title: A single pasture limited treatment approach to estimate production loss from gastrointestinal nematodes in grazing stocker cattle.
abstract: The objective of this study was to evaluate the use of a single pasture, limited treatment methodology to assess the impact of gastrointestinal nematodes on weight gain in grazing cattle. From a group of 450 British crossbred, yearling spayed heifers, 60 animals were randomly selected (prospective randomization) prior to placement on summer pasture. Each of these 60 animals was weighed, a fecal sample obtained for nematode egg count and a uniquely numbered ear tag applied. A randomly assigned group of 30 received treatment with one ivermectin sustained release bolus, while the remaining 30 served as non-treated controls. The treatment and control groups rejoined the remaining non-treated 390 animals, and were grazed as a single group for 165 days. At grazing conclusion, treatment and control cattle were individually weighed, and fecal samples obtained for nematode egg counts. Treatment was associated with a 0.064 kg per grazing day gain increase, or a 10 kg increase over the grazing season (P = 0.02). Nematode egg counts at grazing initiation were not different between treatment and control (P = 0.30), though egg counts in treated cattle at study end were lower than control (P < 0.0001). Results of this study support the use of a single pasture limited treatment approach for measuring the effect that internal nematodes have on weight gain in grazing cattle under commercial range conditions.
authors.affiliation: Department of Veterinary Science, College of Agriculture and Biological Sciences, South Dakota State University, Brookings, SD 57007, USA.
authors.forename: W B
authors.initials: WB
authors.lastname: Epperson
authors.forename: B D
authors.initials: BD
authors.lastname: Kenzy
authors.forename: K
authors.initials: K
authors.lastname: Mertz
authors.forename: M B
authors.initials: MB
authors.lastname: Hildreth
mesh_terms: D000818:Animals; D001835:Body Weight; D002417:Cattle; D002418:Cattle Diseases / Q000453:epidemiology / Q000469:parasitology*; D005243:Feces / Q000469:parasitology; D005260:Female; D005767:Gastrointestinal Diseases / Q000453:epidemiology / Q000469:parasitology / Q000662:veterinary*; D010270:Parasite Egg Count / Q000662:veterinary; D011897:Random Allocation; D013023:South Dakota / Q000453:epidemiology; D018709:Statistics, Nonparametric; D017183:Strongylida / Q000254:growth & development*; D017206:Strongylida Infections / Q000453:epidemiology / Q000469:parasitology / Q000662:veterinary*