Posts Tagged: graze

Lambs grazing on pastures after wildfire show no significant adverse effects

Hopland REC turns 2018 River Fire devastation into research opportunity

Ewes and lambs graze in February 2021 on a Hopland Research and Extension Center pasture that was burned in the 2018 River Fire. UC Davis researchers analyzed meat, wool, soil, plant and water samples to assess the risk of metal contamination in sheep grazed on recently burned pasture regrowth. Photo: Valerie Eviner.

The destructiveness of wildfire flames is easy to see, but dangers may lurk in the ashes they leave behind. A group of UC Davis scientists studied lambs at the UC Hopland Research and Extension Center, investigating whether pastures regrown after a wildfire cause toxic metal residues in grazing animals. The results, published in California Agriculture journal, showed that grazing on regrown pastures did not significantly alter the metal content of the lambs' meat and wool. That's good news for ranchers and consumers from a food safety perspective.

In 2018, the River Fire burned six miles north of Hopland, scorching two-thirds of the land at Hopland REC, including areas in its sheep station. Since Hopland REC conducts ecological and agricultural research, they had data and some meat samples from the sheep flock that lived on site before the River Fire occurred. 

“A bunch of researchers came together to brainstorm how we could take advantage of this unfortunate event,” said Sarah Depenbrock, assistant professor and agronomist in the Medicine and Epidemiology department of UC Davis School of Veterinary Medicine.

Burning has played a role in agricultural processes for many years, but wildfires in California are creating a new fire landscape that interests researchers like Depenbrock. “The problem, now, is that these big wildfires probably interact with agricultural land differently than routine prescribed burns,” she said.

Large, older plants on lands that have not recently burned may contain high concentrations of metals, sequestered over years of growth. Mercury is an example of a potentially dangerous metal that can be sequestered in living things over time. These metals may be distributed in ash after the vegetation burns so the scientists examined lambs that had grazed on Hopland REC's recently burned pastures, during the first plant regrowth.

The researchers compared meat from lambs that grazed on regrown pastures in 2019, after the River Fire, to frozen meat samples that were collected the year before the fire. Lead, mercury, arsenic, molybdenum, cadmium, beryllium, cobalt and nickel were not detected in any animal samples. There were, however, a few (3 out of 26) samples that tested positive for the non-essential (potentially toxic heavy metals) chromium and thallium in the group grazing after the fire.

Due to the small number of samples testing positive, researchers could not determine statistically if this contamination was associated with grazing the burn regrowth. The concentrations of chromium and thallium found may or may not be potentially toxic, depending on the specific forms and how much meat a person consumes.

A view of Hopland Research and Extension Center in October 2018, after the River Fire, before pasture regrowth. Photo by Jennie Lane.

Another aspect of the study included testing lambs' wool to determine if it is a good method of judging the mineral content of its meat. “In general, we learned that it wasn't well-correlated with most meat metal content of interest, which is worth knowing. However, because we did not identify many of the non-essential metals of particular toxologic concern, such as lead or mercury, in any animal samples we could not determine if testing wool would be useful for those metals, as they are in other species,” said Depenbrock. She also notes that the wool from animals whose meat tested positive for chromium and thallium, did not test positive for these metals in their wool.

As the challenges in managing wildfires persist, so does the risk of contamination of food products stemming from grazing livestock.

“We didn't get striking evidence that tells us, when there's a fire, it means everything is contaminated with heavy metals,” said Depenbrock. “But it does raise the question that maybe we should be doing a little bit of surveillance to see if this is spurious or common. And we should be finding a way to screen grazing herds.”

Recommendations to manage copper concerns

“It's a very small study, but it was quite interesting to find that copper was actually lower in the postfire grazing group, which makes me wonder,” Depenbrock said.

Diseases associated with copper deficiency are a major concern in sheep. For example, congenital swayback can result in stillbirth or an animal's inability to stand on its own due to incurable changes to the spinal cord. Other adverse effects include reduced growth rate, anemia, wool defects and fiber depigmentation, and osteoporosis with higher risk of spontaneous fractures. Copper excess can also cause serious and sometimes fatal disease.

Many of the forage sources, grazing areas and rangelands in California are copper deficient, while some feed sources have excess copper. Screening and monitoring livestock herds for trace minerals including copper is crucial.

To test for copper, she advises livestock owners to obtain mineral concentrations from the organs of euthanized or dead animals. Samples from the liver and kidney are the most valuable organs to identify a potential problem in the herd. UC Davis Veterinary Medicine's California Animal Health and Food Safety (CAHFS) labs do this testing routinely.

Second, monitor and record mineral supplementation and, third, maintain updated health records to make informed decisions regarding supplementation based on a herd or flock's known problems. For example, if a producer is not accustomed to supplementing copper, Depenbrock highly recommends working with a veterinarian to start out (as there are numerous copper supplement products of varying concentration on the market), to determine a testing or screening plan, and review health records for problems potentially associated with copper.

To read the full text of the study, visit https://calag.ucanr.edu/Archive/?article=ca.2022a0016.

Burn regrowth at the Hopland Research and Extension Center, December 2018. Researchers did not detect lead, mercury, arsenic, molybdenum, cadmium, beryllium, cobalt or nickel above reporting limits in any meat or wool samples. Photo by Sarah Depenbrock.

Match.Graze and SD Grazing Exchange work to connect landowners and livestock managers

Sarah Keiser of Wild Oat Hollow in Sonoma County moves sheep for the Penngrove Grazing Project to graze her neighbors’ pastures.

Improved soil health, increased profitability, and reduced spread of wildfire are among the many benefits that arise from keeping livestock on the landscape. Efforts are underway in California and South Dakota to connect landowners with livestock managers for their mutual benefit.

Farmers can increase the organic matter in their soil and reduce their fertilizer costs by allowing livestock to graze crop residue or cover crops on their land.

Nick Jorgensen, CEO of Jorgensen Land and Cattle in Ideal, SD, said that grazing every acre allows his operation to increase soil organic matter by up to 0.75% per year and cut fertilizer costs by $50 per acre with no yield loss.

Livestock managers can rest their pastures and reduce their feed costs by seeking out crop residue, cover crops and additional pasture or rangeland for their livestock to graze.

Jorgensen said that grazing cattle on all crop and cover crop acres cuts his feed and manure management costs by up to $2 per head per day.

Grazing livestock is also a cost-effective way to reduce the accumulation of fire fuels on the landscape, helping to slow the spread of wildfires. This can be especially important for land that is too steep, rocky or remote for mowing or chemical treatment.

“I've noticed on several fires, including extreme fires, the fence lines where the fire just stopped. And the one variable, the one difference, was grazing,” CAL FIRE Battalion Chief Marshall Turbeville said.

As this year has proven, fire is a serious risk to California landowners. That's one reason University of California Cooperative Extension has launched Match.Graze. It's a map-based website designed to help livestock owners find pasture, rangeland, cover crops or crop residue available for grazing and help landowners find cattle, sheep, goats and other livestock to graze their land.

“Every property is different and requires thoughtful consideration of how it should best be grazed,” said Stephanie Larson, director of UCCE in Sonoma County, UCCE livestock and range management advisor and co-creator of the livestock-land matchmaking service.  “UC Cooperative Extension is here to serve. Put Match.Graze to work, and let's prevent catastrophic fire while helping landowners and agriculture.”

California landowners and livestock managers can visit MatchGraze.com, set up a free account, create a pin on the map and find a grazing partner.

The California website is based on the South Dakota Grazing Exchange, the original site launched by the South Dakota Soil Health Coalition with work supported by Natural Resources Conservation Service, U.S. Department of Agriculture.

Cattle graze cover crops near Roscoe, South Dakota.

Many farms in South Dakota have moved away from livestock to focus on row crops. However, increased diversity and incorporating livestock are two key principles for good soil health management.

At www.sdgrazingexchange.com farmers can find livestock to graze their crop residue or cover crops in order to capture the soil health benefits for their cropland without having to own livestock. Similarly, ranchers can give their pastures and rangeland a rest and reduce their feed costs by finding farmers with cropland to graze.

The Match.Graze and SD Grazing Exchange websites are not limited to California and South Dakota. Users from anywhere in the nation can create accounts on either website and advertise their land and livestock. The more people who use the websites, the better resources they will become.

When landowners partner with ranchers to keep livestock on the landscape, everyone wins, so the SDSHC will work to help other states create Grazing Exchange websites and connect to the maps and users of Match.Graze and SD Grazing Exchange. For more information, contact Cindy Zenk, SDSHC coordinator, at (605) 280-4190 or sdsoilhealth@gmail.com.

Match.Graze launches to reduce wildfire fuel, feed livestock

Cattle graze dry grass, reducing potential wildfire fuels.Photo by Roger Praplan

Matchmaking grazing animals with grass and rangelands

Professional grazing of overgrown rangelands, pastures and parcels is proven to reduce the spread of dangerous and costly wildfires.

Do you have land but no livestock and feel concerned about fire fuels on your property? Or are you a livestock owner that can provide a grazing service and/or need land and forage for your animals? Match.Graze can help.

Match.Graze is a free online platform connecting landowners statewide who want grazing animals to livestock owners with animals that can provide vegetation management services, created by UC Cooperative Extension. 

From small semi-rural communities to large open spaces, grazing can provide an affordable solution to the inevitable accumulation of fire fuels. Grazing can be more cost-effective for reducing fuels on landscapes that are too steep, rocky or remote for mowing or chemical treatment, or in the wildland-urban interface where burning is not an option.

“I've noticed on several fires, including extreme fires, the fence lines where the fire just stopped. And the one variable, the one difference, was grazing,” said Marshall Turbeville, CAL FIRE battalion chief.

Cattle, sheep, goats and other grazing animals all have different roles to play in grazing for fire fuel reduction. If you want to use livestock to help reduce fire risk in your area, visit MatchGraze.com.

“Every property is different and requires thoughtful consideration of how it should best be grazed,” said Stephanie Larson, director of UCCE in Sonoma County, UCCE livestock and range management advisor and co-creator of the livestock-land matchmaking service. “UC Cooperative Extension is here to serve, put Match.Graze to work and let's prevent catastrophic fire while helping landowners and agriculture.”

To find a local grazing partner, visit MatchGraze.com, set up a free account, create a pin on the map and make a match.

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