A dairy goat eats poison oak in a feeding station at UC Davis. Initial research indicates .. . Dairy goats used to clear poison oak do not transfer toxicant to milk

Brou Kouakou o David Rampersad a Eloy Rodriguez o Dan L. Brown

Dairy goats that eat poison oak do are often cited for their abil- arm helps the skin’absorbthis toxicant. not transfer detectible amounts of ity to induce the : Pacific poison Polyunsaturated side arms are thought to oak (Toxicodendron diversilobum), mostly cause a more serious reaction than satu- the toxic principle, urushiol, to the found on the Pacific West Coast; poison rated ones. milk or to the urine. Furthermore, ivy (T. radicuns), found east of the Rocky this oily, toxic irritant is found in Mountains; and poison (T. vernix), Control of poison oak goat manure at less than 9% of its present in the swamps of the South. Eradication of poison oak is the only concentration in poison oak The active principles causing poison completely effective method for prevent- oak dermatitis make up a family of oleo- ing occupational exposure. Theoretically, leaves. What does all this portend? , referred to collectively as urushiol. digging up the entire and burning it That farmers using dairy goats to The dermatitis is the result of an allergic is the best method of eradication, but it is clear poison oak need not worry reaction, not to umshiol itself but, rather, prohibitively expensive and exposes about contaminating the goats’ to the combination of urushiol and the vic- workers to extremely hazardous milk with urushiol. More studies tim’ own skin proteins. smokeborne urushiol. Biological control Poison oak urushiols consist of appears to be the best way to reduce these are underway. rings with a side chain at the poisonous , in view of the many bar- Most Californians are familiar with the 3 position. Most poison oak urushiols riers to other ways: legal restrictions,envi- painful, often debilitating skin rash (98%)have side chains 17 carbons long ronmental hazards, health concerns and/ (dermatitis) that can result from contact with one, two or three double bonds (see or the expense of using herbicides, such as with poison oak. In the United States, fig. 1).An oxidized form of the catechol glyphosate (Roundup) or triclopyr three native species of the genus ring does the binding, while the long side (Garlon).By itself, 2,4-D does not work

4 CALIFORNIA AGRICULTURE, VOLUME 46, NUMBER 3 very well on poison oak, and 2,4,5-T is no OH tone and methylene chloride. The purified longer leg$ for this application. solutions were injected through a CI8car- Goats have been used to open up graz- tridge column and then filtered before ing lands for other livestock and also for on HPLC analysis at UCD. brush control. Browsing and resulting de- The eluent, a methanol/water mixture foliation of brush by goats lead to subse- (90:10), was pumped by a Waters 510 2 Heptadecenylcatechol quent reduction of plant carbohydrate re- OH HPLC pump through a Pico-Tag c18 re- serves, thereby eventually killing the verse-phase column at 1.2 ml/min. The plants. Goats could be used to inexpen- UV detector (Waters 490) was set at 275 sively control poison oak in pasture land 3 Heptadecadienylcatechol nm. The retention times of the chromato- and recreation areas. With proper man- OH grams were compared with those of the agement this can be accomplished with standards of the different urushiol conge- relatively little damage to nontarget plant ners obtained from the UC Irvine laborato- species and to the environment. 4 Heptadecatrienylcatechol ries (previously identified by IR and GC/ Because the fate of urushiol ingested by Mass Spectrometry). goats is unknown, a concern exists for the Fig. 1. Chemical structure of poison oak uru- The dry leaves were ground and ana- safety of people using goat dairy products shiol congeners. lyzed for dry matter, ash, nitrogen, ether from poison oak-fed goats. This concern, extract, acid detergent fiber (ADF), neutral in addition to American folklore crediting the does were milked by hand. Milk yield detergent fiber, cellulose, lignin, calcium milk from poison oak-fed goats with in- was recorded at each milking, and the and phosphorus, according to standard ducing tolerance, led to testing the follow- milk was sampled every other day, in ad- procedures used at the UC Davis Animal ing hypotheses: dition to the first and last day of the trial. Science Nutrition Laboratory. (1) Urushiol and/or its metabolites will Fresh leaf samples were also collected for The urine samples were analyzed for be found in the milk, urine and feces of analysis of urushiol content, and the by thin layer chromatography goats consuming poison oak. leaves oven-dried at 158°F were kept for (TIC) using KCl8Fplates and methanol: (2) Dairy goats fed poison oak will con- analysis of nutritive value. Fresh leaves water (95:5) as solvent and sprayed with vert unsaturated urushiol to saturated and milk samples were kept frozen at 28°F 1% FeC13. Heptadecatrienylcatechol ob- metabolites. until analysis. On the trial's seventh day, tained from UC Irvine was the standard does were catheterized for urine collection reference catechol. Trial I: poison oak as supplement and fitted with fecal collection bags for to- Six lactating goats at the UC Davis tal fecal collection for 48 hours. Feces and Results (UCD) Dairy Goat Facility were fed ma- urine were kept frozen until extraction. No urushiol was found in the milk of ture poison oak free choice for 3 days, in Leaves and feces were extracted with trial I goats fed mature poison oak foliage addition to their daily feed allotment of 2 (15 ml/g) for 4 days. The crude for 3 days as 7%of their diet. For this rea- kg of corn-alfalfa pellets. The plant mate- extract was filtered through Whatman #1 son, trial II was planned to challenge lac- rial for this trial was collected from the paper. Ten ml of the filtrate were then tating does with a stall-fed diet of 100% Oak Regeneration Research Plot at the Si- evaporated to dryness under a nitrogen poison oak foliage. erra Foothill Range Field Station, trans- stream at room temperature. The oily resi- Table 1 gives the chemical composition ported to the dairy goat facility and stored due was dissolved in 10 ml of methylene of five dry samples of young leaves (first 2 under cover until fed to goats. The foliage chloride and evaporated to dryness. The to 3 weeks of seasonal growth) with a was weighed, offered as leaves and stems, remaining material was purified with hex- small portion of stem (the same portion of and the refused feed (predominatelystem) ane, water and acetonitrile.Milk and urine plant material consumed by the goats). weighed the following morning. Total in- samples were not pre-extracted with ace- The crude protein content was between 18 take was 840 g/d of fresh leaves per feed- ing for all six does. The does were milked twice every day and the milk was sampled every other day, frozen at 28°F and sent to the research laboratories of phytochemistry and toxi- cology at UC Irvine for analysis of LUX- shiol content by High Performance Liquid Chromatography (HPLC)and infrared spectroscopy. Trial II: poison oak as 100% diet Four lactating goats from the UCD Dairy Goat Facility were individually housed in elevated calf pens in the calving barn of the Sierra Foothill Range Field Sta- tion (SFRFS) for 10 days. Poison oak foli- age was collected every morning from the same field as trial I. Goats were individu- ally offered an average of 1.7 kg/d of freshly cut poison oak with no supple- mentation. The refusals were weighed each follow- ing morning, the pens were cleaned, and

CALIFORNIA AGRICULTURE. MAY-JUNE 1992 5 limit of urushiol detection was 117 ng as of structural carbohydrates in the 100% determined by calculation. This is equiva- poison oak diet. lent to ,218 ng/d in the milk. Although rich in energy, protein, cal- The qualitative TLC monitoring for cium and phosphorus, this immature foli- catechol detection (an index of urushiol age lacked the fiber quality and quantity breakdown products) in the urine samples needed to sustain normal rumen function gave a negative response. The reference and feed intake. This diet had no more catechol was easily detected at 0.023 functional fiber than a diet made up of mg/uL. 100% oat grain. While foliage from later in the season contains more fiber, a source of Discussion long roughage should be fed to enhance In these experiments the goats were fed the utilization of this highly nutritive poison oak foliage, but the urushiol was browse species. detected only in the feces. The percentage of total urushiol accounted for by each of Conclusion the four congeners increased in the feces This study is the first phase in a four- except for the highly polyunsaturated con- step project. The overall objective of the gener 4. One explanation for the relative project is to create a complete, low-input paucity of unsaturated urushiol would be biological control system to control poison biohydration (saturation) of urushiol in oak by browsing goats. This study’s spe- the highly reduced rumen or lower-gut cific goal was to determine whether uru- environments. Another possible explana- shiol and/or its metabolites would be tion would be greater oxidation and bio- found in the milk, urine and feces of dairy degradation of the more unsaturated goats eating poison oak. From the data col- urushiols. lected and the procedures used in our ini- Estimated daily total urushiol disap- tial studies, no urushiol was identified in pearance was 20.17 g/d, based on a 48- the urine or in the milk. Urushiols were hour fecal collection. This means that more found only in the feces. than 90% of the urushiol is either catabo- Based on the finding of this initial re- lized somewhere along the GI tract, or ab- search, it is not possible to conclude that sorbed. If absorbed, where did all this uru- potentially immunoactive urushiol me- shiol go? It could have: tabolites are not found in the milk or the (1)been broken down by tissue en- urine, because the procedures used here Researcher obtains milk from a goat fed with zymes. (For example, tyrosinase has been were specific for catechol analysis. In the poison oak. known to break down other catechols and next stage of this project, better methods phenols.) will be developed to trace the fate of uru- (2) been glucouronidated and excreted shiol metabolites in meat and milk, and and 22% with a mean of 19.8%.The mean in the urine. (The extraction method used their elimination products, of dairy goats ADF was 13.5%(range 11 to 17%)and is here would not have recovered this ca- browsing poison oak. The third stage will comparable to oats. The leaves were also tabolite if it exists.) tell us how much and when to browse poi- high in calcium (1.2%)and phosphorus (3) been retained somewhere in body son oak to ensure optimum control. The (0.46%),similar to a legume forage. tissues. final stage is the creation and extension of Feed intakes were very low (mean, SD The reduced milk production in the practical, commercially viable production 0.645,0.066 kg). The milk yield (mean, SD: second trial was probably due to reduced systems including goats as biological con- 0.810,0.191 kg) observed during poison feed intake. These same goats accepted trol for poison oak. oak feeding was less than that observed more mature poison oak foliage after the before the trial. Both feed intake and milk pen trials, and three of them had accepted yield show a tendency to decrease during mature leaf as part of a diet containing al- B. Kouakou conducted these experiments as the last 10 days of the trial. falfa fiber during the previous year. Feed part of his M.S. program in Animal Science at Table 2 gives the concentration of each intake problems during this trial may have UC Davis and is now pursuing a Ph.D. in urushiol congengr, the total urushiol con- been a reaction to confinement or the lack Animal Nutrition, Department of Animal Sci- tent in the leaves (3.21%) and feces ence, University of Arkansas, Fayetteville; (0.28%), and the ratios of feces urushiol to D. Rampersad is a postdoctoral fellow in De- leaf urushiol(8.7%). velopmental and Cell Biology, UC Iwine; Figure 2 shows the percentage of each 0 % of total leaf urushiol E. Rodriguez is Professor of Developmental urushiol congener in the leaf and feces % of total feces urushiol and Cell Biology, UC Iwine; and D. L. Brown samples. There were more of the partially mo 50 n is Associate Professor of Animal Science, UC saturated congeners 2 and 3 in the feces Davis. than in the leaves. The fecal concentration The authors thank Dr. Ed DePeters and of the highly polyunsaturated congener 4 Dr. Art Craigmill for their advice, suggestions is only 1.5%of that found in the leaves. and critical remarks; Mike Connors and his Absolutely no peaks were found in team at the Sierra Foothill Range Field Station milk or urine chromatograms at 9.49, for logistical support; and Scott Taylor, Cathie 12.58,17.74and 20.09 minutes, where the Urushiol congeners Adamson and the nutrition laboratory crew for authentic urushiol congeners 4,3,2 and 1, their help with lab work. Financial support was respectively, were present in standards Fig. 2. Urushiol congeners in leaf and feces provided by LlSDA Animal Health Grant No. and in poison oak leaf extracts. The lower samples. CA-D*-ASC-4989-AH.

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