that it is possible to reduce feed costs without compromising fish production by means of efficient feeding strategies in semi-intensive tilapia culture.
The first study compared production of tilapia in fertilized ponds with the initiation of supplemental feeding at either 45 days or 75 days post-stocking. Seven commercial farms were involved in this study, in which ponds were assigned to each of the two treatments. Tilapia fingerlings (mean weight 0.11 g) were stocked at 4 m-2, and a farm-made feed of rice bran and fish meal were used beginning on either day 45 or day 75 and continued through the 150-day grow-out cycle. Yields, daily weight gains, and survival rates were determined. Cost analyses of the two feeding strategies were carried out using a paired t-test. There were no significant differences observed on growth (mean final weight, mean daily weight gain) and survival (85Ð87%) for the two treatments. The extrapolated fish yields were 5,104 kg ha-1 after 45-day onset versus 4,926 kg ha-1after 75 day onset, but this difference was not statistically significant (P > 0.05). Earlier feeding strategy required 37% more pre
pared feed than the delayed feeding, sharply increasing production cost and reducing profit. The relatively better feed conversion ratio associated with delayed feeding may have resulted from reduced waste or compensatory growth,
or both (Brown et al., 2000).
Our second study (Bolivar et al., 2001) compared growth, survival, and yield of tilapia fed daily at either 100% or 67% of experimentally-determined satiation. Analysis of growth performance demonstrated that the reduction of ration to 67% of satiation had no effect on growth or yield, and again the more moderate feeding strategy was more profitable. A third study combined feeding starting at day 75 and 100% or 67% satiation feeding. Result of this study again proved that feeding of fish at 67% satiation level reduced the production cost in tilapia culture as opposed to the 100% satiation feeding (Bolivar et al., 2003), although the overall profitability of the combined reduction of ration and delayed onset of feeding was compromised, in comparison with the individual feed reduction methods tested previously.
A fourth feeding strategy that was recently tested under the Aquaculture CRSP is provision of prepared feeds to tilapia on alternate days. Consonant with the overall objective of this projectÑto demonstrate efficient feeding strategies for tilapia production in semi-intensive cultureÑthe present study was conducted to determine the effect of alternate day feeding on grow-out efficiency and net profit.
Methods and Materials
Nine commercial tilapia farmers participated in this trial.
At each participating farm site, two ponds of similar sizes were assigned one each of the two feeding schedulesÑdaily feeding and alternate day feeding. The goal of this study was to test feeding strategies under authentic operating farm conditions. Inherent in meeting that goal is the some
Note: Assumed fish survival rates:
First month, 100%;
Second month, 90%;
Third month, 85%; and
Fourth month, 80%.
