Progress report for OW20-355
Larkspurs (Delphinium spp.) are native plants that grow on foothill and mountain rangelands of western North America and have a long history of poisoning grazing cattle. Ranchers who graze cattle in rangelands with large populations of toxic larkspur often have yearly herd mortalities up to 10%. These losses amount to millions of dollars due to animal deaths, increased management, and veterinary treatment costs.
We propose to compare animals from a herd grazed on larkspur-containing pastures (larkspur-native) to cattle from a herd that has never been exposed to larkspur (larkspur- naive). We hypothesize that fewer larkspur-native animals will be lost to larkspur poisoning than larkspur- naive cattle.
The sourcing of replacement cattle from larkspur-native herds could be a simple and sustainable solution for reducing cattle losses and increase the profitability of cattle production on larkspur-infested rangelands. The results from this study will have regional impacts that will affect producers throughout the western U.S. Livestock death losses cause undo stress on livestock owners and reducing that worry and stress by knowing the livestock that are grazing larkspur-infested rangelands are resistant to the plant alkaloids can help enhance the quality of life for livestock producers.
The outcomes from this study will be disseminated through extension fact sheets, a field day, presented at scientific and producer meetings, and a peer-reviewed publication.
The objective of this study is to test the hypothesis that fewer larkspur-native animals will be lost to larkspur poisoning than larkspur-naive cattle. After the grazing season, surviving cattle will subsequently be tested for larkspur resistance at the PPRL as previously described (Green et al., 2014), to determine their larkspur phenotype and genotype. The phenotypes and genotypes will be incorporated into a genetics of larkspur resistance in cattle study currently underway at the PPRL (genotyping costs will be paid by the PPRL).
To complete this objective, grazing studies will be conducted when larkspur is growing and toxic to cattle (May 1 to October 1). Twenty Angus steers, that have not been preselected due to culling practices, and are naive to larkspur poisoning and twenty Angus steers from ranches that have historically preselected animals, due to culling practices, that are more resistant to larkspur (native) will graze together. Preliminary research (Figure 1) with six larkspur-naive Angus steers from the US Meat Animal Research Center, Clay Center, NE (USMARC) had a shorter exercise times after receiving an oral dose of dried ground larkspur compared to the exercise times of twenty-six larkspur-native Angus steers from Montana that received an oral dose of larkspur. The cattle were exercised 24 hours after the oral dose of dried ground D. barbeyi. Larkspur resistant cattle walk longer than larkspur susceptible because the toxins in larkspur cause muscle weakness and resistance to exercise (Green et al., 2019a).
Grazing studies will be conducted during the summer months when larkspur is growing and toxic to cattle (May 1 to October 15). In year 1, six larkspur-naive Angus steers from USMARC, that have not been preselected, due to culling practices, along with six larkspur-native Angus steers from ranches that, due to culling practices, are more resistant to larkspur will be grazed in year one (July 1, 2021 to October 15, 2021). Animals will be placed on a mountain rangeland infested with Delphinium occidentale on a private ranch near Cody, WY (July 1, 2021 to October 15, 2021).
Twenty-five GPS collars were purchased in 2020. These collars will be placed on stocker cattle, that are owned by the livestock producer that grazes these rangelands, for the grazing season (May 1, 2021 to October 15, 2021). Collars have been successfully used to monitor grazing distribution and grazing activity (Anderson et al., 2012). Current technology employs sensors within the collars that allows researchers to develop a decision tree to detect grazing bouts and foraging behavior (Augustine and Derner, 2013). Vegetation maps will be created using ArcGIS software so that the collar data can be overlaid onto the vegetation map to determine grazing patterns.
Bite counts will be taken on the six larkspur-niave and six larkspur-native Angus steers during the period they will be grazing. This will give an indication when cattle start to consume larkspur and how much larkspur is being consumed. Larkspur samples will be collected weekly when cattle are grazing to determine alkaloid content of larkspur.
Cattle will be removed from the rangeland at the end of the grazing period (approximately October 15) and taken to the PPRL. Cattle will be tested for larkspur susceptibility by methods previously described (Green et al., 2014). Whole blood will be collected from each animal for genotyping prior to pasture turnout. A study of the genetics of larkspur resistance in cattle has been ongoing at the PPRL since 2006 and these genotypes (Bovine SNP50 v3 BeadChip microarray, Illumina Corp.) will be added to the genetic database for further analysis (genotyping costs will be paid by the PPRL as it is a separate research project).
In year 2, a new set of six naive and six native Angus steers will graze the same larkspur infested rangeland. Research protocols will follow procedures described in year 1.
Larkspur plants were collected over the growing season, in 2020, to determine alkaloid content of larkspur plants over the growing season. Larkspur collection started in June 18, 2020 and subsequent collections occurred at 3-week intervals through September 24, 2020. Larkspur plants were collected from nine locations. Four locations were selected on the ranch, utilized by two cooperators, that currently graze stocker cattle and has lost cattle in the past from larkspur poisoning. The first location (P.ranch 1; 44.85426951°;-109.50920815°, 2166 m) was located approximately 51 km northwest of Cody, WY. The second location (P.ranch2; 44.85540863°;-109.53971708°, 2121 m) was located approximately 52 km northwest of Cody, WY. The next two locations were on the same ranch but at higher elevation. The third location (P.ranch 3; 44.92723610°;-109.67780830°, 2334 m) was located 67 km northwest of Cody, WY. The fourth location (P.ranch 4; 44.93322795°;-109.63305998°, 2698 m) was located 64 km northwest of Cody, WY. One location was collected in Idaho (Targhee Pass; 44.68116702°;-111.26860801°, 2117 m) 29 km north of Island Park, ID. Four locations were collected in Montana. The first location (Dillon 1; 45.3589483°; -112.9014000°, 2314 m) located approximately 25 km northwest of Dillon, MT. The second location (Dillon 2; 45.3745650°; -112.89917670°, 2458 m) located approximately 26 km northwest of Dillon, MT. The third location (DooLittle 1; 45.7195617°;-113.3276217°, 1927 m) 77 km northwest of Dillon, MT. The fourth location (DooLittle 2; 45.7175567°; -113.3437150°, 1871 m) located approximately 78 km northwest of Dillon, MT. Ten plants were collected from each location and separated into leaves, stems, and reproductive parts. Plants were placed in a 40° C oven to dry. Larkspur plants are currently in the process of being ground, in a Wiley mill to pass through a 1-mm screen, and processed for chemical analysis of larkspur alkaloids. Larkspur plants will be collected again in 2021, at the same locations, following the same procedures to determine if alkaloid concentrations are similar across years.
Bite counts will be analyzed for the effect of larkspur susceptibility (determined by phenotype testing at the lab) by days and years on bites taken on larkspur using an ANOVA with repeated measures. GPS collar positioning data will be overlayed on to a vegetation map and location will be analyzed to determine time spent in larkspur infested areas using an ANOVA with repeated measures. Walking times (phenotype testing) among animals will be compared using Prism (GraphPad Software, San Diego, CA, USA).
Due to the restrictions in travel caused by Covid-19, the grazing study was postponed in 2020 and will begin this year 2021.
Larkspur samples collected from nine locations, in 2020, are currently being processed in the lab for alkaloid analysis to determine alkaloid concentration over the growing season.
Larkspur-naive (6) and larkspur-native (6) cattle have been purchased and are ready to began grazing this summer (2021) as larkspur plants mature. Twenty-five GPS collars have been purchased and are waiting for a collaborating producer to purchase stocker cattle so the collars can be placed on cattle prior to being turned out to graze for the season.
Educational & Outreach Activities
Due to Covid-19 restrictions, there have not been any field days or presentations held. Two agricultural professionals have consulted with a livestock producer and his ranch hand in regard to livestock losses to larkspur.
Outcomes from this project will lead to decrease in death loss of livestock caused by larkspur poisoning.