COPPER, ZINC, MANGANESE AND IRON VARIATION IN FIVE FEEDS FOR RUMINANTS

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Abstract
Samples of legume hay, grass hay, corn silage, oat forage and grains grown throughout British Columbia were analyzed to determine Cu, Zn, Mn and Fe concentrations and these concentrations were compared with the British Agricultural Research Council minimum requirements for cattle. Approximately 95% of all feeds were below 10 ppm Cu, the recommended minimum for cattle. These data provide the first indication of a general simple copper deficiency in British Columbia, whereas previous reports for British Columbia and Canada concerned pockets of copper deficiency resulting from molybdenum toxicity. Some 95% of the samples were below the minimum recommended level of 50 ppm Zn. Manganese concentrations were somewhat higher, with only 40% of the samples below the recommended minimum of 40 ppm Mn. Twenty-five percent of the grass samples contained above 151 ppm Mn. The average Fe concentration for all feeds was well above the suggested minimum requirement of 30 ppm. Some 15% of the samples were sevenfold the minimum recommended. These analyses suggest the need for greatly increased levels of Cu and Zn supplementation for cattle on winter feed. There is also need for Mn supplementation where legume hays and corn silages are fed in British Columbia.

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