Genealogical Analysis of a Closed Herd of Black Hairless Iberian Pigs

Evaluation of β-Actin and Mitochondrial DNA Levels in Determining the Age of Suidae Remains

African Swine Fever (ASF) is an infectious disease affecting pigs and wild boars, causing significant economic losses. Epidemiological surveillance plays an important role in minimizing its impact. The aim of this study was to evaluate the usefulness of β-actin DNA and mitochondrial DNA (mtDNA) levels in determining the age of animal remains from the Suidae family, which could be helpful in epidemiological investigations. The study included selected tissues and internal organs of Sus scrofa domesticus, exposed to natural environmental conditions or kept in stable 4 °C conditions, to assess the levels of β-actin and mtDNA over a period of 18 months. The levels of both tested parameters exhibited the expected decreasing trend over time. However, in most tissues, some discrepancies from this general pattern were observed. The results obtained for bone marrow showed a consistent downward trend and a strong correlation between mtDNA and β-actin, with long-term detectability (up to the 13th month of the study). Therefore, bone marrow could be considered a matrix of choice for age assessment. However, due to various influencing factors, further studies are required.

Pedigree analysis in the mhorr gazelle (Nanger dama mhorr): Genetic variability evolution of the captive population

Breeding programs have an essential role in the recovery of threatened populations through optimal genetic management and mating strategies. The dama gazelle (Nanger dama) is a North African ungulate listed as critically endangered. The mhorr subspecies is extinct in the wild and currently survives thanks to the creation in 1971 of an ex situ breeding program. The aim of the present study was to assess the evolution of genetic variability in this mhorr gazelle captive population, as well as the mating strategy used in two reference populations studied (Almeria and Europe). The entire pedigree, with 2739 animals, was analyzed to measure demographic characters, pedigree completeness level, probability of gene origin, level of relatedness and genetic structure of the population. The population size has been progressively increasing, with up to 264 individuals alive in Europe at the time of the study. The average number of equivalent complete generations was 5.55. The effective number of founders and ancestors was both 3, and the founder genome equivalent was 1.99. The genetic contributions of the four main ancestors were unbalanced. The average values of inbreeding and average relatedness for the whole pedigree were, respectively, 28.34% and 50.14%. The effective population size was 8.7 by individual increase in inbreeding and 9.8 by individual increase in coancestry. F-statistics evidenced a very small level of population subdivision (F ST = 0.033370). The mating strategy used, based on the minimum coancestry of the individuals, has minimized the losses of genetic variability and helped to balance the genetic contributions between ancestors. The strategy also avoided large subdivisions within the population and the appearance of new bottlenecks. This study shows how pedigree analysis can both be used to determine the genetic variability of the population and to assess the influence of the mating strategy used in the breeding program on such variability.

Assessment of the Genetic Diversity of a Local Pig Breed Using Pedigree and SNP Data

Herein, the genetic diversity of the local Přeštice Black-Pied pig breed was assessed by the simultaneous analysis of the pedigree and single nucleotide polymorphism (SNP) data. The information about sire line, dam, date of birth, sex, breeding line, and herd for 1971 individuals was considered in the pedigree analysis. The SNP analysis (n = 181) was performed using the Illumina PorcineSNP60 BeadChip kit. The quality of pedigree and SNPs and the inbreeding coefficients (F) and effective population size (Ne) were evaluated. The correlations between inbreeding based on the runs of homozygosity (FROH) and pedigree (FPED) were also calculated. The average FPED for all animals was 3.44%, while the FROH varied from 10.81% for a minimum size of 1 Mbp to 3.98% for a minimum size of 16 Mbp. The average minor allele frequency was 0.28 ± 0.11. The observed and expected within breed heterozygosities were 0.38 ± 0.13 and 0.37 ± 0.12, respectively. The Ne, obtained using both the data sources, reached values around 50 animals. Moderate correlation coefficients (0.49-0.54) were observed between FPED and FROH. It is necessary to make decisions that stabilize the inbreeding rate in the long-term using optimal contribution selection based on the available SNP data.

A Mix of Old British and Modern European Breeds: Genomic Prediction of Breed Composition of Smallholder Pigs in Uganda

Pig herds in Africa comprise genotypes ranging from local ecotypes to commercial breeds. Many animals are composites of these two types and the best levels of crossbreeding for particular production systems are largely unknown. These pigs are managed without structured breeding programs and inbreeding is potentially limiting. The objective of this study was to quantify ancestry contributions and inbreeding levels in a population of smallholder pigs in Uganda. The study was set in the districts of Hoima and Kamuli in Uganda and involved 422 pigs. Pig hair samples were taken from adult and growing pigs in the framework of a longitudinal study investigating productivity and profitability of smallholder pig production. The samples were genotyped using the porcine GeneSeek Genomic Profiler (GGP) 50K SNP Chip. The SNP data was analyzed to infer breed ancestry and autozygosity of the Uganda pigs. The results showed that exotic breeds (modern European and old British) contributed an average of 22.8% with a range of 2-50% while "local" blood contributed 69.2% (36.9-95.2%) to the ancestry of the pigs. Runs of homozygosity (ROH) greater than 2 megabase (Mb) quantified the average genomic inbreeding coefficient of the pigs as 0.043. The scarcity of long ROH indicated low recent inbreeding. We conclude that the genomic background of the pig population in the study is a mix of old British and modern pig ancestries. Best levels of admixture for smallholder pigs are yet to be determined, by linking genotypes and phenotypic records.

Mitochondrial DNA Diversity in Large White Pigs in Russia

The Large White pig is the most commonly raised commercial pig breed in the world. The aim of this work was to investigate D-loop mtDNA in Large White pigs (n = 402) of various selections bred in the Russian Federation from 2000 to 2019. The general sample consisted of three groups: Old (n = 78) (Russian selection, 2000-2010); Imp (n = 123) (imported to Russia in 2008-2014); New (n = 201) (2015-2019). The synthesized score (Fz) was calculated by analyzing the main PCA (principal component analysis components). An affiliation to Asian or European haplogroups was determined according to the NCBI (National Center for Biotechnology Information). In the study, we defined 46 polymorphic sites and 42 haplotypes. Significant distinctions between groups Old, Imp and New in frequencies of haplotypes and haplogroups were established. The distribution of Asian and European haplotypes in the groups was Old: 50%/50%, Imp: 43%/57%, New: 75%/25%, respectively. The variety of haplotypes and haplogroups in the pigs of the group New is related to the farms in which they breed. Haplotype frequencies significantly differ between the clusters Old_Center, Old_Siberia and Old_South. This study will provide information on the genetic diversity of Large White breed pigs. The results will be useful for the conservation and sustainable use of these resources.

The domestication event of the Tibetan pig revealed to be in the upstream region of the Yellow River based on the mtDNA D-loop

OBJECTIVE

Evidence from previous reports indicates that pig domestication in East Asia mainly occurred in the Mekong region and the middle and downstream regions of the Yangtze River. Further research identified two new origin centers for domestic pigs in the Tibetan Plateau and the islands of Southeast Asia. However, due to the small sample size of Tibetan pigs, details of the origin and spread of Tibetan pigs has not yet been established.

METHODS

We analyzed mitochondrial DNA control region (D-loop) variation in 1,201 individuals from nine Tibetan pig populations across five provinces. Comprehensive Tibetan pig samples were taken to perform the most detailed analysis of Tibetan pigs to date.

RESULTS

The result indicate that Rkaze pigs had the lowest level of diversity, while Changdu pigs had the highest diversity. Interestingly, these two populations were both in the Tibetan Plateau area. If we calculate diversity in terms of each province, the Tibetan Plateau area had the lowest diversity, while the Chinese province of Gansu had the highest diversity. Diversity gradient analysis of major haplotypes suggested three domestication centers of Tibetan pigs in the Tibetan Plateau and the Chinese provinces of Gansu and Yunnan.

CONCLUSION

We found two new domestication centers for Tibetan pigs. One is in the Chinese province of Gansu, which lies in the upstream region of the Yellow River, and the other is in the Chinese province of Yunnan.

Genomic Analysis Reveals Specific Patterns of Homozygosity and Heterozygosity in Inbred Pigs

The inbred strain of miniature pig is an ideal model for biomedical research due to its high level of homozygosity. In this study, we investigated genetic diversity, relatedness, homozygosity, and heterozygosity using the Porcine SNP60K BeadChip in both inbred and non-inbred Wuzhishan pigs (WZSPs). Our results from multidimensional scaling, admixture, and phylogenetic analyses indicated that the inbred WZSP, with its unique genetic properties, can be utilized as a novel genetic resource for pig genome studies. Inbreeding depression and run of homozygosity (ROH) analyses revealed an average of 61 and 12 ROH regions in the inbred and non-inbred genomes of WZSPs, respectively. By investigating ROH number, length, and distribution across generations, we further briefly studied the impacts of recombination and demography on ROH in these WZSPs. Finally, we explored the SNPs with higher heterozygosity across generations and their potential functional implications in the inbred WZSP. We detected 56 SNPs showing constant heterozygosity with He = 1 across six generations in inbred pigs, while only one was found in the non-inbred population. Among these SNPs, we observed nine SNPs located in swine RefSeq genes, which were found to be involved in signaling and immune processes. Together, our findings indicate that the inbred-specific pattern of homozygosity and heterozygosity in inbred pigs can offer valuable insights for elucidating the mechanisms of inbreeding in farm animals.

Assessing effective population size, coancestry and inbreeding effects on litter size using the pedigree and SNP data in closed lines of the Iberian pig breed

The complete pedigree of two closed Iberian pig lines (Gamito and Torbiscal), with 798 and 4077 reproducers, has been used to measure the evolution of coancestry (f) and inbreeding (F) for autosomal and X-linked genes along 16 and 28 respective equivalent discrete generations. At the last generation, the mean values of each line were f = 0.41 and 0.22, F = 0.35 and 0.18, fX  = 0.46 and 0.22 and FX  = 0.47 and 0.19, respectively. Other calculated parameters were the effective number of founders (final values, 6.8 and 35.2) and non-founders (1.5 and 2.4), founder genome equivalents (1.2 and 2.3) and effective population size (16.0 and 57.7). Measures of Torbiscal effective size based on rates of coancestry (66.1), inbreeding (65.0) and linkage disequilibrium (71.0) were estimated from whole-genome SNP genotyping data. Values of new and old inbreeding and their respective rates by generation were computed to detect purging effects of natural selection. The analysis of 6854 Torbiscal litters showed significant negative impacts of new and fast inbreeding on litter size, as expected from the purging hypothesis: -0.20 born piglets per litter by a 10% of new inbreeding, and -0.03 and -0.02 piglets by 1% of total and new inbreeding rates, respectively. The analysis performed on 1274 litters of the Gamito line failed to show purging effects. The only significant results were reductions in -0.91 and -0.17 piglets by a 10% of old and X-linked genes inbreeding, respectively. These results may be useful for some practical issues in conservation programs of farm or captive wild animals.

Genome data from a sixteenth century pig illuminate modern breed relationships

Ancient DNA (aDNA) provides direct evidence of historical events that have modeled the genome of modern individuals. In livestock, resolving the differences between the effects of initial domestication and of subsequent modern breeding is not straight forward without aDNA data. Here, we have obtained shotgun genome sequence data from a sixteenth century pig from Northeastern Spain (Montsoriu castle), the ancient pig was obtained from an extremely well-preserved and diverse assemblage. In addition, we provide the sequence of three new modern genomes from an Iberian pig, Spanish wild boar and a Guatemalan Creole pig. Comparison with both mitochondrial and autosomal genome data shows that the ancient pig is closely related to extant Iberian pigs and to European wild boar. Although the ancient sample was clearly domestic, admixture with wild boar also occurred, according to the D-statistics. The close relationship between Iberian, European wild boar and the ancient pig confirms that Asian introgression in modern Iberian pigs has not existed or has been negligible. In contrast, the Guatemalan Creole pig clusters apart from the Iberian pig genome, likely due to introgression from international breeds.

Implementation of genetic evaluation and mating designs for the endangered local pig breed 'Bunte Bentheimer'

A pedigree including 1538 individuals of the endangered pig breed 'Bunte Bentheimer' and 3008 records of the fertility traits 'number of piglets born alive' (NBA) and 'number of piglets weaned' (NW) were used to i) characterize the population structure, ii) to estimate genetic (co)variance components and estimated breeding values (EBVs) and iii) to use EBVs for the application of the concept of optimal genetic contributions. The average coefficient of inbreeding increased from F = 0.103 to F = 0.121 within the two recent cohorts. Average rate of inbreeding amounted to 1.66%, which resulted in an effective population size of Ne  = 30 animals in the recent cohort. Average generation interval was 3.07 years considering the whole pedigree, and in total, only 612 sows and boars generated offspring. Estimated heritabilities for both traits NBA and NW were 0.12, and the estimated genetic correlation between both traits was 0.96. The variance component due to the service sire was higher than in commercial pig breeds, presumably due to the widespread use of natural service boars. The EBVs for NBA from 333 selection candidates (63 boars and 270 sows) were used to determine optimal genetic contributions. Based on selected animals and their optimal genetic contributions, specific mating designs were evaluated to minimize inbreeding in the next generation. Best results were achieved when using a simulated annealing algorithm and allowing artificial insemination.

Partial short-read sequencing of a highly inbred Iberian pig and genomics inference thereof

Despite dramatic reduction in sequencing costs with the advent of next generation sequencing technologies, obtaining a complete mammalian genome sequence at sufficient depth is still costly. An alternative is partial sequencing. Here, we have sequenced a reduced representation library of an Iberian sow from the Guadyerbas strain, a highly inbred strain that has been used in numerous QTL studies because of its extreme phenotypic characteristics. Using the Illumina Genome Analyzer II (San Diego, CA, USA), we resequenced ∼ 1% of the genome with average 4 × depth, identifying 68,778 polymorphisms. Of these, 55,457 were putative fixed differences with respect to the assembly, based on the genome of a Duroc pig, and 13,321 were heterozygous positions within Guadyerbas. Despite being highly inbred, the estimate of heterozygosity within Guadyerbas was ∼ 0.78 kb(-1) in autosomes, after correcting for low depth. Nucleotide variability was consistently higher at the telomeric regions than on the rest of the chromosome, likely a result of increased recombination rates. Further, variability was 50% lower in the X-chromosome than in autosomes, which may be explained by a recent bottleneck or by selection. We divided the whole genome in 500 kb windows and we analyzed overrepresented gene ontology terms in regions of low and high variability. Multi organism process, pigmentation and cell killing were overrepresented in high variability regions and metabolic process ontology, within low variability regions. Further, a genome wide Hudson-Kreitman-Aguadé test was carried out per window; overall, variability was in agreement with neutral expectations.

Selection in the making: a worldwide survey of haplotypic diversity around a causative mutation in porcine IGF2

Domestic species allow us to study dramatic evolutionary changes at an accelerated rate due to the effectiveness of modern breeding techniques and the availability of breeds that have undergone distinct selection pressures. We present a worldwide survey of haplotype variability around a known causative mutation in porcine gene IGF2, which increases lean content. We genotyped 34 SNPs spanning 27 kb in 237 domestic pigs and 162 wild boars. Although the selective process had wiped out variability for at least 27 kb in the haplotypes carrying the mutation, there was no indication of an overall reduction in genetic variability of international vs. European local breeds; there was also no evidence of a reduction in variability caused by domestication. The haplotype structure and a plot of Tajima's D against the frequency of the causative mutation across breeds suggested a temporal pattern, where each breed corresponded to a different selective stage. This was observed comparing the haplotype neighbor-joining (NJ) trees of breeds that have undergone increasing selection pressures for leanness, e.g., European local breeds vs. Pietrain. These results anticipate that comparing current domestic breeds will decisively help to recover the genetic history of domestication and contemporary selective processes.

Unexpected high polymorphism at the FABP4 gene unveils a complex history for pig populations

Fatty acid bing protein 4 (FABP4) plays a key role in fat regulation in mammals and is a strong positional candidate gene for the FAT1 quantitative trait locus located on porcine chromosome 4. DNA resequencing of the FABP4 gene region in 23 pigs from 10 breeds and wild boar revealed 134 variants in 6.4 kb, representing a silent nucleotide diversity of piS=0.01, much higher than reported so far in animal domestic species. Moreover, this diversity was highly structured. Also strikingly, the FABP4 phylogenetic tree did not show any geographical or breed origin clustering, with distant breeds sharing similar haplotypes and some of the most heterozygous samples pertaining to highly inbred animals like Iberian Guadyerbas (inbreeding coefficient approximately 0.3) or British Tamworth. In contrast, the cytochrome b (mtDNA) phylogenetic tree was coherent with geographical origin. The estimated age of the most recent common ancestor for the most divergent Iberian or Tamworth haplotypes was much older than domestication. An additional panel of 100 pigs from 8 different breeds and wild boar from Spain, Tunisia, Sardinia, and Japan was genotyped for seven selected single nucleotide polymorphisms and shows that high variability at the porcine FABP4 is the rule rather than the exception. Pig populations, even highly inbred, can maintain high levels of variability for surprisingly long periods of time.

Mitochondrial DNA sequence variation and phylogenetic relationships among Iberian pigs and other domestic and wild pig populations

Nucleotide sequences of mitochondrial DNA (mtDNA) cytochrome B gene (1140 bp) and control region (707 bp) were used to determine the phylogenetic relationships among 51 pig samples representing ancient and current varieties of Iberian pigs (26), Spanish wild boars (seven) and other domestic pigs (18) of cosmopolitan (Duroc, Large White, Landrace, Pietrain and Meishan) and local (Spotted Black Jabugo, Basque and Mangalitza) breeds. A neighbour-joining tree constructed from pairwise distances provide evidence of the European origin of both Iberian pigs and Spanish wild boars. The introgression of Asian mtDNA haplotypes in the genetic pool of the Iberian breed seems unlikely. Four estimates of sequence divergence between European and Asian clades were calculated from the two main domains of the D-loop region and the synonymous and nonsynonymous nucleotide substitutions in the cytochrome B gene. The time since the divergence of pig ancestors was estimated at about 600,000 years before present.