Effect of CSN1S1-CSN3 (αS1-κ-casein) composite genotype on milk production traits and milk coagulation properties in Mediterranean water buffalo

Abstract

The aim of this study was to estimate effects of CSN1S1-CSN3 (α(S1)-κ-casein) composite genotypes on milk production traits and milk coagulation properties (MCP) in Mediterranean water buffalo. Genotypes at CSN1S1 and CSN3 and coagulation properties [rennet clotting time (RCT), curd firming time (K₂₀), and curd firmness (A₃₀)] were assessed by reversed-phase HPLC and computerized renneting meter analysis, respectively, using single test-day milk samples of 536 animals. Alternative protein variants of α(S1)-CN and κ-CN were detected by HPLC, and identification of the corresponding genetic variants was carried out by DNA analysis. Two genetic variants were detected at CSN1S1 (A and B variants) and 2 at CSN3 (X1 and X2 variants). Statistical inference was based on a linear model including the CSN1S1-CSN3 composite genotype effect (7 genotypes), the effects of herd-test-day (8 levels), and a combined days in milk (DIM)-parity class. Composite genotype AB-X2X2 was associated with decreased test-day milk yield [-0.21 standard deviation (SD) units of the trait] relative to genotype BB-X2X2. Genotypes did not affect milk protein content, but genotype AB-X1X1 was associated with increased fat content compared with genotype BB-X2X2 (+0.28 SD units of the trait) and AB-X1X1 (+0.43 SD units of the trait). For RCT, the largest difference (+1.91 min; i.e., 0.61 SD units of the trait) was observed between genotype AA-X1X2 and AB-X1X1. Direction of genotype effects on K(20) was consistent with that for RCT. The maximum variation in K₂₀ due to genotype effects (between AA-X1X2 and AB-X1X1 genotypes) was almost 0.9 SD units of the trait. Magnitude of genotype effects was smaller for A₃₀ than for RCT and K₂₀, with a maximum difference of 0.5 SD units of the trait between genotype AA-X1X2 and AA-X1X1. The B allele at CSN1S1 was associated with increased RCT and K₂₀ and with weaker curds compared with allele A. Allele X2 at CSN3 exerted opposite effects on MCP relative to CSN1S1 B. Because of linkage disequilibrium, allele B at CSN1S1 and allele X2 at CSN3 tend to be associated and this likely makes their effects cancel each other. This study indicates a role for casein genes in variation of MCP of buffalo milk. Further studies are necessary to estimate the effects of casein genetic variants on variation of cheese yield.

Polymorphisms of the kappa casein (<i>CSN</i>3) gene and inference of its variants in water buffalo (<i>Bubalus bubalis</i>)

“…The exon IV of this gene encodes 94.7 % of the mature κ-CN in two types of buffalo and other mammals and constitutes the main part of the κcasein domain. Therefore, in recent years, the detection of the CSN3 gene variation in some species mainly focused on exon IV and named κ-CN variants according to the polymorphism of this exon (Farrell et al, 2004;Caroli et al, 2009). In light of this, to study the association between polymorphisms of the CSN3 gene CDS and the traits in buffalo, it is suggested that exon IV should be used as a genetic marker.…”

“…Based on the literature (Caroli et al, 2009;Gallinat et al, 2013), we have reconstructed the amino acid sequences of the various κ-CN variants found in the Bos genus. The sequence alignment of κ-CN variants demonstrated that there were 8 amino acid differential sites within the species of the Bos genus, and 14 amino acid differential sites between buffalo and the Bos genus (Fig.…”

“…The κ-CN variants have been extensively studied in the Bos genus for decades. To date, 13 protein variants (A, B, B 2 , C, D, E, F 1 , F 2 , G 1 , G 2 , H, I and J) and 1 synonymous variant (A 1 ) of κ-CN in the Bos genus have been identified at the protein and DNA levels (Farrell et al, 2004;Chen et al, 2008;Caroli et al, 2009). Previous studies have primarily focused on its two most common genetic variants (A and B), which have been shown to be related to differences in milk composition or yield and curdling characteristics of rennet in animals of Bos taurus (Lara et al, 2002;Tsiaras et al, 2005;Alipanah et al, 2008).…”

Short communication: Predictive ability of Fourier-transform mid-infrared spectroscopy to assess CSN genotypes and detailed protein composition of buffalo milk

“…Prediction of CSN1S1 and CSN3 genotypes, based on infrared information, might be of interest because a relationship between milk protein genotypes and variation in coagulation properties has been previously described (Bonfatti et al, 2012b). Results of discriminant analysis for CSN1S1 are reported in Table 2.…”

“…AJ005430.1), resulting in the AA substitution Leu 178 (A) → Ser 178 (B) of the mature α S1 -CN polypeptide chain (from exon 3 to 17 of the reference sequence O62823). Genotypes at CSN3 corresponded to the T > C transition at nucleotide 467 of the complete coding sequence HQ677596 results in the amino acid substitution Ile 135 (X1) → Thr 135 (X2) of the mature κ-CN polypeptide chain (Bonfatti et al, 2012b). The FT-MIR calibration models were developed using modified partial least square regression (MPLS; Shenk and Westerhaus, 1991) procedures as implemented in the software WinISI II (InfraSoft International, State College, PA).…”