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United States Department of Agriculture

Agricultural Research Service

Title: Heavy Metal Concentrations in Dairy Feed: a Survey of Heavy Metal Concentrations in Wisconsin Dairy Feeds

Authors
item Li, Y - CHINESE ACADAMEY OF SCI
item Mccrory, D - UW-MADISON
item Powell, J Mark
item Saam, H - UW-MADISON
item Jackson-Smith, D - UTAH STATE UNIV

Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 15, 2005
Publication Date: June 15, 2005
Citation: Li, Y., McCrory, D.F., Powell, J.M., Saam, H., Jackson-Smith, D.B. 2005. Heavy metal concentrations in dairy feed: a survey of heavy metal concentrations in Wisconsin dairy feeds. Journal of Dairy Science. 88:2911-2922.

Interpretive Summary: The long-term accumulation of heavy metals in soils of dairy farms may reduce crop and animal productivity, and poses a risk to animal, human and ecosystem health. The heavy metal content of dairy feeds remains poorly documented, particularly in the US. This survey determined the heavy metal content of 203 samples of typical dairy feeds on 54 Wisconsin dairy farms. Lowest heavy metal concentrations were found in homegrown alfalfa hay and haylage, and corn grain and silage. Highest metal concentrations were found in purchased feeds particularly mineral supplements, and to a lesser extent corn- or soybean-based concentrates. The concentration of heavy metals in total mixed rations was highest for zinc, followed by copper, chromium, arsenic and lead. Although no dairy ration was found to contain heavy metal concentrations that could cause direct toxic effects to the dairy cow, copper and zinc were being fed about 25% above NRC recommended levels. This study documented the concentration of heavy metals in feeds on Wisconsin dairy farms and highlighted the possible link between excessive heavy metal concentrations in dairy feed and manure, and heavy metal accumulation in soils and adverse impacts on soil and forage productivity.

Technical Abstract: Wisconsin has the largest numbers of dairy operations in the USA, with the majority producing most of their own feed, and recycling manure through their croplands. The accumulation of heavy metals such as, zinc (Zn), copper (Cu), chromium (Cr), cadmium (Cd), lead (Pb), and arsenic (As) in the soils of dairy systems may reduce crop and animal productivity and poses a risk to animal, human and ecosystem health. The heavy metal content of dairy feeds however, remains poorly documented, particularly in the US. This survey determined the heavy metal content of 203 typical dairy rations components sampled from 54 dairy farms in Wisconsin. Lowest heavy metal concentrations were found in homegrown alfalfa (Medicago sativa L.) hay and haylage, and corn (Zea mays L.) grain and silage. Highest metal concentrations were found in purchased feeds particularly mineral supplements, and to a lesser extent corn- or soybean-based concentrates. The concentration of heavy metals in complete dairy rations (total mixed rations and aggregated component rations) followed the general order of Zn > Cu > Cr > As > Pb >As. With the exception of Pb, the main source of heavy metals in the dairy feed ration were from purchased feed (grain and protein mixes, mineral supplements), imported onto dairy farms. Though no complete dairy ration was found to contain heavy metal concentrations that could cause direct toxic effects to the dairy cow, over half the farms were feeding Cu and Zn above NRC recommended levels. Excessive heavy metal concentrations in dairy feed are likely to be excreted in manure which may have long term negative implications and adversely affect soil and forage productivity.

Last Modified: 7/31/2014
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