Changes in periparturient fecal egg counts in beef cows calving in the spring

A herd of mature Angus and Angus-Holstein-Friesian cows calving between March and May was maintained at 80% and 100% of National Research Council's recommended total digestible nutrient (TDN) levels during the winter. Changes in fecal nematode egg counts of these cows, expressed as eggs/5 g of feces and quantitated by the Wisconsin sugar flotation technique, were detected perinatally and were correlated with breed, nutritional level, and time of year. A limited, yet highly significant (P less than 0.001) increase in egg output was found in cows at calving. Anthelmintic treatment at calving caused postcalving egg counts that were statistically lower than were those from non-treated cows. When breed and nutritional level were considered independently, there was less influence on egg counts than when the interaction of breed and nutritional level was examined. Angus-Holstein-Friesian cows fed 80% TDN requirements had the greatest perinatal increase in egg output, and those fed 100% TDN had the smallest increase of all groups. Angus cows responded in an opposite manner to the nutritional level and had increases in egg counts intermediate to those counts of Angus-Holstein-Friesian cows. This characterization of the periparturient egg output by mature cows aided in evaluating the role of grazing cows in contaminating pastures.