Intensification of goat meat production, in particular, is desirable because goat meat is the region's main source of protein. The major problems with current production methods of the two foods include the following: waste disposal of goat manure, lack of affordable fish food and pond fertilizer, and limited farm space. The average Ilocan family farm is only 1.25 ha. The integration of these two production systems is the key to the optimization of each. Goat manure, which is currently not returned to the farming system, can be used directly in tilapia fish culture as a low-cost feed and pond fertilizer.
This integration system requires greater knowledge and management skills on the part of the farmer, but is well-suited to the small farm. The start up cost of tilapia farming is low, and goat farming requires a low capital investment. Also, risk is reduced, because two subsystems are involved, instead of one.
An experiment was conducted to determine the maximum rate of goat manure loading and stocking density of Nile tilapia (Oreochromis niloticum) per unit area of the fishpond, and to design a goat/fish integrated farming system that could give the highest economic return, using manure as the only added nutrient source. Two 120-day fish-culture periods were coordinated with a 240-day goat-rearing cycle.
The study involved 12 200m2 fishponds. Three goat manure rate applications, zero, 200 and 300 goats per fishpond, were applied to two stocking densities of 10,000 and 20,000.
Newly weaned native goats weighing an average of 8.5 kg each were fed a mixed cut-and-carry feed of grass and legumes three times a day. Average feed per goat was 2 kg.
Goat houses were built to partially overhang the ponds. Each goat had 0.75m x 1.5m of floor space. Goat droppings were collected underneath the goat houses on iron sheets. The manure was weighed and added to the pond each morning. Urine and washings were drained directly into the pond. Water depth was maintained at 0.75 m. Fish growth was monitored monthly. Fifty randomly selected fish were weighed and measured from each treatment. At the end of each growth period the ponds were drained, fish were harvested, and data analyzed.
Average fish yields increased with goat stocking rates and fish stocking density to a maximum of 1,170 kg (300 goats and 20,000 fish/ha). The results imply that the growth rate of tilapia increased with goat stocking rate but decreased as fish stocking density increased.
Second test period. Goats from the first culture period also were used for the second, and weighed about 18 kg. Because the goats were larger they produced more manure and as a result the growth rate and net yields of the fish were higher during the second period. The results of the second trial paralleled the first, only the numbers were slightly higher (see table).
The results indicate that the fish efficiently use the goat manure as feed. A cost analysis revealed that the greatest return was obtained with the 300-goat and 20,000-fish/ha combination, followed by the 300-goat and 10,000-fish/ha. However, the current market values large fish significantly more than small fish, which makes the 300 goats and 10,000 fish combination more profitable. The study is being continued with increased goat populations of 400, 500 and 600/ha with the same fish-stocking densities.
Lydia P. Libunao
DMMMSU, Bacnotan
La Union, Philippines