INJECTABLE Cu COMPLEXES AS SUPPLEMENTARY Cu FOR GRAZING CATTLE

Four preparations of copper (Cu) salts, CuCaEDTA, Cu glycinate from two manufacturers, one in New Zealand (NZ) and the other in the United States (US), and Cu methionate were evaluated as injectable sources of Cu for cattle grazing pastures at four sites in Western Manitoba. There were four treated and one untreated groups of cattle at each site. Treated cattle were injected subcutaneously into the side of the neck. The concentration of Cu in blood serum, as an indicator of Cu status, was measured at 0, 30, 60 and 90 days post-injection. The area that was affected by the volume of swelling at the site of injection, as evaluated 30, 60 and 90 days post-injection, was a measure of the severity of reaction encountered: less than 25 cm 2 , moderate; 25–50 cm 2 , moderately severe; greater than 50 cm 2 , severe. At day 30 with 276 cattle, and day 90 with 133 cattle, serum Cu was higher (P 0.05) between Cu preparations. Responses of serum Cu to injectable Cu preparations were related to the severity of Cu deficiency in cattle on day 0, and to calculated absorption coefficients for Cu and available Cu in forages consumed by cattle at each site. At 30 days post-injection, the percent of cattle with a reaction at the site of injection (severity in brackets) was: CuCaEDTA, 6% (moderate); Cu glycinate (NZ), 23% (moderate); Cu glycinate (US), 48% (moderate to moderately severe); Cu methionate, 89% (moderate to severe). Areas up to 250 cm 2 were affected with Cu methionate. At 90 days moderate reactions were only present with Cu methionate. Body weight at day 90 was not influenced (P > 0.05) by injectable Cu. Although the preparations had similar effects upon serum Cu the severity of reaction at the site of injection may mitigate against the use of some preparations. Key words: Cattle, injectable copper, copper calcium edetate, copper glycinate, copper methionate