Feed from leftovers

Pollution caused by feed not eaten is a major concern for shrimp farmers. Madhusoodana Kurup, professor at Cochin University of Science and Technology, Kerala, used a technology to convert these leftovers into protein-rich feed. Sumana Narayanan understands how this benefits farmers

On why left-over feed is a problem

For healthy growth, shrimp need 45 per cent protein in their feed. But 60-70 per cent of it remains unconsumed and accumulates in the pond bed. This converts into nitrite, a toxic compound and makes the shrimp vulnerable to diseases.

About the technology

We used bioflocs, which is a collection of algae and bacteria found naturally in shrimp farms, to recycle the feed not eaten and fish excreta. By aerating the water, we encouraged the growth of bacteria, which in turn converted the nitrogenous waste into microbial protein. This protein is a natural food for shrimp.

On how it works

To produce microbial protein bacteria also need carbon, which they derive from carbohydrates. Farmers can use tapioca, wheat, rice, potato or yam flour as a cheap and good source of carbohydrate. The optimal carbon-nitrogen ratio should be 1:20.

On economical advantages

Since shrimp feed with high protein content is expensive, the technology will help shrimp farmers switch to feed with less protein content, without compromising on growth and production. Natural recycling of the waste material also helps farmers save on expenses involved in the water treatment.