Abstract
The relationship between bulk tank somatic cell count (SCC) and farm management and infrastructure was examined using data from 398 randomly selected, yet representative, Irish dairy farms where the basal diet is grazed grass. Median bulk tank SCC for the farms was 282,887 cells/ml ranging from 82,209 to 773,028 cells/ml. Two questionnaires were administered through face-to-face contact with each farmer. Herd-level factors associated with bulk tank SCC were determined using linear models with annual somatic cell score (i.e., arithmetic mean of the natural logarithm of bulk tank SCC) included as the dependent variable. All herd level factors were analysed individually in separate regression models, which included an adjustment for geographical location of the farm; a multiple regression model was subsequently developed. Management practices associated with low SCC included the use of dry cow therapy, participation in a milk recording scheme and the use of teat disinfection post-milking. There was an association between low SCC and an increased level of hygiene and frequency of cleaning of the holding yard, passageways and cubicles. Herd management factors associated with bulk tank SCC in Irish grazing herds are generally in agreement with most previous studies from confinement systems of milk production.
Highlights
Ireland produces approximately 5,090 million litres of milk annually
From the 303 bulk tank milk samples taken, 51% of the samples tested positive for the presence of Staphylococcus aureus, varying from 1 CFU to ‘numerous’ (i.e., 40 to 100 CFU); 11% of all milk samples had >40 CFU
Backema et al (1999) reported that factors associated with bulk tank somatic cell count were related to the incidence rate of clinical mastitis caused by S. aureus
Summary
Ireland produces approximately 5,090 million litres of milk annually. Recent research indicates an annual increase in Irish bulk tank SCC of approximately 5,000 cells/ml, which is worrying for the dairy industry (Berry et al 2006). Herd management has been shown in other international studies to be associated with bulk tank SCC (Barkema et al 1998; Kiiman et al 2006; Wenz et al 2007). Wenz et al (2007) documented that bedding material, housing facilities and cluster removers were all associated with bulk tank SCC. Barkema et al (1998) reported that the most important factors associated with bulk tank SCC were teat disinfection after milking, the duration of clinical mastitis treatment and no drying after a wet treatment pre-milking. The management factors deemed to be important vary from farm to farm and country to country. Kiiman et al (2006) concluded that the milking operator was the biggest factor affecting SCC. Wenz et al (2007) documented that bedding material, housing facilities and cluster removers were all associated with bulk tank SCC. Barkema et al (1998) reported that the most important factors associated with bulk tank SCC were teat disinfection after milking, the duration of clinical mastitis treatment and no drying after a wet treatment pre-milking. Rodrigues et al (2005) reported differences in SCC between cows housed in forestalls and stallbarns, and Goldberg et al (1992) documented that confined housing had a higher standard plate count than intensively managed rotational grazing
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