Along the lines of economics ... although FCRs increase as fish get bigger the value of the fish can more than compensate the extra feed. This web article describes how producers can increase profits by growing larger fish. The article has some interesting information on how they use the maintenance/conversion relationships to their best advantage.

Here they mention how the FCR is best below satiation:

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While most of the previous studies were completed by feeding fish to satiation, Cleveland and her team had observed that optimum feeding satiation doesn’t occur at 100 percent of satiation but at 75 percent. Specific growth rate, however, is achieved at 100 percent of satiation.

So SGR is the weight gained daily and they found it is best not to maximize growth because it is not as efficient. (The Gross FCR is not as good). So if you will imagine the Gross FCR versus SFR chart .... the Gross FCR curve would stop approaching the intrinsic FCR limit at the SFR corresponding to 75% satiation. Beyond that feeding rate, the Gross FCR would worsen (increase) indicating the efficiency of assimilation is declining at the increased feed rate. So maximizing SGR doesn't lead to most efficient use of feed.

Another takeaway from the article. Maintenance matters. When delivery must occur at a specific time the best path on feeding may not be minimizing daily FCR in the early going:

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“For example, if a fish needs to get at 3 kg at a specific time, it is more beneficial to feed a fish to a small level of moderate feed restriction during this time because this will result in improved feeding procedure,” she said. This is a better approach compared to feeding the fish through satiation, reaching market weight too early and then feeding maintenance ration through the remainder of the period.

Four percent less feed was consumed in this method, saving the producer $50,000 in feed cost.

To illustrate ... look at the Individual Weight versus Time(days) chart below. The area below each curve is the Maintenance Weight Days of an individual fish growing to 3kg from .5 kg in 180 days. If this metric is multiplied by the SMR it will quantify the weight of feed required to maintain the fish throughout the grow out. The Gross FCR is modestly advantages at 135 days but will be less advantageous by the end of the grow out due to the costs of maintenance. This does not include cost savings of water treatment and oxygenation costs which are part of maintenance and would also contribute to the bottom line.

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Last edited by jpsdad; 05/23/22 06:43 AM.
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