Genetic parameters and single versus multi-trait evaluation of udder health traits

Abstract

Genetic parameters were estimated for lactation average somatic cell score (SCS) and clinical mastitis (CM) for the first three lactations of multiparous Finnish Ayrshire cows. A multi-trait linear sire model was used for estimation of covariance components, and the efficiencies of single-versus multi-trait multi-lactation (MT) sire evaluations were compared. Heritability of SCS and CM in the first three lactations ranged from 0.11 to 0.13 and 0.02 to 0.03, respectively. Within lactation, genetic correlations between SCS and CM ranged from 0.68 to 0.72. Within both traits, across-lactation genetic correlations were lowest between 1 and 3, and highest between 2 and 3, with estimates ranging from 0.75 to 0.86 and from 0.81 to 0.98 for CM and SCS, respectively. Residual and phenotypic correlations were low and ranged from 0.09 to 0.13 and from 0.10 to 0.13, respectively. The absolute difference between genetic and residual correlations was from 0.5 to 0.6. Within-lactation genetic correlations between traits that are much less than unity suggest a multi-trait model for genetic evaluation of mastitis resistance. Comparison of model prediction performance between single-trait (ST) and MT models using a data splitting method showed that the MT model was more stable in predicting breeding values in future records of animals. Especially, for young sires and CM, the SD of EBVs from the MT model was 14 to 23% higher than the ST model, indicating more effective use of information in terms of revealing more genetic variation.

Genetic analysis of clinical mastitis data for Holstein cattle in the Czech Republic

“…Estimates of additive genetic correlations between CM traits, SCS, and milk production, including their standard errors (in parentheses). 2005; Negussie et al, 2006;De Haas et al, 2008;Buch et al, 2011). Additive genetic correlations between CM traits and milk yield in our study are at the lower end of the range of previously cited investigations.…”

Genetic analysis of liability to clinical mastitis, with somatic cell score and production traits using bivariate threshold–linear and linear–linear models

“…However, genetic evaluation of clinical mastitis is particularly Available online at www.sciencedirect.com Livestock Science 117 (2008) 52 -59 www.elsevier.com/locate/livsci difficult because of low heritability and the categorical nature of the trait. As a consequence, multi-trait analyses using correlated traits and information sources have been suggested to increase the efficiency of selection for mastitis resistance (Philipsson et al, 1995;Ødegård et al, 2003;Negussie et al, 2006). Estimates of genetic and environmental correlations between clinical mastitis (CM), somatic cell count (SCS) and production traits are therefore essential for the calculation of optimal selection indices.…”

Longitudinal threshold model analysis of clinical mastitis using linear splines

“…The total number of observations was 888,643 giving an average of about 8 binary responses per cow. In Finnish Ayrshire, the overall average incidence of mastitis is about 9.0, 10.6 and 13.1% in first, second and third lactations, respectively (Negussie et al, 2006a). For the first-lactation data used in this study, the distribution of mastitis incidences is presented in Fig.…”

“…So far, in most countries with national dairy health recording schemes, clinical mastitis is defined as a binary trait averaging incidences over lactation or in a few specific lactation periods. Within these periods, CM is defined based on whether or not a cow has had at least one case of veterinary treated CM during the period from 7 days before calving to 150 or 300 days after calving (Negussie et al, 2006a). This is irrespective of the multiple episodes of infection and subsequent treatments that most cows have during lactation.…”