Heritabilities, genetic and phenotypic correlations between body conformation and milking traits of Holstein-Friesian cows milked by milking robots

Godswill Arinzechukwu Iwuchukwu; Beata Sitkowska; Dariusz Piwczyński

doi:10.2478/aoas-2027-0004

Heritabilities, genetic and phenotypic correlations between body conformation and milking traits of Holstein-Friesian cows milked by milking robots

Annals of Animal Science

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By: Godswill Arinzechukwu Iwuchukwu, Beata Sitkowska and Dariusz Piwczyński

Open Access

|Oct 2026

Abstract

This study estimated heritabilities and genetic correlation (r _G) and phenotypic correlation (r _P) between body conformation traits and milking parameters in 796 primiparous Polish Holstein-Friesian cows milked using Lely Astronaut A4 robotic systems across 7 herds. The objective was to identify genetic relationships affecting milk yield (MY, kg/day), milking efficiency (ME, kg/min), average number of teat cup attachments (AN, n/milking), and attachment time (AT, s/milking) in relation to udder-related (e.g., udder depth, UD; teat length, TL) and non-udder-related traits (e.g., body depth, BD; height at sacrum, HS). A two-trait animal model with Gibbs sampling was applied to 60 days averaged data centered on the time of conformation scoring. Heritability estimates ranged from low to high, spanning from 0.140 (rear teat placement) to 0.598 (HS) for conformation traits and from 0.145 (AT) to 0.390 (ME) for milking parameters. Strong genetic correlations were observed between MY and BD (r _G = 0.973) as well as angularity (r _G = 0.568), whereas a negative relationship was found with UD (r _G = −0.281). ME showed favorable genetic associations with rump width (r _G = 0.662) and unfavorable ones with rear legs set (r _G = −0.382). Attachment-related traits were strongly genetically associated with rear udder width (r _G = 0.977 with AT) and fore udder attachment (r _G = −0.607 with attachment number). Phenotypic correlations were generally weak (|r _P| < 0.310). Overall, the results highlight two main findings: (i) key traits such as ME and HS exhibit moderate-to-high heritability, and (ii) several conformation traits show strong genetic relationships with milking performance and robot-related parameters. These findings suggest the potential usefulness of these traits in selection for improved adaptability to automatic milking systems, emphasizing the importance of balanced udder morphology and overall body structure for enhanced production efficiency and robotic compatibility.

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Articles in this issue

DOI: https://doi.org/10.2478/aoas-2027-0004 | Journal eISSN: 2300-8733 (formerly 1642-3402) | Journal ISSN: 1642-3402

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Language: English

Submitted on: Jan 28, 2026

Accepted on: May 25, 2026

Published on: Oct 28, 2026

Published by: National Research Institute of Animal Production

In partnership with: Paradigm Publishing Services

Publication frequency: 4 issues per year

Keywords:

Conformation traits,

Dairy cows,

Genetic correlations,

Related subjects:

© 2026 Godswill Arinzechukwu Iwuchukwu, Beata Sitkowska, Dariusz Piwczyński, published by National Research Institute of Animal Production
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 License.

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