing, feed
storage conditions and the feeding management. Therefore, feed and feeding practices
for semi-intensive or intensive shrimp farming require a basic understanding of
nutrition and feed requirements.
Shrimp diets may be supplementary or complete. In a extensive system the shrimps
need a complete diet. Although natural food items have good conversion values but
they are difficult to procure in large quantities and maintain a continuous supply.
At present most of the aquaculture farms depend on imported feed with a FCR (Food
Conversion Ratio) of 1:1.5 - 1.8. The feeding could be done by using automatic feed
dispensers, or by broadcasting all over the pond. If feeding trays are employed
in selected pockets in the pond wastage in feed can be reduced.
Feed evaluation using check trays
Nutrient Requirements
Shrimp requires approximately 40 essential nutrients. These nutrients are provided
in various amounts by natural food and supplemental feeds. Although the nutrition
principles are similar for all animals, the quality and quantity of nutrient requirements
vary from species to species. The recommended levels of nutrients and dietary components
for black tiger shrimp are listed in table below.
Recommended nutrient levels for shrimp feed on
percentage fed basis
Shrimp size (gm)
|
Protein (%)
|
Fat (%)
|
Fiber (%)
|
Ash (%)
|
Moisture (%)
|
Calcium (%)
|
Phosphorus (%)
|
0.0-0.5
|
45
|
7.5
|
Max.4
|
Max.15
|
Max.12
|
Max.2.3
|
Min. 1.5
|
0.5-3.0
|
40
|
6.7
|
Max.4
|
Max.15
|
Max.12
|
Max.2.3
|
Min. 1.5
|
3.0-15.0
|
38
|
6.3
|
Max.4
|
Max.15
|
Max.12
|
Max.2.3
|
Min. 1.5
|
15.0-40.0
|
36
|
6.0
|
Max.4
|
Max.15
|
Max.12
|
Max.2.3
|
Min. 1.5
|
(Source : Lin, 1994)
Protein
Shrimp consume dietary protein to obtain a continuous supply of amino acids for
normal growth. About 20 major amino acids make up most of the proteins and 10 are
essential including methionine, arginine, threonine, tryptophan, histidine, isoleucine,
leucine, lysine, valine and phenylalanine. Thus, essential amino acids must be provided
in adequate quantities and qualities (well-balanced) in the diet. On the other hand,
the recommended dietary protein levels for shrimp vary from 30 % to 55 % depending
on the shrimp size and species. It is believed that post-larval shrimp require a
higher protein level than larger shrimp.
Lipid
The lipid requirement of shrimp depends on their essential fatty acids and phospholipid
content. There are four fatty acids, which are considered essential for shrimp,
namely linoleic (18:2n6), linolenic (18:3n3), eicosapentaenoic (20:5n3) and decosahexaenoic
(22:6n3). In general, plant oils are high in 18.2n6 and 18.3n3, while the marine
animal oils are high in 20:5n3 and 22:6n3. The phospholipid requirement is 2 %;
however if lecithin is used this level can be reduced to 1 %. The requirement for
cholesterol ranges from 0.25 % to 0.4 %. In addition, the recommended lipid level
ranges from 6.0 % to 7.5 % and the level should not exceed 10 %.
Carbohydrates
The utilization and metabolism of carbohydrates by shrimp are limited. Their type
and level in the diet have been shown to affect shrimp growth. Starch as the carbohydrate
source is utilized better than dextrin or glucose for Penaeus monodon.
Vitamins
Little is known about vitamin requirements in shrimp. In intensive farming, vitamins
must be supplied in the diet for normal growth. Commercial shrimp feeds are usually
over-fortified with vitamins to overcome shortfalls due to processing loss and feed
storage. The minimum requirement for vitamin C, which is easily lost, is about 50-150
ppm for Penaeus monodon.
Minerals
Shrimp can absorb or excrete minerals directly from the aquatic environment via
gills and body surfaces. The dietary requirement for minerals is largely dependent
on the mineral concentration of the environment in which the shrimp are being cultured.
Among the other minerals, phosphorus is the most important, and is recommended at
0.9% as available phosphorus in the diet. Calcium is not considered to be a dietary
essential. However, its level in feed needs to be monitored because it is important
to maintain calcium to phosphorus ratio of 1:1 to 1:1.5. Calcium should not exceed
2.3% in the diet.
Feed Quality
The use of good quality feed will improve shrimp production and profits, and minimize
the environmental pollution from shrimp farming. The practical indicators of good
quality feed are:
Feed Conversion Ratio (FCR)
An ideal FCR always results in model growth rate, healthy shrimp and clean pond
bottom conditions. Only the superior quality of feed can achieve an FCR of 1.2.
According to recent data, an FCR as low as 1.2 has been achieved, but many farmers
are still obtaining FCRs of higher than 2.2. Therefore, besides the feeding management,
the FCR is also closely related to the quality of feed.
Attractability
The model quality shrimp feed must be highly palatable.
Good Water Stability
Since shrimp are a slow feeder animal, the water stability of suitable feed should
be over 2 hours for Penaeus monodon.
Packaging and Optimal Conditions Storage
Feed quality will rapidly deteriorate if feed is not packed well and properly stored.
Feed should be stored in a dry, cool and well-ventilated place to maintain consistent
moisture and temperature. Feed should not be stored in direct sunlight and should
not be kept longer than 3 months from the time of processing. The spoiled or old
feed should not be used.
Feeding Management
A high FCR or high amount of feed required to produce unit weight gain indicates
overfeeding, and consequently, a poor FCR is usually associated with poor growth
rate, low weight gain, stressed shrimp, mediocre water quality and adverse pond
bottom conditions. Therefore, the proper amount of feed is the most critical factor
of feeding management. The guidelines for feeding adjustment to be made according
to the mean body weight of the shrimp are shown in table below. Since many factors
are involved in shrimp feed consumption, careful and frequent observation of shrimp
is the most reliable approach for determining the optimal feeding amount. There
are many major key factors for successful intensive shrimp culture. Use of good
quality feed with better feeding management by low feed conversion ratios and improved
farm management are the important goals to farmers, not only for gaining greater
profit, but also for minimizing the pollution of shrimp farming area.
Recommended Feeding Rate for Shrimp Based on Body
Weight
Shrimp Live Body Weight (g)
|
Recommended Feeding Rate (% body weight/day)
|
2 – 3
|
8.0 - 7.0
|
3 – 5
|
7.0 - 5.5
|
5 – 10
|
5.5 - 4.5
|
10 – 15
|
4.5 - 3.8
|
15 – 20
|
3.8 - 3.2
|
20 – 25
|
3.2 - 2.9
|
25 – 30
|
2.9 - 2.5
|
30 – 35
|
2.5 - 2.3
|
35 – 40
|
2.3 - 2.1
|
(Source : Lin, 1991)
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