Associations between somatic cell counts at calving or prior to drying-off and future somatic cell counts, in the remaining or subsequent lactation

Abstract

Composite milk somatic cell counts (CMSCC) from four separate datasets, containing 3338, 350, 1408 and 1404 herds, were used. All herds were enrolled in the Norwegian Dairy Herd Recording System (NDHRS). The aim was to investigate associations between CMSCC at calving or prior to drying-off and future CMSCC in the remaining or subsequent lactation. CMSCC was determined using Fossomatic 5000 cell counters (Foss Electric, Hillerød, Denmark) according to IDF recommendations (International Dairy Federation, 1984) and a natural logarithmic transformation of the CMSCC data (lnCMSCC) was performed. Results obtained were arranged according to parity and lactation stage and regression models and general linear mixed models were applied, the latter model to account for clustering between herds. The best associations between CMSCC at calving or prior to drying-off and future CMSCC in the remaining or subsequent lactation were found by using at least two CMSCC test days after calving or prior to drying-off. The geometric mean of the second and third or the first three CMSCC test days explained 50% of the variation in future CMSCC in first parity cows. This information was accessible at 151 days in milk (DIM) in bimonthly tested herds, and at 87 DIM for monthly tested herds. There was not a large difference using two or three single consecutive weighted CMSCC test days compared with the geometric mean of two or three CMSCC test days. Our findings indicate the need of using at least two CMSCC test days and, if only one CMSCC test day is used, it should be obtained after 14 d post-calving or preferably after 30 DIM.

Associations between somatic cell counts at calving or prior to drying-off and clinical mastitis in the remaining or subsequent lactation

“…This means that the same level of SCC will be associated with a lower HR early in the first lactation compared with test-days' results taken later during the first lactation months. This result is in agreement with the finding of Whist & Østerås (2006) who showed a stronger association between the first SCC test-day results and future SCC if the first test-day was taken after 14 DIM.…”

The Influence of Cow Factors on the Incidence of Clinical Mastitis in Dairy Cows

“…To determine the association between previous SCC and IRCM in the current month of lactation, SCC in the previous month in lactation (SCC1) was determined. Also, SCC of the previous lactation was included (Whist and Østerå s, 2006;Green et al, 2007). This variable was defined as the geometric mean SCC from all available test-day records from the previous lactation (SCC2).…”

Genetic associations between somatic cell score and pathogen‐specific subclinical mastitis in Norwegian Red cows

“…SCM was defined based on the cow's test‐day SCC records and bacteriological milk sample results (pathogen data). As the population mean SCC in Norwegian Red is low (Whist & Østerås ; Heringstad et al . ), a threshold of 100 000 cells/ml was used to define SCM in this study.…”

“…SCC was assumed increased due to CM if the test‐day record was taken the day before the CM record or within 27 days after. Test‐day SCC records from the first 14 days after calving were not considered because these are naturally increased and give little information about udder health (Whist & Østerås ). Only cows with at least two test‐day SCC records after the first 14 days of lactation were kept in the data set.…”

“…SCM was defined based on the cow's test-day SCC records and bacteriological milk sample results (pathogen data). As the population mean SCC in Norwegian Red is low (Whist & Øster as 2006;Heringstad et al 2008), a threshold of 100 000 cells/ ml was used to define SCM in this study. SCM was scored as one if two consecutive test-day records had SCC at or above the defined threshold and where neither of them was associated with a case of CM, and 0 otherwise.…”