Organic Waste Recycling

294 Organic waste recycling: technology and management

6.6.2 Fish meal or feed for other animals

This method of utilization is suitable for the fish grown directly on waste, in
order to lengthen the food chain and to reduce the possibility of transference of
pathogens. The waste-grown fish can be used as feed for carnivorous fish or
shrimps, which have high market value when sold for human consumption.
Biological value of protein in fish meal is 74-89% which is quite high
(Williamson and Payne 1978) suitable for feeding to pigs and chicken. For this
purpose, fish in waste-fed ponds can be reared at a higher stocking density and
shorter growing period to obtain high fish yield. Fish can be sun-dried,
grounded, and mixed with other food stuffs to increase the value of fish meal.
Experiments were conducted at AIT to investigate the feasibility of using
Tilapia grown in septage-fed ponds as fish feed ingredients for carnivorous fish
of high market value such as snakehead (Channa striata) and walking catfish
(Clarias batrachus and C. macrocephalus) (Edwards et al. 1987 b). Tilapia
harvested from the septage-fed ponds was used either fresh, or processed, as
silage and mixed with other feed ingredients prior to feeding to the carnivores.
A silage was produced by adding 20% carbohydrate (cassava) to minced Tilapia
(weight/weight) in the presence of Lactobacillus casei. It was found that growth
of these carnivorous fish in ponds fed with Tilapia fish meal, fresh Tilapia or
silaged Tilapia were comparable with that fed with marine trash fish
(conventional fish feed), but poor food conversion efficiencies were obtained
because of excessive rate of feeding (Table 6.5).

Table 6.5 Comparison of growth and food conversion ratios of carnivorous fish fed with
different feeds (Edwards et al. 1987)a

Channa striata Clarias macrocephalus

MWG

(g)

DWG

(g/d)

FCR MWG

(g)

DWG

(g/d)

FCR

Marine trash fish feed

Tilapia meal feed

Tilapia silage feed

Fresh tilapia

26.03

45.77

55.37

52.81

0.30

0.59

0.65

0.62

14.15

33.18

6.45

10.99

35.08

43.84

47.67

51.43

0.26

0.33

0.36

0.39

13.88
12.53
10.15
12.87
a MWG = mean weight gain; DWG = daily weight gain; FCR = food conversion ratio.