Jelinski, Murray2023-01-312023-01-3120222023-062023-01-31June 2023https://hdl.handle.net/10388/14460Gastrointestinal nematodes (GIN) in beef cattle can be a concern for cattle producers due to loss in profit associated with anthelmintic treatment costs and reduced production performance. There is limited current information regarding the epidemiology of GIN in grazing yearling beef cattle in western Canada. Hence, the objectives of this research were to: 1) describe the epidemiology of GIN and assess their impact on weight gain (Chapter 2), and 2) conduct a nemabiome study to determine the diversity and abundance of nematode species within Saskatchewan pastured beef cattle (Chapter 3). Seventeen cohorts of pastured yearling beef cattle were processed in the spring and fall of 2019. Animals were individually weighed, and rectal fecal samples obtained for pooled fecal egg count (FEC). A subset of calves (n = 25) in each herd was administered oral fenbendazole (Safeguard®, Merck, Canada) and a parenterally administered extended-release eprinomectin (LongRange®, Boehringer Ingelheim, Canada), while the remaining cohort was left untreated. Eggs per gram of feces (EPG) were determined in pooled fecal samples using the Modified Wisconsin Sugar Flotation Technique, and deep amplicon nemabiome sequencing of the ITS-2 DNA locus was used to describe nematode species diversity and abundance. Across all cattle (n = 867), there were differences between treatment and control groups regarding FEC (p < 0.01). In the generalized estimating equations (GEE) model, FEC decreased by 44 times over the grazing season, and FEC were 1.8 times greater on pastures located in black/gray soil versus dark brown soil zones. Areas with higher precipitation also had higher FEC. There was no significant difference (p = 0.41) in the ADG across all cattle, but differences were found in the ADG between treated and control cattle in five cohorts. Haemonchus placei was found in all spring cohorts, accounting for 30% of the L3 species composition. Hence, it was one of the dominant species together with Ostertagia ostertagi (40%) and Cooperia oncophora (26.2%). Ostertagia ostertagi (47.5%) and C. oncophora (42.0%) were the most common species recovered at the time of fall sampling. Haemonchus placei represented 5.2% of the species diversity at the time of fall sampling, which is higher than previously reported in western Canada. The lack of correlation between FEC and ADG is likely due to differences in farm-specific environmental conditions (rain, temperature), soil type and husbandry factors.application/pdfenNeamatodesepidemiology, beef cattleThesis2023-01-31