Table 1_Genetic architecture of thermotolerance traits in beef cattle: a novel integration of SNP and breed-of-origin effects.xlsx

BackgroundRising temperatures increasingly expose beef cattle to heat stress, reducing productivity and welfare, especially in tropical climates. Crossbreeding Bos t. taurus and Bos t. indicus has emerged as a critical strategy to balance the production efficiency of taurine breeds with the superior thermotolerance of indicine breeds. Understanding the genetic architecture of thermotolerance traits is essential for improving heat resilience in beef cattle populations.
MethodsPhenotypes for short hair length (SHL, undercoat) and long hair length (LHL, topcoat), sweat gland area (SGA), and thermal stress slope (TSS), a measure of body temperature fluctuations under heat stress, were collected from 3,962 crossbred Angus-Brahman heifers. Heifers were genotyped, and breed-of-origin (BOA) for each marker was determined using LAMP-LD. Genome-wide association studies were conducted using SNP-only, BOA-only, and integrated SNP + BOA models to identify quantitative trait loci (QTLs) associated with thermotolerance traits. Genes in QTL regions were used for functional enrichment analysis using Gene Ontology (GO) and KEGG pathways.
ResultsSignificant QTLs for SHL and LHL were identified on BTA20, overlapping the PRLR gene. A QTL on BTA19 for SHL and LHL was driven solely by BOA effects, with Brahman BOA associated with shorter hair lengths. For SGA, six suggestive QTLs were detected, predominantly linked to Angus-derived alleles associated with reduced sweat gland area. For TSS, a significant QTL on BTA1 exhibited a strong BOA effect, with Angus BOA associated with higher TSS values, indicative of reduced thermoregulatory efficiency. Integrated SNP + BOA models provided greater resolution and revealed novel QTLs compared to single-effect models. Functional enrichment using GO and KEGG identified MAPK and estrogen signaling pathways in both LHL and TSS, indicating potential overlap in the biological processes influencing hair length and thermoregulation.
ConclusionThis study demonstrates the value of integrating BOA with SNP-based models to uncover the genetic architecture of thermotolerance traits in beef cattle. By better capturing breed-specific contributions, these findings enhance our understanding of thermoregulation and provide actionable insights for improving heat resilience in cattle.

研究背景：气温持续升高使得肉牛愈发易遭受热应激，进而降低其生产性能与福利水平，在热带气候区域这一问题尤为突出。将普通肉牛（Bos t. taurus）与瘤牛（Bos t. indicus）进行杂交，已成为兼顾普通肉牛品种生产效率与瘤牛品种优异耐热性的关键策略。解析耐热性状的遗传结构，对于提升肉牛种群的热应激耐受能力至关重要。
研究方法：本研究从3962头安格斯-婆罗门杂交青年母牛中采集了多项表型数据，包括短毛长度（SHL，内层被毛）、长毛长度（LHL，外层被毛）、汗腺面积（SGA）以及热应激斜率（TSS，用于衡量热应激状态下的体温波动情况）。对所有青年母牛进行基因分型，并利用LAMP-LD确定每个遗传标记的血统来源（BOA）。分别采用仅基于单核苷酸多态性（SNP）、仅基于BOA以及整合SNP与BOA的三种模型开展全基因组关联分析，以筛选与耐热性状相关的数量性状基因座（QTLs）。选取QTL区域内的基因，通过基因本体（GO）和京都基因与基因组百科全书（KEGG）通路进行功能富集分析。
研究结果：本研究在BTA20染色体上筛选到与SHL和LHL显著相关的QTL，该位点与PRLR基因区域重叠。在BTA19染色体上存在一个仅受BOA效应调控的SHL与LHL相关QTL，其中携带婆罗门血统的BOA与更短的被毛长度相关。针对SGA，共检测到6个提示性QTL，其主要与安格斯血统来源的等位基因相关，这类等位基因会降低汗腺面积。针对TSS，在BTA1染色体上发现一个显著QTL，该位点具有较强的BOA效应，携带安格斯血统的BOA与更高的TSS值相关，提示其体温调节效率更低。相较于单效应模型，整合SNP与BOA的模型具有更高的分辨率，并揭示了新的QTL。通过GO和KEGG进行功能富集分析发现，丝裂原活化蛋白激酶（MAPK）信号通路与雌激素信号通路同时参与调控LHL和TSS，表明影响被毛长度与体温调节的生物学过程存在潜在重叠。
研究结论：本研究证实了将BOA与基于SNP的模型相结合，能够有效解析肉牛耐热性状的遗传结构。通过更好地捕捉品种特异性的遗传贡献，本研究结果加深了我们对肉牛体温调节机制的理解，并为提升肉牛的热应激耐受能力提供了具有实践指导意义的见解。