Trends in export of dairy Holstein heifers from the United States

摘要

A general overview of the export and testing requirements is given for bred female dairy cattle from the United States (US) to Turkey, Mexico, and Russia, the top three export markets. Disease-by-disease serologic test results are presented for 7,339Holstein dairy heifers tested in quarantine in southeastern Chester County, Pennsylvania for export to Turkey from June 2010 to October 2011. Management practices to decrease the prevalence of diseases of importance to the export market are reviewed. Prevalence rates of serologically positive heifers tested during the quarantine period using the enzyme linked-immunosorbent assay were: bluetongue virus (BTV) 4.9%, Mycobacterium avium subsp paratuberculosis (MAP) 0.65%, and bovine leukemia virus (BLV) 5.7%. Prevalence rate of bovine viral diarrhea virus - persistently infected (BVDV PI) heifers using pooled polymerase chain reaction was 0.68%. Because of the high prevalence of BLV in US cattle, most if not all heifers are routinely screened for BLV priorto purchase and entry into quarantine. Some of the heifers in this data set originating from endemic BTV states were pre-screened for BTV. Because of pre-screening for BLV prior to purchase for export, the prevalence of BLV reported was lower than wouldbe expected in the general population of heifers in the US. The prevalence of BTV would depend on whether heifers came from BTV free or endemic states. Dairy herds wanting to market heifers for export should apply management practices known to decreasethe prevalence of BTV, BLV, MAP, and BVDV PI.