Fermenting an ancient technology for the future

(22.04.09) High-quality tilapia needs high-quality feed. Rapeseed meal and cottonseed meal are potential ingredients because of their availability in the tropics and subtropics. Moreover, both are more affordable than the main protein sources in aquaculture: fishmeal and soybean meal.

Youling Gao, a PhD. student at APC, is trying to improve the quality of rapeseed meal and cottonseed meal for Nile tilapia (Oreochromis niloticus L.) through solid-state fermentation.

Solid-state fermentation is an ancient technology that improves the nutritional value of plant protein sources (in part) by breaking down most of the anti-nutritional factors (ANFs). Youling's hypothesis is that solid-state fermentation can reduce, if not eliminate ANFs in rapeseed meal and cottonseed meal.

Youling has produced both moist and extruded feeds from fermented rapeseed meal and tested them (in triplicate) in pilot feeding trials. Both feed diets were formulated to contain around 40% crude protein and 10% lipid. In the first trial, moist pellets were fed to tilapia for 35 days; in the second trial, extruded pellets were fed for 43 days.

"The preliminary results are mixed," says Youling. "The moist feed showed that fermentation improved the quality of rapeseed meal and improved fish growth. The extruded feed indicated that fermentation changed the characteristics of rapeseed meal? but not necessarily for the better. It is too early to say that one process is better than another, because there are many variables that we have not yet examined: the physical characteristics of the pellet, palatability, digestibility."

But there is one thing Youling does say with certainty, "Solid-state fermentation offers hope for thousands of tilapia famers."