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

Abstract

Data from 350 herds enrolled in the Norwegian Dairy Herd Recording System (NDHRS) were used to investigate the associations between the first two cow-milk somatic cell counts (SCC) test-days' results after calving or the three last SCC test-days prior to drying off in the first lactation and the hazard ratio (HR) of clinical mastitis (CM) during the remaining first or the subsequent second lactation respectively. Altogether, 9519 first lactations and 6046 second lactations were included. Cox regression analyses adjusted for herd frailty effect were used. In the first lactation, SCC>40000 cells/ml on the first or second test-day was significantly associated with an increased risk of a CM event in the remaining first lactation. HR, compared with 10000 cells/ml, increased from 1.6 (1.4) for SCC of 40000-60000 cells/ml to 6.9 (4.2) for SCC >800000 cells/ml, when using the first (second) SCC test-day in the first lactation. Cows with a geometric mean of the three last SCC test-days between 50000 and 100000 cells/ml and between 401000 and 800000 cells/ml in the first lactation had HR of CM during the second lactation of 1.3 and 2.8 respectively compared with a reference group of 10000-20000 cells/ml. If a CM episode in the first lactation occurred, the HR for having a CM event during the second lactation was 1.5. There was a significant frailty effect which disappeared if the incidence rate of CM at herd level was included in the model.

Infection dynamics across the dry period using Dairy Herd Improvement somatic cell count data and its effect on cow performance in the subsequent lactation

“…To further increase production in an ecologically and economically responsible manner, investing in optimal udder health and robust cattle is necessary. For dairy cows, the dry period is an important period for udder health because dry cows can cure from IMI present at dry-off (Bradley and Green, 2000;Dingwell et al, 2004) but udder health can also be threatened as many cows acquire new IMI in the dry period Green, 2000, 2001;Whist and Østeras, 2007).…”

Evaluation of minor pathogen intramammary infection, susceptibility parameters, and somatic cell counts on the development of new intramammary infections with major mastitis pathogens

“…Care must be taken in interpreting the results of experimental studies such as these, however, as the first line of defense (the teat end) is often bypassed by infusion of challenge organisms, making it difficult to compare them to the observational literature. Other studies have shown increased risk of clinical mastitis as SCC rises (Dohoo et al, 1984;Beaudeau et al, 1998;Whist and Østerås, 2007). As bacteriological culturing was not done on these quarters and clinical mastitis was used as the outcome, these papers are presumably documenting the increased probability that cows with subclinical IMI are more likely to develop clinical mastitis.…”

A simulation model to calculate costs and benefits of dry period interventions in dairy cattle

“…In experiments and field trials, selection for treatment was mostly based on SCC and bacteriological culture samples to diagnose IMI (Østerås et al, 1994;Whist and Østerås, 2007). In the Netherlands, farmers generally tend to select cows on the basis of the SCC values of the last 3 test-days and/or the clinical IMI history of the cow.…”