| annual variation in serum antibody concentrations against gastrointestinal nematodes in beef calves from semi-arid rangelands of western canada. | sera from calves originating on a 17,000 ha ranch in southeastern alberta, were collected over three consecutive years (2008-2010) at weaning and analysed for the presence of anti-ostertagia antibodies using the svanovir(®)ostertagia ostertagi-ab elisa kit. faecal samples taken at the same time were analysed for presence of nematode eggs using the modified wisconsin faecal flotation technique. mean optical density ratio (odr) values for all calves were similar in 2008 and 2010 while the 2009 val ... | 2014 | 25086494 |