PSIV-12 - Monitoring ewe forage selectivity and consumption of tall larkspur (Delphinium spp.) in Southern Utah via visual observation and fecal metabarcoding

Abstract: In Southern Utah, sheep are utilized to a greater extent to graze rangeland due to the presence of Tall Larkspur (Delphinium spp.), which is known to be toxic to cattle. The objectives of this study are to quantify to what degree sheep consume tall larkspur and identify forage preferences on a diverse rangeland. We hypothesize that ewes consume tall larkspur based off preferences applied to other forages across range. In this study, ewes (N=400) were grazed across four summer pastures on Cedar Mountain near Cedar City, Utah. Ewe breed types consisted of Suffolk, Targhee, Rambouillet, and their crosses. During the 116 d trial plant consumption type, time of day, forage availability, weather, range utilization, and apparent weight of sheep were monitored and recorded. Data was collected via a 5-minute bite count procedure, noting all variables above, for each observed ewe. Fecal samples were collected and used for fecal metabarcoding (fDNA) at approximately 30% pasture utilization, which measures the proportion of plant DNA in the feces to determine forage species consumed. Plant species were sorted into functional groups (forbs, grass likes, grasses, shrubs, and trees). Data was evaluated through a CART analysis in R v4.1.2, and stratified using the GLM procedure in SAS v9.4. There was an increase in consumption of forbs, shrubs, and grasses over time, (P < 0.001), (P = 0.01), and (P < 0.001), respectively. For the grass-like and lichen plant types, there is little evidence of forage preference, (P = 0.7) and (P = 1.00) respectively. Fecal metabarcoding analysis indicates that protein content of diet originated from forbs, grass likes, grasses, shrubs, and trees by approximately 57%, 1%, 5%, 6%, and 31% respectively. Tall Larkspur appeared in fDNA samples, but did not represent a significant portion of the diet. Our findings indicate that sheep in Southern Utah utilize tall larkspur on range to a small extent in their diet, but do not preferentially graze it over other forb species.