Determination of the value of goat waste from different levels of goat management in fish culture

Present study was conducted to determine the value of goat wastes to aquaculture derived from a stall-fed goat production system in which solid and liquid manures including waste feed stuffs were collected separately. Wastes (HN) from goats fed a diet comprising 60 % (DM basis) of fresh leucaena leaf (Leucaena leucocephala) were compared to those from goats fed fresh grass (Panicum maximum) and fine rice bran only (LN). Both solid and liquid waste productions were analyzed for nutrient content; release characteristics of major nutrients (total N and P) and their value in the fertilization of tank-cultured Nile tilapia (Oreochromis niloticus). Solid and liquid wastes from Leucaena-fed goats were 75-100 % higher in total nitrogen but contained only 30 % of total phosphorus in waste from goats fed grass and rice bran alone. Nutrients were released to maximum levels after 3-4 days in each waste. TKN released from solid wastes reached 10.7 mg N/g DM and 16.5 mg N/g DM from goats fed low and high nitrogen (LN and HN) diets respectively, 0.9 mg N/ml and 1.97 mg N/ml in liquid wastes. Over 60 % of total phosphorus was released as soluble reactive phosphorus (SRP) after 3-4 days (solid; HN 2.1 mg P/g DM, LN 6.6 mg P/g DM; Liquid, HN 0.01 P/ml, LN 0.05 mg P/ml). Fish growth response was compared in tanks receiving liquid wastes only (HNL, LNL), solid wastes only (HNS, LNS) and a mixture of both at the ratio produced by the animals (HNS+HNL, LNS+LNL). Inorganic fertilizers were added as required to ensure all loadings at an isonitrogenal level and standard N:P ratio maintained (3 Kg. N/h/d and 5 respectively). In addition an inorganic only (urea and TSP) and commercial floating pellet (3 % body wt./day) were used as controls. Daily weight gain of treatments varied from 0.39+-0.2 g/fish/day (HNL) to 1.02+-0.03 g/fish/day (Pellet). Growth and survival was poorest in the wet waste treatments and best in pellet and LNS+LNL treatment. Mortality was particularly significant (50 %) in the liquid waste treatments and may be related to goat husbandry practices, including deworming and ectoparasite control, occuring slightly prior to the study.