National bulk milk cell count statistics 2000 to 2019

Report prepared for Dairy Australia by Dr John Morton BVSc (Hons) PhD MANZCVS (Veterinary Epidemiology), Veterinary Epidemiological Consultant with Jemora Pty Ltd.

The primary objective of this work was to calculate the percentages of suppliers whose annual average BMCC in 2019 were, respectively, ≤250,000 cells per mL and >400,000 cells per mL. These were also calculated for all years from 2000, including by region. Arithmetic and geometric mean BMCCs were also calculated for each year.

Methods are documented in detail, so that the same methods can be used in future years. In 2019, 86.1% of suppliers had an annual average BMCC ≤250,000 cells per mL and 1.1% of suppliers had an annual average BMCC >400,000 cells per mL. By region, percentages of suppliers with annual average BMCC ≤250,000 cells per mL varied from 71% to 91%.

Nationally, BMCCs generally increased from 2000 to 2011 but declined markedly since then. Percentages of suppliers whose annual average BMCCs were, respectively, ≤250,000 cells per mL and >400,000 cells per mL improved steadily over this period. For comparison to 2019, in 2011, 60.4% of suppliers had an annual average BMCC ≤250,000 cells per mL (86.1% in 2019) and 4.3% of suppliers had an annual average BMCC >400,000 cells per mL (1.1% in 2019). Arithmetic and geometric mean BMCCs also improved steadily over this period.

Further analyses showed that the decline in BMCCs from 2011 to 2016 nationally is not explained by suppliers ceasing dairying having higher BMCCs than those staying in dairying. However there is some limited evidence that the improvements in national BMCCs in 2017 and 2018 may have been, in part, because suppliers that ceased dairying in late 2016 or during 2017 had higher BMCCs than those staying in dairying.