UC Davis

Intramammary infections, which cause mastitis, can increase treatment and labor costs, decrease milk production, and affect milk quality. Meters that measure quarter somatic cell count (SCC) could be used to make more informed dry cow therapy decisions. The objective of this study was to compare the RT-10 iPhone adapter (RT-10; Dairy Quality Inc., Newmarket, Canada), DeLaval Cell Counter (DSCC; DeLaval, Graiguecullen, Carlow), Porta Check Quick Test (PortaCheck, NJ), California Mastitis Test (ImmuCell, Portland, ME), pH meter (Hanna Instruments, RI), electrical conductivity meter (OHAUS, NJ), and the dual laser infrared temperature thermometer (Klein Tools, IL) for measuring SCC in individual quarters in comparison to a reference standard, the Fourier Transform Spectrometer 600 Combi System (Combi; Bentley Instruments, MN). Meters were evaluated using individual cow quarter samples and bulk-tank samples to measure SCC. To test individual quarter SCC, individual quarter milk samples from 160 cows from 4 commercial dairy herds (40 cows per herd) were collected just before cessation of milking and tested within 4 h of collection. To test bulk-tank SCC, 100 bulk-tank milk samples (25 mL) were collected from UC Davis VMTRC Milk Quality Lab. Meter SCC values were regressed on observed Combi SCC using PROC GLM (SAS Institute, 2021 v. 9.4). Then goodness of fit was evaluated by partitioning of the mean square predicted error (MSPE). For individual quarter SCC, RT-10 had the highest coefficient of determination (R2 = 0.86), lowest mean square predicted error and highest proportion of MSPE due to random variation (96 %). Both the RT-10 and DSCC had the highest sensitivity and specificity for identifying quarter SCC above and below 200,000 cells/mL. For bulk-tank SCC, DSCC had the highest coefficient of determination (R2 = 0.45), lowest mean square predicted error, and highest proportion of MSPE due to random variation (80 %). The RT-10 and DSCC could be used to measure individual quarter SCC to determine which cows to treat at cessation of lactation potentially reducing antibiotic use.KEYWORDS: mastitis, milk meter, somatic cell count