Objective I: Reduce risk of grazing cattle on larkspur-infested rangelands, and
increase our understanding of aspects of cattle poisoning by various larkspur
species. <BR> <BR>
1.1 Determine the interaction between ingestion of toxic alkaloids from larkspur and
bloat in cattle.<BR>
1.2 Determine genetic differences to larkspur toxicity using a small animal model and
genetically divergent cattle populations.<BR> <BR>
1.3 Determine clearance times and toxicokinetics of different toxic and less toxic
alkaloid mixtures in small animal models and cattle.<BR>
1.4 Determine plant genotype and environmental influences on larkspur alkaloids and
evaluate chemotaxonomy,chemical phenology, control strategies, and population
dynamics of larkspurs.<BR> <BR>
1.5 Continue development of management strategies for cattle to safely graze on
1.1 In the first phase, cattle will initially be screened for bloat susceptibility
and for susceptibility to larkspur alkaloids. In the second phase, resistant and
susceptible cattle will be tested for susceptibility to larkspur-associated bloat. In
the third phase, mixtures of MSAL-type alkaloids and consecutive doses of larkspur
will be administered at levels seen in field intoxication.
1.2 Strains of mice will be chosen to provide a diverse representation of minor
haplotypes across the mouse genome, and lethality of MLA will be determined in each.
The second series of experiments will examine the toxicokinetics of MLA in mice.
Further work will characterize differences in gene expression between the selected
mice strains (i.e., resistant and susceptible) after treatment with MLA. The
differences in gene expression between strains will provide candidate genes to
determine if susceptibility is heritable, and to identify genetic markers associated
with MLA toxicity.
1.3 Initial work will examine the effect of deltaline on the toxicity of MLA by
comparing the toxicokinetics and LD50 of alkaloids administered individually to mice
vs. the co-administration of alkaloids at various ratios. Toxicokinetic studies will
then be conducted to determine the kinetics of MLA, deltaline, or a combination of
MLA + deltaline. Various body tissues will be collected and analyzed for alkaloid
concentrations. After work on mice is completed, similar studies will be conducted
1.4 Larkspur flowering stalks representing D. occidentale and D. barbeyi will be
collected throughout their geographical distribution. A chemical fingerprint of
alkaloids will be generated from each sample, and samples will be scored for the
presence or absence of the MSAL-type alkaloids. Studies will elucidate the
biological mechanism(s) responsible for the observed chemical fingerprints.
Reciprocal gardens of D. occidentale plants representing both chemical fingerprints
(putative hybrids and non-hybrids) will be established. Phylogenetic analyses using
individuals representing D. occidentale and D. barbeyi plants containing little or no MSAL type alkaloids (i.e. putative hybrids) will be performed using AFLPs (Amplified
Fragment Length Polymorphisms) to determine if tall larkspur plants that do not
contain MSAL-type alkaloids are derived hybrids.
1.5 Studies will focus on one particular low larkspur, Delphinium andersonii.
Grazing studies of cattle consumption will be conducted at two locations (Idaho,
Nevada) for 2 years each from the vegetative to pod stages of growth. Study pastures
will be delineated based on low larkspur density. The dependent variables will be
daily bite counts of larkspur and other forage components. Bite counts will be taken
during all active grazing periods. Larkspur density, biomass, alkaloid
concentrations, and nutritional quality (i.e., NDF, IVOMD, CP) will be determined in
relation to other forage components.