Quantitative and qualitative detailed milk protein profiles of 6 cattle breeds: Sources of variation and contribution of protein genetic variants

Abstract

Different fractions of milk nitrogenous compounds (not only caseins) have different effects on the nutritional value of milk, its coagulation and curd firming properties, and its cheese-making efficiency. To assess different sources of variation, especially the cows' breed and genetic variants of the main protein fractions, milk samples were collected from 1,504 cows belonging to 3 dairy breeds (Holstein-Friesian, Brown Swiss, and Jersey) and 3 dual-purpose breeds (Simmental, Rendena, and Alpine Grey) reared in 41 multibreed herds. Beyond crude protein, casein (CN), and urea, 7 protein fractions were analyzed using HPLC, and 5 other N fraction traits were calculated. All 15 traits were measured qualitatively (% of milk N) and quantitatively (g/L of milk). The HPLC technique allowed us to discriminate between the main genetic variants of β-CN, κ-CN, and β-lactoglobulin and thus to genotype the cows for the CSN2, CSN3, and BLG genes, respectively. Data were analyzed using 2 mixed models, both including the effects of herd-date, breed, parity, and lactation stage, and only one also including the effects of the genotypes of the milk proteins. Breed of cow explained 2 to 36% of phenotypic variability for all the N fractions, with the exception of the urea and total casein contents of milk and the urea and β-CN proportions of total milk N. Lactation stage had a considerable influence on the amount (g/L) of almost all the protein fractions in milk, but neither the nonprotein N fractions nor the percentage of milk N protein profile were affected. The inclusion of the CSN2, CSN3, and BLG genotypes in the model explained a large part of the total variability in all the milk protein and nonprotein fractions except urea. It also reduced the variance explained by breed and residual factors. An exception was shown by the proportion of α S1 -CN variance explained by breed that moved from 13 to 28%. Similarly, for amount (g/L) of β-CN, the effect of breed became significant (12%), whereas it was almost null before inclusion of genotypes. In terms of percentage of milk N, the genotypes of CSN3 notably affected all the casein fractions, whereas the BLG genotypes had a much greater influence on most noncasein traits. The genotypes of the CSN2 gene exerted an appreciable effect on α S2 -CN and not β-CN, as expected. Comparing the 2 models, we were also able to discriminate the effect of the breed on a milk N fraction, both quantitatively and qualitatively, in 2 quotas: the first due to the milk protein polymorphisms (major genes) and the second due to other genetic factors (polygene), after correcting for the effect of herd-date of sampling, parity, and lactation stage. The knowledge about the detailed milk protein profile of different cattle breeds provided by this study could be of great benefit for the dairy industry, providing new tools for the enhancement of milk payment systems and breeding program designs.

A2 Bovine Milk and Caprine Milk as a Means of Remedy for Milk Protein Allergy

“…Many previous reports have shown that this unique compositional characteristic of caprine milk is highly correlated with the therapeutic and hypoallergenic properties of its milk in infants and especially in CMPA patients [14,[17][18][19]. Amalfitano et al (2020) [1] reported that in terms of percentage of milk N, the genotypes of CSN3 notably affected all the casein fractions, whereas the BLG genotypes had a much greater influence on most non-casein traits. The genotypes of the CSN2 gene exerted an appreciable effect on α S2 -CN and not β-CN.…”

“…2.0 ± 0.17 a-c Different letters denotes significant difference (p < 0.001). 1 Results are shown as the mean ± SEM (n = 3; n = 2 for A 1 ). 2 t pep = reaction time with pepsin.…”

“…Bovine milk allergy caused by protein genetic variants has been regarded as a common milk digestive and allergic disease [1] with various levels of prevalence from 2.5% in children during the first 3 years of life [2] to 12-30% in infants less than 3 months old [3] and an overall frequency in Scandinavia of 7-8% [4]. However, it can go up to even as high as 20% in some countries [3].…”

Nonlinear modeling to describe the pattern of 15 milk protein and nonprotein compounds over lactation in dairy cows

“…Detailed profiling of milk protein and nonprotein nitrogenous compounds was based on 3 groups of information that were reported in our previous study on the effects of breed (Amalfitano et al, 2020). Briefly, the first group was 3 N compounds (protein, CN, and urea) analyzed with the Fourier-transform infrared spectroscopy (FTIR) methods officially used for milk recording (ICAR, 2012).…”

Influence of cattle breed combinations on milk production: results of the Analysis of Variance

“…Like all quantitative traits, the protein content during the crossing is inherited intermediately. However, the increase in the range of variability of the trait enables breeders to use individual selection methods to obtain a positive effect in the next generation (Amalfitano et al, 2020). In the experiment conducted by Shkurko (2005), it was determined that all groups had a high percentage of fat and relatively low protein content.…”