Genomic signatures of long-term selection in the Langhill dairy herd: the power of a five-decade experiment for sustainable dairy cattle breeding

Five decades of directional bull selection in the Langhill dairy Select line increased autozygosity by 24.7% (0.078 vs 0.063) and elevated linkage disequilibrium across 2–300 kb.

• Why it matters: Long-term selection can erode genetic diversity, but quantifying genomic costs and pinpointing where selection acts is difficult without contemporaneous control lines.
• What they did: Archived blood from 1,126 Langhill cows in Select versus Control lines was genotyped, then compared for inbreeding rate, effective population size (~33), linkage disequilibrium, and runs of homozygosity.
• The result: Excess autozygosity was confined to runs >2 Mb and did not localise to specific regions, while multiple differentiation scans converged on loci, including a chromosome 21 SERPINA gene cluster signal.

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