Salmonella link to coarse grade and palleted Magnesium Oxide in Feeds
Over the past few weeks, a number of vets have been reporting Salmonella outbreaks on dairy farms. Our investigations on some of these farms indicate that these outbreaks seem to correlate to use of pelleted Magnesium Oxide being fed in palm kernel based feeds. Although one of the farmers we interviewed, reported some salmonella before feeding the PKE containing the coarsely ground magnesium oxide, he reported that after introducing the feed the disease took off. On discussions with some in the feed industry it would seem that coarsely ground magnesium supplements may have been widely used throughout the feed mill industry over the past 2 seasons. This magnesium is a little different to that used in the past and the pelleted magnesium associated with the outbreaks of salmonella reported in Taranaki. Prior to the last two seasons this coarsely ground form of magnesium oxide was formerly only sold into the fertiliser market and has large particle sizing, ranging from 2mm – 5mm. We believe the same risk factors are involved as those reported in the Taranaki outbreak of 2011 at that time associated to a prilled magnesium oxide product used in those feeds.

A case controlled study was performed in 2011 – 2012 to identify herd-level risk factors for acute Salmonellosis. It is our belief that the most recent outbreak has many of the same issues in common with the earlier outbreak. This summary, identified a number of risk factors that contributed to this sudden outbreak of the infection across a large number of herds, most particularly highlighted was the strong connection between feeding granulated magnesium supplements and prevalence of the disease.

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CONTRIBUTING FACTORS IDENTIFIED IN THIS REPORT WERE AS FOLLOWS:

1) Continuous feed troughs – consumption of supplementary feed from shared troughs varies amongst individual cows where dominant cows will consume more than their allotted daily feed allowance, with submissive cows consuming less. Fluctuations in feed intake could affect the rumen microflora balance, allowing salmonella to multiply and cause infection. Reduce risk by using individual troughs.