Background: Mongolian cattle, a unique breed indigenous to China, represent valuable genetic resources and serve as important sources of meat and milk. However, there is a lack of high-quality genomes in cattle, which limits biological research and breeding improvement. Findings: In this study, we conducted whole-genome sequencing on a Mongolian bull. This effort yielded a 3.1 Gb Mongolian cattle genome sequence, with a BUSCO integrity assessment of 95.9%. The assembly achieved both contig N50 and scaffold N50 values of 110.9 Mb, with only 3 gaps identified across the entire genome. Additionally, we successfully assembled the Y chromosome among the 31 chromosomes. Notably, 3 chromosomes were identified as having telomeres at both ends. The annotation data include 54.31% repetitive sequences and 29,794 coding genes. Furthermore, a population genetic variation analysis was conducted on 332 individuals from 56 breeds, through which we identified variant loci and potentially discovered genes associated with the formation of marbling patterns in beef, predominantly located on chromosome 12. Conclusions: This study produced a genome with high continuity, completeness, and accuracy, marking the first assembly and annotation of a near telomere-to-telomere genome in cattle. Based on this, we generated a variant database comprising 332 individuals. The assembly of the genome and the analysis of population variants provide significant insights into cattle evolution and enhance our understanding of breeding selection.

Penaeid shrimp, with its genomes enriched in short tandem repeats (STRs), presents an ideal model for studying the distribution and biological functions of STRs. In this study, we systematically identified and compared STRs across multiple species, confirming a significantly higher prevalence of STRs (26–32%) in penaeid shrimp, which is markedly higher than that observed in other species, such as mammals (1.3–2.1%) and plants (0.21–0.73%). Further analysis utilizing a cohort of 326 Pacific white shrimp revealed a total of 672,507 high-quality STRs evenly distributed across the genome, with a notably lower frequency of SNPs within these STR regions. Focusing on growth traits as a case study, we conducted a genome-wide association study (GWAS) and correlation analyses to identify the regulatory relationship of STRs on complex traits. We discovered 84 STRs that showed a significant association with body weight. Interestingly, eleven of these STRs, with 81% being composed of an A/T base, showed a significant linear correlation with body weight, revealing the key role of A/T-related STRs in shrimp weight regulation. For instance, a significant association and a negative correlation were found between the copy number of the STR [(A)n] at NW_020872788.1:580574 and body weight. The cytokinesis protein 7-like (LOC113800912) gene, which contains this STR in its splice region, exhibits differential expression associated with body weight variation. These findings introduce a model for STR copy number regulation in non-human species, illuminating the influence of STRs on growth traits. It offers a valuable framework for investigating complex traits and the biological functions of STRs in agricultural animals.

The genome of Penaeus vannamei is rich in short tandem repeats (STRs), occupying 18.96% of the genome, with 68.6% of loci showing high polymorphic information content, highlighting their potential as molecular markers. Accordingly, we performed an integrative GWAS leveraging STR, SNP, and InDel markers to identify 78 growth-associated loci, including 17 additional STRs compared with single-marker GWAS and six high-linkage regions containing metabolic, molting, and other growth-related genes. Four markers were validated in an independent population. In genomic prediction, STRs outperformed SNPs under the GBLUP model at low marker densities (20–50 loci), with accuracy gains up to 183%. GWAS-informed marker selection improved cross-population prediction performance, with STR-Top sets enhancing accuracy by 0.6%–3.0% under the GBLUP model, while SNP-Top sets achieved greater and more consistent gains under the KRR model. These results demonstrate the utility of STRs and support multi-marker integration for trait dissection and breeding in aquatic animals.

Low-density SNP panels are widely used to reduce genotyping costs in genomic selection (GS) in aquaculture, but sparse marker density can constrain prediction accuracy, particularly in species with rapid linkage disequilibrium decay. In this study, we evaluated a locally enriched multi-SNP (mSNP) strategy derived from a conventional 1K SNP panel in a family-based breeding population of Pacific white shrimp (Penaeus vannamei). Targeted sequencing was used to recover multiple nearby variants surrounding each marker locus, and conventional SNP and mSNP panels were compared for genomic features, imputation performance, and genomic prediction accuracy for body weight. The mSNP panel exhibited higher polymorphism and broader gene-region coverage than the corresponding SNP panel. The original mSNP panel improved prediction accuracy by 11.6% over the original 1K SNP panel. This advantage was maintained or slightly improved when mSNPs were restricted to on-target variants within ±300 bp of the target markers. A locus-matched comparison further showed that enriched mSNPs consistently outperformed conventional SNPs derived from the same target loci, with a 12.0% improvement at the full 961-locus panel. Although imputation improved the 1K SNP panel, the original mSNP panel already outperformed the imputed SNP panel and reached 0.509 after imputation. These findings demonstrate that locally enriched mSNP markers provide an effective and practical strategy for improving low-density GS in aquaculture species with rapid LD decay.