Abstract:
On-line somatic cell count (SCC) analysers automatically test for SCC during milking for individual cows, providing farmers with more measurements than conventional herd testing. The purpose of this study was to determine whether more frequent milk sampling increases detection of elevated SCC due to mastitis. We compared the rate of detection of mastitis events using on-lineSCC analysers with that using conventional herd testing with a simulated dataset of 100 random herds of 1,000 cows. Five herd test scenarios (two, four, six, eight, or ten herd-test dates per lactation) were compared to20 on-line SCC analyser scenarios (varying based on whether cows were milked once or twice daily and the proportion of on-line SCC analysers installed on bails, ranging from 2% (i.e. one in 50 bails) up to 100%). Random mastitis events for each cow were modelled based on composite cow SCC and individual quarter bacteriological data derived from a dataset of 2,345 cow-lactations. We then calculated the average probability of on-line SCC analysers and of herd testing detecting these mastitis events, assuming 280 days of lactation. Herd testing four or ten times per lactation was found to detect47% or75% of mastitis cases, respectively. On-line SCC analysers installed on 10% of bails with once-a-day milking detected84% of cases. We observed that on-line SCC analysers, even on a small proportion of bails, were more likely to detect mastitis events than standard herd testing, in a simulated dataset.