The Feed Conversion Ratio and Other Performance Indicators in Farmed Fish

Feed expenses are often the main budget item on fish farms. Therefore, reliable indicators are needed in order to determine the level of performance obtained from a feed or an additive. The feed conversion ratio (F.C.R.) is a relevant example of such indicators as it reflects how effective a feed strategy can be. What other variables are required in order to complement the F.C.R and thereby evaluate the profitability of a fish farm? 
 

The Feed Conversion Ratio, a major indicator of feed efficiency in fish farming

The feed conversion ratio is an indicator that is commonly used in all types of farming, as well as in the field of research. It can provide a good indication of how efficient a feed or a feeding strategy can be.
In the context of aquaculture, the F.C.R. is calculated as follows: F.C.R.  = Feed given / Animal weight gain.
In other words, the F.C.R. is the mathematical relationship between the input of the feed that has been fed and the weight gain of a population. There are no measurement units used in writing the F.C.R. The lower the F.C.R, the higher the weight gain obtained from the feed. When applied to aquatic animals, this F.C.R is generally lower than that of land animals, as shown in the table below.

Its calculation requires the following variables:

• The initial biomass – i.e. the number of fish in a farm population, multiplied by their individual weight -- of the production unit under study (pond, cage, pool...);
• The final biomass of the same production unit;
• The amount of feed distributed.

The F.C.R is simple and objective. For these reasons, it is a valuable indicator in the context of fattening farms. It is determined by comparing the initial input of feed (initial amount of feed fed) with the final output of the fish or shrimp that are produced.

The practical limitations of the F.C.R.

Even though the F.C.R. formula is simple, its practical application is much more complex. What other sources of information are available at the farm level in order to provide a more exhaustive idea for the efficiency of a feed?

• Population or sample: should a farmer weigh his entire animal population or just a sample of it? If it is the whole population, the problem is solved. Otherwise, he/she needs to know the exact number of individuals making up that population so the amount of feed needed for calculating the F.C.R can be determined. He/she also has to ensure that the chosen sample is, to a sufficient level, representative of that population.
• Consideration of mortality rate: all mortalities occurring between the date of initial weighing and the date of final weighing are to be deducted from the final biomass. Therefore, their effect on the F.C.R. is negative. Their impact is all the more significant if death occurs late. However, this limiting variable is not so much a problem in the case of livestock management, as only live farm animals can be commercialized.
• Amount of feed distributed: provided that a daily register of activities is held at the farm, this information is usually easy to obtain.
• Actual consumption of feed: from the initial amount of distributed feed, we must find out how much has been consumed. This information can be difficult to obtain.

Other performance indicators related to feed efficiency

When it comes to evaluating the level of performance obtained from a feed, there are other indicators that can complement the F.C.R. A useful indicator for farm management is one that highlights a poor technical result. Its regular application also grants the ability to keep track of the improvements that have resulted from the ensuing corrective actions taken.

• Viscerosomatic index (VSI): the net amount of filet produced should also be monitored closely. A substantial gross weight gain can result from an increase in the mass of viscera; yet, these parts of fish are not as valued as filets. The visceral somatic index (weight of animal viscera / animal weight) can therefore be a very helpful parameter when applied to fish.
• The homogeneity of fish and shrimp outputs is also important. F.C.R. calculations, no matter how objective, can hide significant discrepancies in performance within the same pond.
• The comparison between the various indicators should eventually be carried out methodically. Only the results obtained within similar rearing conditions are relevant:  same species, same genetic lineage, even same rationing method, as well as operators and production systems of similar technical levels.

The TECHNA Group assists feed manufacturers, as well as fish and shrimp farmers, in keeping track of their performance results. To this end, a wide range of additives are offered. For instance, additives such as Aquaviance increase the growth performance and farm profitability.  For more information, please contact our experts!