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Fish feed management is one of the most important elements to fish farming, so knowing what constitutes a good quality feed is crucial, writes Adam Anson, TheFishSite Reporter.

Fish farmers who experience poor production results will generally blame either one of two things: the hatchery that sold them the fingerlings, or the feedmiller that sold the feed. Often whilst farmers understand what may be affecting production, they do not understand why. Consequently, this hampers their ability to solve the issue.

Lukas Manomaitis, Technical Director of aquaculture at the American Soybean Association International Marketing Programme, brought this issue to light at the VIV Asia Conference 2009. According to him, this lack of awareness is a problem for both farmers and feedmillers alike. Feedmillers should ensure the loyalty of farmers by helping them to understand how to get the most out of their budget and their feed.

"What farmers often lack is information," he says. They need to know what the best kind of feed is and how it should be treated. A good way to define the quality of feed is by looking at the Feed Conversion Ratio (FCR). The FCR is a formula that does not use the total biomass at harvest or the true amount of weight gain from actual fish sold.

According to Mr Manomaitis, using true FCR is important because it allows "comparison across varied systems" and "tells us how much of feed is becoming a source of growth". FCR can be calculated using the following formula:

FCR = amount of feed used / total fish weight gain

FCR is a guide to how effectively feed is being used and how well a farm is being managed. A lower FCR is better than a higher one, which is typically a consequence of a higher quality fish feed. Different types of fish feed will also affect the FCR. Whereas one feed may cost more than another by weight, overall savings can be seen if the FCR is significantly better. Farmers need to see past these initial costs if they are to receive the benefits.

What Makes a Quality Fish Feed

The quality of fish feed is dependent on a variety of factors, says Mr Manomaitis. Protein and lipid content are the primary measurements of this quality, but another factor is down to the way that the fish feed is manufactured.

Feed can be produced either by steam processing, producing compacted, sinking pellets; or by extrusion, which produces expanded floating pellets. The benefits of sinking or floating pellets can also be ascertained using the FCR. ASAIM believe that in general floating pellets offer numerous advantages over their sinking counterparts.

One benefit is that they are simply more digestible as a result of the better cooking process attained through extrusion. A second benefit is that they have a lower FCR, and a third is that they are more stable in water. The increased starch geletanisation means that they tend to disintegrate less quickly.

According to research from ASAIM, feeds should be stable in water for the time it takes for them to be completely consumed. This should be at least 10 minutes. Feed that is not consumed within this time is wasted. Not only does this carry economical repercussions, but also environmental ones, adding to the waste load on the environment, reducing carrying capacity and increasing turnover risk.

Because they float they are also visible to the farmer, who can determine if the feed is being consumed or left and make rationing applicable to the behaviour, increasing efficiency. Another side effect is that farmers can visually monitor the health and behaviour of the fish whilst they come to the surface to feed. These benefits all add up to a higher economic return.

Keeping the Feed at a High Quality

"Feed is money," says Mr Manomaitis, "treat it that way; transport handle store and use it well."

Feed produced in the mill is usually of good quality, but by the time it reaches a farmer's pond that quality may have been dramatically reduced. Danger starts as soon as the Feed is transported. If they are not protected from the elements or unloaded carefully they can begin to turn to powder or mush.

When feeds are stored they should be done so in dry, well ventilated rooms with a minimum temperature change and containment for control of pests. ASAIM suggests that feed should be used within two months of production, rather than bought in advanced and saved. Over time mould growth can occur, vitamin potency can decrease and fat rancidity can emerge.

Proper storage is a simple, but essential part of feed management, which all fish farmers should learn. Taking feed samples and learning how to keep records on feed are also important, says Mr Manomaitis. According to him, bad feed is better thrown away than it is used.

April 2009

the Fish Site Editor

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