Abstract

The aim of this study was to identify genomic regions associated with 305‐day milk yield and lactation curve parameters on primiparous (n = 9,910) and multiparous (n = 11,158) Holstein cows. The SNP solutions were estimated using a weighted single‐step genomic BLUP approach and imputed high‐density panel (777k) genotypes. The proportion of genetic variance explained by windows of 50 consecutive SNP (with an average of 165 Kb) was calculated, and regions that accounted for more than 0.50% of the variance were used to search for candidate genes. Estimated heritabilities were 0.37, 0.34, 0.17, 0.12, 0.30 and 0.19, respectively, for 305‐day milk yield, peak yield, peak time, ramp, scale and decay for primiparous cows. Genetic correlations of 305‐day milk yield with peak yield, peak time, ramp, scale and decay in primiparous cows were 0.99, 0.63, 0.20, 0.97 and −0.52, respectively. The results identified three windows on BTA14 associated with 305‐day milk yield and the parameters of lactation curve in primi‐ and multiparous cows. Previously proposed candidate genes for milk yield supported by this work include GRINA, CYHR1, FOXH1, TONSL, PPP1R16A, ARHGAP39, MAF1, OPLAH and MROH1, whereas newly identified candidate genes are MIR2308, ZNF7, ZNF34, SLURP1, MAFA and KIFC2 (BTA14). The protein lipidation biological process term, which plays a key role in controlling protein localization and function, was identified as the most important term enriched by the identified genes.

Highlights

  • Milk production is mainly dependent on the shape of the lactation curve, defined as the graphical representation of milk yield over the course of the lactating period (Do et al, 2017; Ehrlich, 2011; El‐Awady, 2013)

  • The results identified three windows on BTA14 associated with 305‐day milk yield and the parameters of lactation curve in primi‐ and multiparous cows

  • The objective of this study was to identify genomic regions associated with milk yield and the shape of lactation curve in Holstein dairy cows

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Summary

Introduction

Milk production is mainly dependent on the shape of the lactation curve, defined as the graphical representation of milk yield over the course of the lactating period (Do et al, 2017; Ehrlich, 2011; El‐Awady, 2013). The shape of the lactation curve is characterized by the slope of the initial rise of the curve, peak yield, time to peak, the slope of the curve after peak yield (lactation persistency) and lactation length (El‐Awady, 2013; López et al, 2015; Rekik, Gara, Hamouda, & Hammami, 2003). All these characteristics are responsible for total milk yield. The MilkBot model is flexible enough to accommodate disease and management effect, and can provide more accurate estimates of dairy milk yield (Cole, Ehrlich, & Null, 2012)

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