JPH0659174B2 - Feed for zooplankton - Google Patents

Description

Detailed Description of the Invention

[0001]

INDUSTRIAL APPLICABILITY The present invention can efficiently cultivate zooplankton, which is a biological feed for larvae and fry used for seed production of fish and crustaceans, and enhance nutritionally docosahexaenoic acid. The present invention relates to feed for zooplankton.

[0002]

2. Description of the Related Art In recent years, technological advances in cultivated fisheries and aquaculture have been remarkable, and the ratio of cultured fish to all edible fish has been increasing. Behind the increase in seedling production is the development of biological feed for larvae and fry, and improvement of seedling production technology by using rotifer, which has been found to be suitable as an initial feed for hatched larvae.

As a culture feed for rotifers, yeasts have been used so far because they are suitable for large-scale culture.
Rotifers cultivated with yeast have a low feed effect on juvenile larvae, and in order to improve them, secondary culture with marine chlorella or culture with combined feeding of marine chlorella and yeast has been performed in recent years.

The nutritional value of rotifers as feed for larvae and larvae, especially marine fish, is that of ω3 highly unsaturated fatty acids such as eicosapentaenoic acid (hereinafter referred to as EPA), which is an essential fatty acid, and docosahexaenoic acid (hereinafter referred to as DHA). It depends on the content. It is said that the EFA content of rotifer is greatly influenced by the fatty acid composition of the culture feed.

It is known that marine chlorella has a high EPA content of 20 to 30% in total fatty acids, and the EPA content of rotifers using it as a culture feed is also 20% or more, thus improving the nutritional value. However, for these, DHA
Is hardly included (Bulletin of Japanese Soc
society of Scientific Fisheries 45 (7) p883-8
89, Oil Chemistry 31 (2) p77-90).

[0006] Recently, it has been reported that red sea bream and striped horse mackerel have higher effects as essential fatty acids on larvae of marine fish than on EPA (Abstracts of the Spring Meeting of the Fisheries Society of Japan in 1989). Collection p39, Collection of Abstracts of Spring Meeting of the Fisheries Society of Japan in 1990 p
44). From this, it is expected that if DHA can be included in the feed, the nutritional value will be higher than that currently used, leading to an improvement in the yield and vitality of marine fish seedling production.

As a method for improving the nutritional value of rotifers currently used, it is conceivable to use fish oil using DHA or its methyl ester, or oleaginous yeast in which DHA is incorporated into yeast as a culture feed. Also, there are drawbacks such as the rotifer culture seawater being easily contaminated and the rotifer's mortality rate being high, which is not preferable.

[0008]

DISCLOSURE OF THE INVENTION The object of the present invention is to train zooplankton as a feed having a higher nutritional value than the conventional feed for larvae of larvae and containing DHA which is an essential fatty acid of marine fish. The present invention is to provide a feed for zooplankton which is free from the above problems.

[0009]

[Means for Solving the Problems] The inventors of the present invention conducted a search for algae to achieve the above-mentioned object, and found that Isochrysis
The present invention has been completed by finding that some algae belonging to the genus have a remarkable DHA content and that the algae can be used as a feed for zooplankton.

That is, the present invention relates to a feed for zooplankton using a single cell alga containing DHA as a raw material.

The unicellular alga used in the present invention is a seawater containing DHA, for example, as belonging to Haptophyta, Haptophyta, Isochrysis, Isochrysis, Isochrysis sp., Isochrysis sp. Isochrysis galbana) and so on. These are the Culture Collection of Algaeand Pro
tozoa (UK, abbreviation: CCAP), Culture Collection
It is easily available from algae research institutes such as of Algae at the University of Texas at Austin (USA, abbreviation: UTEX). That is, CCAP as Isochrysis sp
927/12, CCAP927 / 14, UTEX LB
1292, UTEX2307, etc., Isochrysis g
As albana, CCAP927 / 1, UTEX LB9
There are 87 etc. These algae are generally 1
It contains 0 to 50% by weight of lipid and the DHA content in the total fatty acids is 1 to 50% by weight.

The zooplankton referred to in the present invention refers to those commonly used as biological feeds, such as the water rotifer, Artemia and Daphnia (freshwater Daphnia, brackish water Daphnia).

The above-mentioned unicellular algae are sodium nitrate 0.
01-0.1 g / liter, sodium dihydrogen phosphate 0.001-0.01 g / liter, iron, copper,
100 to 10 in a seawater medium (pH 5 to 10 and preferably 6 to 9) containing trace elements such as zinc, cobalt and manganese and thiamine and cyanocobalamin as vitamins.
Under illumination of 000 lux, 5-40 ° C, preferably 15-
It can be obtained by shaking or aeration culture at 25 ° C for 5 to 50 days. The algal cells thus obtained are concentrated or dried by usual operations such as centrifugation, precision or ultrafiltration, reduced pressure, spraying, etc., and are mixed or mixed alone or with other feed ingredients, It is used as a feed for zooplankton such as the water rotifer, Artemia, and Daphnia. The zooplankton cultivated with such a feed and the zooplankton subjected to the secondary culture have an increased or enhanced DHA content in their total fatty acids, and thus have an amount of 10 to 3
It becomes 0% by weight.

[0014]

Example 1 40 ml of a medium having the composition shown in Table 1 was added to Isochrysis sp.
hitian strain) (CCAP927 / 14) was inoculated and aerobically cultured in a test tube at 20 ° C. in the light (1500 lux). The resulting culture solution (dry algal cell weight of 0.
(Corresponding to 01 g) was subcultured in 500 ml of the same medium, and aerobically cultured in a flat culture flask for 4 weeks under the same conditions to obtain a culture solution. This was centrifuged at 2500 rpm for 10 minutes, and the algal cells were freeze-dried to obtain about 0.1 g of the dried algal cells as the feed of the present invention.

[0015] Chloroform /
20 ml of a mixed solvent of methanol was added, and the algal cells were crushed with a hyscotron for 1 minute, followed by filtration and solvent removal. About 5 ml of a sulfuric acid / methanol mixture was added to the obtained extract, and
After refluxing for 5 hours and methyl esterification, 5 ml each of hexane and water was added thereto for extraction, and the fatty acid composition in the solvent layer was analyzed by gas chromatography. The DHA content in the total fatty acids was 24% by weight. Met. The lipid content in the algal cells was 40% by weight.

[0016]

[Table 1]

Example 2 Using 50 ml of the composition medium shown in Table 1, Isochrysis galbana Park
Seed culture of e (UTEX LB987) was performed in the same manner as in Example 1. However, the culture temperature was 25 ° C and the illuminance was 300 lux. The obtained culture solution (corresponding to a dry algal cell weight of 0.05 g) was cultivated in a glass flask charged with 3 liters of the same medium under the same conditions for 6 weeks, and the culture solution was centrifuged to obtain wet algal cells. 7.5 g was obtained. The lipid content in the present algal cells measured by the same operation as in Example 1 was 30% by weight, and the DHA content in the total fatty acids was 10% by weight.

Example 3 Using the medium having the composition shown in Table 1, Isochrysis sp.
927/12) was subjected to aeration culture in a 1-liter flat culture flask and used as a seed for expansion culture in a 100-liter Panlite water tank using the same medium. Vp (Packed C
ell Volume, which represents the wet weight of algal cells in 1 liter of culture solution)
Was grown to 0.5 to 3.0, and the algal cells were centrifuged, concentrated and washed with water.

An aeration rate of 0.1 to 0.5 V / V / M (aeration rate per minute per liter of culture solution (liter)) was applied to 10 rotifers (mixed culture of S-type and L-type). Using a liter water tank, 70% seawater whose water temperature was adjusted to 25 ° C. was set so that the rate of 100 individuals / ml at the start of culture was set.
The algal cells were administered to this so that the Vp was 0.1 to 0.5, and the number of individuals of the water rotifer per 1 ml was counted over time. The result is shown in FIG.

[0020] In addition, after culturing for about 100 hours, the water rotifer was recovered with a nylon net having an opening of 50 µm, and the algal cells were completely removed by washing with water, and fatty acid as a lipid in the water rotifer was tested. When analyzed by the same method as in Example 1, the DHA content in the total fatty acids was 15 to 20% by weight.

Example 4 DHA is not accumulated in the rotifer of Basidiomycetes that has been proliferated by baker's yeast and freshwater chlorella. Such a horned rotifer is a 1-percent with an air flow rate of 0.1-0.5 V / V / M.
The water temperature was adjusted to 25-28 ° C using a 0 liter water tank.
It was set in 0% seawater so as to be 200 to 1000 individuals / ml at the start of culture. In the same manner as in Example 3, the cultured, concentrated and washed Isochrysis sp. Algal cells had Vp of 0.1 to 0.
It was dosed at 5. When the white rotifer was sampled with time and the fatty acid composition in the lipid was analyzed in the same manner as in Example 1, the DHA content gradually increased immediately after the administration of the algal cells and became as shown in FIG.

Example 5 Artemia durable eggs produced in Great Salt Lake, Utah, North America were put into a 100 liter Artemia incubator adjusted to a water temperature of 25 to 27 ° C. with 70 to 100% seawater and 1 g / liter of durable eggs was added. The seawater was strongly aerated so as not to settle. After putting the durable eggs in the temperature-controlled seawater, stop aeration at 24 hours, separate the eggshell from the hatched Artemia nauplius, and culture 100 seawater at the same water temperature as the conditions used for hatching the Artemia nauplius. It was set in a 100-liter Panlite water tank under a strongly ventilated condition so that the amount became / ml.

Is cultured, concentrated and washed in the same manner as in Example 3
The ochrysis sp. algal cells were administered to the aquarium at Vp 0.1 to 0.5 and fed for 24 hours, and the DHA content in the total fatty acids of Artemia nauplii immediately after hatching was 1% by weight or less. However, 1 after administration of Isochrysis sp. Algal cells
It was confirmed by the analysis method of Example 1 that the content had risen to 8% by weight.

Example 6 Brackish water Daphnia (Diaphanoso) grown in tetraselmis
ma sp.) at 50 individuals / ml in 50% seawater at a water temperature of 25 ° C.
Set in a 10 liter beaker with 0.3V / V / M
Vented with. Here, in the same manner as in Example 3, culture, concentration,
The washed Isochrysis sp. Algal cells were administered at Vp0.5, and 2
When DHA was fortified for 4 hours, D in the initial total fatty acid
The HA content was 0.5 to 1.0% by weight, and it was almost not contained, but after strengthening it was 12 to 20% by weight.
Had improved to. The analysis of this fatty acid composition was carried out in Example 1.
Compliant with.

[0025]

According to the feed of the present invention, D in total fatty acids
It becomes possible to stably train zooplankton having an HA content of 10 to 30% by weight.

[0026]

[Brief description of drawings]

FIG. 1 is a diagram showing the relationship between the number of days of culture and the increase in the number of individuals of the hornworm, Pemphigus rotifer according to Example 3.

FIG. 2 is a diagram showing the relationship between the culture time and the DHA content of Cyperus rotifer according to Example 4.

Claims (3)

[Claims] 1. A feed for zooplankton made from algae containing 10% by weight or more of docosahexaenoic acid in total fatty acids. 2. The feed for zooplankton according to claim 1, wherein the alga is a unicellular alga belonging to the genus Isochrysis. 3. The feed for zooplankton according to claim 1, wherein the zooplankton is rotifer, artemia, or daphnia.