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A new ranking system identifies the total financial worth of
milk-producing cows in a dairy herd. Dairy producers can use the
rankings in making breeding decisions for peak milk production and
profits. Originally, the system was developed by ARS scientists for
evaluating dairy bulls. Known as Net Merit, the new system is based on
the economic value of a dairy cow's geneticsits milk quality, productive
lifespan and resistance to mastitis, a dairy cow disease. It goes beyond
the practice of measuring common pounds of milk a year as a yardstick for
a cow's performance. A report of the ranking data, updated twice a year,
is available to producers nationwide. It's also part of commercially
available computer databases. Net Merit rankings also help farmers pick
animals to sell to artificial insemination and embryo transfer
services.
Animal Improvement
Laboratory, Beltsville, MD
Duane Norman, (301) 504-8092
Scientists no longer need to slaughter pigs to evaluate the animal's
production of lean meat versus fat. ARS researchers have adapted
medical technology that gives accurate information on body composition
while the hogs are still alive. Magnetic resonance imaging (MRI) shows
"slices" of a pig's body, recording data on the animal's fat distribution,
total body fat and muscle. Another system, Dual-Energy X-ray
Absorptiometry (DEXA), provides a whole body scan of a live pig.
Scientists now chart changes in a pig's body composition as it grows.
These technologies could become especially useful in selecting breeding
animals that produce the most lean meat.
Growth Biology
Laboratory, Beltsville, MD
Al D. Mitchell, (301) 504-7124
Corn residues from distilling ethanol can be used to feed tilapia fish
at a fraction of the cost of current fishmealand the fish taste just as
good. Corn-based feed costs about 18 to 23 percent less than
commercial fishmeal. In ARS tests, tilapia gained about a pound of weight
for every two pounds of feed when they ate either corn gluten meal, corn
distillers' grain with solubles or corn gluten feed, plus soybean meal for
extra protein. Researchers' next goal: refining the ration so weight
gained per pound of feed is equivalent to that achieved from fish meal
rations. Tilapia sales are among the fastest-growing in U.S. aquaculture.
Consumers in 1994 bought about 66.5 million pounds live weight of tilapia,
of which 50 million pounds were imported.
Biopolymer Research, Peoria,
IL
David J. Sessa, (309) 681-6351
Refrigeration apparently lowers the viability of sperm used to
artificially inseminate commercial turkey hens. ARS tests found that
sperm numbers on the turkey egg yolk membranea good gauge of egg
fertilityare about 80 percent higher with fresh sperm versus refrigerated
sperm. A turkey hen's body selects and stores sperm in reproductive tract
tubules for fertilizing eggs throughout the 26-week egg-laying cycle.
Typically only about one percent of fresh sperm make it to the tubules.
When sperm's been refrigerated 24 hours, the number drops even lower. To
compensate for drawbacks of stored sperm, growers double up on
insemination doses or inseminate more frequently. Virtually all
commercially grown turkeys are produced by artificial insemination, and
increasing storage time for semen would be beneficial to the industry.
Germplasm and Gamete
Physiology Laboratory, Beltsville, MD
Ann M. Donoghue, (301) 504-8580
A longer grazing season can be gained by ranchers who graze their
animals on switchgrass pastures. ARS and Iowa State University
scientists added cool-season, nitrogen-fixing plants to pastures already
planted with warm-season switchgrass. After a year, the legume plants
provided enough nitrogen to increase growth of switchgrass. In
northcentral states, the best switchgrass forage yields come in June
through August, while the legumes produce their highest yields in cooler
months. By growing legumes such as alfalfa, sweetclover, red clover and
birdsfoot trefoil with switchgrass, livestock producers can ensure a good
forage supply through a greater part of the year.
Field Crops Research, Ames, IA
Dwayne R. Buxton, (515) 294-9654
Rhizoma peanut is a popular forage for cow-calf producers on the Gulf
Coast. A new study shows an additional use: Cattle may gain enough
weight grazing rhizoma peanut to go directly from pasture to slaughter
without the usual feedlot stint. Fat color and off-flavor problems often
associated with forage-finishing apparently don't occur when steers eat
rhizoma peanut. But the new study shows these animals' meat may be
darker-colored and less tender, for a slight overall reduction in quality
compared with steers fattened on grain-based feed. Producers planning to
use rhizoma peanut to finish cattle may want to choose a cattle breed with
greater genetic potential for tender meat.
Subtropical
Agricultural Research Station, Brooksville, FL
Andrew C. Hammond, (904) 796-3385
Last updated: October 29, 1996
Return to: Quarterly Report
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