Trends in Bulk Milk Somatic Cell Count in the Netherlands from 2018 – 2023
C.G.M. Scherpenzeel1, N.D. Fabri1 and G. van Schaik1,2 1Royal GD, Deventer, the Netherlands 2Utrecht University, Utrecht, the Netherlands
WHY?
Since 2002, the Dutch cattle health surveillance system (CHSS) has been carried out at Royal GD on behalf of the sector and the Ministry of Agriculture, Nature and Food Quality. Four times per year, a large number of cattle health indicators are analysed, including udder health parameters for dairy cattle twice a year. This data analysis has shown that the bulk milk somatic cell count (BMSCC) of dairy cattle has been rising slightly since 2018, and this increase accelerated from 2022 onwards (Figure 1). This is an unfavourable trend, as it is an indication of reduced udder health in dairy herds in the Netherlands.
Aim
The aim of this study was to provide an explanation for the unfavorable trends in BMSCC of dairy cattle, and to estimate the influence of various explanatory variables on BMSCC.
Materials and Methods
For the analyses, variables that are routinely collected on dairy farms (e.g. herd size, milk production level) were avialable. In addition, variables related to weather conditions were included to estimate the influence of e.g. temperature and humidity on udder health indicators. In total, three udder health indicators were considered i.e. BMSCC, prevalence of high SCC cows (HSCC), and herds with a >25% incidence of HSCC in primi- and multiparous cows during the start of the lactation (first 60 days). A high SCC is over 150.000 cells per ml for primiparous cows and over 250.000 cells per ml for multiparous cows. The association between these udder health indicators and the explanatory variables were analysed using population averaged multivariable regression with appropriate distributions (gaussian and binomial) and link functions (identity and logit).
Main results
The average Dutch BMSCC is highest in the autumn and lowest in the spring. There is a clear increase in the period 2018 to 2023, with the increase in 2022 being particularly striking. The annual average BMSCC at the end of 2019 was around 170,000 cells per ml, while it was over 200,000 cells per ml at the end of 2023. Important factors associated with an increased BMSCC are the use of an automatic milking system (AMS; +22,000 cells/ml when using an AMS) as described earlier by Frössling and others (2017), a higher age of cows on the farm (+2,000 cells/ml per additional month of life) and a herd size over 181 adult cows (+19,000 cells/ml
100kg to more than 60 euros per 100kg, which explains +12,000 cells/ml, and the implementation of the European international calibration reference took place on January 1st, 2022. With a higher milk price, farmers may continue to milk cows with a slight increase in SCC for longer, because of economic advantage.
Take home points:
1. The unfavourable trend in the SCC-related udder health indicators during the entire (2018-2023) is partly explained by the increase in:
- the percentage of farms using an AMS;
- the average age of the herd and;
- the average herd size in the Netherlands.
2. The additional increase in the BMSCC in 2022 can be explained by:
- the rapid increase in the milk price to more than 60 euros per 100 kilograms of milk in 2022,
compared to an average Dutch farm). These explanatory variables also increase throughout the period analysed, making it likely that the increasing trend of the BMSCC in the period 2018-2023 is explained by these variables. However, this probably does not explain the additional increase in 2022. A higher milk price (+6,000 cells/ml for each increase in milk price by 10 euros/100L) and the implementation of the European International calibration reference at Qlip from January 2022 onwards (+4,000 cells/ ml) seem to explain this additional increase in 2022. The milk price sharply rose in 2022 from less than 40 euros per
- the implementation of the European International calibration reference at Qlip from January 2022 onwards
3. The effect of the weather conditions was difficult to capture in monthly characteristics and therefore explained little variation in the cell counts.
