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NMSU Study Lowers Antibiotic Residues in Market Dairy Cows

LAS CRUCES - Rather than shipping dairy cows straight from the milk parlor to the meat processor, a New Mexico State University study suggests holding off 45 days and spending the time beefing up these milquetoasts.



Holding dairy cows like these near Mesquite an extra 45 days before shipping to market improves meat quality and assures that antibiotic residues are long gone, a NMSU study reports. Dairy specialist Mike Looper with NMSU's Cooperative Extension Service said more than a third of New Mexico's dairy cow are processed as beef each year. (02/04/2002) NMSU agricultural communications photo by Norman Martin

The time not only allows dairy producers to improve meat quality, it assures that antibiotic residues are long gone by the time the dairy cows are shipped to market. Of the 278,000 dairy cows in New Mexico, more than a third are processed as beef each year. These so-called cull cows are often used for hamburger, but they're just as likely to end up in fajita meats, frozen entrees or at your family-style steakhouse.

"We're excellent at producing milk," says Mike Looper, the dairy specialist with New Mexico State University's Cooperative Extension Service in Las Cruces. "What we want to do is make sure we're excellent at producing beef, and part of that means making sure any antibiotic clears the system."

Unfortunately, Looper said, New Mexico has had some antibiotic residue violations from the U.S. Department of Agriculture's Food Safety Inspection Service. When cows are sent to market, they're screened for antibiotic use. If antibiotic levels exceed the threshold for a particular drug, then the animals will be set aside and cannot be used for human consumption, he said. Antibiotics are generally given to dairy cows for infections, usually some sort of udder problem.

Using a grant from the National Cattlemen's Beef Association in Englewood, Colo., a NMSU dairy research team last year began placing 77 Holstein dairy cows from four different New Mexico dairies on a high-energy concentrate diet for an additional 30 or 60 days beyond their normal market shipping dates. The feed was a mix of 40 percent from high-quality alfalfa and 60 percent corn, soybean meal, soybean hulls and fat. After the extended feeding period, the cows were shipped to Lone Star Packing in San Angelo, Texas, for processing and data collection.

"It looks like it's going to be economically feasible to feed out these cows for an additional 45 days," said Cat Rogers, a NMSU graduate student who conducted the field trials and completed the data analysis in January. The researchers found that at 30 days the cows had not adjusted to the feed ration, and by 60 days the gains had begun to decrease.

The extended ration added about three pounds a day per cow. Thanks to an abundance of body energy reserves, ranch jargon for having a thick fat cover, the dairy cows were less likely to bruise during transportation to the sales floor or processing facility.

Reduced bruising means less meat is trimmed when the carcass is processed, which means more money for the dairy producer, Rogers said. The extra time also decreased the likelihood of selling cows with antibiotic residues.

Falling onto a dairy's cull list for market shipment can occur for any variety of reasons. Primarily it's because a cow's milk production has ceased or dropped below a breakeven point where it's economically viable to keep the cow. A dairy cow begins producing milk at about two years, and normally stays in the herd for another three years. New Mexico ranks seventh in total milk production in the United States.

"We want to increase the awareness of dairy producers that not only are they milk producers, but they're beef producers as well," Looper said.