Genetic evaluation of mastitis liability and recovery through longitudinal analysis of transition probabilitiesFranzén, Jessica; Thoburn, Daniel; Urioste, Jorge; Strandberg, Erling
Background: Many methods for the genetic analysis of mastitis use a cross-sectional approach, which omitsinformation on, e.g., repeated mastitis cases during lactation, somatic cell count fluctuations, and recovery process.Acknowledging the dynamic behavior of mastitis during lactation and taking into account that there is more thanone binary response variable to consider, can enhance the genetic evaluation of mastitis.
Methods: Genetic evaluation of mastitis was carried out by modeling the dynamic nature of somatic cell count(SCC) within the lactation. The SCC patterns were captured by modeling transition probabilities between assumedstates of mastitis and non-mastitis. A widely dispersed SCC pattern generates high transition probabilities betweenstates and vice versa. This method can model transitions to and from states of infection simultaneously, i.e. boththe mastitis liability and the recovery process are considered. A multilevel discrete time survival model was appliedto estimate breeding values on simulated data with different dataset sizes, mastitis frequencies, and geneticcorrelations.
Results: Correlations between estimated and simulated breeding values showed that the estimated accuracies formastitis liability were similar to those from previously tested methods that used data of confirmed mastitis cases,while our results were based on SCC as an indicator of mastitis. In addition, unlike the other methods, our methodalso generates breeding values for the recovery process.
Conclusions: The developed method provides an effective tool for the genetic evaluation of mastitis whenconsidering the whole disease course and will contribute to improving the genetic evaluation of udder health.
Published inGenetics Selection Evolution
2012, volume: 44:10, pages: 1-10
UKÄ Subject classification
Genetics and Breeding
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