In this review, we highlight information on microRNA (miRNA) identification and functional characterization in the beef for muscle and carcass composition traits, with an emphasis on Qinchuan beef cattle, and discuss the current challenges and future directions for the use of miRNA as a biomarker in cattle for breeding programs to improve meat quality and carcass traits. MicroRNAs are endogenous and non-coding RNA that have the function of making post-transcriptional modifications during the process of preadipocyte differentiation in mammals. Many studies claim that diverse miRNAs have an impact on adipogenesis. Furthermore, their target genes are associated with every phase of adipocyte differentiation. It has been confirmed that, during adipogenesis, several miRNAs are differentially expressed, including miR-204, miR-224, and miR-33. The development of mammalian skeletal muscle is sequentially controlled by somite commitment into progenitor cells, followed by their fusion and migration, the proliferation of myoblasts, and final modification into fast- and slow-twitch muscle fibers. It has been reported that miRNA in the bovine MEG3-DIO3 locus has a regulatory function for myoblast differentiation. Likewise, miR-224 has been associated with controlling the differentiation of bovine adipocytes by targeting lipoprotein lipase. Through the posttranscriptional downregulation of KLF6, miR-148a-3p disrupts the proliferation of bovine myoblasts and stimulates apoptosis while the miR-23a~27a~24-2 cluster represses adipogenesis. Additional to influences on muscle and fat, bta-mir-182, bta-mir-183, and bta-mir-338 represent regulators of proteolysis in muscle, which influences meat tenderness.

The PLIN1 gene produces a phosphorylated protein wrapped in lipid droplets in adipocytes. This phosphorylation assists the mobilization of fat into adipose tissue. The purpose of the experiment was to study the polymorphism of the PLIN1 gene and its relationship with the body and carcass characteristics of Qinchuan cattle to find molecular genetic markers that can be used for breeding. The expression level of the PLIN1 gene was determined in various tissues by qRT-PCR. The results showed that the highest level of PLN1 expression was found in subcutaneous fat, followed by the heart and longissimus muscle, and the lowest level was found in the kidney. Five SNP loci of the PLIN1 gene were identified in 510 Qinchuan cattle, including g.3580T>C (SNP1), g.3898G>A (SNP2), g.8333G>A (SNP3), g.10517T>C (SNP4), and g.10538G>T (SNP5). The results show that SNP1, SNP2, SNP3, and SNP4 were moderately polymorphic (0.25 < PIC < 0.5), while SNP5 was minimally polymorphic (PIC < 0.25). SNP2, SNP3, and SNP5 were within Hardy–Weinberg equilibrium (P > 0.05), but SNP1 and SNP4 were not (P < 0.05). Correlation analysis showed that the five SNPs of the PLIN1 gene were correlated with back-fat depth, intramuscular fat, and chest depth of Qinchuan cattle. The double haplotype H2H4 in Qinchuan beef was associated with body and carcass traits. We conclude that variants mapped within PLIN1 can be used in marker-assisted selection for carcass quality and body traits in breed improvement programs for Qinchuan cattle.

Kalmyk cattle are an important meat breed in Kazakhstan, valued for their strong physique, genetic stability, and adaptability. In this study, we investigated the mRNA expression of ELOVL fatty acid elongase 6 (ELOVL6) and CREB-regulated transcription coactivator 2 (CRTC2) across multiple tissues, and further examined their genetic variations and associations with growth and carcass traits in 200 Kalmyk cattle. Expression analysis showed that CRTC2 was most highly expressed in the heart and liver, whereas ELOVL6 was predominantly expressed in the spleen and large intestine, highlighting their tissue-specific expression patterns. In addition, we identified a polymorphic SNP (g.16511290A > G) in the 3'UTR of ELOVL6, with three genotypes (AA, AG, GG) and the G allele being dominant (0.520). Polymorphism information content (PIC) analysis indicated high genetic diversity at this locus. Importantly, this SNP was significantly associated with live weight and body oblique length (p < 0.05), and individuals carrying heterozygous AG genotype showed higher body weight and length. Collectively, these findings suggest that g.16511290A > G within ELOVL6 may serve as useful molecular markers for body measurements and meat traits, providing valuable resources for marker-assisted selection in beef cattle breeding programs.

In Kazakhstan, meat–fat-tailed sheep breeding is crucial for breed development and high-quality mutton production. Understanding variations in candidate genes may improve selection for meat quality and growth traits. Therefore, this study aimed to investigate the relative mRNA expression levels of the DGAT1, CAST, IGF-1, POU1F1 genes using qRT-PCR in tissues from three 12-month-old male Degeres sheep, identify SNP variations by PCR and Sanger sequencing, and assess their associations with growth traits in 18-month-old female Degeres sheep (n = 380). Relative mRNA expression revealed tissue-specific expression patterns of the studied genes, with DGAT1 showing the highest expression in abdominal fat (p < 0.001), CAST in the abomasum (p < 0.01), IGF-1 in the liver (p < 0.001), and POU1F1 in the testis (p < 0.05). The findings uncovered a previously reported synonymous SNP (c.1461 C > T) in the DGAT1 gene and polymorphism information content (PIC) exhibited low polymorphism. Moreover, the identified SNP deviated from Hardy–Weinberg equilibrium (HWE) and was significantly associated with chest width (p = 0.001), with the “TT” genotype exhibiting greater chest width. Therefore, further studies with larger sample sizes are required to validate its potential use in marker-assisted selection (MAS) to optimize sheep breeding.

In the article, the peculiarities of the accumulation of adipose tissue in the body of bulls of different types of the Kalmyk breed are studied and described. In our work, economic and scientific observation of bulls according to the type of constitution of the Kalmyk breed was carried out. During the study, three groups were formed, large-bodied bulls were selected in group I, medium-sized bulls in group II, and compact-type bulls in group III. That is, the peculiarities of the accumulation and qualityof adipose tissue in young Kalmyk breed (large, medium, compact) were studied. As a result of the study, it was established that the amount of accumulated adipose tissue in the calves of the compact type compared to their calves of medium and large body type was more than 1.86 kg or 7.81% (P>0.99) and 2.96 kg or 13.02% (P>0.999), and the amount of accumulated subcutaneous adipose tissue was 0.39 kg or 5.90% (P>0.95) and 0.41 kg or 6.22% (P>0.95); intermuscular -0.27 kg or 3.80% (P>0.95) and 0.35 kg or 4.98% (P>0.95); abdominal fat -1.20 kg or 11.89% (P>0.99) and 2.20 kg or 27.17% (P>0.999). The chemical composition of adipose tissue varied depending on the type of physique of the young. The content of dry matter was higher in the tissues of medium and large calves, up to 0.32 and 0.36%, respectively