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Posts Tagged: UC Davis School of Veterinary Medicine

Tips for cattle health and safety during dry times

Cattle need special care in times of drought.
Long before Governor Brown declared an official drought for the state, many of California's ranchers knew this would be a tough year. Drought can increase the risks of animal poisonings and nutritional imbalances, and necessitate additional vigilance to assure cattle health and productivity. Veterinary toxicologists Robert H. Poppenga and Birgit Puschner, with the California Animal Health and Food Safety Laboratory System at UC Davis School of Veterinary Medicine, provide this critical information to dairy and beef producers to keep their livestock healthy during the drought. Key threats to cattle include:

Water quality — Water is the most critical factor in the diet of food animals. When cattle don't drink enough clean and safe water every day, feed intake and productivity declines. Drought conditions can potentially affect all sources of water, including groundwater, but surface waters are especially vulnerable. It is important to frequently monitor water quality, especially as quantity becomes more limited, and test for basic water quality parameters such as total dissolved solids, sodium, sulfates, and nitrates/nitrites. Blooms of blue-green algae in water are also an issue. These cyanobacteria can produce toxins that can affect the liver and nervous system. Depending on the specific toxin and amount ingested, animals may die suddenly, or suffer from weakness, staggering, or photosensitization. 

Feed quality and nutritional deficiencies — Drought conditions frequently result in the need to feed poor quality forages or to switch to alternative feed sources. Both can affect animal nutrition and increase the risk for intoxications. Use of poor quality forages can cause or exacerbate deficiencies of important minerals such as selenium, copper, and phosphorus and vitamins such as vitamins A and E. In addition, drought affected forages are often deficient in energy and protein. Even in non-drought years, deficiencies in selenium and copper are common in California cattle, particularly beef cattle. Copper deficiency causes reduced production, diarrhea, decreased resistance to infectious agents and parasites, poor vaccine response, loss of bone strength in calves, weakness and wobbling in neonates, reproductive failure, and sudden death of adult animals. Selenium deficiency also results in less resistance to infectious agents and parasites, and causes white muscle disease of skeletal and heart muscle resulting in stiff gaits, slow movement, heart damage and weak neonates. Primary vitamin A deficiency occurs in beef cattle on dry range pasture during periods of drought. Clinical signs include night blindness, dry eye, retarded growth rate, reproductive failures, and increased mortality. Maternal deficiency of vitamin A can cause abortions, stillbirths, or calves born alive but blind and weak that die within 1 to 3 days. Cows should be given an injection of vitamin A (and D) about 30 days prior to calving and calves should be given a vitamin A injection at birth.

Increased incidence of plant poisonings — Cattle will seek out and consume plants that they would not otherwise find palatable during drought conditions. Nitrate poisoning is one of the most common plant associated intoxications diagnosed by the California Animal Health and Food Safety Laboratory. The potential for nitrate poisoning to occur is increased when livestock water sources also contain elevated concentrations. The first sign of nitrate poisoning is often the sudden and unexplained deaths of one or more animals. Other clinical signs include drowsiness, weakness, muscle tremors, increased heart and respiratory rates, staggering, and recumbency. Signs can develop with several hours of ingesting a toxic amount. Nitrate concentrations can be easily and cheaply determined from samples submitted to a veterinary diagnostic laboratory for testing. 

During periods of drought, cattle producers should be especially careful about the quality of feed and water available for their animals. Sick animals should be tested for various nutritional deficiencies and dead animals can undergo necropsies to determine cause of death so that other animals in the herd can be treated appropriately. Additional information and testing is available at the California Animal Health and Food Safety Laboratory System. For laboratory location and contact info, visit A longer, more detailed version of these tips may be found here.

Robert H. Poppenga and Birgit Puschner, veterinary toxicologists with the California Animal Health and Food Safety Laboratory System at UC Davis School of Veterinary Medicine, contributed to this article. 


Posted on Tuesday, August 26, 2014 at 7:34 AM

California's lead ammunition ban was product of years of research

California recently passed a law that will ban the use of lead ammunition when taking wildlife with a firearm. The intent is to protect scavenging birds and other wildlife from the threats of lead poisoning from spent lead ammunition.  

While the new law, which was passed on Oct. 11, 2013, will be phased in over the next six years, the research that helped shape it has been going on for some time and much of it was done by researchers at the University of California, Davis.  

UC Davis wildlife epidemiologist Terra Kelly with a golden eagle.
UC Davis wildlife epidemiologist Terra Kelly (in photo at right) studied the effects of big game hunting on lead exposure in carrion-eating birds like eagles and turkey vultures and monitored the effect of a 2008 law that made it illegal to hunt with lead ammunition in eight counties within the California condor range. Kelly did her doctoral work with wildlife health expert Christine Johnson, associate professor of epidemiology at UC Davis School of Veterinary Medicine.  

Scavenging birds and other animals are susceptible to lead poisoning when they inadvertently ingest spent pellets or bullet fragments in the tissues of animals killed by lead-based ammunition. 

"Lead is a soft metal, so it fragments upon impact leaving hundreds of pieces around the wounded area of the animal," Kelly said. "Many scavengers forage in large groups, meaning a single carcass or gut-pile containing spent lead ammunition can expose many individuals."

Kelly and Johnson’s studies were funded by the California Department of Fish and Wildlife and published by the journal PLoS ONE in 2011. 

While their research illuminates the threat posed by lead ammunition, Kelly and Johnson make clear that hunting itself is not the issue at hand.  

"Hunting is an irreplaceable tool for wildlife management, especially now that we have fewer large predators but more invasive species like wild pigs," said Johnson in 2011, when the studies were published. "Yet we know that accidental consumption of lead can make animals and people sick."

"It just makes good sense to use non-lead ammunition, wherever it is available, to protect wildlife as well as eliminate any potential risk to hunters and their families," she added.

Lead poisoning has been an ongoing issue for birds at rehabilitation facilities, with Golden Eagles being hit especially hard.  

"By the time they get to the center, we’re often unable to treat them because they’re so close to death," said Michelle Hawkins, director of the school's California Raptor Center. "We put in our best efforts, but very commonly it’s a losing battle. Prevention is definitely the way to keep these birds from having this problem."

National Geographic published a story about the lead ban on Oct. 11, quoting Johnson on the need for long-term monitoring of birds. She and Kelly say it should start right away so that wildlife can be tracked between now and 2019, when the law must be in full effect. 

Posted on Thursday, October 31, 2013 at 1:40 PM

Perils of illegal marijuana crops

Mourad Gabriel with a CA fisher

Rodenticides used on illegal marijuana farms have already been shown to pose serious harm to the fisher—a cat-sized carnivore found in forests across Canada and four regions in the U.S. (Previous news article.)

Mourad Gabriel, a doctoral candidate with the Veterinary Genetics Laboratory at UC Davis School of Veterinary Medicine, provides a more comprehensive look at the situation in the recent issue of The Wildlife Professional, put out by The Wildlife Society. (Article here.)

New information looks at risks to other species and to the ecologists and biologists conducting wildlife research on community and public lands where more of these crops are being cultivated.

Highlights include: 

  • Newly documented fisher mortalities (necropsies done at UC Davis’ California Animal Health and Food Safety Laboratory System)

  • New data documenting just a glimpse of potential environmental degradation possibly occurring on our public lands

  • First mention of toxicants like carbamates and organochlorides (DDT etc...) that are being found in California grow sites

  • Provides readers with information on how some of these toxicants are placed at grow sites to maliciously poison wildlife

  • New info and discussion points of "what are" the potential effects of ...such as damming water courses, putting toxic slurry of chemicals in dammed creeks, cutting riparian zones, human feces (affects salmon and many other species)

  • First-hand accounts of ecologists and biologists conducting wildlife research being shot at, chased and threatened

  • Quantifies the loss of project area access, and data from fisher projects in California public lands

There is also a link to a video that offers a first account visual representation of what a fisher looks like, the unfortunate visual effects of toxicosis and the realistic outcome to wildlife from these illicit activities on tribal and public lands.

For more information, contact Mourad Gabriel, or Trina Wood, 

Posted on Tuesday, April 2, 2013 at 1:20 PM

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