Gene-Polymorphism Effects on Growth Efficiency in the Kalmyk Breed of Central Asia

Understanding the genetic basis of growth and fat deposition is crucial for improving beef productivity in Kalmyk cattle, a breed well adapted to the extreme climatic conditions of Kazakhstan. The present study aimed to determine the effects of single-nucleotide polymorphisms (SNPs) in the CRTC2 and ELOVL6 genes on intramuscular fat content and to evaluate their associations with growth and meat quality traits in 18-month-old Kalmyk heifers raised under different environmental conditions.

A total of 400 clinically healthy Kalmyk heifers (200 from LLP "Qazaq Asyldary" and 200 from LLP "Agrofirma Turikpen") were examined. All animals originated from closed breeding herds, and only unrelated individuals without common ancestors to the third generation were included. Zootechnical measurements- live weight, withers height, chest depth, chest girth, and body length-were performed twice by a trained specialist. Backfat thickness and musculus longissimus dorsi depth were measured postmortem. Blood samples were collected for genomic DNA extraction using the GeneJET purification kit, and DNA quality was assessed by Nanodrop, Qubit, and agarose gel electrophoresis. Target fragments of CRTC2 and ELOVL6 were amplified (150-200 bp) and sequenced on an ABI 3500 system. SNP identification, allele frequencies, and genotyping were performed by alignment to the Bos taurus ARS-UCD1.2 reference genome. Statistical analyses were conducted in RStudio using linear and mixed models with "farm" as a random effect.

Only one informative polymorphism, g.133528A>G in ELOVL6, was detected. Three genotypes (AA, AG, GG) were observed, with the heterozygous AG genotype showing significantly higher live weight, greater body length, and improved linear measurements compared to AA and GG. No significant associations were detected with backfat thickness or muscle depth. The g.133528A>G polymorphism in ELOVL6 positively influences growth traits without increasing fatness, aligning with the naturally lean phenotype of Kalmyk cattle.

The AG genotype may serve as a promising marker for selecting faster-growing animals in marker-assisted breeding programs.