A52-75-2007E.pdf - AgroMedia International Inc

Health51Bovine whey proteins inhibit the interaction of Staphylococcusareus and bacteriophage KCorresponding AuthorSabour, P.M.AAFC Food Research ProgramCollaboratorsGill, J.J.University of GuelphLeslie, K.E.University of GuelphGriffiths, M.W.University of GuelphJournal of Applied Microbiology (2006) Vol. 101 p. 377-386.Staphylococcus aureus (SA) is the most costly and problematic pathogencausing intramammary infections (IMI) of dairy cattle. Poor cure rates andthe continued emergence of multiple drug resistant strains of SA haveprompted the search for alternative treatments. One such potential alternativeis the use of bacteriophages (phages)—viruses that infect and killtheir host bacteria. Earlier works exploring the use of phages to control SAhave yielded mixed results. In this study bacteriophage K was effective inlysing (killing) SA cells in broth culture (in vitro) but, when administeredinto the mammary glands of cows (in vivo) experimentally infected withSA, or when raw milk or whey were used as the culture medium, phage Kwas much less effective. These divergent results suggested that some componentof whey may inhibit attachment of the phage to SA cells. This studyidentified a component of whey protein as the inhibiting factor—treatmentof whey with heat, protease or ultrafiltration removed the inhibition.Furthermore, suspension of SA in whey, followed by resuspension in brothalso reduced phage binding due to the adhesion of whey protein to theSA cell surface. These observations explain the divergent results obtainedfrom studies of SA-phage efficacy in broth culture compared with thosefrom animal trials. In addition, these results highlight the importance ofconducting through in vitro experiments prior to animal experiments.52The relationship between herd level disease incidence and returnover feed index in Ontario dairy herdsCorresponding AuthorMcLaren, C.J.University of GuelphCollaboratorsLissemore, K.D.University of GuelphDuffield, T.F.University of GuelphLeslie, K.E.University of GuelphKelton, D.F.University of GuelphGrexton, B.CanWest DHI ServicesCanadian Veterinary Journal (2006) Vol. 47 p. 767-773.The objective of this study was to examine associations between herdprofitability and the herd level incidence of health disorders in 48 Ontariodairy herds. Profitability was calculated as the difference between milkincome and feed cost (return over feed, ROF). No significant associationswere found between ROF and incidence of displaced abomasum, retainedplacenta, clinical or subclinical mastitis (assessed with the California MastitisTest), milk fever, clinical ketosis or lameness. However, a negative relationshipwas found between ROF and subclinical ketosis, detected usinga cow-side test for betahydroxybutyrate in milk. Each percentage unit increasein herd incidence of subclinical ketosis was associated with a decreasein ROF of $0.15/cow/day.Health 91