Larval FeedsLarval Feeds

Dr. Craig KasperDr. Craig Kasper

IntroductionIntroduction

• Last time…we spoke about live feeds for larval fish. Last time…we spoke about live feeds for larval fish.

• Most live feeds are preferred over processed diets for Most live feeds are preferred over processed diets for many reasons, most involving superior fish performance many reasons, most involving superior fish performance when on the feeds.when on the feeds.

• If you decide to feed diets which are not live, then you If you decide to feed diets which are not live, then you have several choices to make.have several choices to make.

• Today we will consider options to traditional live feeds Today we will consider options to traditional live feeds for larval fish.for larval fish.

Table 1 Composition of (chicken) Egg

Whole egg

egg white

egg yolk

Protein, % 48.8 76.9 32.8

Fat, % 43.2 - 62.2

Gross energy, kcal/kg 5 830 3 070 6 910

Metabolizable energy (ME), kcal/kg

4 810 2 533 5 700

ME: protein ratio 9.8 3.3 17.3

Calcium, % 0.2063 0.0427 0.2653

Phosphorus, % 0.873 0.282 1.020

Eggs or Not?Eggs or Not?

• Raw egg contains Raw egg contains avidinavidin (growth inhibitor) de- (growth inhibitor) de-activated with heat. activated with heat.

• Cooking unprocessed egg, however, causes Cooking unprocessed egg, however, causes irreversible separation of the two egg fractions, yolk irreversible separation of the two egg fractions, yolk and white, due to denaturation of protein components and white, due to denaturation of protein components in both fractions. in both fractions.

• Blending the two fractions requires binders ($$$). Blending the two fractions requires binders ($$$).

Is my fish full??Is my fish full??

• Wolf’s index is usful for some applications, but you Wolf’s index is usful for some applications, but you have to sacrifice fish to make it work.have to sacrifice fish to make it work.

• Sometimes you can just look!Sometimes you can just look!

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Feed TrainingFeed Training

• Nearly every larval fish will eat a microorganism, but Nearly every larval fish will eat a microorganism, but getting them to take to man-made diets is something getting them to take to man-made diets is something else.else.

• Some fish don’t care (i.e. channel catfish, convict Some fish don’t care (i.e. channel catfish, convict cichlids) while others won’t eat unless extensive cichlids) while others won’t eat unless extensive feed feed trainingtraining takes place (yellow perch). takes place (yellow perch).

• Other challenges include: confirmation of diet Other challenges include: confirmation of diet ingestion, feedingestion, feed efficacy, and feeding rates, etc.efficacy, and feeding rates, etc.

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Feed Training continued…Feed Training continued…

• Feed training isn’t difficult, but time consuming.Feed training isn’t difficult, but time consuming.

• The goal is to put as much food in front of the fish’s The goal is to put as much food in front of the fish’s face as the system can withstand!face as the system can withstand!

• Start hand feeding as soon as the fish are free Start hand feeding as soon as the fish are free swimming if you suspect you’ll be feed training.swimming if you suspect you’ll be feed training.

YeastYeast

• Easy to maintain batches. Easy to maintain batches.

• Good source of protein and complexGood source of protein and complex

B vitamins.B vitamins.

• Sometimes Brewer’s yeast is better,Sometimes Brewer’s yeast is better,

but often more expensive.but often more expensive.

Microencapsulated FeedsMicroencapsulated Feeds

• Designed to deliver the maximalDesigned to deliver the maximalamount of nutrition in the smallestamount of nutrition in the smallestpackage.package.

• Difficult manufacturing processDifficult manufacturing process(and you pay for it in the end) due (and you pay for it in the end) due to the grinding process needed to maketo the grinding process needed to makethe starter paste.the starter paste.

• Capsules actually can interfere with some fish guts and cause Capsules actually can interfere with some fish guts and cause problems.problems.

Krill?Krill?

• Not as is (too big), but an excellent attractant!!Not as is (too big), but an excellent attractant!!

• Can get fish which aren’t eating to start eating.Can get fish which aren’t eating to start eating.

• Expensive, but a littleExpensive, but a little

goes along way.goes along way.

Organ and Blood ProductsOrgan and Blood Products

• Great for flavor.Great for flavor.

• Difficult to get due to “mad cow” prion scare.Difficult to get due to “mad cow” prion scare.

• Might be able to contact a local butcher here.Might be able to contact a local butcher here.

• Some dried blood products don’tSome dried blood products don’t

work as well, due to oxidation.work as well, due to oxidation.