
A Better Way to Measure Catfish Feed Intake,
GrowthBy Tara
Weaver-Missick August 4, 1999Tiny glass beads mixed with catfish
feed are helping Agricultural Research
Service scientists track how food intake affects catfish growth. Research geneticist Jeffrey T. Silverstein, based at the ARS
Catfish Genetics
Research Unit in Stoneville, Miss., developed this technique. Until now,
its been difficult to measure how much food an individual fish eats
daily, because all fish are raised together in a pond and fed simultaneously. Its easier to measure feed intake with land animals, because feed can
be weighed before and after, and then calculated to determine what each animal
consumed, according to Silverstein. Generally, catfish producers record feed intake based on simple observation,
but this method assumes that fish consumed all the feed delivered and that they
all ate the same amount. Silverstein adapted an innovative technique from salmon feeding
studies--tiny glass beads in the feed--and customized it for channel catfish.
The opaque glass beads are about 0.4 millimeters in diameter. They are mixed
into the feed in low concentrations of about 1 percent of the feed. After
feeding, catfish are anesthetized and x-rayed. This allows the beads to be
counted so that an accurate feed calculation consumed by each fish can be
taken. Fish with superior feed intake and conversion of feed into filet meat
can be identified, so this trait can be incorporated into breeding programs.
Silverstein has perfected the technique even more by automating the bead
counting process. This allows him to view 600 scanned x-ray images a day,
versus 200 images over a few weeks when done by hand. Automation is nearly 100
percent accurate. In indoor tank studies ARS scientists found different catfish strains
consume feed at different rates. This information will help them to make
genetic improvements in channel catfish. An article on the research also appears in the August issue of Agricultural Research magazine.
The story is also on the World Wide Web at: http://www.ars.usda.gov/is/AR/archive/aug99/feed0899.htm Scientific contact: Jeffrey T. Silverstein, ARS Catfish Genetics
Research Unit, Stoneville, Miss., phone (601) 686-3591, fax (601) 686-3567,
[email protected]. U.S. Department of Agriculture | |