Dairy cattle

Genetic Parameters and Genome-Wide Association Analysis for Lactation Traits in High-Altitude Dairy Cattle

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Abstract

Dairy production on the Xizang Plateau occurs under extreme environmental conditions characterized by chronic hypoxia, strong ultraviolet radiation, and large diurnal temperature variation. The region currently relies on Holstein and Jersey cattle introduced over the past several decades, along with crossbred populations derived from indigenous cattle carrying Bos indicus and Chinese yellow cattle ancestry. Although traditional dairy products such as butter and milk tea have deep cultural importance, the supply of milk remains insufficient to meet growing demand. Furthermore, systematic dairy herd improvement (DHI) programs have not been implemented in Xizang, leading to limited phenotypic and genetic information to support breeding decisions and herd management at high altitude. To address this gap, a DHI program for high-altitude dairy cattle in Xizang was initiated since 2023. Six lactation traits were recorded, including daily milk yield, fat yield, protein yield, lactose yield, milk urea nitrogen, and somatic cell score. After data cleaning and quality control, the final dataset included 8,879 test-day records from 1,932 cows. Genotyping was performed using the GGP Bovine 100K SNP chip. Influencing factors for lactation traits were screened and repeatability animal models were used to estimate genetic parameters. A genome-wide association analyses (GWAS) was conducted to detect genomic regions associated with lactation performance and possible physiological adaptation to high altitude. The average daily milk yield was 13.92 kg, with mean milk fat and protein contents of 4.23% and 3.55%, respectively. Herd, parity, calving season, days in milk, and temperature-humidity index exerted significant effects on most traits. Crossbred cows with higher proportions of Holstein ancestry generally demonstrated improved milk yield and component production under plateau conditions. Heritabilities were moderate for milk yield, fat yield, protein yield, and lactose yield (0.32 to 0.35), but lower for milk urea nitrogen (0.13) and somatic cell score (0.05). The top three principal components were included as covariates to account for population structure. GWAS identified 54 candidate genes enriched in molecular functions such as DNA-binding transcription factor activity, RNA polymerase II-specific binding. Notably, ELL2 has been implicated in the regulation of immune proteins. Immune dysregulation at high altitudes is a known factor contributing to altitude sickness. Another key gene, ADIPOR1 plays a crucial role in metabolic regulation by mediating fatty acid oxidation and glucose uptake. For instance, previous studies on Tibetan populations identified ADIPOR1 among the top genes showing strong selection signals related to high-altitude adaptation. This study provides the first comprehensive evaluation of genetic architecture of lactation performance in high-altitude dairy cattle, offering foundation for sustainable breeding and herd improvement in the Xizang Plateau.

Keywords: 2026

How to Cite:

Xu, J., Li, B., Wang, Y. & Zhang, H., (2026) “Genetic Parameters and Genome-Wide Association Analysis for Lactation Traits in High-Altitude Dairy Cattle”, World Congress on Genetics Applied to Livestock Production Digital Archive 2026(1): 2286203. doi: https://doi.org/10.31274/wcgalp.23879

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