Hot Topics in research

Cow/Calf Safflower Supplementation Linoleic and oleic fatty acids have been the focus of a great deal of research in ruminant nutrition for several years. Animal scientists from Wyoming, Montana and New Mexico continue this work by comparing the effects of safflower seed supplements with different fatty acid profiles. They recently compared safflower seeds high in linoleic acid with safflower seeds


Safflower Supplementation

Linoleic and oleic fatty acids have been the focus of a great deal of research in ruminant nutrition for several years. Animal scientists from Wyoming, Montana and New Mexico continue this work by comparing the effects of safflower seed supplements with different fatty acid profiles.

They recently compared safflower seeds high in linoleic acid with safflower seeds high in oleic acid. They wanted to know how the different acids affected cow body weight change, body condition score and milk production. They also looked at the different acids' effects on calf weight gain, cow serum metabolites and metabolic hormones.

Angus-Gelbvieh cross cows fed safflower supplements were compared with controls fed a corn-soybean supplement. All cows had free access to native grass hay and trace-mineralized salt.

The researchers found the different fatty acid contents didn't influence post-calving reproductive performance. Body condition score and milk fat percentage, however, were influenced by the fatty acid profile of the supplement.

The selective use of high-linoleic safflower seeds may be useful to increase body condition score when pre-calving energy deficiencies are present or when poor body condition scores exist at calving. Researchers say, though, that in moderate-condition cows, supplementation with oilseeds was not accompanied by increased animal performance.

Journal of Animal Science 2002 80:2023-2030.

Test Improves Grub Monitoring

More targeted control of cattle warble grubs may soon benefit cow-calf and feedlot production, thanks to a new breakthrough diagnostic test.

Scientists at the Lethbridge Research Centre in Alberta, Canada, collaborated with Spanish scientists to develop a test that's 95% accurate in diagnosing active grubs. What's more, the test can be used on all age classes of animals. The previous test was inaccurate and only reliable on calves after their first pasture season, researchers say.

Extremely sensitive, the new test detects very small traces of a protein secreted by the parasite as it migrates through the animal.

Researchers explain that adult flies lay eggs on the legs and underside of cattle. When the eggs hatch, the tiny maggots burrow into the animal's skin and migrate through the animal's connective tissue by excreting enzymes that break down tissue for the developing maggot to ingest.

Feedlots typically treat cattle for grubs as part of broad-spectrum internal parasite treatments. Researchers say the new test not only can monitor treatment effectiveness but also prevent overuse of such products, thus preventing a resistance buildup.

For more information about the test, contact Doug Colwell at 403/317-2254.

Identifying Parasites

New serological and genetic tests may help researchers distinguish a host of insidious look-alike parasites, such as Toxoplasma gondii and Neospora caninum, which cause abortion and other health problems in livestock.

According to researchers at the USDA's Agricultural Research Service (ARS), the ability to make such distinctions will help define the distribution of single-celled parasites in domestic animals, wild animals and people.

Millions of infectious-stage oocysts are excreted in the feces of infected animals on or near farmland. When the oocysts come in contact with feed, livestock can get infected.

But the two protozoans' oocyst stages are virtually indistinguishable, making sensitive tests necessary to diagnose or distinguish the infections from each other.

ARS scientists are working to discern how many cyst-forming parasitic species exist, how they're related to one another, and how to tell them apart. To do that, they look at variations in genes by genotyping strains of parasites taken from all classes of food animals.

A better understanding of the epidemiology of these parasites and assessing the risk are the ultimate goals of the research.

For more information, contact the ARS information staff at 301/504-1617.

Grazing Birdsfoot Trefoil

Animal scientists in Missouri investigated the performance of steers grazing rhizomatous birdsfoot trefoil (RBT) compared to nonrhizomatous birdsfoot trefoil (NRBT). The birdsfoot trefoil was seeded in pure stands and interseeded with endophyte-free tall fescue (Festuca arundinacea).

Researchers say beef producers could improve the performance of grazing steers by interseeding birdsfoot trefoil to tall fescue pastures. In addition, no nitrogen fertilizer would be needed for interseeded pastures compared to pure tall fescue pastures. Thus, the cost to produce beef would likely be lower for interseeded pastures.

Compared to NRBT, the ability of RBT to spread by rhizomes didn't lead to greater total forage production or livestock performance in this short-term study. Perhaps RTB will have improved persistence in the longer term, but at present it appears NRBT provides the same benefits.

Journal of Animal Science 2002 80:1970-1976.


Improving BVD Vaccines

One particular strain of bovine viral diarrhea (BVD) virus, BVDV1b, has been found in cattle with shipping fever but isn't currently in most commercial vaccines. But researchers from Oklahoma State University (OSU) are working to remedy that.

In two studies observing calves from mixed sources for four to five weeks, BVDV infections occurred and often appeared to contribute to shipping fever, researchers say.

What's more, a recent study demonstrates antigenic differences between subtypes BVDV1a and BVDV1b. The former is in current modified-live and killed vaccines, but only one killed vaccine and no modified-live vaccines have BVDV1b.

Researchers say the ability of BVDV1a vaccines to protect against BVDV1b strains has not been demonstrated, and they plan to conduct additional studies in this area.

Ultimately, researchers hope to improve BVD vaccines so they provide cross protection to the diverse strains. They say BVDV1b strains eventually might be incorporated into the BVDV1a vaccines. Already, two U.S. veterinary biologics companies have asked the research group to prepare a budget for an improved vaccine.

For more information, contact OSU's Robert Fulton at 405/744-8170 or e-mail>

Corn Flaking

The digestibility of starch from corn grain is limited by the protein matrix that encapsulates starch granules. It's also limited by the compact nature of the starch itself, say researchers from the University of California-El Centro.

Disruption of the protein matrix (by shear forces on hot grain during flaking) is the first limiting step toward optimizing starch digestion. Five critical production factors influence the quality of steam-flaked corn: steam chest temperature, steaming time, roll corrugation, roll gap and roll tension.

For optimal shear, it's important that rolls be hot and that kernels be hot when flaked. Steam chests should be designed to allow a steaming time of at least 30 minutes at maximum roller mill capacity producing a flake of 24 lb./bushel. As little as 5% moisture uptake during steaming appears adequate. The rate of flaking and distribution of kernels across the rolls also are critical.

Proper steam flaking will increase normal yellow corn's net energy for maintenance (NEm) and for gain (NEg) values by 15% and 18%, respectively. Current feeding standards underestimate the NEg value of steam-flaked corn by 3.8% and overestimate the NEg value of dry-rolled corn by 5.5%, researchers say.

The increase in digestibility depends on disruption of the protective protein matrix surrounding the starch granules, rather than simply increasing starch solubility. Flaking of corn increases extent of digestion of starch both in the rumen and in the small intestine; this can largely explain the increased net energy value of the grain.

The availability of starch can be estimated from various measures — flake density, flake thickness, starch solubility and nutrient release during incubation with amylase. But the adequacy of steam flaking can be predicted most reliably and directly by measuring the starch concentration of feces.

Journal of Animal Science 2002 80:1145-1156.

Carcass Quality

Testing for E. coli In Water

Detecting E. coli O157:H7 in water just got easier and faster, thanks to ARS researchers. Usually spread in contaminated food, E. coli is sometimes waterborne. Researchers have developed a rapid, easy-to-use test to detect and count E. coli O157:H7 bacteria in natural and constructed bodies of water.

The test uses magnetic beads coated with anti-E. coli monoclonal antibodies that bind to the bacteria. This makes it possible to count the bacteria.

Until now, testing methods were designed only to detect the bacteria, not to measure how many are present. The number of E. coli bacteria present is crucial information since the levels that cause infection can vary depending on a person's health status.

The new method also makes it possible to detect E. coli in water samples in a day or less, compared with traditional testing that took up to four days.

Investigations are under way to assure no other bacteria cross-react with the magnetic beads. However, if this test proves to be accurate and selective, it should allow for detection of E. coli in a variety of liquid samples, such as swimming pools and other recreational water.

For more details, contact the ARS information staff at 301/504-1617.