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Two experiments were conducted at the Living Aquatic Resource Research Centre, in Naong Thang village, Vientiane province, Laos, from April to October 2006, to study: (i) growth of larvae on substrates of fermented fish and jackfruit, together with pig manure; and (ii) the growth of frogs fed basal diets of fly larvae or earthworms with or without duckweed.
In experiment I, the design was a 2*4 arrangement, the factors being: Substrate (fermented fish waste + pig manure or Jackfruit waste + pig manure); and Biodigester effluent (application of 100, 150, 200 or 250 mg N/m2 of substrate surface). There were 2 replicates of each treatment in a completely randomized design. The substrates were put in brick-lined enclosures with floor area of 0.25 mē. The substrates were rapidly colonized by house flies (Mosca spp) and the larvae appeared within 20 to 24 hours after introducing the substrates. Six days after introducing the substrates, the larvae were harvested by immersing the substrates in water, and collecting the larvae which remained floating on the water surface.
There was no effect of the level of effluent and no interaction between substrate and effluent. Conversion rates were better for the substrates with fermented fish: 9 kg waste DM to 1 kg larval DM and 3.5 kg crude protein in the waste to 1 kg of protein in the larvae.
In experiment 2, frogs were purchased as 20 day-old fingerlings and raised in ponds. After a period of adaptation, they were allocated to 4 dietary treatments arranged as a 2*2 factorial with 3 replications using a completely randomized design. The factors were: addition or not of duckweed to the feed; and earthworms or fly larvae as the main diet. At the start of the trial the frogs weighed on average 19 g and were fed the experimental diets for 90 days.
Growth rates and feed conversion (for DM and crude protein) were better, and mortality was lower, when frogs were fed earthworms rather than larvae and when they had access to fresh duckweed mixed with the larvae/earthworms. The net increase in live weight (252 g in 90 days) on the best diet (earthworms plus duckweed) was better than in one report concerning frogs fed an artificial diet (200 g in 120 days).
Based on the results in this thesis, it is concluded that:
Frog cultivation in a waste recycling system is important for sustainable aquaculture, to reduce expenditure on costly feeds.
Earthworms, Larvae and Duckweed could be the basis of a system to replace the high protein concentrate feed traditionally used in intensive frog culture