Trials - The only way to make the right feed choice
For any fish farm, it is important to make the right decision about the optimum feed for the farming conditions and targeted production of this specific farm. To make the right feed choice, feed trials must be conducted at the farm level - BioMar can assist in this.
Traditionally, the choice of feed type and feeding strategy was determined on the basis of information available from feed suppliers’ catalogues and staff, supplemented by own experience. But this information is often not sufficient for making a relevant choice for a specific farm and its goals.
Two feed types may carry almost identical product declarations, and their manufacturers may use almost identical arguments in support of the quality of the feed. Yet in practice their performance will not be identical. Therefore, the information required to make the right choice should include results of carefully conducted trials.
BioMar is on a regular basis undertaking benchmark trials. By doing this, we can compare our different feed types and feed from other suppliers. The trials are conducted both under controlled conditions in one of our feed trial units and at commercial farms.
Feed must be tested under similar conditions
Trials should start out with a homogeneous group of fish, which means fish of the same strain, lot, and grade. As a rule of thumb, the fish must at least double their weight throughout a trial before the trial can be approved as being valid.
The breeding units – that is cages, ponds, channels, or tanks - must be identical with regard to size, shape, water quality (including oxygen content and water flow).
For the water quality to be identical in all units, these must receive their water supply from the same source – if on land – or be equally exposed to the sea current - if at sea.
Examples of trial layout. Color codes represent different trial codes. To the left a simple trial layout for a flow through farm where two feed types are being tested. To the right an example of trial layout for a cage farm testing five types of feed.
Moreover, the units receiving the same trial code should not be placed in sequence. For instance, if one unit with trial code ”A” is located before the unit with trial code “B”, the fish in the next units have to be fed in the reverse order, i.e. “B” before “A”.
Minimum two units on each trial code
It is necessary to have a minimum of two units (cages/ponds/channels/tanks) on each trial code in order to obtain a reliable result. By using two or more units for each trial code, the variation in the results will give an idea of the spread and the reliability of the trial. Three units on each code are even better, but rarely feasible at farm level.
Accuracy, attention and registration are important to a successful trial
It is important for the processing and evaluation of the trial results that all observations have been recorded. BioFarm can assist in establishing registration schemes suited for trials on any farm.
When it comes to weighing fish at the beginning and end of the trial, measuring daily feeding, collecting and registering dead fish the need for accuracy is obvious,
But in situations where it becomes necessary to deviate from the original plan accuracy is just as important. Do not stop the trial just because something unexpected happens. Record what has happened and, if necessary, contact BioFarm to discuss what measures might be required.
It is also important to record minor and less obvious differences between the trial units. This applies to all aspects of daily work and the behaviour of the fish such as appetite, agitation etc. It may also be useful to record observations relating to the texture of the faeces, sediment quantities and any particles in the water.
It is often possible to adjust for any mistakes during the processing of the trial data. However, this is only possible if everything has been properly recorded.
It is very important to register and keep information for each individual trial unit separately. The figures should not be totalled e.g. for each type of feed. The value of the trial is considerably reduced if the pieces of information are not recorded separately - and in the case that one trial unit must be taken out, the trial will not be compromised that much if data is registered at unit level.
During the trial, daily registration should comprise:
- Feed consumption
- Dead fish (kg or number)
- Water temperature
- Observations regarding weather, precipitation, polluted water, fish behaviour, disease, amount of faeces and eventually its texture, etc.
Choice of feeding strategy during the trial
It is important that the choice of feeding strategy for the trial is based on an evaluation of the criteria which are important for the targeted production. The criteria may be a wish to achieve one of the following:
- A low Feed Conversion Ratio (FCR)
- High growth rate (Daily Growth Rate - DGR)
- Lowest cost per kg of produced fish
- Minimal nutrient discharge
If the target is a low FCR and / or minimal nutrient discharge, it is essential to exploit the potential of the feed to a maximum. The fish should therefore be given just enough feed to avoid feed waste, or in other words, the feeding should be kept at a restrictive level. However, it is important to avoid an insufficient daily feed allocation, as this will result in an increased FCR as a disproportionate amount of the allocated feed will be used for maintenance.
The strategy to use for trials comparing different feed types is to give the fish the same amount of energy per day of the different feed types. This strategy is called isocaloric feeding. If the feed involved is of different brands, the way in which the declared energy content of the feed is calculated may vary, but the basis should be to compare the amount of digestible energy in the feeds.
If the purpose is to determine the lowest cost per kg growth, the feeding strategy is the same as when the objective is to achieve a low FCR.
Depending on the purpose of the trial - maximize total production, low FCR or high growth - one have to pay attention to the interaction of FCR, DGR and daily feed allocation.
Flow through farm
The article is available in BioMar Magazine December 2018 issue in English, Greek, Spanish, French, Danish, Polish, Finnish and German and Italian. Please ask your local contact person to receive a copy.