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20 Ton Tilapia Farm – Part 9 – Daily Feed

Now we get down into the design and work out our daily feed rates for each week in production on our 20 ton Tilapia farm.  From our previous calculations on feed, we break it down into each stage and watch our biomass grow.  We have included the mortalities each week, through each stage and compare what happens when we adjust our feed conversion ratio. In our quarantine we have to work our daily feed rate percentage (%bw/day) back from the 6% per day we calculated in the previous step because that was for the last week in production.  So our newly introduced fish start out at 6.2% per day and reduces to 6.02% in the last week.  These numbers are best used as a guide and adjusted for on-farm actual growth. In the above chart we have changed in our FCR to a lower value as previously discussed to show the difference in the daily feed rate.  The difference at maximum biomass for the quarantine is not large enough to be overly concerned about.  The difference between 1.49 kg/day and 1.24 kg/day is only minor.  However we will look at what that does in the grow out shortly.   Now we have removed the mortality all together and managed to keep all the fish alive.  Note the change in biomass of 33 kg from 24 kg and the increase in feed per day from 1.5 kg to 2kg per day.  This is quite significant.  However there is very little chance you will not have a small amount of mortality in the quarantine so it is best to allow for it and cull if need be to manage the system biomass so it is not overloaded. As this is a small system increase the capacity can be built into the formula or simply just make the life support system 30% larger.  It is an insignificant cost in the overall project and allow for those times where you may get larger fingerlings from your supplier.  Happens more often than not. Back to our design scenario: The above chart is the fingerling stage in our production which takes us up to 20 weeks.  This stage, you will remember is 15 weeks.  Each week will require you check the growth progress of the fish.  Note the reduction in fish numbers which will allow for 10 or 20 fish to be culled for measuring.  The same as the quarantine the feed rate will have to be adjusted to suit the fish.  There are going to be days where they may go off their feed (depending on your handling) and other days they will eat more.  Very important to keep good records of daily inputs into the system. We have changed the FCR to 1.0, 1.2 and 1.5.  Again there is a decrease in the feed loading, even though our biomass growth is the same through out when we change the FCR.  This is an example for how these slight changes in FCR can make large differences to the life support systems.  Keep in mind this is only for one cohort, there is another 2 cohorts in this stage, so that increase will be across them as well.  We will cover the total system loading in the next part. Lastly, we see the final stage in our farm.  This feed rate table takes our fish right up to our set market size of 500 grams from the first stage in the series.  Now we are starting to load the system with feed at around 40 kg per day even though out feed rate percentage has dropped to 2%.   From these tables we can work out the size and amount of feed through the farm production which is critical for pre-ordering your feed from the supplier and gaining a cost estimate for the feed per kg of fish produced when calculation your cash flow budget. Feed Supply Sidebar:  When ordering your feed, allow for at least 6 months of supply and no more.  If the fish feed is stored correctly (cool and dry away from rodents), it should remain stable for that period.  Be sure to check with the supplier their storage requirements and the length it can be stored and remain viable. A final look at the same changes to the FCR.  I will continue to highlight this as it is critical to designing the life support systems on the farm.  Getting it wrong can be fatal.  You will note we reduced the feed by 7 kg per day for this one batch of fish.  Combine that with the previous 2.5 kg reduction then multiply that by 3 (you will have fish at various stages of growth), you will design your filtration, flow rates, oxygen for a system loaded with around 30 kg of feed less per day.  If you end up feeding that extra feed, your system may not cope. Next we take a look at the complete system biomass and load from which we will start the life support system design parameters….

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