Genetic relationship of lactation persistency with milk yield, somatic cell score, reproductive traits, and longevity in Slovak Holstein cattle
Abstract. The objective of this study was to estimate the breeding values (BVs) of lactation persistency, the test day of milk yield, the somatic cell score, reproductive traits (calving interval, days open), longevity in Slovak Holstein dairy cattle. BVs were used for the detection of relationships among the persistency of lactation and other selected traits. Data for the estimation of BVs of milk production and somatic cell score were collected from 855 240 cows. BVs for reproductive traits were estimated for 352 712 cows and for longevity for 528 362 cows. The highest correlations were confirmed between the BV of persistency and the BV of test day milk yield at 100, 200, and 305 days (−0.88, −0.65, and −0.61). Correlations between the BV of lactation persistency and the BV of somatic cell score at day 305 or the BV of somatic cell score persistency were favorable: −0.05 and −0.12, respectively. The relationship between the BV of persistency and the BV of the calving interval or the BV of days open was 0.11 and 0.10 respectively. The selection for the persistency of lactation may not improve longevity because there is no relation between the BV of persistency and the BV of longevity (rg = 0.06).