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Some health disorders, such as obesity and type 2 diabetes, are associated with a poor diet and low quality of the fat in it. The type and duration of the diet have an impact on the liver. This investigation uses the proteomic approach to identify changes in the mouse liver protein profile in adaptation to high-fat diets with different saturated fatty acid contents and linoleic acid (18:2n-6) to α-linolenic acid (18:3n-3) fatty acid ratios.

In dairy cattle, oxidative stress is a predominant problem associated with diseases and reproductive health issues. This study aimed to detect the variation in the antioxidant biomarkers by adding different concentrations of β-hydroxybutyric acid (BHBA) and sought to elucidate its effects on the gene expression levels of growth hormone (GH) and antioxidant biomarkers in bovine hepatocytes.

Aims: The current review aims to outline and summarize the latest research on aflatoxin, with research studies describing natural, herbal and chemical compound applications in animal (pig) models and in vitro cellular studies. Aflatoxin, a carcinogenic toxin metabolite, is produced by Aspergillus flavus in humid environments, posing a threat to human health and crop production. The current treatment involves the prevention of exposure to aflatoxin and counteracting its harmful toxic effects, enabling survival and research studies on an antidote for aflatoxin., Objectives: To summarize current research prospects and to outline the influence of aflatoxin on animal forage in farm production, food and crop processing. The research application of remedies to treat aflatoxin is undergoing development to pinpoint biochemical pathways responsible for aflatoxin effects transmission and actions of treatment., Significance: To underline the environmental stress of aflatoxin on meat and dairy products; to describe clinical syndromes associated with aflatoxicosis on human health that are counteracted with proposed treatment and preventive interventions. To understand how to improve the health of farm animals with feed conditions.

The effect of dietary supplementation with sodium butyrate, β-glucan and vitamins (A, D3, E, K, C) on breeding indicators and immune parameters of juvenile African catfish was examined. The fish were fed with unenriched (group C) and enriched feed with a variable proportion of sodium butyrate/β-glucan, and constant content of vitamins (W1-W3). After the experiment, blood and the middle gut were collected. The microbiome of the gut was determined using Next Generation Sequencing (NGS). Liver tissue was collected for determination of expression of immune-related genes (HSP70, IL-1β, TNFα). W2 and W3 were characterized by the most favorable values of breeding indicators ( p < 0.05). The highest blood cortisol concentration was in group C (71.25 ± 10.45 ng/mL), and significantly the lowest in W1 (46.03 ± 7.01 ng/ mL) ( p < 0.05). The dominance of Cetobacterium was observed in all study groups, with the largest share in W3 (65.25%) and W1 (61.44%). Gene expression showed an increased number of HSP70 genes in W1. IL-1β and TNFα genes peaked at W3. The W3 variant turns out to be the most beneficial supplementation, due to the improvement of breeding and immunological parameters. The data obtained can be used to create a preparation for commercial use in the breeding of this species.

The dietary recommendation encourages reducing saturated fatty acids (SFA) in diet and replacing them with polyunsaturated fatty acids (PUFAs) n-3 (omega-3) and n-6 (omega-6) to decrease the risk of metabolic disturbances. Consequently, excessive n-6 PUFAs content and high n-6/n-3 ratio are found in Western-type diet. The importance of a dietary n-6/n-3 ratio to prevent chronic diseases is linked with anti-inflammatory functions of linolenic acid (ALA, 18:3n-3) and longer-chain n-3 PUFAs. Thus, this review provides an overview of the role of oxylipins derived from n-3 PUFAs and oxylipins formed from n-6 PUFAs on inflammation. Evidence of PUFAs' role in carcinogenesis was also discussed. In vitro studies, animal cancer models and epidemiological studies demonstrate that these two PUFA groups have different effects on the cell growth, proliferation and progression of neoplastic lesions.

During the early stages of pregnancy, the uterine endometrium undergoes dramatic morphologic and functional changes accompanied with dynamic variation in gene expression. Pregnancy-stage specific differentially expressed gene (DEG)-transcript-probes were investigated and identified by comparing endometrium transcriptome at 9th day (9D), 12th day (12D) and 16th day (16D) of early pregnancy in Polish large-white (PLW) gilts. Endometrium comparisons between 9D-vs-12D, 9D-vs-16D and 12D-vs-16D of early pregnancy identified 6049, 374 and 6034 highly significant DEG-transcript-probes ( p < 0.001; >2 FC). GO term enrichment analysis identified commonly shared upregulated endometrial DEG-transcript-probes ( p < 0.001; >2 FC), that were regulating the gene functions of anatomic structure development and transport ( TG ), DNA-binding and methyltransferase activity ( ZBTB2 ), ion-binding and kinase activity ( CKM ), cell proliferation and apoptosis activity ( IL1B) . Downregulated DEG-transcript-probes ( p < 0.001; >2 FC) were involved in regulating the gene functions of phosphatase activity ( PTPN11), TC616413 gene-transcript and Sus-scrofa LOC100525539. Moreover, blastn comparison of microarray-probes sequences against sus-scrofa11 assembly identified commonly shared upregulated endometrial DEG-transcript-probes (E < 0.06; >2 FC), that were regulating the gene functions of reproduction and growth ( SELENOP ), cytoskeleton organization and kinase activity ( CDC42BPA ), phosphatase activity ( MINPP1 ), enzyme-binding and cell-population proliferation (VAV3), cancer-susceptibility candidate gene ( CASC4 ), cytoskeletal protein-binding ( COBLL1 ), ion-binding, enzyme regulator activity ( ACAP2 ) Downregulated endometrial DEG-transcript-probes (E < 0.06; >2FC) were involved in regulating the gene functions of signal-transduction ( TMEM33), catabolic and metabolic processes ( KLHL15) . Microarray validation experiment on selected candidate genes showed complementarity to significant endometrial DEG-transcript-probes responsible for the regulation of immune response ( IL1B, S100A11 ), lipid metabolism ( FABP3, PPARG ), cell-adhesion ( ITGAV ), angiogenesis ( IL1B ), intercellular transmission ( NMB ), cell-adhesion ( OPN ) and response to stimuli ( RBP4 ) was confirmed by RT-PCR. This study provides a clue that identified pregnancy-stage specific microarray transcript probes could be considered as candidate genes for recognition and establishment of early pregnancy in the pig.

Global gene expression in liver transcriptome varies among cattle breeds. The present investigation was aimed to identify the differentially expressed genes (DEGs), metabolic gene networks and metabolic pathways in bovine liver transcriptome of young bulls. In this study, we comparatively analyzed the bovine liver transcriptome of dairy (Polish Holstein Friesian (HF); n = 6), beef (Hereford; n = 6), and dual purpose (Polish-Red; n = 6) cattle breeds. This study identified 895, 338, and 571 significant ( p < 0.01) differentially expressed (DE) gene-transcripts represented as 745, 265, and 498 hepatic DE genes through the Polish-Red versus Hereford, Polish-HF versus Hereford, and Polish-HF versus Polish-Red breeds comparisons, respectively. By combining all breeds comparisons, 75 hepatic DE genes ( p < 0.01) were identified as commonly shared among all the three breed comparisons; 70, 160, and 38 hepatic DE genes were commonly shared between the following comparisons: (i) Polish-Red versus Hereford and Polish-HF versus Hereford; (ii) Polish-Red versus Hereford and Polish-HF versus Polish-Red; and (iii) Polish-HF versus Hereford and Polish-HF versus Polish-Red, respectively. A total of 440, 82, and 225 hepatic DE genes were uniquely observed for the Polish-Red versus Hereford, Polish-HF versus Hereford, and Polish-Red versus Polish-HF comparisons, respectively. Gene ontology (GO) analysis identified top-ranked enriched GO terms ( p < 0.01) including 17, 16, and 31 functional groups and 151, 61, and 140 gene functions that were DE in all three breed liver transcriptome comparisons. Gene network analysis identified several potential metabolic pathways involved in glutamine family amino-acid, triglyceride synthesis, gluconeogenesis, p38MAPK cascade regulation, cholesterol biosynthesis (Polish-Red versus Hereford); IGF-receptor signaling, catecholamine transport, lipoprotein lipase, tyrosine kinase binding receptor (Polish-HF versus Hereford), and PGF-receptor binding, (Polish-HF versus Polish-Red). Validation results showed that the relative expression values were consistent to those obtained by RNA-seq, and significantly correlated between the quantitative reverse transcription PCR (RT-qPCR) and RNA-seq (Pearson's r  > 0.90). Our results provide new insights on bovine liver gene expressions among dairy versus dual versus beef breeds by identifying the large numbers of DEGs markers submitted to NCBI gene expression omnibus (GEO) accession number GSE114233, which can serve as useful genetic tools to develop the gene assays for trait-associated studies as well as, to effectively implement in genomics selection (GS) cattle breeding programs in Poland.

Background: RNA-seq is a useful next-generation sequencing (NGS) technology that has been widely used to understand mammalian transcriptome architecture and function. In this study, a breed-specific RNA-seq experiment was utilized to detect putative single nucleotide polymorphisms (SNPs) in liver tissue of young bulls of the Polish Red, Polish Holstein-Friesian (HF) and Hereford breeds, and to understand the genomic variation in the three cattle breeds that may reflect differences in production traits., Results: The RNA-seq experiment on bovine liver produced 107,114,4072 raw paired-end reads, with an average of approximately 60 million paired-end reads per library. Breed-wise, a total of 345.06, 290.04 and 436.03 million paired-end reads were obtained from the Polish Red, Polish HF, and Hereford breeds, respectively. Burrows-Wheeler Aligner (BWA) read alignments showed that 81.35%, 82.81% and 84.21% of the mapped sequencing reads were properly paired to the Polish Red, Polish HF, and Hereford breeds, respectively. This study identified 5,641,401 SNPs and insertion and deletion (indel) positions expressed in the bovine liver with an average of 313,411 SNPs and indel per young bull. Following the removal of the indel mutations, a total of 195,3804, 152,7120 and 205,3184 raw SNPs expressed in bovine liver were identified for the Polish Red, Polish HF, and Hereford breeds, respectively. Breed-wise, three highly reliable breed-specific SNP-databases (SNP-dbs) with 31,562, 24,945 and 28,194 SNP records were constructed for the Polish Red, Polish HF, and Hereford breeds, respectively. Using a combination of stringent parameters of a minimum depth of ≥10 mapping reads that support the polymorphic nucleotide base and 100% SNP ratio, 4,368, 3,780 and 3,800 SNP records were detected in the Polish Red, Polish HF, and Hereford breeds, respectively. The SNP detections using RNA-seq data were successfully validated by kompetitive allele-specific PCR (KASPTM) SNP genotyping assay. The comprehensive QTL/CG analysis of 110 QTL/CG with RNA-seq data identified 20 monomorphic SNP hit loci (CARTPT, GAD1, GDF5, GHRH, GHRL, GRB10, IGFBPL1, IGFL1, LEP, LHX4, MC4R, MSTN, NKAIN1, PLAG1, POU1F1, SDR16C5, SH2B2, TOX, UCP3 and WNT10B) in all three cattle breeds. However, six SNP loci (CCSER1, GHR, KCNIP4, MTSS1, EGFR and NSMCE2) were identified as highly polymorphic among the cattle breeds., Conclusions: This study identified breed-specific SNPs with greater SNP ratio and excellent mapping coverage, as well as monomorphic and highly polymorphic putative SNP loci within QTL/CGs of bovine liver tissue. A breed-specific SNP-db constructed for bovine liver yielded nearly six million SNPs. In addition, a KASPTM SNP genotyping assay, as a reliable cost-effective method, successfully validated the breed-specific putative SNPs originating from the RNA-seq experiments.

Examination of bovine pituitary gland transcriptome by strand-specific RNA-seq allows detection of putative single nucleotide polymorphisms (SNPs) within potential candidate genes (CGs) or QTLs regions as well as to understand the genomics variations that contribute to economic trait. Here we report a breed-specific model to successfully perform the detection of SNPs in the pituitary gland of young growing bulls representing Polish Holstein-Friesian (HF), Polish Red, and Hereford breeds at three developmental ages viz., six months, nine months, and twelve months. A total of 18 bovine pituitary gland polyA transcriptome libraries were prepared and sequenced using the Illumina NextSeq 500 platform. Sequenced FastQ databases of all 18 young bulls were submitted to NCBI-SRA database with NCBI-SRA accession numbers SRS1296732. For the investigated young bulls, a total of 113,882,3098 raw paired-end reads with a length of 156 bases were obtained, resulting in an approximately 63 million paired-end reads per library. Breed-wise, a total of 515.38, 215.39, and 408.04 million paired-end reads were obtained for Polish HF, Polish Red, and Hereford breeds, respectively. Burrows-Wheeler Aligner (BWA) read alignments showed 93.04%, 94.39%, and 83.46% of the mapped sequencing reads were properly paired to the Polish HF, Polish Red, and Hereford breeds, respectively. Constructed breed-specific SNP-db of three cattle breeds yielded at 13,775,885 SNPs. On an average 765,326 breed-specific SNPs per young bull were identified. Using two stringent filtering parameters, i.e., a minimum 10 SNP reads per base with an accuracy ≥ 90% and a minimum 10 SNP reads per base with an accuracy = 100%, SNP-db records were trimmed to construct a highly reliable SNP-db. This resulted in a reduction of 95,7% and 96,4% cut-off mark of constructed raw SNP-db. Finally, SNP discoveries using RNA-Seq data were validated by KASP™ SNP genotyping assay. The comprehensive QTLs/CGs analysis of 76 QTLs/CGs with RNA-seq data identified KCNIP4, CCSER1, DPP6, MAP3K5 and GHR CGs with highest SNPs hit loci in all three breeds and developmental ages. However, CAST CG with more than 100 SNPs hits were observed only in Polish HF and Hereford breeds.These findings are important for identification and construction of novel tissue specific SNP-db and breed specific SNP-db dataset by screening of putative SNPs according to QTL db and candidate genes for bovine growth and reproduction traits, one can develop genomic selection strategies for growth and reproductive traits., Competing Interests: The authors have declared that no competing interests exist.

The carcasses of yellow-fat rabbits may be attractive to modern consumers, because they have a relatively high content of biologically active compounds. One of the main candidate genes associated with the yellow-fat trait is β-carotene 9',10'-oxygenase (BCO2). This study is the first report of the novel AAT-deletion mutation at codon 248 of the BCO2 gene, which has been found in homozygous yellow-fat rabbits. The deletion mutation, located at the beginning of exon 6, results in the absence of asparagine in protein. We also developed a PCR-RFLP test that supports intravital genotyping of indel polymorphism based on genomic DNA.

Allele and haplotype segregation at the polymorphic sites within the promoter (23indel) and intron 1 (12indel) regions of the PRNP gene was analyzed in Polish Holstein-Friesian cattle. More 23del/del homozygotes and fewer 23ins/ins homozygotes than expected were observed in the offspring of ♂ 23ins/del × ♀ 23ins/del parents. In the offspring of ♂ 23ins/del × ♀ 23del/del parents and ♂ 23del/del × ♀ 23ins/del parents, a trend toward more 23del/del animals and fewer 23ins/del animals than expected was noted. At the 12indel polymorphic site, the only trend found was one toward fewer 12ins/ins genotypes and more 12ins/del and 12del/del genotypes than expected in the offspring of ♂ 12ins/del × ♀ 12ins/del parents. An analysis of haplotype segregation revealed more 23del-12del/23del-12del diplotypes and fewer 23ins-12ins/23ins-12ins diplotypes at the significance threshold than expected in the offspring of ♂ 23ins-12ins/23del-12del × ♀ 23ins-12ins/23del-12del parents.

Recent attempts to discover genetic factors affecting cattle resistance/susceptibility to bovine spongiform encephalopathy (BSE) have led to the identification of two insertion/deletion (indel) polymorphisms, located within the promoter and intron 1 of the prion protein gene PRNP, showing a significant association with the occurrence of classical form of the disease. Because the effect of the polymorphisms was studied only in few populations, in this study we investigated whether previously described association of PRNP indel polymorphisms with BSE susceptibility in cattle is also present in Polish cattle population. We found a significant relation between the investigated PRNP indel polymorphisms (23 and 12 bp indels), and susceptibility of Polish Holstein-Friesian cattle to classical BSE (P < 0.05). The deletion variants of both polymorphisms were related to increased susceptibility, whereas insertion variants were protective against BSE.

The allele, genotype, and haplotype frequencies among 837 Polish Holstein-Friesian cattle were determined at two regulatory indel polymorphisms of the PRNP gene. Allele frequencies at the 23 bp indel promoter polymorphism were 0.622 (del) and 0.378 (ins), with 0.613 and 0.387 in sires and 0.633 and 0.366 in dams. Allele frequencies at the 12 bp indel intron polymorphism were 0.527 (del) and 0.473 (ins), with 0.529 and 0.471 in sires and 0.543 and 0.456 in dams. Four haplotypes were identified in this population (23-12del, 23-12ins, 23del-12ins, and 23ins-12del). Haplotype 23-12del occurred most frequently in both sire and dam groups. Comparative analysis of Polish Holstein-Friesian and German Holstein populations revealed a similar genetic structure for the 23 bp indel polymorphism and a significantly different one for the 12 bp indel polymorphism. In allele and haplotype analysis, significant differences were observed between the Polish Holstein-Friesian population and a BSE-free German Holstein population.

The polymorphic loci of the bovine prion protein (PRNP) gene, comprising 23-bp insertion/deletion (23-bp indel) within the promoter sequence and 12-bp insertion/deletion (12-bp indel) within the intron 1 sequence, are located in regions which play a key role in gene expression. The objective of this study was to determine whether the 23-bp and 12-bp insertion/deletion polymorphism within the PRNP gene leads to significant differences in the blood lymphocyte profile and to investigate changes in the composition of these cells in cattle naturally infected with Bovine Leukemia Virus. An analysis of the effect of the bovine PRNP gene polymorphism on the blood lymphocyte profile revealed considerable differences between animals with the 23-bp indel genotypes, and small and statistically non-significant differences between those with the 12-bp indel genotypes. 23-bp del/del homozygotes had a significantly lower percentage of T lymphocytes with the phenotypes CD2 (P < 0.01), CD8 (P < 0.01) and WC1-N2 (P < 0.05), and a higher ratio of CD4 to CD8 T lymphocytes, compared to animals with the 23-bp ins/ins genotype. The obtained results indicate that the 23-bp indel polymorphism, in contrast to the 12-bp indel polymorphism, has a significant effect on changes in the blood lymphocyte profile. The size of blood lymphocyte subpopulations was also found to change under the influence of enzootic bovine leukosis. The direction of those changes in EBL-positive animals is consistent with that observed in 23-bp del/del homozygotes, which may testify to the adverse effect of this genotype on immunological efficiency.

The aim of the present study was to identify deletion/insertion polymorphism of the bovine prion protein (PRNP) gene within the promoter sequence (23 bp indel), intron 1 (12 bp indel) and the 3' end untranslated region (14 bp indel). The experiment was performed on three groups of animals protected under a genetic resources conservation program: 139 Polish Red (PR) cows, 79 Polish White-backed cows and 50 European bison (Bison bonasus L., 1758). White-backed cattle were characterized by a higher frequency of ins/del heterozygotes and a relatively lower frequency of ins/ins homozygotes within the promoter sequence region (23 bp indel), compared to Polish Red cattle. At the polymorphic locus of intron 1 (12 bp indel) the genetic structure of both cattle populations was similar. Monomorphism, expressed by the occurrence of one genotype variant in each of the analyzed sequence regions, was observed in European bison. Five haplotypes were found in Polish White-backed cows, four haplotypes in Polish Red cows and only one in analyzed group of bison. Differences between the observed and expected number of PRNP haplotypes were recorded in Polish Red cattle.

The aim of the present study was to identify the deletion/insertion polymorphism of the bovine prion protein gene (PRNP) within the promoter sequence (23 bp), intron 1 (12 bp) and 3' untranslated region (14 bp). DNA was isolated from blood of 234 randomly tested Polish Holstein-Friesian cows and from semen of 47 sires used for artificial insemination (AI) in 2004. No statistically significant differences were found in the frequency of genotypes and alleles between cows and breeding bulls in the 3 analysed polymorphic sites within the PRNP gene. Only 3 haplotypes were identified in sires and 4 haplotypes in cows.

The molecular basis of BLAD is the D128G mutation of the gene coding for the CD18 subunit of beta-2 integrin. This mutation is lethal, since homozygous (BL/BL) animals die before they reach sexual maturity. In the 1990s, BLAD was the most widespread genetic disease in HF cattle worldwide. The aim of the present study was to determine the frequency of BLAD carriers among 4645 young breeding bulls in Poland in 1995-2006. The frequency of carriers of the mutated allele showed a clear decreasing trend. The highest frequency (7.9%) was recorded while implementing the BLAD control program (1995-1997). Regular monitoring has enabled a great reduction of this threat to the tested population. Today only sporadic cases of BL/TL heterozygotes are reported (ca. 0.8% in 2004-2006).

The diacylglycerol o-acyltransferase 1 gene (DGAT1) was investigated in Polish Black-and-White cattle. The frequency of the K allele was 0.60, 0.68 and 0.48 for AI sires (n=150), young bulls (n=139) and cows (n=213), respectively. The method of selective genotyping for identification of the quantitative trait nucleotide was verified through identification of DGAT1 effect on milk production traits. Daughters of six heterozygous bulls were selectively genotyped based on their milk traits. The genotypic frequencies differed between high and low yield groups representing milk and fat contents. The Kruskal-Wallis test revealed a highly significant effect of DGAT1 K232A in cows with extremely low fat content and a significant effect in cows with extremely high protein content of milk. No significant effect of AI sires' genotypes on their breeding value was found.

We report on a PCR-RFLP procedure for recognising of a silent point mutation of ITGB2 CD18 subunit gene in cattle. Polymorphism screening was performed in a Polish Black-and-White cattle population (n=210). The genotype and allele frequencies were established in the sires and cows. Further research is needed to explain the possible applications of the CD18 silent point mutation as a potential molecular marker for high milk productivity.

The study was conducted on full-families of Black-and-White cattle obtained as 25 AI sire families and 355 cows, as well as their progenies, mostly heifers at the age of 1-3 months. The sire group was composed by the casual qualification of 10 PRNP 6/6 and 15 PRNP 6/5 individuals on the basis of accessible young progenies. The randomly selected group of cows is characterised by a very high frequency of PRNP 6/6 (74.9%), followed by lower frequency of PRNP 6/5 (24.5%) and a very low frequency of PRNP 5/5 genotype (0.6%). The progenies represent all expected genotypes, such as: PRNP 6/6 (60.5%), PRNP 6/5 (35.8%) and PRNP 5/5 (3.7%), respectively. Taking into consideration the genotypes of parents and progenies, the segregation of PRNP 6 and PRNP 5 alleles was analysed. Results of the non-informative mating variant of male symbol PRNP 6/6 x female symbol PRNP 6/6 (n = 87) are affected by the PRNP 6/6 progeny genotype in all cases. Subsequently, the results of mating variants male symbol PRNP 6/6 x female symbol PRNP 6/5 (n = 29) and male symbol PRNP 6/5 female symbol PRNP 6/6 (n = 179) showed statistically non-significant differences in both above-mentioned alternations. The progeny group related from male symbol PRNP 6/5 x female symbol PRNP 6/5 parental mating obtained fully informative and most valuable results based on the presented research concept. In the common group of 58 calves, the genotype PRNP 6/6 is represented by 26 individuals (44.8%), PRNP 6/5 - by 19 individuals (32.8%) and PRNP 5/5 - by 13 individuals (22.4%). Therefore, the theoretical genotype rate (25% : 50% : 25%) is drastically deformed and the differentiation between the observed and expected numbers of animals is statistically highly significant (chi(2) = 12.72; 2 df.). These differences are affected by two times higher PRNP 6/6 homozygous (chi(2) = 9.12; 1 df.) and responsively by the low number of PRNP 6/5 heterozygous animals (chi(2) = 3.45; 1 df.). Further investigations are carried out to explain the genetic determination of abnormal PRNP octa-peptide repeat allele segregation, which suggests possible lethal cis-trans linkage effects.

The study was carried out in a Polish Black-and-White cattle population, represented by 167 AI sires, 200 young tested bulls, 190 bull-dams, and 606 randomly chosen cows from commercial herds. The fragment of the bovine prion protein gene (PRNP) coding the octapeptide-repeat sequence, was identified by PCR analysis. Two different gene variants of 349 bp and 373 bp in size, produced three genotypes: PRNP 6/6, PRNP 6/5 and PRNP 5/5, respectively. Allele frequency in all examined populations, on average 0.894 for PRNP 6 and 0.106 for PRNP 5, shows a significant difference between the group of cows from commercial herds, characterised by high frequency of PRNP 5 (q = 0.137) in comparison to AI sires (q = 0.077), young tested bulls (q = 0.052) and bull-dams (q = 0.084). Moreover, both analysed female groups of bull-dams and cows from commercial herds are distinguished by the presence of PRNP 5/5 homozygous animals, which were not recorded in the AI sires and young tested bulls, and had never been recognised in earlier examined Holstein-Friesian populations. Analysis of the genetic equilibrium indicates a very high conformity between observed and expected number of animals in the separate PRNP genotype groups. However, some tendency of difference is observed in highly selected cows, qualified as bull-dams on the basis of very high level of milk performance traits.

A herd of cows of the same age, kept in a stable system under controlled environmental conditions, was used to estimate the repeatability of diagnostic blood and milk indices in several stages of the I, II and III lactation. Attention was paid to genetic and non-genetic sources of phenotypic variation. Statistically significant values of the regression coefficient were found for the following milk parameters: fat and protein content, milk density, calcium, potassium and lysozyme levels, as well as the following blood parameters: leucocytes' number, lymphocytes and neutrophils number, uric acid content, leucocytes acid phosphatase activity, lysozyme and blood serum alkaline phosphatase activity. Examined indices were analysed which proved to be suitable for prognostic and breeding application.