Genetic analysis of processed in-line mastitis indicator data

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The aim of this study was to estimate heritability of elevated mastitis risk (EMR), a trait derived from in-line measurements of cell counts expressing risk of mastitis on a continuous scale, and its genetic correlation with in-line somatic cell counts. Log-transformed somatic cell counts (SCC; n = 855,181) based on in-line measurements (OCC, DeLaval, Sweden) in automatic milking systems were collected from 2007 to2013 in 7 herds from a total of 1986 first and second parity cows (5 to 305 d in milk). Only data from the lactation with most measurements was used from each cow. A bio-model based on exponential smoothing of the SCC values followed by factor analysis for estimation of the latent variable EMR was used. Finally, EMR was expressed as a continuum
on the interval [0;1] using sigmoid transformation. Thus, an EMR value close to zero indicates low risk of mastitis and a value close to one indicates high risk of mastitis. The EMR values were summarized for each cow using the log-transformed median EMR. A second trait was defined as the median of the log-transformed SCC values from 5 to 305 d in milk. A bivariate animal model was used for estimation of co-variance components for the 2 traits. The fixed part of the model included herd and parity. Estimates of heritability were 0.08 (SE =
0.04) and 0.14 (SE = 0.05) for EMR and SCC, respectively. The genetic correlation between the 2 traits was 0.97 (SE = 0.08). The high genetic correlation indicates that the 2 traits are influenced by common genes, as expected because EMR values are based on SCC measurements. The heritability of SCC is reduced when SCC measurements are processed into EMR values but with similar standard errors. The EMR values are useful in a management context for early mastitis detection and health surveillance; however the present results suggest that SCC values are preferable to EMR values for estimation of breeding values
TidsskriftJournal of Animal Science
NummerE-Supplement 2
Sider (fra-til)173-174
Antal sider2
StatusUdgivet - 8 jul. 2013
BegivenhedADSA-ASAS Joint Annual Meeting : JAM 2013 - Indianapolis, Indiana, USA
Varighed: 8 jul. 201312 jul. 2013
Konferencens nummer: 2013


KonferenceADSA-ASAS Joint Annual Meeting
ByIndianapolis, Indiana

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