Abstract
In this study, the contribution of management practices, herd characteristics, and seasonal variables to the herd somatic cell count (SCC) was quantified in herds with low (<150,000 cells/mL), medium (150,000–200,000 cells/mL), and high (>200,000 cells/mL) herd SCC (HSCC). Selection of the variables was performed using a linear mixed effect model; HSCC was calculated as the arithmetic mean of the individual cow's SCC. The data concerning management practices were derived from 3 questionnaires on mastitis prevention and management practices on 246 Dutch dairy farms. The monthly Dairy Herd Improvement test data of these 246 farms were used to calculate the herd characteristics and seasonal effects. None of the management practices were associated with HSCC in all 3 HSCC categories. Some variables only had a significant association with HSCC in one HSCC category, such as dry premilking treatment (−9,100 cells/mL in the low HSCC category) or feeding calves with high SCC milk (11,100 cells/mL in the medium HSCC category). Others had an opposite effect on HSCC in different HSCC categories, such as average parity (−6,400 and 11,000 cells/mL in the low and medium HSCC category, respectively) and feeding calves with fresh milk (10,300 and −9,700 cells/mL in the low and high HSCC category, respectively). We conclude that, given the individual Dairy Herd Improvement data and information on management practices of an individual farm, it is possible to provide quantitative insight into the contribution of these different variables to the HSCC of an individual farm. Being able to provide such insight is a prerequisite for interpretation, prediction, and control of HSCC on individual dairy farms.
Highlights
The herd-level somatic cell count (SCC) is a result of multifactorial cow factors, management practices, and seasonal fluctuations
The pathogen distribution among the herd influences the level of herd SCC (HSCC); herds that are Staphylococcus aureus-positive in the bulk milk have higher bulk milk SCC (BMSCC) than Staph. aureus-negative herds (Pitkalaet al., 2004; Olde Riekerink et al, 2006)
The reason to divide the farms into 3 categories is derived from the used data set of Barkema et al (1998a,b), which described the difference in management variables related to different categories of BMSCC
Summary
The herd-level SCC is a result of multifactorial cow factors, management practices, and seasonal fluctuations. Dry cow treatment, milking technique, postmilking teat disinfection, and antibiotic treatment of clinical mastitis are examples of management factors with a significant effect on BMSCC (Igono et al, 1988; Wilson et al, 1997; Barkema et al, 1998a; Barnouin et al, 2004). Seasonal fluctuations such as the summer peak can have a major effect but do not occur in all herds (Igono et al, 1988; Green et al, 2006). It is important to know in farms that may exceed a cutoff value what is needed to bring it below the bonus program requirements
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