- Author: Saoimanu Sope
Hopland REC turns 2018 River Fire devastation into research opportunity
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.
Uncertain results raise more questions
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.
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.
/h3>/h3>/h3>- Author: Rebecca Ozeran
A few months ago, I was asked about the toxicity of various plants in a horse pasture after the death of a miniature horse using that pasture. While many of the identified plants were chemically harmless (such as filaree [Erodium spp] and some native clovers), the pasture did have fiddleneck (Amsinckia spp) and popcorn flower (Plagiobothrys spp), two native forbs with potentially toxic chemistry.
Popcorn flower (above) has small white flowers. Fiddleneck (below) has slightly larger yellow flowers. Both plants have similar overall shapes: slender flowering stems, relatively small leaves, and hairs on all parts except the flowers themselves.
Fiddleneck is a known alkaloid accumulator and popcorn flower is similarly suspected to accumulate alkaloids. There are no cases that I have found where popcorn flower was identified as a cause of toxicity, however. Most research on popcorn flower chemistry focuses on insect herbivores which like to eat plants with alkaloids, to protect themselves against predation (e.g. Hartmann et al. 2004) – but that's a topic for another blog!
Alkaloids are secondary organic compounds produced by many plants. Different types of alkaloids have different interactions with animal biology, some of which are benign or beneficial, and others which are harmful. Some alkaloids you may have heard of include morphine, nicotine, and quinine. Pyrrolidizine alkaloids, the type found in fiddleneck and popcorn flower, have harmful effects. Toxicity often occurs when animals eat feed or hay contaminated with fiddleneck seeds, and some cases have been documented from animals grazing the plant in a pasture. Fiddleneck alkaloids can cause liver disease and death of horses, cattle, and pigs, but sheep seem to be less vulnerable (Craig et al. 1985).
Both fiddleneck and popcorn flower may also accumulate nitrates. Nitrates convert into nitrites once the animal eats the plant. Nitrites then react with hemoglobin in the blood and make it unable to carry oxygen. This oxygen deficiency can cause death in a matter of hours depending on the concentration of nitrates in the animal's diet. Sheep, pigs, and horses seem more resistant to nitrate poisoning while cattle are most vulnerable (Tucker et al. 1961).
How to avoid livestock poisoning by fiddleneck and popcorn flower
The best way to prevent livestock poisoning by these forbs is to make sure there is plenty of good forage available. Livestock don't typically seek out fiddleneck or popcorn flower. Fiddleneck and popcorn flower have more stem than leaf, so they aren't very palatable, and they are densely covered in hairs that tend to discourage grazing. In a pasture with plenty of grasses and desirable forbs, then, animals will easily avoid these harmful plants.
The risk of poisoning arises when there is little else for the animals to eat. As a pasture that has been overgrazed or a pasture experiencing a drought therefore might have too few plants for the animals to be able to avoid popcorn flower and fiddleneck. When possible, having more than one pasture can help keep animals safe. Animals should be moved out of pastures where the only available plants may be toxic.
Body size is also a factor in many cases of toxicity. A fully grown 1,000-lb animal may be unaffected by a small amount of these toxins in their diet (such as this horse, pictured above, who ate a mouthful of grass plus a single fiddleneck plant right in front of me), while a young or small animal might become seriously ill after eating just a few plants. Whether an animal develops clinical signs of toxicity or poisoning depends on the concentration of toxin in the forage, the quantity of forage consumed, and the animal's size. However, any amount could be harmful and if you notice your animals are consuming toxic plants, please contact your veterinarian.
Can fiddleneck and popcorn flower be controlled?
You are not likely to eradicate them, but there are ways to control these plants if you are concerned about them.
Both fiddleneck and popcorn flower can be hand-pulled – gloves recommended to protect against the hairs – if present in small patches. On small acreages, mowing an infested pasture before the plants produce seeds in the spring can help reduce the population. Some herbicides can also help kill these plants; generally speaking, you will need to apply herbicides when the plants are young and small, to prevent seed production for the year. Contact your local UCCE office for more specifics if you want to consider chemical treatments.
Long-term, re-seeding bare patches in pastures and ensuring moderate grazing can also help outcompete these species. Because they have relatively small leaves, popcorn flower and fiddleneck rely on plenty of open space and sunshine to grow. As a result, they are less common in pastures that are densely populated by desirable forages that shade smaller plants.
For more on establishing a healthy pasture, even if you have dryland pastures or pastures with animals other than horses, the free guide here is a great place to start: Establishing and Managing Irrigated Pasture for Horses.
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If you are concerned that your animals may have been exposed to toxic plants, contact your veterinarian. If you have concerns about plants in your pastures, feel free to contact your local UCCE office for assistance with plant ID.
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Check out CalFlora to see the geographic distribution of these and many other plant species in California
References:
Craig, A.M., L.L. Blythe, E.D. Lassen, and M.L. Slizeski. 1985. Resistance of sheep to pyrrolizidine alkaloids. Israel Journal of Veterinary Medicine 42:376-384.
Hartmann, T., C. Theuring, T. Beuerle, L. Ernst, M.S. Singer, and E.A. Bernays. 2004. Acquired and partially de novo synthesized pyrrolizidine alkaloids in two polyphagous arctiids and the alkaloid profiles of their larval food-plants. Journal of Chemical Ecology 30(2):229-254.
Tucker, J.M., D.R. Cordy, L.J. Berry, W.A. Harvey, and T.C. Fuller. 1961. Nitrate Poisoning in Livestock. California Agricultural Experiment Station. Circular 506, 12p.
- Author: John M Harper
Join us for our next webinar on Wednesday, June 17th at 1pm PDT, which will feature Dr. Tina Saitone, CE Specialist in Agricultural and Resource Economics, presenting "Can you Insure Against Drought? Information and Outcomes from the Pasture, Rangeland, and Forage Insurance Program".
Register at https://tinyurl.com/WRWs4
(we will email registrants a Zoom meeting link morning of the webinar)
Working Rangelands Wednesdays is a bi-weekly webinar series where we explore topics around rangeland agriculture in California and across the West.
You can view previous Working Rangelands Wednesdays sessions on the UC Rangelands YouTube channel.
For questions, please contact Grace Woodmansee at gwoodmansee@ucdavis.edu.
![Working Rangelands Tina Saitone Working Rangelands Tina Saitone](/blogs/blogcore/blogfiles/71545.png)
- Author: Pamela Kan-Rice
Two new studies on the costs and returns of establishing and producing irrigated pasture in the Sierra Nevada Foothills have been released by UC Agriculture and Natural Resources' Agricultural Issues Center. Ranchers in Nevada, Placer and surrounding counties may find the cost estimates useful for planning.
Based on 40 acres of leased ground, the studies focus on establishment by tilling the soil, using conventional cultural practices and re-establishment of pasture using no-till cultural practices. The two separate studies, by Dan Macon, UCCE livestock and natural resources advisor, and Donald Stewart of the Agricultural Issues Center, estimate the cost of establishing or re-establishing a pasture and producing pasture over its 30-year life span.
There are two methods of establishing a pasture. One method uses conventional cultural practices, destroying the existing pasture and preparing the soil, or seed-bed, using conventional tillage practices.
The other no-till method of re-establishing the pasture uses high-intensity grazing and herbicides to destroy the existing pasture and plant new pasture using a no-till seed drill.
Their analysis reports the differences of machinery costs and methods. The reported prices for materials, equipment and custom services are based on January 2020 figures.
UC Cooperative Extension farm advisors, specialists, grower cooperators and other agricultural associates provided input and reviews. The authors describe the assumptions used to identify current costs for pasture establishment and production, material inputs, cash and non-cash overhead. A ranging analysis table shows profits over a range of prices and hay yields.
The new studies are “2020 - Sample Costs to Establish or Reestablish and Produce Irrigated Pasture in the Sierra Nevada Foothills, Flood Irrigated” and “2020 - Sample Costs to Produce Irrigated Pasture in the Sierra Nevada Foothills, Flood Irrigated.”
Both studies can be downloaded from the UC Davis Department of Agricultural and Resource Economics website at http://coststudies.ucdavis.edu. Sample cost-of-production studies for many other commodities are also available on the website.
For additional information or an explanation of the calculations used in the studies, contact Donald Stewart at the Agricultural Issues Center at (530) 752-4651 or destewart@ucdavis.edu.
For information about irrigated pasture establishment and production in Placer, Nevada, Sutter and Yuba counties, contact UCCE livestock and natural resources advisor Dan Macon at dmacon@ucanr.edu.
- Author: Jeannette E. Warnert
When San Juan Bautista resident Michael Cent was looking for ways to rehabilitate a large backyard pasture infested with invasive foxtail weeds, he called Devii Rao, the UC Cooperative Extension range and natural resources advisor in San Benito County.
Though Rao works mainly with large, commercial producers, she was intrigued by Cent's well thought out plans to replace foxtail with more desirable plants using sustainable practices. She paid him a visit.
Behind the home sits a two-acre fenced pasture where previous owners grazed llamas and ran horses. The picturesque setting adjoins San Juan Creek and frames a panorama of farm fields and the Diablo Mountain Range. But the tableau was spoiled by fence-to-fence foxtails, an exotic plant that hails from the Mediterranean, offers poor forage value and presents nuisance characteristics.
“The seed heads get stuck in the eyes, ears and noses of livestock and pets,” Rao said. “Foxtail is an annual grass that is difficult to control, but that didn't stop Michael Cent from trying.”
Cent is a pharmacist and self-described plant nerd.
“He turned his foxtail problem into a science project,” Rao said.
As a pharmacist, Cent said he is technically a chemist. “When you look at botany as chemistry, if you drill down into all the chemical reactions going on, it's amazing.”
Cent tested the soil Ph and nutrients. He identified 12 plants that would thrive under his pasture conditions and potentially out-compete the foxtails.
“In my research, much of what I see is not native,” Cent said. “My expectations to plant only natives have tempered. It's good to do within reason, but if a benefit of a non-native species outweighs a lesser advantage of being native, I'll go with the non-native species.”
Cent borrowed a tractor to break up the soil and reseeded by hand with his chosen grass and broad leaf plants. He kept detailed notes.
- Birdsfoot trefoil grew a dense carpet that choked out everything.
- Crimson clover germinated and grew quickly early in the season, but didn't do as well as anticipated.
- Harding grass was seeded specifically to out-compete the bristly ox-tongue, another undesirable plant.
- Chicory has a deep taproot, which helps it survive the dry season.
- Oxalis has come in like gangbusters, even though it wasn't seeded.
At first Cent regularly mowed the pasture to keep down the foxtails, but when the job became forbidding, he contracted with a company to bring in goats to aid control.
After four years of effort to overcome foxtail with grazing goats and seeding plants, Cent has come to a realization.
“I thought I could set it in motion and it would take care of itself,” Cent said. “But it's going to take a sustained effort.”
What drives Cent's devotion to rehabilitating a pasture with extensive plant research and management? The miracle of life, he said.
“The marvel of putting a seed in the ground, managing it and seeing what becomes of it. It's fascinating,” Cent said.