Beef herd health and productivity and exposure to the petroleum industry in west-central Alberta

Abstract

Intensive biological accounting methods were developed to measure the health and productivity of cow-calf herds surrounding a new sour gas processing plant. From the fall of 1991 through calving 1997, cow production records from all 7040 recorded bull contacts were examined from seven area cow-calf herds. Detailed information was also collected on other risk factors known to influence beef herd productivity. The median risks for non-pregnancy, abortion, calving late, stillbirth, and calf mortality for local herds did not differ from other published reports. There was no significant change in the risk of non-pregnancy, abortion, calving late, stillbirth, calf mortality, median calving date or crude weaning weight. Herd average age-adjusted weight for both male and female calves significantly improved. Total sulfation and H2S deposition data were used as markers for the complex mixture of compounds found in emissions from sour gas processing plants and sour flares. Cumulative exposure assessments were made from detailed records of individual animal movements between pastures. No consistent associations were found between either total sulfation or H2S deposition and productivity parameters across the three cow-calf production cycles examined. There were, however, five examples of associations between increasing exposure to total sulfation and decreased productivity in the 18 models examined for exposure beginning with first bull contact. The association between cow-calf productivity and cumulative animal proximity to petroleum field facilities and gas flared from oil and gas batteries was then examined. Increased risk of non-pregnancy was sometimes associated with exposure to one or more of the following facility types: sour flaring battery facilities, all battery flaring sites, active gas wells, and larger field facilities. The associations were not however, consistent among years or even among risk periods for the same year. Facility proximity and flaring were not associated with increased abortion risk. Volume of flared sour gas from battery sites was associated with increased risk of stillbirth. Finally, sour flaring was associated with increased calf mortality risk for the 1992-93 calf crop. Several examples of associations between exposure and increased productivity were also found in the analysis most of which involved either oil wells or all well sites.