Evaluation of the Effect of Replacing Maize with Cattle Rumen Waste Meal in Feed for Production of Nile Tilapia, Oreochromis Niloticus

This study determined the nutritive values of cattle rumen waste (CRW) meal used for replacement of maize in the diets of Nile tilapia Oreochromis niloticus. CRW (20.9% CP) was used to replace maize (10.1 CP) at 0%, 25%, 50%, 75% and 100% making diets (D1-D5). The diets were fed to the fish (5.59±0.37g) to apparent satiation twice daily in three replicates. Results showed that the bacterial count of fresh CRW sample was 3.2 x 10⁵Cfu/g while the fungal count was 1.2 x 10⁵sfu/g, but after sun drying at constant moisture of 8.0%, the bacterial and fungal counts reduced by 90% and 100% respectively. The weight gain, specific growth rate and feed intake declined with increasing levels of CRM. Fish fed D1 had the best feed conversion ratio (FCR) of (1.29) while the group fed D5 gave the poorest FCR of (1.66). The results also revealed that increasing dietary levels of CRW resulted in marginal increase in carcass ash and fibre. The bacterial and fungal counts of fresh fish samples ranged between 2.4 x10⁴ – 3.4 x10⁴ Cfu/g and 0.4 x 10⁴ – 1.5 x 10⁴ Sfu/g, respectively, but the organisms disappeared after drying the fish at mean constant moisture of 6.21%. In conclusion, CRW can replace up to 50% of maize in the diets of Nile tilapia. The use of the rumen meal would reduce costs of fish production and increase the profit margin. It will also boost fish production and rural economy and serve as an economic means of environmental management.

Keywords
African catfish; cattle rumen meal; alternative feed; environmental friendly aquaculture