Feed to FilletsWhat Makes Catfish
By counting the opaque glass pellets visible in x-rayed catfish, scientist can
calculate the amount of feed the fish have consumed.
How does feed intake affect catfish growth? To answer that question,
geneticist Jeffrey T. Silverstein has developed a technique that tracks tiny
glass beads mixed with catfish feed as they move through a fish's body.
Until now, it's been difficult to measure how much food an individual fish
eats daily, because all fish are raised together in a pond and fed
"It's easier with land animals, because feed can be weighed before and
after mealtime and then calculated to determine what each animal
consumed," says Silverstein, who is in the
ARS Catfish Genetics Research Unit at
Catfish production researchers generally record feed intake based on simple
observation. But this method assumes that fish consume all the feed delivered
and that they all eat the same amount.
In developing a more precise way to measure catfish feed intake, Silverstein
adapted an innovative technique from salmon feeding studiesputting tiny
leaded glass beads in the feedand customized it for channel catfish.
About 0.4 millimeters in diameter, the x-ray opaque glass beads are mixed
into the feed in low concentrationsreplacing about 1 percent of it. After
feeding, catfish are caught, anesthetized, and x-rayed. Silverstein then counts
the beads in the fishes' stomachs, so he can accurately calculate feed consumed
by each one. The procedure is not lethal.
Fish with superior feed intake and conversion into fillet meat can be
identified, says Silverstein, so this trait can be incorporated into breeding
"In indoor tank studies, we've found different catfish strains consume
feed at different rates," he says. "This information will help us to
make genetic improvements in channel catfish."By
Agricultural Research Service Information Staff.
Jeffrey T. Silverstein is in the
Genetics Research Unit, P.O. Box 38, Experiment Station Rd., Stoneville, MS
38776; phone (662) 686-3591, fax (662) 686-3567.
"Feed to FilletsWhat Makes Catfish Grow" was
published in the August 1999
issue of Agricultural Research magazine.