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Milk protein polymorphism and genetic structure of Croatian simmental catlle

The aim of this research was to study the genetic structure of Croatian Simmental from the point of view of milk protein polymorphism. Milk samples (621)were taken from the area of seven breeding units (Bjelovar, Koprivnica, Veliki Zdenci, Đurđevac, Vrbovec, Čakovec and Đakovo) and were genotyped, using iso-electric focusing, for asl, b, k- casein and b- lactoglobulin. The genetic structure of population was modelled by Wright's F-statistics (F st, F sl and F ll coefficients) and was related only to milk protein polymorphism. Fou models were buit for that purpose: (a) a model that included Austrian, German, Hungarian, Swiss and Croatian Simmental as subpopulations, (b) a model that included Austrian, German and Croatian Simmental as subpopulations, (c) a model that included breeding units as subpopulations, and (d) a model where hypothetical subpopulations were formed on the basis of the blood origin. Frequencies of milk protein alleles for Croatian Simmental breed were sinimar to other Simmental populations. Two alleles in a sl-casein locus B (0, 94) and C (0, 06), foour alleles in b-casein locus A1 (0, 19) , A2 (0, 63), B (0, 15) and C (0, 03) and three alleles in k-casein locus A (0, 64), B (0, 30) and C (0, 06) were present with corresponding related frequencies marked in parentheses- Two alleles A and B with frequencies 0, 52 and 0, 48, respectively, were persent in the b-lactoglobulin locus. In spite of these similarites and constant immigration ogf genes from other Simmental populations, there was a significant genetic heterogeneity among Austrian, Croatian and German Simmental (Fst= 0, 0056), as well as among Austrian, Croatian and German, Hungarian and Swiss Simmental (Fst=0, 0083). Significant genetic heterogenety was also observed among breeding units (Fst=0, 0114). The genetic heterogeity among breeding units is a consequence of the organization of Croatia Simmental catlle breeding and should be taken into account: (a) in the population and quantitative genetic research related to milk protein polymorphism, and (b) when milk protein polymorphisms are going to be implemented as additional information in breeding of Croatia Simmental catlle. Approximately equal frequencies of alleles A and B for b-lactoglobulin locus in all Simmental breeds, as well as in breeding units of Croatian Simmental, in addition to negative values of Fls coefficients in alll models indicate a natural topic for further research.

Genetic structure; milk protein polymorphism; Croatian Simmental

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