The effect of body condition on disposition of alkaloids from silverylupine (Lupinus argenteus Pursh) in sheep1

S. Lopez-Ortiz*, K. E. Panter†2, J. A. Pfister‡, and K. L. Launchbaugh*

*Rangeland Ecology and Management Department, University of Idaho, Moscow 83844-1135; and†ARS-USDA, Poisonous Plant Research Laboratory, Logan, UT 84341

ABSTRACT: Several species of lupine (Lupinus spp.)are poisonous to livestock, producing death in sheepand “crooked calf disease” in cattle. Range livestockcope with poisonous plants through learned foragingstrategies or mechanisms affecting toxicant disposition.When a toxic plant is eaten, toxicant clearance may beinfluenced by the animal’s nutritional and/or physiolog-ical status. This research was conducted to determinewhether differences in body condition or short-term nu-tritional supplementation of sheep altered the disposi-tion of lupine alkaloids given as a single oral dose ofground silvery lupine (Lupinus argenteus) seed. Ewesin average body condition (ABC, n = 9) and low bodycondition (LBC, n = 10) received a single dose of groundlupine seeds including pods (8.5 g/kg BW) via gavage onthe first day of the experiment, and were then randomlyassigned to one of two nutritional supplement treat-ments. Blood samples were taken 0 to 60 h after dosingto compare blood alkaloid concentration and to evaluatealkaloid absorption and elimination profiles. Concen-trations of total alkaloid and anagyrine, 5,6 dehydrolu-

Key Words: Body Condition, Lupinus, Quinolizidine Alkaloids, Sheep, Toxic Plants

2004 American Society of Animal Science. All rights reserved. J. Anim. Sci. 2004. 82:2798–2805

Introduction

Poisonous plants impose a high negative economiceffect, exceeding $340 million, on the livestock industrythrough production losses that include birth defects,

1The authors acknowledge the ARS-USDA-US Sheep Exp. Stn.and G. Lewis (research leader) for access to facilities and sheep usedin this study. We also thank M. Hale, D. Patten, M. Jones, and A.Ganguli for their help in plant material collection and animal han-dling, and T. Wierenga for her help in laboratory blood analysis. Wethank P. Talcott for reviewing the manuscript and the associate editorand anonymous reviewers, whose helpful comments have improvedthe clarity and interpretation of the manuscript.

2Correspondence: 1150 E. 1400 N. (phone: 435-752-2941; e-mail:kpanter@cc.usu.edu).

Received July 29, 2002.Accepted May 28, 2004.

2798

panine, lupanine, and alkaloid E were measured in se-rum. These four alkaloids constituted 78 and 75% ofthe total alkaloid concentration in serum for LBC vs.ABC groups, respectively. Initial analysis indicatedthat short-term supplementation had no effect on alka-loid disposition, and supplementation was removedfrom the statistical model. The highest concentrationof total alkaloids was observed 2 h after dosing. Overall,serum total alkaloid and anagyrine levels (area underthe curve) were higher (P < 0.01) for sheep in the LBCgroup. Serum peak concentrations of total alkaloid andanagyrine were higher in LBC vs. ABC groups (P <0.05). Serum elimination of anagyrine, unknown alka-loid E, and lupanine was decreased in LBC vs. ABCtreatments (P < 0.05). These results demonstrate thatbody condition is important in the disposition of lupinealkaloids; however, further research is needed to deter-mine the potential benefit, if any, that short-term nutri-tional supplementation might have on alkaloid dispo-sition.

morbidity, decreased reproductive efficiency, and mor-tality (James et al., 1992). Range livestock adapt toand usually survive encounters with poisonous plantsthrough learned foraging strategies to avoid theseplants or by inherent mechanisms of detoxification(Provenza et al., 1992; Launchbaugh et al., 2001). Ac-quired preferences and aversions based on ingestivefeedback allow herbivores to select plants and plantparts in inverse proportion to their toxicant content todecrease poisoning (Bernays et al., 1989; Pfister, 1999).Livestock also possess metabolic abilities to negate ordecrease the toxic effects of plant toxins once they areingested (Freeland and Janzen, 1974; McArthur et al.,1991; Smith, 1992; Launchbaugh, 1996).

Many animal and plant characteristics affect the abil-ity of an animal to practice selective intake or to detoxifyallelochemicals. An important, though little studied,

Body condition affects alkaloid disposition 2799

factor that undoubtedly influences the detoxification ofingested phytotoxins is the nutritional status or bodycondition of a grazing animal. Well-fed animals mayeffectively process toxins from plants, whereas nutri-ent-deprived animals may be more likely to eat poison-ous plants or they may be metabolically compromisedin their ability to detoxify or excrete the toxins (Foleyet al., 1995).

The objective of this experiment was to determinewhether body condition and/or short-term supplemen-tation of energy would affect the concentration and dis-position (absorption and elimination) of quinolizidinealkaloids from silvery lupine (Lupinus argenteus) in-gested by domestic sheep (Ovis aries). Primary empha-sis was placed on anagyrine due to its importance in“crooked calf disease” (Panter et al., 1999).

Materials and Methods

Plant Material Collection and Alkaloid Analysis

Silvery lupine seedpods, with seeds intact, were col-lected on a mountain foothill site near Humphrey, ID(44°30′N; 112°14′W), during July and August 2000.Plant material was dried at ambient temperature andthen finely ground to pass a 1-mm screen in a Wileymill (Thomas Scientific, Swedesboro, NJ). Total andindividual alkaloids in seedpods were determined bygas chromatography (GC; Hewlett Packard 5890,Agilent, Palo Alto, CA) according to Gardner and Panter(1993). Briefly, a 100-mg sample of ground lupine seedwas combined with 5 mL of 1N HCl and 4 mL CHCl3

and placed in a mechanical shaker for 15 min, andthen centrifuged to separate the aqueous and organicphases. The aqueous fraction was transferred to a cleantube and basified to a pH between 9 and 9.5 by drop-wiseaddition of concentrated NH4OH. The basified solutionwas extracted twice with CHCl3 (4 mL, then 2 mL).The combined CHCl3 fractions were filtered throughanhydrous Na2SO4, dried under a stream of N2 at 50°C,and then reconstituted in 5 mL of CHCl3 for analysis.Two microliters of this final solution was injected intoan HP 5890 GC equipped with a split/splitless injector,flame ionization detector, and a J&W DB-5 (30 m × 0.33mm i.d.) capillary column (Agilent). Injector tempera-ture was 250°C and operated in the split mode. Splitvent flow rate was 60 mL/min and was purged after 1min. Oven temperature was programmed as follows:100°C for 1 min, 100 to 200°C at 50°C/min, and 200 to320°C at 5°C/min. Alkaloid peaks, retention times, andpeak areas were compared with two known standardplant samples: Lupinus caudatus (USDA accession No.82-7), containing quinolizidine alkaloids, and L. formo-sus (USDA accession No. 87-3), containing piperidinealkaloids (Gardner and Panter, 1993, 1994). Peak iden-tifications were based on GC/mass spectroscopy analy-sis (Thermo-Finnigan, Austin, TX) and comparison ofretention times with those alkaloid peaks from the stan-

dard plant samples (Figure 1). The interassay variationof 85 replicates over the last 6 yr was less than 5% (T.Weirenga, ARS-USDA Poisonous Plant Research Lab,Logan, UT, unpublished data).

Animal Conditioning Period

All methods involving animals were approved by theUniversity of Idaho, Animal Care and Use Committee(Protocol 2001-56). Research was conducted at the U.S.Sheep Experiment Station near Dubois, ID (44°15′N;112°15′W) with 19 lactating Columbia ewes. The lambswere weaned at 43 to 47 d of age. Ewe conditioningconsisted of a 9-wk feeding period starting 3 wk afterparturition. During this conditioning time, ewes werepenned individually with lambs and had free access towater and trace-mineral salt. Ten ewes were fed a low-nutrient diet, and nine were fed a high-nutrient diet toattain low and average body conditions (LBC and ABC,respectively). Ewes were fed and housed individuallyin outdoor pens (2.3 × 4.6 m). The diets were formulatedto provide DE and CP at 17% below or 20% above re-quirements for lactating ewes (NRC, 1985) and wereoffered to ewes being conditioned to LBC or ABC, re-spectively. The amount of diets offered was readjustedwhen lambs were weaned and the presentation of thefeeds was changed as outlined later in this section (allamounts are reported on an as-fed basis). During wk1 to 5, the low-nutrient diet was a chopped mixturecontaining 60% alfalfa hay (1-00-066; NRC, 1985) and40% barley straw (1-00-498; NRC, 1985). The high nu-trient diet comprised chopped alfalfa hay and 200 g ofrolled corn (4-02-931; NRC, 1985) per ewe, per day. Thediets were offered at 3% of BW for ewes in both groups.From wk 6 to 9, the diets were changed to a pelletedfeed. The pelleted low-nutrient diet consisted 50% al-falfa and 50% barley straw, with no additional supple-ment, whereas the high-nutrient diet consisted of 100%alfalfa pellets and an additional 400 g of rolled cornper ewe, per day. The amount of pellets offered wasgradually increased over 5 d from 1.50 to 2.25% BWfor LBC ewes, and from 2.50 to 3.25% BW for ABC ewes.These amounts were divided into two daily allotmentsoffered at 0700 and 1900, and all feed was consumed.

Body condition was scored on a 0-to-5 scale by tactileand visual estimation of body fat depositions (AmericanSheep Industry Association, 1997) by two trained tech-nicians on a weekly basis during conditioning. Only oneof these technicians was blind to the treatments. Themean body condition at the end of the conditioning pe-riod was 1 for LBC and 2.5 for ewes in ABC. The meanBW (±SD) of ewes in LBC at the beginning and at theend of the conditioning were 76.7 ± 6.2 and 62.8 ± 5.5kg, respectively, whereas the weights for ABC were83.9 ± 5.6 and 81.2 ± 6.2 kg. The average BW of ABCewes was higher than that of LBC ewes before (P <0.05) and after (P < 0.05) the conditioning period. How-ever, LBC ewes lost a greater percentage of BW during

Lopez-Ortiz et al.2800

Figure 1. Chromatograms from gas chromatography analysis of extracted alkaloids from Lupinus argenteus seedpods(a), and sheep serum before (b) and after (c) a single dose of 8.5 g/kg of BW of ground L. argenteus seed pods. A =5,6-dehydrolupanine, B = lupanine, C = anagyrine, D, E, F are unidentified alkaloids, M = unknown compounds, andBC = blood compounds.

conditioning than did ABC ewes (18.1 ± 4.3% vs. 3.2 ±5.7% respectively; P < 0.05).

Two days before the experiment began, all ewes werefed 2.2% BW of a basal diet divided into two allotmentseach day at 0700 and 1900 to provide similar rumenfill and nutrient intake between groups. The basal dietconsisted of a coarsely chopped mixture of grass andalfalfa hay that had 16% CP and 58% in vitro DM digest-ibility.

Ewes in ABC and LBC were assigned randomly totreatments with supplement (S) or without daily sup-plement (NS). Ewes assigned to the supplement treat-ments (five ewes in LBC and five in ABC) were offered

a supplement at 0.4% BW that consisted of 50% soybeanmeal (5-04-610, NRC, 1985) and 50% corn meal (4-02-931, NRC, 1985). This supplement was intended to pro-vide a supply of both protein and energy, and the leveloffered was fixed at 0.4% BW. The supplement wasoffered in two portions at 0800 and 2000 each day begin-ning the day of the experiment and continuing throughthe 60-h sampling period.

Experimental Procedure

The experimental measurements began after all ewesreceived a single oral dose of 8.5 g of ground silvery

Body condition affects alkaloid disposition 2801

lupine seed and pods/kg of BW of at 1100. Lupine(ground to 1-mm particle size) was diluted in 5 L oflukewarm tap water and gavaged using a livestockpump system (The Magrath Co., McCook, NE). Bloodsamples (30 mL) were drawn via jugular vein punctureat 0, 0.5, 1, 2, 3, 4, 6, 8, 12, 18, 24, 36, 48, and 60 hafter gavaging. Blood was allowed to clot for 1 h at roomtemperature and was then centrifuged for 30 min at1,060 × g. Serum was immediately harvested and frozenin a standard chest freezer (−5 to −10°C).

Serum alkaloid content was determined by GC afteracid/base extraction similar to that for plant material(Gardner and Panter, 1993, 1994). Briefly, a 10-mLaliquot was basified with 10 drops of concentratedNH4OH, and then extracted twice with CHCl3 (4 mLboth times) with mechanical shaking for 15 min. Aftershaking, the samples were centrifuged to separate thephases. The organic (CHCl3) phase was transferred toa clean tube and acidified with 5 mL of 1N HCl, mechan-ically mixed for 5 min, and then centrifuged to separatephases. The aqueous phase was transferred to a cleantube, basified with 1.1 mL of concentrated NH4OH, andthen extracted twice with CHCl3 (4 mL, then 2 mL).The combined CHCl3 fractions were filtered throughanhydrous Na2SO4, and then dried under a stream ofN2 at 50°C and reconstituted in 200 �L of CHCl3 foranalysis. Conditions for GC analysis were the same asthose described for plant material; peak identificationwas confirmed by GC/mass spectroscopy. This methodwas validated in serum using caffeine as an internalstandard and total and individual alkaloids were mea-sured against a standard curve for anagyrine (S. T. Lee,ARS-USDA Poisonous Plant Research Lab, Logan, UT,unpublished data). Coefficients of variation for anagyr-ine in plant standards and in serum were 5.1 and5.5%, respectively.

Two standard plant samples (USDA Accession No.82-7 and 87-3) were used for quality control and com-parison of alkaloid peak areas. These two standardplant samples were run with each batch of serum ex-tractions to ensure adequacy of the extraction process.

Toxicokinetic Evaluation

Absorption and elimination profiles were analyzedusing standard pharmacokinetic software (PK Solu-tions for Non-Compartmental Pharmacokinetic DataAnalysis, Summit Research Services, Montrose, CO).A curve-stripping procedure was used to determine thebasic pharmacokinetic parameters of half-life, rate andconcentration intercept for each phase of the blood levelcurve. The following parameters were determined fortotal alkaloid and anagyrine: intercept: Cn = Coefficientof each exponential term; slope: s = −λn/2.303; rate con-stant: λn = −2.303 s; half-life: t¹⁄₂ = 0.693/λn; Cmax =maximum observed concentration; Tmax = time point atCmax; and AUC ∞ (area under the curve).

A trapezoidal method was used to determine the AUCof a concentration vs. time graph. The general equation

describing the disposition of drugs in serum is given bythe summation expression: C = ΣCn exp (−λnt), whereCn and λn are the zero-time intercepts and rate con-stants, respectively, for each exponential term. The cor-responding triexponential function can be written as:C = Ae−αt + De−βt + Ee−γt. In this expression, the inter-cepts are given letter designations indicating the threecommon drug disposition phases that are typically en-countered after an oral dose: Absorption, Distribution,and Elimination.

Statistical Analyses

Four treatments resulted from combinations of bodycondition (LBC or ABC) and supplementation (S or NS):LBC-S, LBC-NS, ABC-S, and ABC-NS. Comparison ofserum alkaloid levels in these groups was accomplishedwith a repeated-measures ANOVA, with time as therepeated measure. This initial analysis indicated thatshort-term supplementation had no effect on alkaloiddisposition, and supplementation was removed fromthe statistical model.

Subsequently, the experiment was reanalyzed as acompletely randomized design with two treatments.Variables analyzed were serum alkaloid concentration(�g/mL) over sampling time, biological half-life (h) ofthe alkaloids, and AUC for specific alkaloids. Mixed-model analysis of variance for correlated repeated mea-sures (MIXED procedure using the ARI option for covar-iance structure; SAS Inst., Inc., Cary, NC) was per-formed to examine the effect of body condition on serumalkaloid concentrations. The AUC for total alkaloid andanagyrine in serum was analyzed separately. Becausebiological half-life of absorption or elimination did nothave the time factor, these variables were analyzedusing two-way analyses of variance to test the effectsof body condition and supplementation (PROC GLM ofSAS). For all analyses, multiple comparisons for maineffects were performed to delineate differences usingleast squares means after significant (P < 0.05) F-tests.

Results

Alkaloids in Lupine Plant Material

Six alkaloids were observed in the Lupinus argenteusplant material used for this experiment (Figure 1).Three peaks in the chromatograms represented knownalkaloids (anagyrine, 5,6-dehydrolupanine, and lupan-ine). Three other peaks represented alkaloids whosechemical structures were not elucidated (alkaloids D,E, and F, as designated in the USDA-ARS PoisonousPlant Research Laboratory records; K. E. Panter, un-published results). The peaks representing alkaloids D,E, and F appeared in the chromatograms at about 10.9,11.3 and 10.1 min, respectively (Figure 1). The plantmaterial contained 1.64% total alkaloids (dry weightbasis). The major alkaloids were anagyrine (28.8%),alkaloid E (28.3%), alkaloid D (16.0%), 5,6 dehydrolu-

Lopez-Ortiz et al.2802

Table 1. Biological half-life (h ± SD) of absorption and elimination of alkaloids in serumof sheep in either low (LBC) or average (ABC) body condition after a single dose byruminal infusion with 8.5 g/kg of BW of silvery lupine (Lupinus argenteus)

Unknown 5,6-Dehydro- TotalTreatment Anagyrinea alkaloid E Lupanine lupanine alkaloids

Absorption, h

ABC 0.57 ± 0.04b 0.70 ± 0.09 0.76 ± 0.20 1.67 ± 0.20 0.96 ± 0.14LBC 1.13 ± 0.20c 0.97 ± 0.19 0.94 ± 0.19 1.46 ± 0.16 0.94 ± 0.10

Elimination, h

ABC 2.85 ± 0.16b 1.46 ± 0.11b 4.47 ± 0.55b 7.88 ± 0.78 6.88 ± 0.55LBC 3.58 ± 0.32c 2.44 ± 0.21c 6.23 ± 0.67c 7.15 ± 0.39 6.32 ± 0.44

aAnagyrine absorption, P = 0.01; anagyrine elimination, P = 0.06.b,cWithin each comparison of ABC and LBC, means with a different superscript letter differ (P < 0.05).

Means in each comparison that do not have superscripts are not significantly different.

panine (11.5%), and lupanine (8.2%). These five alka-loids accounted for about 93% of the total alkaloid con-tent in the plant material.

Animal Response Rates of Alkaloid Absorptionand Elimination

Basic toxicokinetic parameters were determined fortotal alkaloid and for anagyrine in the LBC and ABCgroups (Table 1, Figure 2). Absorption, distribution,elimination, and peak height were evaluated as AUCusing the trapezoidal rule to calculate AUC. There wasa difference in AUC between LBC and ABC for totalalkaloid (P = 0.003) and anagyrine (P = 0.001; Figure2). This difference strongly suggests that overall dispo-sition of lupine alkaloids, and especially the teratogenanagyrine, is altered in a relatively dramatic way basedon body condition. Although further research is neededto evaluate the mechanism of this difference, these datasuggest that animals in thin body condition are morevulnerable and respond differently than animals inhigher body condition when ingesting lupine.

The disposition of the lupine alkaloids in sheep serumfollowed a first-order rate of elimination, as demon-strated by the relative linearity of the semilog plots inFigure 2 for anagyrine and total alkaloid respectively.Biological half-life of absorption for total and individualalkaloids did not differ among treatments (P = 0.90),except for anagyrine, whereby the absorption half-lifewas significantly larger (P = 0.02) for LBC. However,some differences in elimination half-life were observedfor other individual alkaloids (Table 1) and were sig-nificant for anagyrine, lupanine, and alkaloid E. Lowbody condition ewes experienced slower elimination oflupanine and alkaloid E than ABC ewes (P < 0.01),whereas the elimination of anagyrine was marginallyaffected by body condition (P < 0.06). These data wouldexplain the increased serum alkaloid levels (calculatedby AUC) noted in Figure 2 for both anagyrine and to-tal alkaloids.

The dose of lupine used in this research resulted ina single total oral alkaloid dose of 139 mg/kg BW. Thisdose generated no clinical signs of toxicity at any time

after dosing. Gardner and Panter (1993) also reporteda lack of observed toxicosis when sheep were dosedwith a single 150-mg/kg BW dose of alkaloids from L.argenteus containing 1.92% total alkaloids.

Blood samples from the sheep contained measurablelevels of alkaloids beginning 0.5 h after dosing, andpeaked by 2 to 3 h (Figure 3). Alkaloids could be detectedin the blood stream for up to 48 h (Figure 2). Anagyrinefell below detection limits between 24 and 36 h afterdosing. All alkaloids observed in the plant material,except alkaloid D, were detected in serum (Figure 1).Alkaloid F occurred at such low concentrations (<1.5�g/mL) for a very short time (<3 h) that analyses werenot performed. There was an effect of time on totalalkaloid and anagyrine concentration (P < 0.001), butno interaction between time and body condition wasobserved. Lupanine, 5,6-dehydrolupanine and alkaloidE (data not shown) cleared from the body by 36, 48,and 18 h, respectively, and clearance of these alkaloidsfollowed a pattern similar to that of anagyrine andtotal alkaloid as shown in Figure 3. These data clearlysuggest that body condition is an important factor indisposition of lupine alkaloids.

Four unknown compounds appeared in chromato-gram of serum after dosing (Figure 1c), and we proposethese to be lupine alkaloid metabolites. These unknownpeaks were also reported by Gardner and Panter (1993),and further research is needed to evaluate and identifythese apparent lupine metabolites in the serum.

Discussion

The quinolizidine alkaloid, anagyrine, was identifiedas the primary teratogen in most lupines known tocause “crooked calf disease” in cattle (Keeler, 1976).Anagyrine is one of the key alkaloids of interest in thisstudy as it relates to the incidence of lupine-induced“crooked calf disease” in the western United States(Panter et al., 1999). Understanding the disposition ofthis and other alkaloids from lupines in the mammaliansystem is important in providing key information toevaluate management strategies to reduce livestocklosses. As range animals are introduced to summer pas-

Body condition affects alkaloid disposition 2803

Figure 2. Semilog plot for concentration-time curve ofanagyrine and total alkaloid levels in blood from ewesin low vs. average body condition after receiving an oraldose of silvery lupine (Lupinus argenteus). Area under thecurve (AUC ± SE) for anagyrine was 2,313 ± 121 and 966± 243 for low and average body condition respectively(P < 0.001). The AUC for total alkaloid was 7,343 ± 296vs. 4,352 ± 735 for low vs. average body condition, respec-tively (P = 0.003).

tures in varying body condition, understanding the re-lationship between body condition, nutritional status,and alkaloid absorption and elimination is important.

Differences in rates of alkaloid absorption and elimi-nation strongly suggest that overall disposition of lu-pine alkaloids, and especially the teratogen, anagyrine,is altered in a relatively dramatic way based on bodycondition. Although further research is needed to evalu-ate the mechanism of this difference, these data suggestthat animals in thin body condition maintain higherlevels of serum alkaloids for a greater duration thando animals in higher condition when ingesting lupine.Therefore, fetal exposure to these alkaloids may be al-tered because of maternal body condition. Furthermore,

Figure 3. Concentrations of anagyrine and total alka-loid in serum of sheep in varying body condition (lowand average) within 60 h after a single dose with 8.5 g/kg of BW of silvery lupine (Lupinus argenteus).

it has been observed that thin cows grazing lupinerangelands consume greater amounts of lupine thancows in higher body condition (Lopez-Ortiz, 2002).

These data suggest that physiological differences, in-cluding body condition, influence lupine alkaloid dispo-sition in the mammalian system. These differences mayoccur during absorption, distribution, biotransforma-tion, or elimination of the alkaloids (Rozman and Klaas-sen, 1995). Each of these processes can be affected bymultiple factors varying among individuals, includingphysiological state, body composition, and diet compo-sition.

Lopez-Ortiz et al.2804

Differences expected between LBC and ABC animalsinclude a smaller size and mass of splanchnic organs,primarily the liver (Noziere et al., 1999). If animals inlow body condition lose liver mass, this may decreasedetoxification capacity for animals with low conditionscores. It is uncertain, but doubtful, that a decreasedliver detoxification capacity in LBC ewes explains thedifferences observed in this study. Most of the quinolizi-dine alkaloids contained in Lupinus caudatus do notundergo major biotransformation in sheep, cattle, orgoats (Gardner and Panter 1993, 1994). Similarly, Pet-terson et al. (1994) recovered two quinolizidine alka-loids largely unchanged in the urine of humans within72 h of dosing.

Low body condition can also lead to a decrease inmuscle mass and fatty deposits (Birnie et al., 2000). Areduction of these tissues may have decreased the massfor alkaloid dissolution in the body of LBC ewes. Inthis case, the toxicants would be more likely to bind toplasma proteins, and one could expect higher circulat-ing levels in the blood stream (DeBethizy and Hayes,1989; Smith, 1992). Rozman and Klaassen (1995) con-tended that the concentration of a toxicant in blooddepends largely on its volume of distribution, indicatingthat body water volume could influence the measuredtoxin concentrations and may have been a factor in thehigher blood concentration of some alkaloids in theseanimals. It is unlikely however, that body water volumeaffected this study because body water increases asbody fat decreases (Scholz et al., 1990; Zahn et al.,1991), and thinner ewes had higher serum concentra-tions of alkaloids than did fatter ewes.

Foley et al. (1995) proposed that toxin breakdownduring detoxification requires energy and substratesfor biotransformation and elimination. Thus, if bio-transformation of lupine alkaloids takes place in theanimals, high alkaloid concentration in blood mightindicate a decreased energy supply for detoxification orelimination in LBC animals. Smith (1992) suggestedthat plant compounds undergoing phase II biotransfor-mations are conjugated with co-substrates of detoxifi-cation to carry and eliminate them. Those substratescan be deficient in animal tissues, thus reducing thecapacity to detoxify by decreasing elimination. How-ever, detoxification of lupine alkaloids may consist ofsimply eliminating the original alkaloids from the sys-tem. Meeker and Kilgore (1991) found substantialamounts of anagyrine and lupanine in milk after dosinglactating goats with lupine.

There were unidentified compounds in the GC pro-files of blood serum after dosing that did not matchwith either the plant profile or the ewe’s serum beforedosage, possibly indicating postabsorptive metabolismof lupine alkaloids. Gardner and Panter (1993) observedthese compounds in their blood profiles as well. Theseunidentified compounds could be metabolites or conju-gated alkaloids, and their identification will requirefurther work.

Implications

This research strongly suggests that body conditionaffects the disposition of quinolizidine alkaloids insheep. This study implies that livestock in good bodycondition may be better able to cope with lupine toxicitywhile grazing lupine-infested rangelands. Additionalresearch is needed to investigate the metabolic fate ofthese alkaloids in ruminants. Likewise, further re-search to document the toxicokinetics of the major lu-pine alkaloids, especially the teratogen, anagyrine, incattle is needed.

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