Production type of Slovak Pinzgau cattle in respect of related breeds

© Slovak University of Agriculture in Nitra Faculty of Agrobiology and Food Resources, 2015 http://www.fapz.uniag.sk/ DOI: 10.15414/afz.2015.18.02.25–29


Introduction
Pinzgau is an traditional cattle breed of mountainous areas of Slovakia, introduced approximately 2 centuries ago (Kasarda et al., 2008).It was imported from region of the Austrian Alps (Pšenica, 1990).System of cattle recording has started in territory of Slovakia in 1923.The size of population increased and in 1958 it was officially accepted as Slovak Pinzgau breed (Kadlečík et al., 2013).Thanks to its unique traits as longevity, fertility, health, grazing ability it had been bred in mountain regions of northern Slovakia (Pavlík et al., 2013).From the beginning, only purebred animals were used in breeding.Approximately 60 years ago started grading-up crossbreeding with other breeds due to increasing of milk production while unique dual-purpose character was preserved.Jersey breed was used rather experimentally whereas Ayrshire, Meuse Rhine Issel (MRI), Red Holstein have been successfully proved and Red Holstein is used up to now.Nowadays there are used sires born in Slovakia, however, due to their small number also Austrian sires.Austrian Pinzgau has been bred with Red Holstein and Simmental since the second half of the last century.Due to significant decline of the population size in recent years this breed is considered endangered (Kadlečík et al., 2004).
Molecular markers based on DNA have a high polymorphism level, and they have been successfully used for evaluation of genetic diversity and variation in breeding programmes with an impact on the level of genetic conservation schemes (Židek and Kasarda, 2010).Genomic technologies, such as high-throughput genotyping based on SNP arrays provided background information concerning genome structure in domestic animals (Mastrangelo et al., 2014).Among livestock species, this technology has been applied most successfully in cattle, because factors such as evolutionary history, genetic structure and economics make cattle particularly suitable for the application of genome assisted selection (Nicolazzi et al., 2014).One of the important steps in development of efficient autochthonous breed protection programs is characterization of population genetic variability and to assess the genetic structure (Simčič et al., 2008).

Materials and methods
Whole active AI Pinzgau bulls in Slovakia were analysed.DNA of 19 animals was isolated from semen doses.Genomic DNA for each of the semen samples was genotyped at a commercial lab using the Illumina BovineSNP50 v2 BeadChip.The genotyping array contained 54,609 SNPs.To understand the genetic relationship within and among breeds, genotypes from 103 other animals belonging to 5 domesticated bovine breed were used (Decker et al., 2014a;Decker et al., 2014b;Gautier et al. 2010a;Gautier et al., 2010b) without information on sex of individuals (Table 1).Despite the fact that Decker et al. (2014a) and Gautier et al. (2010a) removed closely related individuals from the dataset if pedigree data were available, current numbers of Slovak Pinzgau cattle did not allow us to perform the same exclusion.Moreover, such selection is not needed for this type of analysis, confirming by the studies of Edea et al. (2013) and Mastrangelo et al. (2014).
Due to using more data sets new genetic map was created.In order to minimize risk of genotype errors and excluding poorly performing SNPs individual quality control was performed.All markers with unknown position as well as those that had been assigned to chromosome X were removed.According to Decker et al. (2014) SNPs with minor allele frequency less than 0.0005 were discarded.Excluded were also animals with more than 5% and SNP markers with more than 10% of missing genotypes by PLINK (Purcell et al., 2007).Further analyses were performed including information from 42 854 autosomal SNPs common to all breeds.
The Bayesian clustering algorithm implemented by the STRUCTURE 2.3.4 software (Falush et al., 2003) was used to infer the population structure.The program enables estimation of a 'hidden structure' , that is the number of different clusters (populations) obtained without using any a priori information about individual membership (breed).Furthermore, the program is able to determine the corresponding fraction of an individual's genome derived from an ancestry in one of the clusters (K) determined by the program.The program STRUCTURE estimates the natural logarithm of the probability (Pr) of the observed genotypic array (G), given a preassigned number of clusters (parameter K) in the dataset [ln Pr (G|K)].In a Bayesian set-up the estimate of ln Pr(G|K) is a direct indicator of the posterior probability of having K number of clusters, given the observed genotypic array (G).Lengths of the burn-in and Monte Carlo Markov Chain were 105 steps followed by 10 5 iterations.To obtain a representative value of K in the data set, 10 independent runs of the Gibbs sampler for each K between 1 and 5 were performed.In all runs we used default settings, that is, an admixture model with correlated frequencies and the parameter of individual admixture alpha set to be the same for all clusters and with a uniform prior.
Based on level of admixture in observed breeds the classification to groups according production type was investigated.

Results and discussion
Genotype data were analysed using a Bayesian clustering algorithm to search for admixture between populations and to infer population structure.In order to illustrate a decision on the most likely parameter K, in figure 1, we presented ln Pr(G|K) values for all runs.Over the all 122 monitored individuals, ln Pr(G|K) increased from K = 1 to K = 3, after which it balanced.It was assumed that the most likely K is that where ln Pr(G|K) is maximised as noted by Druml et al. (2007).Results from analysis of admixture considering a range from 1 through 5 potential clusters pointed out that the greatest average likelihood value with the smallest variance among replicates was obtained for K = 3. Similarly the genotyping data have been used by Mastrangelo et al. (2014) for analysis of population structure.They found that whole population observed was divided into the 4 separately clusters with connection of 136 breeds.The optimal number of K was caused by different number of investigated cattle populations compared to the present study.
Regardless of the correct outcome of the study was the attention focused on K = 2, assuming affiliation individual breeds into one of the production type groups.Historically, investigated populations were used in formation of Slovak Pinzgau breed, particularly in order  to improve its performance.Pinzgau cattle are divided into two separate populations.The first is represented by dual-purpose type and the second by suckler cows (beef ).According the observation all populations have been taken into account, assuming correct classification into one of the populations.A quantification of how likely each breed and each individual belong to specific group is given in figure 2 and figure 3, respectively.Generally, in table 2, studied breeds created Holstein (classification to cluster 2 = 99.9%) and Simmental (classification to cluster 1 = 99.7%)population.Holstein and Ayrshire are assumed as dairy breeds and others as dual-purpose confirming high ratio of breeds 2, 3 and 5 in cluster 1.Although Ayrshire is originally breed with high milk production, it was separated to the Simmental group, probably caused by its origin in native breeds with small body frame, bad feed utilization and low milk production.Surprisingly, Slovak Pinzgau is more similar to Holstein (milk production) than to Simmental (dualpurpose) despite the fact that primary Pinzgau belongs to dual-purpose or even beef type.Based on genetic insight into Slovak Pinzgau population systematic selection due to increasing of milk production is evident.A similar study was performed by Edea et al. (2013), who successfully distinguished between highland agroecology and lowland cattle breeds.Further Grasso et al. (2014) andPerez O'Brien et al. (2015) have demonstrated the assignment of individual groups based on their genetic similarities, thereby providing information about the number of ancestral population underlying the observed genetic diversity.

Figure 1 2 Figure 3
Figure 1 Ln Pr(G|K) values presented as a function of the number of clusters.The largest ln Pr(G|K) values within each K (among 10 runs) are presented with circles.In the right sight there are the values of all runs for K = 2

Table 1
List of 122 animals used in the study

Table 2
Proportion of membership of each predefined population in one of the 2 clusters However, the level of admixture is visible just from two separate clusters.Pedigree data present monitored Slovak Pinzgau bulls as 100% purebred, though the historical formation of the breed should be taken into account.Similarity of populations with common history is clear.The results were controversial because Ayrshire as a dairy breed has been assigned to the Simmental group.All animals in that group are known as a Red and White spotted cattle what may denote the historical point explaining the structurness of observed populations.Surprisingly, according to our results Slovak Pinzgau is closer to Holstein (dairy cattle) than to Simmental (dualpurpose cattle) what could be caused by significant "holsteinization" in recent years.Confirming to other studies genetic data are suitable tool for distinction of local breeds of cattle.Detailed character of population structure is a subject of further investigation.It will be focused on finding admixture of populations with exact ratio of each population that contributed to origin of Slovak Pinzgau cattle.This should provide a basis for preservation of the breed in the original phenotype favoured by the current selection schemes and breeding programmes.
The average value of ln Pr(G|K) increased up to K = 3 and balanced afterwards, assuming 3 clusters as the most suitable division of evaluated populations.