Farmed shrimp can thrive on soy and canola meal blend: Malaysian team

© iStock.com/Turbotroll

A vegetable-based diet protects shrimp growth and feed utilization, say researchers. 

A team of Malaysian and Japanese researchers tracked the influence of a combination of soybean meal (DSM) and canola meal (CM) supplemented with crystallized amino acids (CAA), fish soluble (FS) and phytase (PT) as an alternative to diets containing varying amounts of fishmeal for the production of farmed shrimp.

The group published their results in the journal Aquaculture.

“A feeding trial was conducted to develop plant protein based diets for kuruma shrimp by gradually eliminating dietary fishmeal with a blend of CM and DSM (4:6), and supplementation of CAA, PT and FS,” said the researchers.

The group found that the vegetable-based diet ingredients could produce similar results to diets including high levels of fishmeal.

“Canola meal and soybean meal could be effectively utilized as major protein sources by kuruma shrimp,” noted the authors. “The dietary fishmeal could be reduced to only 6% (85% replacement) with a blend of canola meal and soybean meal [SBM], and supplementation of methionine, lysine, phytase and fish soluble without compromising growth, feed utilization, body composition and health of juvenile kuruma shrimp.”

Why replacement diets?

Kuruma shrimp are an important commodity in Japan. However, as wild catch is decreasing, reliance on farmed species is increasing, said the researchers.

Aquaculture producers face a challenge producing shrimp diets with the limited amounts of fishmeal available, they said. That scarcity makes research efforts to find replacement ingredients a priority.

“Replacement of fishmeal with cost-effective alternative protein sources, even in minor quantities from a feed formulation is desirable as it will obviously reduce the feed cost as well as farm production costs (Amaya et al., 2007),” they said. “CM and SBM are two important plant proteins for shrimp.”

Several vegetable proteins have been tested in shrimp diets including soybean meal, canola meal, lupin meal, peanut meal and spirulina meal, said researchers. However, those experiments have found a wide range of replacement amounts from 20-70% as being workable.

“In most cases, a single source plant protein cannot be effectively utilized by shrimp species because of the negative effects emulated by plant proteins including imbalanced amino acids, specially lysine and methionine, anti-nutritional and toxic factors, low palatability and indigestible carbohydrates,” they said.

An earlier study demonstrated that supplemental CAA or FS could improve the amount of vegetable-based replacement proteins that could be used in the diet, said the researchers. But it was unclear how much could be replaced with mixed supplements.

The study 

In the experiment, researcher tested four isocaloric diets in shrimp production. The diets reduced the amount of fishmeal included by 0% (FM40), 70% (FM12), 85% (FM6) and 100% (FM0).

Canola meal and soybean meal were blended in a 4:6 ratio in the experimental diets, said the researchers. Plant diets also had supplemental lysine, FS, methionine and phytase.

Shrimp tanks were tested in replicate per diet for a period of 60 days, they said. And, 180 shrimp were used in the experiment.

Weight gain and survival was recorded every 10 days and at the experiment conclusion, they said. Shrimp were checked for whole body composition at the beginning and end of the experiment.

They were also assessed for moisture, ash, crude protein content, total lipid levels and protease activity, they said.

Results

Feed intake was similar for shrimp getting all of the diets, said the researchers. “Fishmeal free diet (FM0) supported growth equivalent to that of the 100% fishmeal based control diet (FM40) and there were no significant differences in the final body weight (FBW, varied between 3.15 and 3.46 g) and specific growth rate (SGR, varied between 1.04 and 1.24% day− 1) of shrimp fed the FM40, FM12, FM6 and FM0 diets,” they added.

However, the feed conversion increased for the shrimp getting the fishmeal free diet, while the protein efficiency ratio declined, they said. And protein gain and retention and total hemocyte courts and viable cell values were reduced in shrimp getting fishmeal-free diets.

No negative influence was found on whole body composition, they said. And, whole body moisture crude protein, total lipid and ash levels were similar.

“Significant effect was also not found on the protease activity (unit mg− 1 protein) in the digestive tract of shrimp fed the FM40, FM12 and FM6 diets, while the value was significantly decreased in shrimp fed the FM0 diet,” said the researchers. “The values for the total hemocyte count (cells ml− 1) and viable cells (%) were lowest in the FM0 group, however these parameters were not significantly varied among the dietary treatments.”