THE SEVERITY OF HYPOCUPREMIA IN SELECTD HERDS OF BEEF CATTLE IN NORTHWESTERN MANITOBA

Abstract

Hypocupremia, a condition whereby blood serum copper (Cu) is less than 9.4 μmoles/L was monitored in 40 selected herds of beef cattle from northwestern Manitoba. Data from 27 herds, blood sampled in the spring and autumn of 1974, were from a study to evaluate, as a supplemental source of Cu, a single dose of injectable Cu glycinate in the spring; an additional 13 non-experimental herds were blood sampled in the autumn of 1974. The severity of hypocupremia was determined by the change in concentration of Cu in blood serum of non-Cu-injected cattle between spring and autumn, and the effect of injectable Cu glycinate upon this change of concentration of Cu in blood serum. Within groups of herds, injectable Cu either increased (P < 0.05) mean serum Cu in treated cattle, beyond that of untreated cattle, or prevented (P < 0.05) a large drop of mean serum Cu level between spring and autumn. A modified (moved 5 to 10 km eastward) eastern boundary of the Ashville Geological Formation divided northwestern Manitoba into two subregions. In the eastern subregion, a moderate hypocupremia in selected herds was due primarily to an insufficiency of Cu in pasture forage, while the moderately to extremely severe hypocupremia in selected herds from the western subregion appeared to be due to a molybdenum (Mo) toxicity. A single dose of injectable Cu was an effective source of supplemental Cu in selected herds from the eastern subregion. The severity of Cu deficiency in herds of cattle from northwestern Manitoba was not related to calculated absorption coefficents for Cu and available Cu, based on the Cu, Mo and total sulfur content of pasture forages. Differences in the severity of hypocupremia were due to differences in the concentration of Mo in forages. Key words: Beef cattle, hypocupremia, copper deficiency, molybdenum toxicity, northwestern Manitoba