# Prolactin gene diversity and its influence on milk yield traits in Ayrshiredairy cattle from Southern Russia

## TL;DR

This study explores genetic variations in the prolactin gene of Ayrshire cows in southern Russia and their impact on milk production.

## Contribution

The study identifies a significant association between PRL gene genotypes and milk yield in Ayrshire cattle.

## Key findings

- Cows with the PRL_AA genotype produced 10.96% more milk than those with the PRL_BB genotype.
- The PRL gene showed allelic diversity in the studied Ayrshire population.
- Genetic equilibrium was preserved in the population (χ² = 0.2879).

## Abstract

The objective of this research was to discover single-nucleotide variations in the ­prolactin (PRL) gene and to evaluate their correlation with milk production characteristics in Ayrshire cows reared in southern Russia.

DNA (deoxyribonucleic acid)samples were extracted from the blood of cows (n = 300) using a commercial kit. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique was employed to identify and quantify genotypes and allele frequencies. Genetic indices were calculated, and statistical processing was performed. A general linear model was used to investigate the relationship between single-nucleotide polymorphisms and milk productivity in cows.

The distribution of the AA, AB, and BB genotypes in the studied population was 90%, 0%, and 10%, respectively. The genetic equilibrium in the Ayrshire cow population was preserved (χ² = 0.2879). The results indicate the presence of allelic diversity in the prolactin gene in this ­population. The milk yield per lactation in cows with the PRL_AA genotype was 7,378.50 kg, and for PRL_BB, it was 6,569.63 kg. Ayrshire cows with the PRL_BB genotype yielded less milk compared to their PRL_AA counterparts by 10.96% (p < 0.05).

Using the obtained results in the future selection of offspring with desirable PRL ­genotypes at an earlier age could significantly increase the efficiency of breeding work in the studpulation and accelerate the process of creating a herd with higher productivity potential.