Associations between total sulfation, hydrogen sulfide deposition, and beef-cattle breeding outcomes in western Canada

Beef cows sometimes are pastured close to oil- and gas-production and proce ssing facilities. We measured the health and productivity of cow-calf herds with differing exposure to sour-natural-gas processing facilities in weste rn Canada. In seven cow-calf herds, the numbers of eligible mature females included in the study for the breeding seasons beginning in 1993, 1994, and 1995 were 1177, 1251, and 1236, respectively. Outcomes included pregnancy status, calving interval, and the occurrence of twins, abortions, stillbirt hs, and neonatal mortality. Information also was collected on other risk fa ctors known to influence beef-herd health and productivity. Monthly measurements from a network of passive air-monitoring devices were used to estimate exposure. Total sulfation and H2S deposition were used as markers for the complex mixture of compounds found in emissions from sour-g as processing plants and sour flares. Most herds were managed in multiple p asture groups. Cumulative exposure assessments were made from records of in dividual-animal movements between pastures. Generalized estimating equation s were used to evaluate the association between exposure and outcome and to adjust for potential confounders and clustering of binomial outcomes withi n herd. No consistent associations were found between either total sulfatio n or H2S deposition and productivity parameters across the cow-calf product ion cycles. There were, however, five examples of significant associations between increasing cumulative exposure to total sulfation and decreased pro ductivity in the 18 models examined. (C) 2001 Elsevier Science B.V. All rig hts reserved.