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BOVINE neonates are born virtually agammaglobulinaemic (Klaus and others 1969) and successful passive transfer of maternal immunoglobulin depends on efficient absorption of an adequate volume of colostrum of sufficient quality. However, colostrum may also represent a potential source of pathogens such as Mycobacterium avium subspecies paratuberculosis (MAP), Salmonella species (Houser and others 2008) and Mycoplasma bovis (Maunsell and others 2011) to newborn calves. The presence of MAP in colostrum may occur either through direct shedding from the mammary gland (Sweeney and others 1992, Streeter and others 1995) or contamination of colostrum with MAP shed in faeces (Pithua and others 2011). The hygienic collection of colostrum has therefore been suggested as a critical control point for the control of paratuberculosis in infected dairy farms (McAloon and others 2015).
Elevated colostral bacterial counts may also have a detrimental effect on passive transfer by negatively impacting the efficiency of immunoglobulin absorption (Gelsinger and others 2015). This phenomenon has been attributed to direct binding of bacteria to immunoglobulins in the gut, reducing immunoglobulin available for absorption, and binding of bacteria with enterocyte receptors involved in immunoglobulin absorption, resulting in reduced absorption of available immunoglobulin (Johnson and others 2007).
Measurement of total aerobic bacterial count (TBC) and total coliform count (TCC) has been recommended as a method of evaluating the level of contamination in colostrum samples, with thresholds of ≤100,000 colony-forming units (cfu)/ml and 10,000 cfu/ml recommended for TBC and TCC, respectively (McGuirk and Collins 2004). There are little published data on the degree of …