Investigating the genetic polymorphism of sheep milk proteins: a useful tool for dairy production

Abstract

Sheep is the second most important dairy species after cow worldwide, and especially in the Mediterranean and Middle East regions. In some countries, the difficult environmental conditions require a peculiar adaptation and, in these contexts, sheep are able to provide higher quality protein than cattle. In the least-developed countries, the amount of dairy sheep and ovine milk production is progressively increasing. In order to improve dairy productions, in particular those with local connotations, it is necessary to obtain in-depth information regarding milk quality and rheological properties. The genetic polymorphisms of milk proteins are often associated with quantitative and qualitative parameters in milk and are potential candidate markers that should be included in breeding strategies similar to those already available for cattle. Due to the current and growing interest in this topic and considering the large amount of new information, the aim of this study was to review the literature on sheep milk protein polymorphisms with a particular emphasis on recent findings in order to give scientists useful support. Moreover, the effects of different protein variants on milk yield and composition are discussed.

Genotyping of the kappa‐casein and beta‐lactoglobulin genes in Anatolian water buffalo by PCR‐RFLP

“…Although the proportion of whey proteins is relatively low, casein is the most important protein in milk and buffalo milk contains 4.0 g of casein in 100 g of milk (Zicarelli 2004). Among a variety of caseins, j-CN constitutes about 15% of the total caseins and contains cysteine (Selvaggi et al 2014). Kappa-casein protein is encoded by kappa-casein gene which was mapped to chromosome 7 in water buffalo (Iannuzzi et al 2003).…”

“…Beta-lactoglobulin (b-LG) is a globular protein member of the lipocalin family and is the main whey protein of ruminant milk (around 50% of total whey proteins) (Selvaggi et al 2014). The complete amino acid sequence of b-LG has been reported, and genetic variation in amino acid sequence has been identified (Rachagani et al 2006).…”

“…Milk production traits are under the control of several genes, and the genetic polymorphisms of milk proteins are strongly associated with quantitative and qualitative milk parameters in different ruminant species (Selvaggi et al 2014). Therefore, the aim of this study was to identify the j-CN and b-LG gene polymorphisms in native Anatolian water buffalo and to explore the genetic variation in these animals in terms of genetic conservation.…”

β-Lactoglobulin Gene Polymorphisms in Sheep and Effects on Milk Production Traits: A Review

“…However, goat and sheep milks have peculiar composition and properties and, as a consequence, specific productive destinations (Selvaggi et al, 2014a). In fact, sheep milk is used mainly for cheese production (Selvaggi and Tufarelli, 2012;Selvaggi et al, 2014b). There is a strong association among milk protein polymorphisms and milk yield, composition and technological aspects.…”

Polymorphism Studies of Kappa-casein (k-CN), Beta-lactoglobulin (beta-Lg) and DRB3 Genes in Indian Murrah Buffalo

“…Among variety of casein, Kappa-casein protein (about 15% of the total caseins) is encoded by Kappa-casein (k-CN) gene and Beta-lactoglobulin (β-LG), a globular protein member of the lipocalin family, is the main whey protein of ruminant milk; around 5% of the total whey proteins (Selvaggi et al, 2014). Several single nucleotide polymorphisms and their association with milk production traits have been reported in the bovine milk protein gene (Caroli et BoLA-DRB3 exon 2 alleles in cattle have been found to be associated with resistance or susceptibility to various diseases.…”