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Cow, Farm, and Herd Management Factors in the Dry Period Associated with Raised Somatic Cell Counts in Early Lactation

M. J. Green^*,,1, A. J. Bradley, G. F. Medley and W. J. Browne

^* School of Veterinary Medicine and Science, University of Nottingham, Sutton Bonington Campus, Sutton Bonington, LE12 5RD
School of Mathematical Sciences, University of Nottingham, Nottingham, NG7 2RD, UK
Department of Clinical Veterinary Science, University of Bristol, Langford House, Langford, Bristol, BS40 5DT, UK
Ecology and Epidemiology Group, Department of Biological Sciences, University of Warwick, Coventry, CV4 7AL, UK

¹ Corresponding author: martin.green{at}nottingham.ac.uk

This study investigated cow characteristics, farm facilities, and herd management strategies during the dry period to examine their joint influence on somatic cell counts (SCC) in early lactation. Data from 52 commercial dairy farms throughout England and Wales were collected over a 2-yr period. For the purpose of analysis, cows were separated into those housed for the dry period (6,419 cow-dry periods) and those at pasture (7,425 cow-dry periods). Bayesian multilevel models were specified with 2 response variables: ln SCC (continuous) and SCC >199,000 cells/mL (binary), both within 30 d of calving. Cow factors associated with an increased SCC after calving were parity, an SCC >199,000 cells/mL in the 60 d before drying off, increasing milk yield 0 to 30 d before drying off, and reduced DIM after calving at the time of SCC estimation. Herd management factors associated with an increased SCC after calving included procedures at drying off, aspects of bedding management, stocking density, and method of pasture grazing. Posterior predictions were used for model assessment, and these indicated that model fit was generally good. The research demonstrated that specific dry-period management strategies have an important influence on SCC in early lactation.

Key Words: mastitis • somatic cell count • dry period • Bayesian multilevel model