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30 RANGELANDS 24(2)

A Close Look At Locoweed On Shortgrass Prairies Management recommendations to help reduce the risk of locoweed poisoning to livestock.

By Michael H. Ralphs, J. David Graham and Lynn F. James

ocoweed poisoning is a sig- The Effects Of Locoweed severely poisoned steers lost $282 nificant impediment to live- Poisoning per head. Lstock production, particularly Table 1 lists the A s t r a g a l u s a n d Locoed steers going on to the feed- on shortgrass prairies. Early obser- O x y t ro p i s species that have caused lot were slower to start gaining vations confused locoweed - locoism, or have been shown to con- weight, and finished approximately ing with starvation since the inci- tain the toxic . 66 lbs. lighter than healthy steers dence of poisoning increased during Swainsonine inhibits essential en- from the same lot (Duff, unpub- seasons of feed shortage and on zymes in glycoprotein metabolism, lished data) – thus increasing the o v e rgrazed rangelands (Marsh resulting in buildup of hybrid sugars time and expense of finishing to the 1909). which “constipate” the cells in all desired market condition. Animals started eating locoweed in body systems, and disrupt hormone A secondary, but significant effect the late winter and early spring be- and enzyme synthesis and receptor is the compromised immune system fore new grass started growing. binding (Stegelmeier et al. 1999). (Stegelmeier et al. 1998a), leading to They seemed to thrive at first, then Outward effects on animals in- other feedlot diseases and poor im- rapidly fell off in body condition as clude reduced fertility of both sexes, munologic response to vaccines. poisoning progressed. Marsh con- neurological disturbances ranging Although the signs and effects of cluded that an abundance of good from extremes of depression to ag- poisoning linger, swainsonine is feed resulting from improved range gression, compromised immune sys- rapidly cleared from the body conditions would greatly reduce and tem resulting in increased disease, (Stegelmeier et al. 1998b). A conser- perhaps eliminate the problem. and impaired ability to eat or drink vative withdrawal period of 28 days Range conditions have improved leading to weight loss and eventual from the time animals consume lo- greatly over the last 100 years, yet starvation. coweed to slaughter will satisfy food locoweed poisoning continues to be Reproductive loss is the greatest safety requirements. a significant problem. Many of the economic cost associated with lo- semiarid locoweed species experi- coweed poisoning (Panter et al. Livestock Find Locoweed ence extreme population cycles; in- 1999). Abortions are common. Palatable creasing in wet years and dying out Of fspring that are born are small and The early literature suggested lo- during drought (Ralphs and Bagley weak, death rates are high, and they coweeds were distasteful and ani- 1988, Ralphs et al. 2001a). The large are often retarded and lack the in- mals were forced to start eating them bank in the (56 to 370 stinct to nurse. Young that survive, because of hunger (Kingsbury s e e d s / f t2, Ralphs and Cronin 1987) and even healthy offspring, receive 1964). However, once started, ani- allows it to exploit environmental swainsonine through their mothers mals seemed to become addicted to conditions and maintain the “boom milk and become lethargic, de- locoweeds. Recent research showed and bust” populations cycles. During pressed and have lower weight gains. that locoweeds are not addicting, but the outbreak years, catastrophic live- Stocker cattle loose weight while are relatively more palatable than as- stock losses continue to occur. grazing locoweed and do not gain sociated forages during various sea- This review of locoweed research again for several weeks after they sons of the year (Ralphs et al. 1989). presents several management recom- stop eating the poisonious plant Both sheep (Ralphs et al. 1991) and mendations to reduce the risk of poi- (Ralphs et al. 2000). Torell et al. cattle (Ralphs et al. 1993) that were so n i n g . (2000) estimated moderately poi- severely locoed, ceased grazing lo- soned steers lost $75 per head, and April 2002 31

Table 1. Locoweed ( and ) species, habitat and distribution

Species Common name Habitat Distribution A. allochrous Rattleweed Desert grassland AZ, NM A. asymmertricus Horse loco Annual grasslands CA A. bisulcatus1 Two-grooved milkvetch Limestone, shale, high in Se MT, ND, WY, CO, NM, Ut A. didymocarpus Creosote deserts CA, AZ, NV A. drummondii1 Drummond milkvetch Prairies, sage, oak, P/J MT, WY, CO, NM, UT A. emoryanus2 Red stem peavine Creosote, Mesquite, P/J NM, TX A. humistratus Ground cover milkvetch P/J woodlands AZ, NM A. lentiginosus Spotted locoweed salt-desert shrub, sage, P/J AZ, UT, NV, ID A. lonchocarpus Great rushy milkvetch P/J woodlands CO, UT, AZ, NV A. missouriensis Missouri milkvetch Shortgrass prairies to TX A. mollissimus Woolly loco Shortgrass prairies CO, KA, OK, TX, NM A. nothoxys Beaked milkvetch Oakbrush, P/J woodlands AZ A. oxyphysus Diablo loco Desert grasslands CA A. praelongus1 Stinking milkvetch Sandstone, shale high in Se UT, NM, AZ A. pubentissimus Green river milkvetch Salt-desert shrub CO, WY, UT A. purshii Pursh loco Sagebrush, P/J woodlands WY, MT, ID, NV A. pycnostachyus Brine milkvetch Salt marshes and beaches CA A. tephrodes Ashen milkvetch Oakbrush, P/J woodlands AZ, NM A. thurberi Thurber milkvetch Creosote, Oak, P/J woodlands AZ, NM A. wootoni Garbancillo Creosote desert AZ, NM, TX O. besseyi Red loco Gravely hill tops MT, WY O. campestris Yellow loco Prairies, Mt. meadows MT, Canada O. lambertii Lambert locoweed Short and mid-grass prairies MT, ND, SD, WY, CO, NM O. sericea White locoweed rocky , foothills and Mt. MT. SD, WY, CO, NM, UT 1Also contains . 2Also contains nitro . There are many varieties, especially of A. lentiginosus, A. mollissimus, and O. sericea, that have been referred to as separate species in the past. Species taken from Marsh 1909, Molyneaux et al. 1991, Smith et al. 1992, Fox et al. 1998. coweed when green grass became coweed matured and became coarse fed Garbancillo (James and plentiful. and rank (Ralphs et al. 1993– VanKampen 1974), or prevent cattle Preference for locoweed is relative 2001c). from grazing white locoweed to what other forage is available. On mixed grass prairies on the (Allison and Graham 1999). Many locoweeds are cool-season eastern foothills of the Rocky Electrical charges on clay minerals species that green-up and start Mountains in northern Colorado, may bind to swainsonine, but a vari- growth early in the spring, then re- cattle ceased grazing white lo- ety of clays and minerals were not sume growth in fall. Livestock gen- coweed when it matured following e ffective in preventing or reducing erally prefer the green-growing lo- flowering in mid June, and became locoweed poisoning (Bachman et al. coweeds to dormant grass. Sheep rank and unpalatable in 1998. 1992, Pulsipher et al. 1994). Neither preferred the regrowth foliage of However they continued to graze it did vitamin E/selenium injections Green River milkvetch to dormant throughout the summer in 1999 hasten recovery from locoweed poi- grasses during late fall and early when abundant summer precipita- soning (Richards et al. 1999). winter on desert range in eastern tion caused locoweed leaves to re- On the other hand, there was con- Utah (James et al. 1968). Cattle main succulent (Ralphs et al. cern that growth implants may en- readily grazed Wahweap milkvetch 2001b). hance locoweed poisoning. An estra- in proportion to its availability on diol implant did not cause steers to desert winter range in southeastern Management Strategies That select more locoweed in a grazing Utah (Ralphs et al. 1988). Didn’t Work trial, and did not affect the degree of In a series of grazing studies in S u p p l e m e n t s —Many minerals poisoning or rate of recovery in a lo- Northeast New Mexico, cattle readi- and feed additives have been investi- coweed feeding trial (Mikus et al. ly grazed white locoweed in March, gated to prevent poisoning. 2001). April and May, but stopped grazing supplements did not prevent poison- Anecdotal evidence suggested cat- it in June as warm-season grasses ing, nor delay symptoms in sheep tle on a higher plane of nutrition, became abundant and white lo- such as alfalfa hay or grazed on win- 32 RANGELANDS 24(2) ter wheat, may be more inclined to boundaries to provide seasonal con- forages in preference to white lo- graze locoweed in the spring. trol of grazing. Reserving locoweed- coweed (Ralphs et al. 1984). The However, these practices did not in- free pastures for grazing during criti- heavy grazing pressure associated crease locoweed consumption cal periods in spring and fall can with short-duration grazing systems (Ralphs et al. 2001c, Ralphs et al. prevent locoweed poisoning. may also induce poisoning problems. 1997b). 2) Consider herbicide contro l s . 5) Train animals to avoid lo- Native Cattle and Bre e d s — Locoweed-free areas can be created coweed. Conditioned food aversion Poisonous plant literature is filled by strategic herbicide use (McDaniel can be used as a management tool to with statements that native livestock 1999, Ralphs and Ueckert 1988). train animals to avoid grazing lo- are less likely to be poisoned than H o w e v e r, natural population cycles coweed (Ralphs et al. 1997a). In the n e w, inexperienced livestock. should be considered to determine conditioning protocol, animals are Locoweed poisoning does not follow the practicality of spraying larg e brought into a pen and fed fresh- this general trend. Cattle that are fa- areas and the potential lifetime of picked locoweed, then lithium chlo- miliar with locoweed will likely se- control. With the abundant seed bank ride (an emetic that causes gastroin- lect it first (Ralphs et al. 1987). in the soil, locoweeds are sure to ger- testinal distress) is administered by Early observations by Marsh (1909) minate and reestablish when environ- stomach tube. The animals associate suggested that black cattle and black- mental conditions are favorable. the induced illness with the taste of faced sheep were more inclined to be 3) Sort out animals that graze lo- the plant and subsequently avoid poisoned by locoweed than white- coweeds. Animals that start eating eating it. Naive animals that are un- faced cattle and sheep. In a recent locoweed may influence others to familiar with the target plant form grazing study comparing breeds, start. Social facilitation or peer pres- strong and lasting (> 3 years) aver- Brangus steers consumed more lo- sure is a very strong influence induc- sions following a single dose. coweed than Hereford and Charolais ing others to start eating locoweed Averted animals must be kept sep- steers (Duff et al. 2001). The gregari- (Ralphs et al. 1994b). Graham de- arate from non-averted animals on ous nature of Brangus cattle may veloped the “eat and pull” manage- locoweed areas to prevent social fa- have facilitated the social acceptance ment strategy, whereby livestock cilitation from extinguishing the of locoweed among the steers. should be watched closely and re- aversions. Aversion conditioning moved if they start eating locoweed may be feasible where losses are Grazing Management to prevent poisoning and prevent heavy and persist year after year. Recommendations them from influencing others to start 1) Restrict Access. L i v e s t o c k (Torrell et al. 2000). Conclusions should be denied access to lo- 4) Don’t overstock locoweed-in- Locoweed is the most widespread coweeds during critical periods when fested are a s . Grazing pressure can poisonous plant problem in the west- they are relatively more palatable also force cattle to begin grazing lo- ern U.S. Knowledge of sites where than associated forages. On short- coweed when they run short of de- locoweeds grow and environmental grass prairies of northeastern New sirable forage (Ralphs 1987, Ralphs conditions when they cause prob- Mexico, stocker cattle should not be et al. 1994a). Ranchers should not lems is necessary to manage live- turned onto locoweed-infested range- overstock locoweed-infested ranges, stock and prevent poisoning. lands until warm season grasses start but rather should ensure adequate Since locoweeds are relatively growth in late May or early June. forage is always available. palatable and many locoweeds are Cattle on rangeland year- r o u n d Improper use of some grazing sys- the first plants to start growing in the should be removed from locoweed- tems can cause livestock to graze lo- spring and may also regrow in the infested areas in the spring when it is coweed. Rest-rotation grazing sys- fall, livestock generally prefer the green and growing, and warm season tems are designed to force livestock green-growing locoweeds to other grasses remain dormant. They can be to uniformly graze all forage in a forage that is dormant in the fall, returned to locoweed-infested pas- pasture. This caused cattle and hors- winter, and spring. tures in summer when warm season es to start grazing spotted locoweed The most effective management grasses are abundant. in western Utah (James et al. 1969). strategy is to deny livestock access Most locoweed species are endem- Changing to a 3-herd, 4-pasture de- to locoweeds during critical periods ic, growing only in certain habitats ferred rotation grazing system when they are more palatable than or on specific soils. Fences could be stopped locoweed poisoning by re- associated forage. Reserving lo- constructed on soil or vegetation ducing the grazing pressure and al- coweed-free pastures or controlling lowing the cattle to select alternative existing locoweed populations with April 2002 33 herbicides can provide "safe" pas- James, L.F., K.R. Van Kampen, and Ralphs, M.H. and D.N. Ueckert. 1988. tures for critical periods. Wa t c h i n g G.R. Stacker. 1969. L o c o w e e d Herbicide control of locoweeds: a re- animals closely and removing those (Astragalus lentiginosus) poisoning in view. Weed Tech. 2:460–465. cattle and horses. J. Am. Vet. Med. Ralphs, M.H., L.F. James, D.B. Nielsen, that begin eating locoweed can pre- Assoc. 155:525–530. and K.E. Panter. 1984. Management vent further intoxication and prevent James, L.F. and K.R. VanKampen. practices reduce cattle loss to locoweed them from influencing others to 1974. Effect of protein and mineral sup- on high mountain range. Rangelands. start. Condition food aversion is an- plementation on potential locoweed 6:175–177. other effective practice and may be (Astragalus spp.) poisoning in sheep. J. Ralphs, M.H., L.V. Mickelsen, and D.L. am. Vet. Med. Assoc. 164:1042–1043. economical where losses are larg e Turner. 1987. Cattle grazing white lo- Kingsbury, J.M. 1964. Poisonous Plants coweed: diet selection patterns of native and persistent. of the and Canada. and introduced cattle. J. Range Manage. Bottomline, good range manage- Prentice-Hall, Englewood Cliffs, NJ. 40:333–335. ment and wise grazing strategies can Marsh, C.D. 1909. The loco-weed disease Ralphs, M.H., L.F. James, D.B. Nielsen, provide adequate forage for livestock of the plains. USDA Bur. Anim. Ind. D.C. Baker, and R.J. Molyneux. 1988. Bull. 112. Cattle grazing Wahweap milkvetch in and avoid critical periods of the year McDaniel, K.C. 1999. Controlling lo- when locoweed is relatively more southeastern Utah. J. Anim. Sci. coweed with herbicides. pp. 52-53 in: 66:3124–3130. palatable than associated forages. T.M. Sterling and D.C. Thompson (eds), Ralphs, M.H., K.E. Panter, and L.F. Locoweed Research Updates and James. 1989. Feed preferences and ha- Authors are Rangeland Scientist, Highlights, New Mexico Agr. Exp. Sta. bituation of sheep poisoned by lo- USDA/ARS Poisonous Plant Lab, 1150 E. Res. Rep. 730 coweed. J. Anim. Sci. 68:1354–1362. 1400 N., Logan UT 84341; County Mikus, J.H., G.C. Duff, C.R. Krehbiel, Ralphs, M.H., K.E. Panter, and L.F. Extension Agent, Clayton NM, 88415, and D.M. Hallford, D.A. Walker, J.D. James. 1991. Grazing behavior and for- Research Leader, USDA/ARS Poisonous Graham, and M.H. Ralphs. 2001. age preference of sheep with chronic lo- Effects of an estradiol implant on lo- Plant Lab. Much of this research was con - coweed toxicosis suggest no addiction. coweed consumption, , and re- ducted under a cooperative research agree - J. Range Manage. 44:208–209. covery in growing beef steers. Prof. ment between USDA/ARS Poisonous Plant Ralphs, M.H., D. Graham, R.J. Moly- Anim. Sci. 17:109–114. Lab and New Mexico State Univ. neux, and L.F. James. 1993. S e a s o n a l Molyneux, R.J., L.F. James, K.E. Panter and M.H. Ralphs. 1991. grazing of locoweeds by cattle in north- Analysis and distribution os swainso- eastern New Mexico. J. Range Manage. References nine and related polyhydroxyin- 46:416–420. dolizidine by thin layer chro- Ralphs, M.H., D. Graham, and L.F. Allison, C. and J.D. Graham. 1999. matography. Phytochem. Analys. 2:125- James. 1994a. Cattle grazing white lo- Reducing locoism with management de- 129. coweed in New Mexico: influence of cisions. pp. 64–66 in: T.M. Sterling and Panter, K.E., L.F. James, B.L. grazing pressure and phenological D.C. Thompson (eds), Locoweed Stegelmeier, M.H. Ralphs and J.A. growth stage. J. Range Manage. Research Updates and Highlights, New Pfister. 1999. Locoweeds: effects on re- 47:270–274. Mexico Agr. Exp. Sta. Res. Rep. 730. production in livestock. J. Nat. . Ralphs, M.H., D. Graham, and L.F. Bachman, S.E., M.L. Galyean, G.S. 8:53–62. James. 1994b. Social facilitation influ- Smith, D.M. Hallford, and J.D. Pulsipher, G.D., M.L. Galyean, D.M. ences cattle to graze locoweed. J. Range Graham. 1992. Early aspects of lo- Hallford, G.S. Smith, and D.E. Kiehl. Manage. 47:123–126. coweed toxicosis and evaluation of a 1 9 9 4 . Effects of graded levels of ben- Ralphs, M.H., D. Graham, M.L. Galyean, mineral supplement or clinoptilolite as tonite on serum clinical profiles, meta- and L.F. James. 1997a. Creating aver- dietary treatments. J. Anim. Sci. bolic hormones, and serum swainsonine sions to locoweed in naive and familiar 70:3125_3132. concentrations in lambs fed locoweed cattle. J. Range Manage. 50:361–366. Duff, G.C., M.H. Ralphs, D. Walker, D. (). J. Anim. Sci. Ralphs, M.H., D. Graham, M.L. Galyean, Graham, J.D. Rivera, and L.F. James. 72:1561–1569. and L.F. James. 1997b. Influence of 2001. Influence of beef breeds Ralphs, M.H. 1987. Cattle grazing white over-wintering feed regimen on consump- (Hereford, Charolais, Brangus) on lo- locoweed: influence of grazing pressure tion of locoweed by steers. J. Range coweed consumption. J. Anim. Sci. (in and palatability associated with pheno- Manage. 50:250–252. review). logical growth stage. J. Range Manage. Ralphs, M.H., D. Graham, G. Duff, B.L. Fox, W.E., K.W. Allred, and E.H. 40:330–332. Stegelmeier and L.F. James. 2000. Roalson. 1998. A guide to the common Ralphs, M.H. and V.L. Bagley. 1988. Impact of locoweed poisoning on graz- locoweeds and milkvetches of New Population cycles of Wahweap ing steer weight gains. J. Range Manage Mexico. New Mexico Agr. Exp. Sta. milkvetch on the Henry Mountains and 53:86–90. Cir. 557. seed reserve in the soil. Great Basin Nat. Ralphs, M.H., D.R. Gardner, J.D James, L.F., K.L. Bennett, K.G. Parker, 48:541–547. Graham, G. Greathouse and A.P. R.F. Keeler, W. Binns, and B. Ralphs, M.H. and Cronin, E.H. 1987. Knight. 2001a. Influence of defoliation Lindsay. 1968. Loco plant poisoning in Locoweed seed in soil: density, longevi- on locoweed vigor, longevity and toxici- sheep. J. Range Manage. 21:360–365. ty, germination, and viability. Weed Sci. ty. J. Range Manage. (in press). 35:792–795. 34 RANGELANDS 24(2)

Ralphs, M.H., G. Greathouse, A.P. Smith, G.S., K.W. Allred, and D.E. Stegelmeier, B.L., L.F. James, K.E. Knight and L.F. James. 2001b. Cattle Kiehl. 1992. Swainsonine content of Panter, M.H. Ralphs, D.R. Gardner, preference for Lambert locoweed over New Mexican locoweeds. Proc. West. R.J. Molyneuc, and J.A. Pfister. 1999. white locoweed throughout their pheno- Sec. Amer. Soc. Anim. Sci. 43:405–407. The pathogenesis and toxicokinetics of logical stages. J. Range Manage. (in Stegelmeier, B.L., P.D. Snyder, L.F. locoweed (A s t r a g a l u s and O x y t r o p i s) press). James, K.E. Panter, R.J. Molyneux, poisoning in livestock. J. Nat. Toxin. Ralphs, M.H., G. Greathouse, A.P. D.R. Gardner, M.H. Ralphs, and J.A. 8:35–45. Knight, D. Doherty, J.D. Graham, Pfister. 1998a. The immunologic and Torrell, L.A., L.P. Owen, K.C. B.L. Stegelmeier and L.F. James. toxic effects of locoweed (A s t r a g a l u s McDaniel, and D. Graham. 2000. 2001c. Prior feeding practices do not in- l e n t i g i n o s u s) intoxication in cattle. pp. Perceptions and economic losses from fluence locoweed consumption. J. 285-290 in: T. Garland and A.C. Barr locoweed in northeastern New Mexico. Range Manage. (in press). (Eds), Toxic Plants and Other Natural J. Range Manage. 53:376–383. Richards, J.B., D.M. Hallford and G.C. . CAB International, Duff. 1999. Serum luteinizing hormone, Wallingford, Oxon, GB. testosterone, and thyroxine and growth Stegelmeier, B.L., L.F. James, K.E. responses of ram lambs fed locoweed Panter, D.R. Gardner, M.H. Ralphs (Oxytropis sericea) and treated with vit- and J.A. Pfister. 1998b. Tissue swain- amin E/selenium. Theriogenology sonine clearance in sheep chronically 52:1055-1066. poisoned with locoweed. J. Anim. Sci. 76:1140–1144.

Photo taken south of Buffalo, South Dakota. Photo by Aaren L. Nellon.