Browsing by Author "Mäkelä, Heini"

Including feed efficiency in a selection index and its estimation on farms cannot be done by dry matter intake, because it’s not possible to measure dry matter intake on farms. It could be possible to evaluate dry matter intake by using rumination time as an indicator trait. Many farms already have devices to observe rumination. To be a useful candidate trait in selective breeding, rumination time needs to be heritable. The aim of this study was to evaluate genetic parameters of daily rumination time in first three lactations in Finnish Ayrshire. The data was received from FABA co-op and it contained production-, insemination-, calving- and herd data as well as pedigree data of Finnish Ayrshire cows. In addition, rumination data collected by Heatime and SenseHub equipments, were included in the study with the permission of SCR Engineers Ltd. The data was edited into the form to be processed and examined with RStudio, pedigree data was processed with RelaX2 and variance components for daily rumination time and daily milk production were computed by REML method with DMU. Tables and graphs were made in their final form with Excel spreadsheet software. Two separate materials were made from the data: the data of first-time calved cows and the data of 1 to 3 times calved cows. The data was studied as two-trait repeatability model in which observations of rumination time were from all lactation stages. The heritability of rumination time was 0,14 (SE 0,05) for primiparous cows and 0,19 (SE 0,02) for cows having 1 to 3 lactations. The genetic correlation between rumination time and milk production was 0,05 (SE 0,21) for primiparous cows and 0,31 (SE 0,06) for cows having 1 to 3 lactations. Daily rumination time is a heritable trait and hence it can be used as a direct or indicator trait in selective breeding. Further studies of the genetic correlations between rumination time and dry matter intake should be done to evaluate the usability of rumination time as an indicator of dry matter intake.