Alpha S1-casein genetic variations in Bulgarian sheep breeds and significance on milk casein fractions

Deyana Gencheva1, Darina Pamukova3, Nikolina Naydenova3, Petya Veleva2 and Milena Tzanova4
1 Department of Genetics, Breeding and Reproduction, Faculty of Agriculture, Trakia University, Stara Zagora, 6000 Bulgaria
2 Department of Agricultural Engineering, Faculty of Agriculture, Trakia University, Stara Zagora, 6000 Bulgaria
3 Department of Animal husbandry – Ruminants and Dairy Science, Faculty of Agriculture, Trakia University, 6000 Stara Zagora, Bulgaria
4 Department of Biochemistry, Microbiology and Physic, Faculty of Agriculture, Trakia University, Stara Zagora, 6000 Bulgaria

Abstract

Gencheva, D., Pamukova, D., Naydenova, N., Veleva, P. & Tzanova, M. (2022). Alpha S1-casein genetic variations in Bulgarian sheep breeds and significance on milk casein fractions. Bulg.J. Agric. Sci., 28 (3), 526–533

Single nucleotide polymorphism (SNP) of the exon III at CSN1S1 gene encoding alpha S1-casein (αS1-CN) was investigated by means of the PCR-RFLP analysis in two sheep breeds – Bulgarian Dairy Synthetic Population (BDSP, n = 89) and Pleven Blackhead sheep (PLBH, n = 38) with an aim to establish the possible effect of a particular genotype on the casein content and distribution of milk fractions. The homozygous CC genotype was observed in 63.2% of the studied ewes, while the homozygous AA genotype was established in 4.5 % of the individuals. The calculated mean values of observed (Hо = 0.323) and expected (He = 0.321) heterozygosity at CSN1S1 locus indicated a moderate degree of genetic variability in the examined sheep populations. The estimated negative values of the coefficient (Fis = –0.001 ÷ –0.006) showed a low level of inbreeding. The results of the associative analysis indicated that CSN1S1 genotypes were significantly associated with the milk αS1-CN in the BDSP 2 population (P < 0.05). The highest casein percentage in this population (35.24 ± 3.96) was associated with ewes carrying the heterozygous AC genotype. No significant differences (P > 0.05) were established for CSN1S1 genotypes in terms of casein content in the studied PLBH sheep population.

Keywords: sheep milk; caseins; CSN1S1gene; SNP; PCR-RFLP

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