Estimation of genetic and crossbreeding parameters of milking characteristics of grazing dairy cows

Abstract

Milk harvesting requires the largest labour input on most New Zealand dairy farms, where the herd milking time is influenced by individual cow milking characteristics. The objectives of this study were to evaluate the breed and heterosis effects and estimate genetic parameters for milking characteristics in grazing dairy cows milked without pre-milking stimulation. Data on electronically recorded milking characteristics from 621,116 test-day records on 1555 cows in two New Zealand dairy herds during the 2011–12 season were available. Milking duration adjusted for milk weight (RMDmw; deviation from the regression of milk yield on milking duration) was 38.5 s longer for Jersey compared with Friesian cows, but no breed differences were observed for milking duration adjusted for milksolids yield (RMDms). Estimates of heritability were 0.15 for milk weight (MW), 0.27 for milking duration (MD), 0.27 for average milk flow rate (AMF), 0.29 for RMDmw and 0.40 for RMDms. The genetic correlation between RMDms and MS yield was −0.21 and was not significantly different to zero. Selection for RMDms can be used to identify and select efficient milking animals without negatively affecting milksolids yield.