Determining the frequencies of B1, B2, B3 and E alleles of the &lt;i&gt;CSN1S1&lt;/i&gt; gene and their effects on milk yield and composition in Saanen goats

D Turhan Dincel,H Samli,F Balci,S Ardicli

doi:10.4314/sajas.v46i2.9

Abstract

The aim of the study was to determine the frequencies of B1, B2, B3 and E alleles of the CSN1S1 gene and their effects on milk yield and composition in the Saanen goat breed. Milk samples were collected to identify milk composition with Fourier transform infrared (FTIR) spectroscopy. The polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method was used to characterize the alleles of CSN1S1 gene. The allelic frequencies of the B1, B2, B3 and E alleles were 0.927, 0.073, 0.390, and 0.272, respectively. B1 and B2 alleles did not affect milk yield and composition. B3 allele had significant effects on protein, fat, total solid (TS), solid not fat (SNF), casein and lactose percentages, but not on lactose yield. E allele significantly influenced fat and TS percentages of milk in the Saanen goat breed. The protein (3.58%), fat (3.83%), TS (12.06%), SNF (8.60%) and casein percentages (2.80%) were higher in B3/B3 goats than in B3/NB3 (NB3: non-B3) and NB3/NB3 goats. For E allele, NE/NE (NE: non-E) goats displayed higher fat (4.06%) and TS (12.42%) percentages of milk than their E/E and E/NE counterparts. As a result, the potential for improving milk composition by selecting for B3 and E allele may be significant in Saanen goats. Keywords: Capra hircus , PCR-RFLP, SNP, milk production

Highlights

In ruminants, 80% of milk proteins consist of four types of casein (Ramunno et al., 2004)
For B3 allele of CSN1S1 gene single undigested fragment (231 bp) was observed for B3 homozygote individuals, when two fragments of 97 and 134 bp were observed after the digestion of DdeI restriction enzyme for ‘non-B3’ (NB3) homozygote individuals (Figure 3)
Hardy-Weinberg equilibrium and χ2-values were not estimated owing to the genotypic frequency for B1 and B2 alleles (n 0.05)

Summary

Introduction

80% of milk proteins consist of four types of casein (αS1, β, αS2 and κ) (Ramunno et al., 2004). AlphaS1-casein (αS1-CN), beta-casein (β-CN), alphaS2-casein (αS2-CN) and kappa-casein (κ-CN) are expressed in goat milk and encoded by CSN1S1, CSN2, CSN1S2 and CSN3 genes, respectively (Martin et al, 2002). These are organised as a cluster in a 250 kilobase (kb) genomic DNA segment in chromosome 6 in goats (Martin et al, 2002). It is known that 18 alleles of CSN1S1 gene have been identified so far, which are associated with different expression levels of αS1-CN in milk (Küpper et al, 2010). The E allele consists of the insertion of long interspersed repeated elements (LINE) of 457-458 bp at the 124th nucleotide of exon 19 (Jansá-Perez et al, 1994)

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