Abstract
Mastitis in dairy cows is an unavoidable problem and variation in recovery from mastitis is therefore of interest, in addition to resistance to mastitis. Genetic parameters for mastitis resistance and recovery were estimated for Danish Holstein-Friesian cows using data from Automatic Milking Systems equipped with online somatic cell count (OCC) measuring units. The OCC measurements were converted to elevated mastitis risks (EMR), a continuous variable (on a [0-1] scale) indicating the risk of mastitis. EMR values above 0.6 were assumed to indicate that a cow had mastitis. For each cow and lactation the sequence of health states (mastitic or healthy) was converted to weekly transitions: 0 if the cow stayed within the same state and 1 if the cow changed state. The result was two series of transitions: one for healthy to diseased (HD, to model mastitis resistance) and the other for diseased to healthy (DH, to model recovery). The two series of transitions were analyzed with a bivariate threshold model including a linear combination of systematic effects and of a function of time. The model included effects of herd and parity, herd-test-week, permanent environment (to account for the repetitive nature of transition records from a cow) plus two time-varying effects (lactation stage and time within episode). In early lactation, there was an increased risk of getting mastitis but the risk remained stable afterwards. Mean recovery rate was 45.7%. Posterior mean of correlations between the traits were -0.853 (PSD=0.108), -0.909 (PSD=0.076), -0.292 (PSD=0.105) and 0.052 (PSD=0.157) for the random effects of genetic, permanent environment, cow-parity interaction, and herd-test-week, respectively. Heritabilities were 0.080 (PSD=0.026) for HD and 0.075 (PSD=0.030) for DH. Recovery could be considered as a new trait for selection even though the negative correlation suggests that a cow that easily contracts mastitis has greater difficulty to recover.
Originalsprog | Engelsk |
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Publikationsdato | jun. 2016 |
Status | Udgivet - jun. 2016 |
Begivenhed | 5th International Conference on Quantitative Genetics - Madison, USA Varighed: 12 jun. 2016 → 17 jul. 2016 http://www.icqg5.org/ |
Konference
Konference | 5th International Conference on Quantitative Genetics |
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Land/Område | USA |
By | Madison |
Periode | 12/06/2016 → 17/07/2016 |
Internetadresse |