Percentage of motile spermatozoa data from Spanish Holstein bulls were used to estimate variance components by the RRM method. Age at collection (AC) and days from first collection (DP) were considered as time variables. The model included systematic effects year-month of collection and year-age at first collection, and random genetic and permanent environmental animal effects. Legendre polynomials of different order were tested. Analyses were performed in a Bayesian framework computing the log of the marginal density (LMD) and the predictive ability (D) as model comparison criteria. Considering LMD and D values, models fitting polynomials of 4-5 order for either time variables and with heterogeneous residual variance were recommended. Border effects at the beginning of AC trajectory were reflected in an overestimation of the genetic and permanent variances. Heritabilities ranged between 0.11 to 0.27 and 0.07 to 0.14 for AC and DP variables, respectively.
Proceedings of the World Congress on Genetics Applied to Livestock Production, Volume , , 25.14, 2006
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