Start Date: Feb 11, 2008
End Date: Feb 10, 2013
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 using cattle. 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.