Use of fermented cow manure as a feed substrate for fish polyculture in stagnant water ponds

Abstract

The possibility was tested of replacing part or all of fish feed pellets (15% fish meal, 16% soybean meal, 69% sorghum and/or wheat) with cow manure recently fermented for methane production. Nine stagnant, fresh-water ponds were stocked with fingerlings of common carp, tilapia, and silver carp which were grown to market size. The following results were obtained: Substitution of 46% of the pellets by fermented cow manure at a replacement rate of 1:4.6 (weight of dry matter), respectively, did not reduce the total fish yield. Complete substitution of the pellets by fermented cow manure caused a 47% decrease in the total fish yield, mainly the result of decreased growth rate of common carp. Tilapia were much less affected. The data for silver carp showed no clear trend. The variability of fish yield among ponds receiving the same feed/manure ration increased as the pellet portion was decreased and the fermented cow manure was increased. Addition of sorghum grains to ponds receiving fermented cow manure improved only the growth of common carp. The possible effect of pond dimensions on fish yield is discussed.