Genetic diversity and admixture of indigenous cattle from North Ethiopia: implications of historical introgressions in the gateway region to Africa

Genome-wide diversity and admixture of five indigenous cattle populations from the Tigray region of northern Ethiopia

The Tigray region, where we found around eight per cent of the indigenous cattle population of Ethiopia, is considered as the historic centre of the country, with the ancient pre-Aksumite and Aksumite civilisations in contact with the civilisations of the Fertile Crescent and the Indian subcontinent. Here, we used whole genome sequencing data to characterise the genomic diversity, relatedness, and admixture of five cattle populations (Abergelle, Arado, Begait, Erob, and Raya) indigenous to the Tigray region of Ethiopia. We detected 28 to 29 million SNPs and 2.7 to 2.9 million indels in each population, of which 7% of SNPs and 34% of indels were novel. Functional annotation of the variants showed around 0.01% SNPs and 0.22%-0.27% indels in coding regions. Enrichment analysis of genes overlapping missense private SNPs revealed 20 significant GO terms and KEGG pathways that were shared by or specific to breeds. They included important genes associated with morphology (SCN4A, TAS1R2 and KCNG4), milk yield (GABRG1), meat quality (MMRN2, VWC2), feed efficiency (PCDH8 and SLC26A3), immune response (LAMC1, PCDH18, CELSR1, TLR6 and ITGA5), heat resistance (NPFFR1 and HTR7) and genes belonging to the olfactory gene family, which may be related to adaptation to harsh environments. Tigray indigenous cattle are very diverse. Their genome-wide average nucleotide diversity ranged from 0.0035 to 0.0036. The number of heterozygous SNPs was about 0.6-0.7 times higher than homozygous ones. The within-breed average number of ROHs ranged from 777.82 to 1000.45, with the average sum of the length of ROHs ranging from 122.01 Mbp to 163.88 Mbp. The genomic inbreeding coefficients differed among animals and breeds, reaching up to 10% in some Begait and Raya animals. Tigray indigenous cattle shared a common ancestry with Asian indicine (85.6%-88.7%) and African taurine (11.3%-14.1%) cattle, with very small, if any, European taurine introgression. This study identified high within-breed genetic diversity representing an opportunity for breeding improvement programs and, also, significant novel variants that could increase the number of known cattle variants, an important contribution to the knowledge of domestic cattle genetic diversity.

Genetic Diversity and Population Structure of Selected Ethiopian Indigenous Cattle Breeds Using Microsatellite Markers

Background

In Ethiopia, livestock contributes 45% of agricultural GDP. Despite the economic role played by the sector, there have been little efforts to genetically improve the indigenous cattle. Morphological characterization of selected Ethiopian indigenous cattle has been made for (Bonga, Jimma, and Kerayu) cattle types. But, the selected indigenous cattle were not characterized at molecular level (genetic diversity information). Hence, this work was initiated to detect and determine the genetic diversity and population structure of selected Ethiopian indigenous cattle ecotypes using microsatellite markers.

Results

Different alleles were identified (131) and thirty-three of these alleles were unique to specific ecotypes. All loci used were informative with PIC values ranging from 0.5 (TGLA126) to 0.84 (ETH10) with a mean of 0.70 per locus. The Shannon information index ranged from (I = 1.02) ILST006 to (I = 1.63) ETH10 with an average of 1.28 revealing there is genetic diversity. Moreover, analysis of molecular variance (AMOVA) revealed 84% genetic variation within a population and 13% variation among populations. The value of F-statistics (Fst) (0.129 = 13%) indicated that there was moderate genetic differentiation among ecotypes. The (UPGMA) revealed, Bonga and Jimma clustered together while Kerayu cattle were relatively distinct, Principal coordinates analysis (PCOA) and structure analysis grouped the individual into different clusters confirming the presence of ecotype admixture due to geographical origins and uncontrolled mating.

Conclusion

In general, this study has successfully characterized the genetic diversity and population structure of Bonga, Jimma, and Kerayu cattle ecotypes using high polymorphic/informative microsatellite markers. According to this study, Kerayu cattle have high AR and PA when compared to Bonga and Jimma cattle populations. So, the Kerayu population is more diverse than others and it is the hotspot for genetic diversity study. The generated information is very relevant for breeder and genetic conservation.

Genetic Differentiation among Livestock Breeds-Values for Fst

(1) Background: The Fst statistic is widely used to characterize between-breed relationships. Fst = 0.1 has frequently been taken as indicating genetic distinctiveness between breeds. This study investigates whether this is justified. (2) Methods: A database was created of 35,080 breed pairs and their corresponding Fst values, deduced from microsatellite and SNP studies covering cattle, sheep, goats, pigs, horses, and chickens. Overall, 6560 (19%) of breed pairs were between breeds located in the same country, 7395 (21%) between breeds of different countries within the same region, 20,563 (59%) between breeds located far apart, and 562 (1%) between a breed and the supposed wild ancestor of the species. (3) Results: General values for between-breed Fst were as follows, cattle: microsatellite 0.06-0.12, SNP 0.08-0.15; sheep: microsatellite 0.06-0.10, SNP 0.06-0.17; horses: microsatellite 0.04-0.11, SNP 0.08-0.12; goats: microsatellite 0.04-0.14, SNP 0.08-0.16; pigs: microsatellite 0.06-0.27, SNP 0.15-0.22; chickens: microsatellite 0.05-0.28, SNP 0.08-0.26. (4) Conclusions: (1) Large amounts of Fst data are available for a substantial proportion of the world's livestock breeds, (2) the value for between-breed Fst of 0.1 is not appropriate owing to its considerable variability, and (3) accumulated Fst data may have value for interdisciplinary research.

Unraveling the Genetic Diversity and Population Structure of Bangladeshi Indigenous Cattle Populations Using 50K SNP Markers

Simple Summary

Indigenous cattle have extraordinary adaptation capability to diverse environments under low input production system. However, the population size is declining rapidly in Bangladesh due to massive imports of high yielding dairy breeds. The genetic diversity measures are important for assessing population architecture as well as for development of conservation strategies. The aim of this study was to investigate genetic variability and population structure of indigenous cattle genetic resources of Bangladesh using Illumina Bovine SNP50K BeadChip genotyped data. Similar to other zebu populations, low genetic diversity measures were found in Bangladeshi cattle populations. Our findings revealed their distinct genetic structure but showed low levels of genetic differentiation among the six indigenous cattle populations. Moreover, admixture and phylogenetic analysis highlighted historical gene flow among the studied populations. Altogether, our findings provide a comprehensive genomic information on indigenous cattle populations of Bangladesh that could be utilized in their future conservation and breeding research.

Abstract

Understanding the genetic basis of locally adapted indigenous cattle populations is essential to design appropriate strategies and programs for their genetic improvement and conservation. Here, we report genetic diversity measures, population differentiation, and structure of 218 animals sampled from six indicine cattle populations of Bangladesh. Animals were genotyped with Illumina Bovine SNP50K BeadChip along with genotyped data of 505 individuals included from 19 zebu and taurine breeds worldwide. The principal component analysis (PCA) showed clear geographic separation between taurine and indicine lineages where Bangladeshi indigenous cattle clustered with South Asian zebu populations. However, overlapped clusters in PCA, heterozygosity estimates, and Neighbor-Joining phylogenetic tree analysis revealed weak genetic differentiation among the indigenous cattle populations of Bangladesh. The admixture analysis at K = 5 and 9 suggests distinct genetic structure of the studied populations along with 1 to 4% of taurine ancestry. The effective population size suggested a limited pool of ancestors particularly for Sahiwal and North Bengal Grey cattle. In conclusion, these findings shed insights into the genetic architecture of six indigenous cattle populations of Bangladesh for the first time and suggested as distinct gene pools without potential admixture with zebu or taurine populations.

An Overview of the Use of Genotyping Techniques for Assessing Genetic Diversity in Local Farm Animal Breeds

Simple Summary

The number of local farm animal breeds is declining worldwide. However, these breeds have different degrees of genetic diversity. Measuring genetic diversity is important for the development of conservation strategies and, therefore, various genomic analysis techniques are available. The aim of the present work was to shed light on the use of these techniques in diversity studies of local breeds. In summary, a total of 133 worldwide studies that examined genetic diversity in local cattle, sheep, goat, chicken and pig breeds were reviewed. The results show that over time, almost all available genomic techniques were used and various diversity parameters were calculated. Therefore, the present results provide a comprehensive overview of the application of these techniques in the field of local breeds. This can provide helpful insights into the advancement of the conservation of breeds with high genetic diversity.

Abstract

Globally, many local farm animal breeds are threatened with extinction. However, these breeds contribute to the high amount of genetic diversity required to combat unforeseen future challenges of livestock production systems. To assess genetic diversity, various genotyping techniques have been developed. Based on the respective genomic information, different parameters, e.g., heterozygosity, allele frequencies and inbreeding coefficient, can be measured in order to reveal genetic diversity between and within breeds. The aim of the present work was to shed light on the use of genotyping techniques in the field of local farm animal breeds. Therefore, a total of 133 studies across the world that examined genetic diversity in local cattle, sheep, goat, chicken and pig breeds were reviewed. The results show that diversity of cattle was most often investigated with microsatellite use as the main technique. Furthermore, a large variety of diversity parameters that were calculated with different programs were identified. For 15% of the included studies, the used genotypes are publicly available, and, in 6%, phenotypes were recorded. In conclusion, the present results provide a comprehensive overview of the application of genotyping techniques in the field of local breeds. This can provide helpful insights to advance the conservation of breeds.

Single nucleotide polymorphisms of leptin gene in five Ethiopian indigenous cattle breeds and the Korean Hanwoo breed

Considering the escalating number of scientific reports on the association between the leptin gene and diverse physiological traits and performance of cattle populations, this study was directed towards identifying SNPs in the leptin gene among five indigenous cattle breeds of Ethiopia. DNA samples were extracted from the nasal swabs of the Ethiopian indigenous cattle breeds: Arsi (n = 18), Horro (n = 20), Begait (n = 21), Boran (n = 19), and Fogera (n = 17) and the Korean Hanwoo (a representative taurine breed) (n = 20), followed by PCR amplification of exon 2 and exon 3 regions of the leptin gene and sequence analysis of the PCR products. Five SNPs, two (generating missense mutations) on exon 2 and three (generating silent mutations) on exon 3 regions, were explicated in this study. Allele frequency and genotype frequency distribution pertaining to the SNPs were recorded for the studied cattle breeds besides the minor allele frequency and deviation from the Hardy-Weinberg equilibrium. Positive F_IS index values were recorded for all the markers except SNP2, illustrative of heterozygote deficiency. MEGA X software-based evolutionary divergence analysis of the phylogenetic tree based on the SNP data revealed that the large-sized breeds, Hanwoo, Begait, Boran, and Fogera, were more closely clustered compared to the small-sized Arsi breed. Among the seven haplotypes documented from the various breeds, sequence analysis was suggestive of haplotypes 1 and 2 to be ancestral haplotypes for the leptin gene. This study is envisaged to accelerate molecular breeding programs for the genetic improvement of the Ethiopian cattle breeds.

Genome-wide scan reveals divergent selection among taurine and zebu cattle populations from different regions

In this study, to identify genomic signatures of divergent selection, we genotyped 10 cattle breeds/populations (n = 275), representing eight Ethiopian cattle populations (n = 229) and two zebu populations (n = 46) adapted to tropical and sub-tropical environments, using the high-density single-nucleotide polymorphisms (SNPs) derived mainly from Bos indicus breeds, and using five reference taurine breeds (n = 212). Population genetic differentiation (F_ST ) values across sliding windows were estimated between zebu and reference combined taurine breeds. The most differentiated regions (F_ST  ≥ 0.53), representing the top 1% smoothed F_ST values, were considered to represent regions under diversifying selection. In total, 285 and 317 genes were identified in the comparisons of Ethiopian cattle with taurine and Asian zebu with taurine respectively. Some of these genes are involved in stress responses/thermo-tolerance and DNA damage repair (HSPA4, HSF1, CMPK1 and EIF2AK4), pigmentation (ERBB3 and MYO1A), reproduction/fertility (UBE2D3, ID3 and PSPC1), immune response (PIK3CD and AKIRIN2) and body stature and size (MBP2, LYN and NPM1). Additionally, the candidate genes were associated with functional terms (e.g. cellular response to stress, DNA repair, inflammatory response) important for physiological adaptation to environmental stresses. The results of our study may shed light on the influence of artificial and natural selection in shaping the genomic diversity of modern cattle breeds and also may serve as a basis for further genetic investigation of traits of tropical adaptation in cattle.

Variations in mitochondrial cytochrome b region among Ethiopian indigenous cattle populations assert Bos taurus maternal origin and historical dynamics

Objective

This study was carried out to assess the haplotype diversity and population dynamics in cattle populations of Ethiopia.

Methods

We sequenced the complete mitochondrial cytochrome b gene of 76 animals from five indigenous and one Holstein Friesian×Barka cross bred cattle populations.

Results

In the sequence analysis, 18 haplotypes were generated from 18 segregating sites and the average haplotype and nucleotide diversities were 0.7540±0.043 and 0.0010±0.000, respectively. The population differentiation analysis shows a weak population structure (4.55%) among the populations studied. Majority of the variation (95.45%) is observed by within populations. The overall average pair-wise distance (F_ST) was 0.049539 with the highest (F_ST = 0.1245) and the lowest (F_ST = 0.011) F_ST distances observed between Boran and Abigar, and Sheko and Abigar from the indigenous cattle, respectively. The phylogenetic network analysis revealed that all the haplotypes detected clustered together with the Bos taurus cattle and converged to a haplogroup. No haplotype in Ethiopian cattle was observed clustered with the reference Bos indicus group. The mismatch distribution analysis indicates a single population expansion event among the cattle populations.

Conclusion

Overall, high haplotype variability was observed among Ethiopian cattle populations and they share a common ancestor with Bos taurus.

On-farm phenotypic characterization of Mursi cattle in its production environment in South Omo Zone, Southwest Ethiopia

This study was conducted to characterize the morphological peculiarities and performance characteristics of Mursi cattle in its production environment managed by Bodi and Mursi pastoral communities in Southern Ethiopia. A structured questionnaire survey, group discussion, cattle morphological measurements and morphological descriptions were used to collect data. One hundred and two household heads were selected to administer the questionnaire and 201 adult cattle were selected for morphological description and body measurements. The Mursi cattle population was found to have variable coat colour type (85.9 percent) and coat colour pattern (51.3 percent). Body length, chest girth, withers height, rump width and rump length of Mursi cattle were 122.1 ± 0.9, 144.5 ± 0.9, 113 ± 0.1.1, 36.9 ± 0.3 and 20.4 ± 0.3 cm, respectively. Morphological measurements of most linear traits show no difference in the two locations but all measurements vary (P< 0.001) between males and females. Estimated age at first calving was 4.6 years and was significantly (P< 0.0001) higher in the Mursi area, while the calving interval (14.5 months) and cow reproductive life (14.2 years) were the same in both locations. Average daily milk yield (2.1 litres) and lactation length (7.8 months) of Mursi cattle in the two locations were similar. Cattle production was constrained by high disease prevalence, seasonal feed availability, and water shortage, with frequent drought. Trypanosomosis, black leg, anthrax and skin diseases are major cattle diseases reported in the two study areas. Because of its peculiar morphological characteristics, including large body frame, higher production performance, and survivability in the harsh environment, the Mursi cattle can be used as an alternative genetic resource for production improvement programs.

Genome-wide genetic diversity, population structure and admixture analysis in African and Asian cattle breeds

Knowledge about genetic diversity and population structure is useful for designing effective strategies to improve the production, management and conservation of farm animal genetic resources. Here, we present a comprehensive genome-wide analysis of genetic diversity, population structure and admixture based on 244 animals sampled from 10 cattle populations in Asia and Africa and genotyped for 69,903 autosomal single-nucleotide polymorphisms (SNPs) mainly derived from the indicine breed. Principal component analysis, STRUCTURE and distance analysis from high-density SNP data clearly revealed that the largest genetic difference occurred between the two domestic lineages (taurine and indicine), whereas Ethiopian cattle populations represent a mosaic of the humped zebu and taurine. Estimation of the genetic influence of zebu and taurine revealed that Ethiopian cattle were characterized by considerable levels of introgression from South Asian zebu, whereas Bangladeshi populations shared very low taurine ancestry. The relationships among Ethiopian cattle populations reflect their history of origin and admixture rather than phenotype-based distinctions. The high within-individual genetic variability observed in Ethiopian cattle represents an untapped opportunity for adaptation to changing environments and for implementation of within-breed genetic improvement schemes. Our results provide a basis for future applications of genome-wide SNP data to exploit the unique genetic makeup of indigenous cattle breeds and to facilitate their improvement and conservation.

Assessing introgression of Sahelian zebu genes into native Bos taurus breeds in Burkina Faso

A total of 350 samples were analyzed to estimate zebu gene proportions into two different taurine cattle breeds of Burkina Faso (Lobi and N'Dama) using 38 microsatellites and various statistical methodologies. West African and East African zebu samples were sequentially used as reference parental populations. Furthermore, N'Dama cattle from Congo, the composite South African Bonsmara cattle breed and a pool of European cattle were used successively as second parental populations. Independently of the methodology applied: (a) the use of West African zebu samples gave higher admixture coefficients than the East African zebu; (b) the higher zebu proportions were estimated when the European cattle was used as parental population 2; and (c) the use of the N'Dama population from Congo as parental population 2 gave the more consistent zebu proportion estimates for both the Lobi and the N'Dama breeds. In any case, the zebu admixture proportions estimated were not negligible and were always higher in the N'Dama cattle than in the Lobi cattle of Burkina Faso. This suggested that the introgression of Sahelian zebu genes into the taurine cattle of Southern West Africa can follow a complex pattern that can depend on local agro-ecological features. The current research pointed out that the estimation of admixture coefficients is highly dependent on both the assumptions underlying the methodologies applied and the selection of parental populations. Our analyses suggest that either too high or nil genetic identity between the parental and the expectedly derived populations must be avoided.

Genetic diversity, population structure and relationships in indigenous cattle populations of Ethiopia and Korean Hanwoo breeds using SNP markers

In total, 166 individuals from five indigenous Ethiopian cattle populations – Ambo (n = 27), Borana (n = 35), Arsi (n = 30), Horro (n = 36), and Danakil (n = 38) – were genotyped for 8773 single nucleotide polymorphism (SNP) markers to assess genetic diversity, population structure, and relationships. As a representative of taurine breeds, Hanwoo cattle (n = 40) were also included in the study for reference. Among Ethiopian cattle populations, the proportion of SNPs with minor allele frequencies (MAFs) ≥0.05 ranged from 81.63% in Borana to 85.30% in Ambo, with a mean of 83.96% across all populations. The Hanwoo breed showed the highest proportion of polymorphism, with MAFs ≥0.05, accounting for 95.21% of total SNPs. The mean expected heterozygosity varied from 0.370 in Danakil to 0.410 in Hanwoo. The mean genetic differentiation (F_ST; 1%) in Ethiopian cattle revealed that within individual variation accounted for approximately 99% of the total genetic variation. As expected, F_ST and Reynold genetic distance were greatest between Hanwoo and Ethiopian cattle populations, with average values of 17.62 and 18.50, respectively. The first and second principal components explained approximately 78.33% of the total variation and supported the clustering of the populations according to their historical origins. At K = 2 and 3, a considerable source of variation among cattle is the clustering of the populations into Hanwoo (taurine) and Ethiopian cattle populations. The low estimate of genetic differentiation (F_ST) among Ethiopian cattle populations indicated that differentiation among these populations is low, possibly owing to a common historical origin and high gene flow. Genetic distance, phylogenic tree, principal component analysis, and population structure analyses clearly differentiated the cattle population according to their historical origins, and confirmed that Ethiopian cattle populations are genetically distinct from the Hanwoo breed.

Evaluation of genetic diversity and population structure of West-Central Indian cattle breeds

Evaluations of genetic diversity in domestic livestock populations are necessary to implement region-specific conservation measures. We determined the genetic diversity and evolutionary relationships among eight geographically and phenotypically diverse cattle breeds indigenous to west-central India by genotyping these animals for 22 microsatellite loci. A total of 326 alleles were detected, and the expected heterozygosity ranged from 0.614 (Kenkatha) to 0.701 (Dangi). The mean number of alleles among the cattle breeds ranged from 7.182 (Khillar) to 9.409 (Gaolao). There were abundant genetic variations displayed within breeds, and the genetic differentiation was also high between the Indian cattle breeds, which displayed 15.9% of the total genetic differentiation among the different breeds. The genetic differentiation (pairwise FST ) among the eight Indian breeds varied from 0.0126 for the Kankrej-Malvi pair to 0.2667 for Khillar-Kenkatha pair. The phylogeny, principal components analysis, and structure analysis further supported close grouping of Kankrej, Malvi, Nimari and Gir; Gaolao and Kenkatha, whereas Dangi and Khillar remained at distance from other breeds.