Estimates of intra- and interclass correlation coefficients for rump touches and the number of steps during estrus in postpartum cows

摘要

Estrus traits have economic value in dairy productionsystems and could be incorporated into geneticselection indices. In an effort to further understand selectionresponses, 2 studies were performed to estimatethe intra- and interclass correlation coefficients for estrustraits. Holstein-Friesian cows (n = 1,197; study 1)across 5 pasture-based grazing dairy herds were fittedwith a capacitive touch sensing (CTS) device on therump (FlashMate, Farmshed Labs Limited, Hamilton,New Zealand). The daily number of rump toucheswere subjected to a peak detection program to objectivelyidentify periods of increased rump touches abovebaseline (indicative of estrus). The number of timestouched and the sum of the touch duration were used tocompare farms and estimate the intraclass correlation(repeatability). For study 2, postpartum Holstein (n =85) and Guernsey (n = 5) cows in a confinement-styledairy were used. Cows were fitted with an IceQubeaccelerometer (IceRobotics Ltd., Edinburgh, UnitedKingdom) to measure steps taken per hour and a CTSdevice was applied to both rumps. The interclass correlationfor the number of rump touches and numberof steps taken during estrus was calculated. Data collectedfrom 5 herds (study 1) demonstrated a 2- to3-fold difference between herds in the number of rumptouches and total touch time during estrus. The intraclasscorrelation (repeatability; estimates of maximumheritability) for rump touches during estrus was 0.22.For study 2, the number of steps and the number ofrump touches during estrus increased in a synchronousmanner. The intraclass correlation (repeatability) fornumber of steps during estrus was 0.26. The interclasscorrelation (r) for the number of rump touches and thenumber of steps was 0.46 (R2 = 0.21). Based on theR2, at least 20% of the variation in the number of stepsduring estrus was explained by the number of touchesto the rump of the cow. Selecting cows for the numberof steps taken during estrus could increase the numberof rump touches (mounts, chin rests, and so on, receivedfrom other cows) if a genetic correlation exists for thephenotypic correlation that we observed.