Estimation of genetic parameters for milking and teat traits in Holstein dairy cattle.

This study aimed to estimate variance components and genetic parameters for milking and teat traits in Holstein cattle. The 1001 cows had their certain teat traits measured before morning milking, and their milking traits were determined four times over four months. Restricted Maximum Likelihood (REML) was used to estimate the variance components in the mixed model. In addition to fixed factors, animal effect and permanent environmental effects were included in the model as random factors. The repeatability model was not used for teat traits. Means of rear teat length (RTL), rear teat thickness (RTT), rear teat distance (RTD), and udder depth (UD) were 4.5, 2.7, 4.4, and 58.7 cm, respectively. The average values for the milking duration (MD) and milking speed (MS) were 5.1 min and 2.9 kg/min, respectively. For teat traits, the heritability was between 0.14 and 0.79. For milking traits, however, heritability and repeatability were estimated between 0.24 and 0.38 and 0.66–0.90, respectively. Heritability were found 0.34 and 0.35 for residual milking duration (RMD) and residual milking speed (RMS), respectively. On the other hand, heritability and repeatability were found to be 0.17 and 0.55 for milk yield at per milking. In addition, genetic correlations were found as -0.94, 0.58, -0.34, 0.46, and − 0.24 for MD-MS, RTL-MD, RTL-MS, RTT-MD, and RTT-MS, respectively. As a result, the findings of this study indicate an existence of a substantial genetic variation to achieve genetic improvement by the selection process in the teat and milking traits. In addition the current study provided a basis for including milking traits (RMD or RMS etc.) of Holstein cattle in the breeding objectives.