Genetic parameters for female fertility in Nordic Holstein and Red Cattle dairy breeds

摘要

Genetic evaluation of female fertility in Danish,Finnish, and Swedish dairy cows was updated in 2015to multiple-trait animal model evaluation, where heiferand cow fertility up to third parity are considered asseparate traits. A model for conception rate was alsodeveloped, which required variance component estimationfor Nordic Holstein and Nordic Red Dairy Cattle.We used a multiple-trait multiple-lactation sire modelto determine variance components for interval fromcalving to first insemination, length of service period,and conception rate. Monte Carlo Expectation MaximizationREML allowed estimation of all 11 traits simultaneously.Study data were sampled from Swedish Holstein(n = 140,040) and Red Dairy Cattle (n = 101,315)heifers and cows. Conception rate observations arebinomial observations with various numbers of failurespreceding an observation of success. Using a simulationstudy, we confirmed that including a service number effectinto the conception rate model allowed us to modelthe change in expectation of successful AI with increasingnumber of services. Heifers outperformed cows in allfertility traits according to the phenotypic means in therecords. Heritabilities for the traits varied from 3 to 7%for interval from calving to first insemination, from 1to 5% for length of service period, and from 1 to 3% forconception rate. Genetic correlations within traits (i.e.,between parities) were favorable, ranging from moderateto high; genetic correlations between heifer and cowtraits were lower than between cow traits in differentparities. Lowest genetic correlations between traitswere for interval from calving to first insemination andconception rate, intermediate for interval from calvingto first insemination and length of service period, andhighest for length of service period and conception rate.The variance components estimated in this study havebeen used in Nordic fertility breeding value evaluationssince 2016.