Chemical and nutritional quality of fermented fish silage containing potato extracts, formalin or ginger extracts

Abstract

Fermented fish silages were prepared from whole tilapia ( Oreochromis niloticus), 15% molasses and 5% Lactobacillus plantarum starter culture. After fermentation for 72 h, potato extracts (PE), formalin or ginger extracts (GE) were added at 5 ml/kg silage as proteolytic inhibitor or lipid antioxidant, and incubated at 30°C for 30 days. The effects of presence or absence of these additives on various protein and lipid quality parameters were periodically examined. PE had a slight and insignificant effect on protein solubilization and proteolytic activity; hence it was not effective as a proteolytic inhibitor. Formalin prevented further hydrolysis of protein and reduced ammonia production. GE proved effective as an antioxidant in fermented tilapia silage, as the thiobarbituric acid value remained low after 30 days' incubation. The tilapia silages were incorporated into dry tilapia diets and the digestibility of nutrients determined. The formalin-treated tilapia silage diet gave significantly reduced ( P < 0·5) digestibility of dry matter, nitrogen or lipid compared to the control, PE-treated or GE-treated silage diets.