Understanding and using somatic cell counts to improve milk quality

Abstract

The production of high quality milk is a requirement to sustain a profitable dairy industry and somatic cell count (SCC) values are routinely used to identify subclinical mastitis and define quality standards. The objective of this paper is to review the use of SCC as a diagnostic tool for subclinical mastitis in order to improve milk quality on dairy farms. Mastitis is detected based on inflammation subsequent to intramammary infection (IMI) by pathogenic organisms. Individual cow SCC values are used to detect the inflammation that results from IMI and are necessary to define the prevalence and incidence of subclinical IMI. A threshold of <200,000 cells/mL is considered to be of the most practical value used to define a mammary quarter as healthy. The development of IMI is the most significant factor that influences milk SCC and assessment of monthly values to determine newly and chronically increased SCC can be highly diagnostic for resolving problems with increased bulk tank SCC. Methods to reduce the development of new IMI are well known and adoption of best management practices for milking and herd management have consistently been shown to result in reductions in bulk tank SCC. Implementation of mastitis control programmes can be improved by focusing on three practical recommendations: 1) Farmers should work with their advisors to develop an annual udder health plan that includes clear goals for milk quality. 2) The annual udder health plan should emphasise prevention of new IMI. 3) Farmers must identify and manage chronically infected cows. Proactive management of IMI can be extremely effective in helping farmers produce milk that meets industry standards for milk quality.