Lori-Bakhtiari Sheep Research Articles

The comparisons of non-linear models to describe the growth performance of Lori-Bakhtiari sheep.

The study of growth traits is of interest to many animal scientists, regardless of specialization, due to the economic importance of growth rate, mature weight and other related traits. This study aimed to compare six non-linear models for describing the growth of Lori-Bakhtiari sheep. In order to collect weight data, 85 lambs (41 males and 44 females) were reared from birth to 140 days of age, and their growth patterns were recorded by measuring their body weight at 10-day intervals. Various mathematical functions, including the negative exponential, Brody, Gompertz, Logistic, Morgan-Mercer-Flodin (MMF) and Weibull, were used to model the relationship between body weight records and age. The results showed that the MMF and Gompertz models provided the best fit to the body weight data, whereas the negative exponential model exhibited the worst fit. In all models, the asymptotic weight of male lambs was higher than females. The research also revealed differences in growth patterns between male and female lambs. Overall, females had a lower absolute growth rate than males, but they reached their peak growth at an earlier period, and their growth rate declined faster. The differences in growth patterns between males and females indicate the importance of analysing male and female data separately when describing growth. As a result, Gompertz model can be recommended to Lori-Bakhtiari female and male lamb breeders to determine more accurate growth traits. In addition, it should be considered that feeding male and female lambs separately according to absolute growth rate values may increase growth performance.

Association of Palm gene mutations with structure and function of paralemmin proteins in Lori-Bakhtiari and Zel sheep Breeds

The aim of current study was to survey genetic variability of PALM gene’s exon 3 and 4 by PCR-SSCP and DNA sequencing in Zel and Lori Bakhtiari sheep breeds. The SIFT (Sorting Intolerant from Tolerant) and PHyre2 program were used to predict the possible impact of amino acid substitutions on performance and structure of the paralemmin protein. A total of 140 animal's from 2 Iranian sheep breeds with different fat metabolisms, Lori-Bakhtiari and Zel sheep breeds were considered. The results showed that there are two polymorphic sites including a nonsynonymous substitution and an insertion mutation (49bp). Non-synonymous mutation deduced Thr20Ala amino acid exchange and ensuing two different structures for paralemmin protein that could be potentially affect protein structure and function during the interaction with glutamate in the cytosolic surface of plasma membrane. PALM gene, according to evolutionary path, is classified into two separate categories. In first covey, Gallus gallus and in second one, other species in several branches, so that the sequence of cow and sheep is placed in a sub-branch which forms a clade beside goat. Comparison of illustrated coding region sequences, PALM gene among different species, is of orthologous which are derived from a common ancestor.

Fatty acids composition and health indices in different fat and muscle locations of lambs from crossbreeding between Lori-Bakhtiari and Romanov sheep breeds

The current study aimed to evaluate the fatty acids (FAs) profile of five different locations in pure Lori-Bakhtiari (LL genotype) fat-tailed sheep and their crosses (RL genotype) with the Romanov-tailed breed. After slaughtering, samples were collected from longissimus thoracis (LT) and semi-membranous (SM) as muscle, and fat-tail (FT), subcutaneous (SC), and abdominal (AB) fat as adipose tissues. After extracting the ether extract of samples according to the recommendations by the AOAC, the fatty acid composition of the samples was determined using gas chromatography. The main FAs were C14:0, C16:0, C18:0, and C18:1 for all locations. These FAs accounted for about 80–88 % and 85–90 % of the total FAs in muscle and adipose tissues, respectively. The results showed that for many of the FAs in muscle tissues, there were no significant differences between the LL and RL genotypes; However, the genotypes had a significant difference in proportions of C14, C16:1, C18:0, C18:3, C20:0, and C20:1 (P < 0.05) in all locations, as the LL genotype had lower C18:0 and C20:0 than the RL genotype.Genotypes did not show significant differences in classic ratios and health indices in muscle tissues and AB fat; While in FT and SC tissues, the genotypes had significant differences regarding saturated fatty acids (SFAs), monounsaturated fatty acids (MUFAs), the unsaturated fatty acid to saturated fatty acid ratio (U/S), the saturation index (SI), and the trombogenic index (TI). The comparison of fatty acids and indices between muscle (LT and SM) and adipose (FT, SC, and AB) tissues showed that these two tissues were statistically different in terms of many individual fatty acids and indices (P < 0.05; P < 0.01). Also, adipose tissues had different amounts of C12:0 (0.22 vs. 0.45), C15:0 (0.82 vs. 0.36), C16:0 (26.51 vs. 27.73), C16:1 (3.37 vs. 2.75), C17:1 (1.29 vs. 0.49), C18:1c (39.05 vs. 43.80), C18: 1 t (1.57 vs. 0.76), C18: 2n6 (3.15 vs. 3.86), and C20:1 (0.84 vs. 0.58).The n-6/n-3 and h/H ratios were significant difference between fat and muscle tissues (P < 0.05). it can be concluded that RL genotype was not superior than the LL genotype regarding the FAs, the ratios, and health indices. Therefore, crossbreeding native fat-tailed Lori-Bakhtiari sheep with Romanov sheep does not improve the meat quality; however, it can decrease the total body fat content.

Genome-wide identification of copy number variation and association with fat deposition in thin and fat-tailed sheep breeds

Copy number variants (CNVs) are a type of genetic polymorphism which contribute to phenotypic variation in several species, including livestock. In this study, we used genomic data of 192 animals from 3 Iranian sheep breeds including 96 Baluchi sheep and 47 Lori-Bakhtiari sheep as fat-tailed breeds and 47 Zel sheep as thin-tailed sheep breed genotyped with Illumina OvineSNP50K Beadchip arrays. Also, for association test, 70 samples of Valle del Belice sheep were added to the association test as thin-tailed sheep breed. PennCNV and CNVRuler software were, respectively, used to study the copy number variation and genomic association analyses. We detected 573 and 242 CNVs in the fat and thin tailed breeds, respectively. In terms of CNV regions (CNVRs), these represented 328 and 187 CNVRs that were within or overlapping with 790 known Ovine genes. The CNVRs covered approximately 73.85 Mb of the sheep genome with average length 146.88 kb, and corresponded to 2.6% of the autosomal genome sequence. Five CNVRs were randomly chosen for validation, of which 4 were experimentally confirmed using Real time qPCR. Functional enrichment analysis showed that genes harbouring CNVs in thin-tailed sheep were involved in the adaptive immune response, regulation of reactive oxygen species biosynthetic process and response to starvation. In fat-tailed breeds these genes were involved in cellular protein modification process, regulation of heart rate, intestinal absorption, olfactory receptor activity and ATP binding. Association test identified one copy gained CNVR on chromosomes 6 harbouring two protein-coding genes HGFAC and LRPAP1. Our findings provide information about genomic structural changes and their association to the interested traits including fat deposition and environmental compatibility in sheep.

Genome-wide association study and genomic heritabilities for blood protein levels in Lori-Bakhtiari sheep

Serum protein levels are related to physiological and pathological status of animals and could be affected by both genetic and environmental factors. This study aimed to evaluate genetic variation of serum protein profile in sheep. Blood samples were randomly collected from 96 Lori-Bakhtiari ewes, a heavy meat-type breed. Total protein, albumin, globulin, α1, α2, β and γ globulins and IgG levels were measured in blood serum. The samples were genotyped using the Illumina OvineSNP50 BeadChip. The studied traits adjusted for age, birth type, birth season and estimate of breeding value for body weight were considered as pseudo-phenotypes in genome-wide association analysis. In the GWAS model, the first five principal components were fitted as covariates to correct the biases due to possible population stratification. The Plink, R and GCTA software were used for genome-wide association analysis, construction of Q-Q and Manhattan plots and estimation of genetic variances, respectively. Noticeable genomic heritabilities ± SE were estimated for total and γ globulins (0.868 ± 0.262 and 0.831 ± 0.364, respectively), but other protein fractions had zero or close to zero estimates. Based on the Bonferroni adjusted p values, four QTLs located on 181.7 Mbp of OAR3, 107.7 Mbp of OAR4, 86.3 Mbp of OAR7 and 83.0 Mbp of OAR8 were significantly associated with α1, β, β and γ globulins, respectively. The results showed that the PKP2, IGF2R, SLC22A1 and SLC22A2 genes could be considered as candidate genes for blood serum proteins. The present study showed significant genetic variations of some blood protein fractions.

Inferring causal relationships among growth curve traits of Lori-Bakhtiari sheep using structural equation models

This study aimed to infer the causal effects of birth weight on growth curve traits as well as, assessment of causal relationships among the growth curve traits in Lori-Bakhtiari sheep using structural equation modeling. The body weight-age records were collected from birth to 390 days of age from 1995 to 2012 in Shooli Breeding Station of Lori-Bakhtiari sheep, Shahr-e Kord, Iran. Initially, five non-linear models including Brody, Logistic, Negative exponential, Gompertz and von Bertalanffy were fitted on 22,546 body weight-age records for determining the best model describing the growth curve. Among the tested non-linear growth models, Brody model showed the best goodness of fit. Then, data on growth curve traits of 3,168 lambs from 217 rams and 1,211 ewes were considered for genetic evaluation of growth curve traits including asymptotic weight (A), integration constant related to initial animal weight (b), and maturation rate (k).The causal effect of birth weight (BW) on growth curve traits under two models including standard multivariate model (SMM) and fully recursive model (FRM) were fitted via a Bayesian approach. The posterior means of heritability for the growth curve traits were similar under both SMM and FRM, while the posterior means of genetic correlations among the traits were statistically different under both SMM and FRM. Structural coefficients related to causal effects of BW on b, k and A, were statistically significant with values −0.19, 0.01and 12.58, respectively. Therefore, considering the causal effects of BW on growth curve traits is essential for accurate genetic analysis of growth curve traits of Lori-Bakhtiari sheep.

Bayesian estimate of genetic parameters for growth traits in Lori Bakhtiari sheep.

The information of birth (10,017 records), weaning (9439 records), 6months (7669 records), 9months (4536 records), and yearling weights (417 records) collected from 1989 to 2016 by the Lori Bakhtiari (Sholi) sheep breeding station located in Shahrekord were used to estimate the genotypic and phenotypic parameters of growth traits of Lori Bakhtiari sheep. The components of variance and genetic parameters were estimated by the Bayesian statistical method based on the Gibbs sampling technique due to the high accuracy of this method. Factors including birth year, lamb sex, birth type, and maternal age at lambing have significant effects on all of these traits (P < 0.01) and were considered fixed effects in the statistical model for estimation of genetic parameters. Lamb weight at weaning was used as a covariate in the model. Based on the models with the lowest Akaike information criterion, direct heritability for birth, weaning, 6-month, 9-month, and yearling weights were 0.36, 0.18, 0.21, 0.27, and 0.32, respectively. The moderate heritability obtained for the studied traits pointed up the effectiveness of selection in genetic improvement, but the environmental conditions should be improved for better performance of weight traits.

Genome-wide association study for postweaning weight traits in Lori-Bakhtiari sheep.

Marker-assisted selection is an effective method in novel animal breeding programs. This study was conducted to perform a genome-wide association study to detect candidate genes and quantitative trait loci associated with postweaning weight traits in meat-type sheep. Body weight records were collected during 29 years (1989 to 2017) in Lori-Bakhtiari sheep flock of the Shooli Breeding Station in Iran. A total of 132 animals were selected based on estimates of breeding values (EBVs) for body weight, using two-tailed and random selection strategies. Genomic DNA was extracted from whole blood samples. The samples were genotyped using Illumina OvineSNP50 BeadChip. De-regressed EBVs for postweaning body weight traits were used as pseudo-phenotypes in a genome-wide association study. One SNP on chromosome 10 (rs406324209) and two SNPs on chromosome 13 (rs401963094 and rs418761613) were significantly (Bonferroni-adjusted p-values < 0.05) associated with postweaning body weight traits. The significant variants accounted for 0.20% and 0.48% of the total genetic variances for 6- and 9-month body weights, respectively. Genomic heritabilities estimated for 6-, 9- and 12-month weights and postweaning weight gain were 0.28 ± 0.34, 0.35 ± 0.29, 0.37 ± 0.34, and 0.16 ± 0.33, respectively. Two significant SNPs were located within the ATP8A2 and PLXDC2 genes, on chromosomes 10 and 13, respectively. Based on the known gene ontologies, both ATP8A2 and PLXDC2 could be considered as candidate genes for postweaning body weight traits.

Genome-Wide Association Study of Weaning Traits in Lori-Bakhtiari Sheep

Abstract Weaning traits, including preweaning daily gain (PWDG) and weaning weight (WW) are important economic traits, especially for meat type mammals, with high impacts on growth performance and survival rate in higher ages. This study was conducted to perform a genome-wide association study (GWAS) on weaning traits in a meat type breed of sheep. Body weight records of 7557 Lori-Bakhtiari sheep with PWDG and WW records were used to estimate breeding values (EBVs) using an animal mixed model. A total of 132 animals were selected by two-tailed selection strategy, based on EBVs for body weight and then were genotyped using Illumina 50k Ovine SNP chip. After quality control, a total of 130 animals and 41323 SNPs were remained for further analyses. De-regressed estimates of breeding values were used as a pseudo-phenotype in GWAS analysis. Based on Bonferroni-adjusted p-values, five SNPs, located on chromosomes 2, 3, 4, 12 and 22 were significantly (p &lt; 0.05) associated with weaning traits and accounted for 5.06% and 0.37% of total genetic variations of PWDG and WW, respectively. Two SNPs on chromosomes 2 and 3 were located near to previously reported QTLs for weaning traits. Three genes, including ANGPTL7, mTOR and WDR11, were found within 50 kbp distances from the significant SNPs and thus could be considered as candidate genes for weaning traits. The detected QTLs and candidate genes could be studied for construction of breeding programs for genetic improvement of growth performance in meat type sheep.

Population structure of Lori-Bakhtiari sheep in Iran by pedigree analysis

The objective of this study was to describe the population genetic structure and evaluate the state of conservation of genetic variability of Lori-Bakhtiari sheep in Iran. As such, pedigree information of 10,644 lambs lambed from 1989 through 2016 in the stud flock of Lori-Bakhttiari sheep was included in the analysis. Our first goal was to estimate mean and variance of family size across sires and dams using pedigree data. Our second goal was to estimate population structure in Lori-Bakhtiari sheep including estimation of pedigree completeness (PC), genetic conservation index (GCI), effective population size (Ne), effective number of founders (fe), effective number of ancestors (fa), generation interval (L), individual inbreeding coefficient (F) and average relatedness coefficient (AR) using the ENDOG software. The results showed that the average number of progenies per ram and ewe in their lifetime were 26.44 (15–152) and 3.6 (1–15), respectively. The mean and variance of family size of sires differ across years. The pedigree completeness (PC) was equal to 0.61. The fe and fa were 109 and 98, respectively with a ratio of 1.11. The number of ancestors explaining 50% of genetic diversity was 30. The Ne also varied from 142.68 to 144.13 during the study period. The average generation interval was 4.11 years. The mean inbreeding coefficient was 2.5% in inbred lambs and 1.26% in whole population with an annual increase of 0.09% per year and 0.87% per generation. The AR of the total population was estimated to 2.27% with an incremental trend of 0.10% per year and 0.59% in each generation. The average GCI was 11.75 units with an incremental trend of 0.76 per year. The effects of birth type and year of birth were found to be significant on most of the studied demographic parameters. Though there is an increasing inbreeding coefficient trend over a number of generations, it is still lower than the maximum acceptable recommendation of 1% per generation. This provides us an opportunity for maintaining genetic diversity and implementation of the improvement breeding program. However, unbalanced use of rams led to the creation of family size variation over years. Therefore, this study warrants a comprehensive mating plan with minimum inbreeding rate to maintain genetic variability in Lori-Bakhtiari sheep.

The comparison of alternative models for genetic evaluation of growth traits in Lori-Bakhtiari sheep: Implications on predictive ability and ranking of animals

The aim of present study was to investigate the performance of standard multivariate model (SMM), fully recursive models (FRM) and temporal recursive model (TRM) for genetic evaluation of growth traits in Lori-Bakhtiari sheep. The pedigree and phenotypic data of growth traits including birth weight (BW), average daily gain from birth to weaning (ADG1), weaning weight (WW), average daily gain from weaning to six-month weight (ADG2) and six-month weight (6 MW) collected from 1995 to 2012 were used. Firstly, three models (SMM, FRM and TRM) were fitted via Bayesian approach with 200,000 Gibbs samples and the first 50,000 samples were considered as burn-in period with thinning intervals of 10 samples. Contrary to FRM and TRM, in SMM causal relationships between the studied traits were ignored. Deviance Information Criterion (DIC) values obtained under three considered models indicated superiority of models with causal relationships on SMM. Also, based on DIC, within models containing causal relationships, TRM performed better than FRM for genetic evaluation of the studied growth traits. The posterior means for structural coefficients between BW-ADG1, ADG1-WW, WW-ADG2 and ADG2-6 MW were 9.343, 0.03, 10.632 and 0.14, respectively and were statistically significant (P < 0.05). Results of comparisons of rank correlations between posterior means of direct genetic effects for the studied growth traits under SMM and TRM revealed that taking the causal relationships among the studied growth traits into account may cause considerable re-ranking for the animals in terms of the estimated breeding values, especially for the top-ranked animals. Model comparisons based on goodness of fit and predictive ability applying mean square error (MSE) and Pearson’s correlation coefficients between the observed and predicted records (ry,yˆ(revealed that in general TRM performed better than SMM in terms of goodness of fit and predictive ability. In general, the results indicated that considering causal relationships between growth traits is very important and including these relationships in models for genetic evaluation is beneficial in terms of predictive ability.

Genome-wide association study of four composite reproductive traits in Iranian fat-tailed sheep.

Composite reproductive traits are a combination of growth and reproductive traits. They have the advantage of being better attuned to the market drivers since producers are paid on a per kilogram basis and not on a per head basis. In this study, 124 Lori---Bakhtiari ewes were genotyped using the medium-density Illumina Ovine SNP50 array. A genome-wide association study was performed on estimated breeding values of four composite reproductive traits and genetic parameters were also estimated. The traits were litter mean weight at birth, litter mean weight at weaning, total litter weight at birth and total litter weight at weaning. Several suggestive and associated single nucleotide polymorphisms (SNPs) were identified. Neighbouring the top SNPs there were five genes, inhibin β E subunit (INHBE), inhibin β C subunit (INHBC), testis expressed 12 (TEX12), β-carotene oxygenase 2 (BCO2) and WD Repeat Domain 70 (WDR70) identified as possible candidate genes for composite reproductive traits of the Lori-Bakhtiari sheep. These genes are in pathways known to be relevant to fertility and growth characteristics. The results provide new information for the functional annotation of genes associated with fertility traits and add new evidence towards a consensus of quantitative trait loci associated with reproductive traits in sheep.

Genome-wide association study of birth weight in sheep

Birth weight is the earliest available growth trait with considerable impacts on lamb survivability and growth performance traits. This study was conducted to perform a genome-wide association study of birth weight in a meat-type sheep. A total of 132 Lori-Bakhtiari sheep were selected based on estimated of breeding values (EBVs) for BW analyses. The selected animals were genotyped using Illumina Ovine SNP50 Bead Chip. After quality control, a total of 41 323 single-nucleotide polymorphisms (SNPs) and 130 sheep were used for subsequent analyses. Plink 1.90 beta software was used for the analyses. Seven SNPs on chromosomes 1, 16, 19 and 22 were detected based on genome-wide unadjusted P-values (P <10−6), which jointly accounted for 1.2% of total genetic variation. However, based on Bonferroni-adjusted P-values, only three SNPs on chromosome 1 had significant associations with EBVs for birth weight (P <0.05), which jointly explained 0.8% of total genetic variation. A total of seven genes were found in 50 kb intervals from the three significant SNPs on chromosome 1, but only three genes, including RAB6B (a member of RAS oncogene family), Tf serotransferrin and GIGYF2 (a GRB10 interacting GYF protein 2), could be considered as candidate genes for birth weight in future studies. The results of this study may facilitate potential use of the genes involving in growth and production traits for genetic improvement of productivity in sheep.

Simple hierarchical and general nonlinear growth modeling in sheep

Differential equations and advanced statistical models have been used to predict growth phenomena. In the present study, general nonlinear growth functions such as von Bertalanffy, Gompertz, logistic, and Brody, along with hierarchical modeling were applied to investigate the phenotypic growth pattern of Iranian Lori-Bakhtiari sheep. Growth data from 1410 Lori- Bakhtiari lambs were used in the present study. The results showed that the Brody function outperformed the other three nonlinear growth functions. In addition, including hierarchical growth modeling results allowed the adoption of many random effect structures, suggesting that hierarchical growth modeling has a useful role in growth data modeling. This method provides an estimation of growth parameters based on individual animals, improving individual growth selection. The results suggest this approach for growth modeling. Combining the strength of individual growth modeling with general growth modeling, e.g., von Bertalanffy, Gompertz, logistic, and Brody would be deeply appealing in the future. In this regard, dealing with sheep growth phenomenon using pure mathematical models, i.e. grey system theory models that could be new powerful prediction tools for breeders and experts, has not been done yet. However, running the analysis on large datasets will require significantly higher computational power than is ordinarily available.

Genome-wide association study to identify genomic regions affecting prolificacy in Lori-Bakhtiari sheep.

Several causative mutations in candidate genes affecting prolificacy have been detected in various sheep breeds. A genome-wide association study was performed on estimated breeding values for litter size in Lori-Bakhtiari sheep. Prolific ewes with twinning records and others with only singleton records were genotyped using the medium-density Illumina Ovine SNP50 array. Four single nucleotide polymorphisms (SNPs) associated with litter size were identified on chromosomes 3, 6 and 22. The region on sheep chromosome 3 between 75739167 and 75745152bp included two significant SNPs (s52383.1 and OAR3_80038014_X.1) in high linkage disequilibrium with each other. The region that surrounds these SNPs contains a novel putative candidate gene: luteinizing hormone/choriogonadotropin receptor (LHCGR), known to be involved in ovarian steroidogenesis and organism-specific biosystem pathways in sheep. Known prolificacy genes BMPR1B, BMP15 and GDF9 were not associated with litter size in Lori-Bakhtiari sheep, suggesting that other biological mechanisms could be responsible for the trait's variation in this breed.

Effect of crossbreeding on growth, feed efficiency, carcass characteristics and sensory traits of lambs from Lori-Bakhtiari and Romanov breeds

This study compares the growth performance, carcass characteristics, and sensory traits of pure lambs of Lori-Bakhtiari fat-tailed sheep (LL genotype) and their crosses with Romanov tailed sheep breed (RL genotype). After weaning, the average daily gain (ADG) and feed conversion ratio (FCR) of male lambs were recorded at a fattening period of 80 days. Twenty-three male lambs were slaughtered, and the left sides of the carcasses were separated into six pieces to determine the lean meat, bone, subcutaneous fat (SCF), and inter muscular fat (IMF). Genotypes had different ADG (LL: 296.50 ± 11.57 v. RL: 249.11 ± 12.92 g/day) and FCR (LL: 6.12 ± 0.26 v. RL: 6.98 ± 0.30) (P < 0.05). The fat-tail weight in the crossbred lambs was about 80% less, but the weights of SCF and IMF were 55% and 33% greater than the purebred lambs, respectively (P < 0.01); however, the difference in the back-fat thickness (12–13th rib) was not significant between the two genotypes (LL:4.29 ± 0.32 v. RL:4.62 ± 0.37 mm) (P = 0.41). While abdominal fat (AF) was 65% greater than that of the purebreds (P < 0.001), the total body fat in the crossbred lambs was about 34% less than the purebreds (P < 0.001); it had been displaced with about 23% more lean meat (P < 0.001). A trained panel evaluated the tenderness and flavor of the LL and RL meat through a sensory evaluation. Tenderness score (LL: 6.75 ± 0.94 v. RL: 5.16 ± 0.94) was significantly affected by the genotype (P < 0.01); however, the panelists could not detect a significant difference in flavor score between the two genotypes (LL: 7.01 ± 0.82 v. RL: 6.85 ± 0.82). It can be concluded that crossbreeding the indigenous Lori-Bakhtiari sheep with Romanov breed can significantly improve carcass traits and increase meat production. The present data showed that, even though crossbred lambs could not compete with purebred in terms of ADG, FCR, and tenderness, the lower total body fat in crossbred lambs (34%) compensated the inferior high fat in the Lori-Bakhtiari breed.

Estimation of the variance due to parent-of-origin effects for productive and reproductive traits in Lori-Bakhtiari sheep

Parent-of-origin effects are often excluded from models used for estimating of additive and non-additive genetic variances. Omission of parentally-linked genetic factors, such as imprinting, from statistical models has potential to induce profound bias during the estimation. In this study, parent of origin variance for productive and reproductive traits in Lori-Bakhtiari sheep was estimated using a gametic relationship matrix approach. The data set were obtained from a total of 7568 animals, collected from 1994 to 2012 from the Lori-Bakhtiari research flock at Shooli station in Shahrekord, Iran. Growth traits were included birth weight (BWT), weaning weight (WWT), 6-month weight (WT6), 9-month weight (WT9), yearling weight (WT12), average daily gain from birth to weaning (ADGa), and from weaning to 6-month (ADGb). In addition, litter size at birth (LSB), litter size at weaning (LSW), litter mean weight per lamb born (LMWLB), and litter mean weight per lamb weaned (LMWLW) were analyzed as basic reproductive traits, and total litter weight at birth per ewe lambing (TLWB) and total litter weight at weaning per ewe lambing (TLWW) as composite reproductive traits. Models including or excluding maternal and paternal imprinting effects were compared using the ayesian information criterion (BIC). For all growth traits, except WT6 and WT12, adding maternal imprinting effects into the models decreased BIC, with estimates ranging from 10.5% (WWT) to 23.3% (BWT) of the total phenotypic variance. Paternal imprinting effects, in the other hand, was estimated as 6.9% of the total phenotypic variance for ADGb. For reproductive traits, maternal imprinting effects explained up to 6% of total phenotypic variance for TLWW. Adding paternal or maternal imprinting to the models decreased the direct additive genetic, maternal additive genetic and maternal permanent environmental variance for the growth traits.

Screening for Causative Mutations of Major Prolificacy Genes in Iranian Fat-Tailed Sheep.

BackgroundThe presence of different missense mutations in sheep breeds have shown that the bone morphogenetic protein receptor 1B (BMPR1B), bone morphogenetic protein 15 (BMP15) and growth differentiation factor 9 (GDF9) genes play a vital role in ovulation rate and prolificacy in ewes. Therefore, the present study aims to investigate BM- PR1B, BMP15 and GDF9 gene mutations in prolific ewes of Iranian fat-tailed Lori-Bakhtiari sheep.Materials and MethodsIn the present experimental study, genomic DNA was extracted from whole blood of 10 prolific Lori-Bakhtiari ewes with at least two twinning records in the first four parities to identify point mutations of the BMPR1B, BMP15 and GDF9 genes, using DNA sequencing.ResultsThe results obtained from DNA sequencing showed a new synonymous mutation (g.66496G>A) in exon 8 of the BMPR1B gene, without any amino acid change. Sequencing of the BMP15 gene revealed a deletion of 3 bp (g.656_658delTTC) in exon 1, leading to an amino acid deletion (p.Leu19del). Four single nucleotide polymorphisms (G1:g.2118G>A, G2:g.3451T>C, G3:g.3457A>G and G4:g.3701G>A), were detected in exons 1 and 2 of the GDF9 gene, two of which caused amino acid substitutions (G1: p.87Arg>His and G4: p.241Glu>Lys). These amino acid alterations are proposed to have a benign impact on structure and function of the GDF9 polypeptide sequence.ConclusionThree major prolificacy genes (BMPR1B, BMP15 and GDF9) were polymorphic in Lori-Bakhtiari sheep, although none of the major causative mutation was detected in this sheep type. Further studies using high throughput methods such as genome-wide association study (GWAS) and evaluation of other candidate genes are necessary in the future.

Molecular genetics and bioinformatics analysis of EDG1 and AKIRIN2 genes in Iranian fat-tailed and nonfat-tailed sheep breeds

This study was conducted to detect different allelic forms and its association with fat-tail traits, and also investigation of domains variants in 5/- and 3/-UTR regions of EDG1 and AKIRIN2 genes in Iranian fat-tailed (Lori-Bakhtiari) and nonfat-tailed (Zel) sheep breeds. Blood samples were randomly collected from 300 sheep (150 samples per each breed) and genomic DNA was extracted by modified salting out method. Two primer pairs were designed by oligo7 software for amplification of fragments with the length of 516 and 454bp from EDG1 and AKIRIN2 genes, respectively. The results of genotyping by SSCP assay and silver nitrate staining showed that, in both breeds, there was no incidence of mutation in AKIRIN2 gene. But, the EDG1 was highly polymorph in studied sheep breeds, so that, six banding patterns with different frequencies of A (36.73 and 31.19%), B (8.84 and 21.6%), C (7.48 and 41.12%), D (29.93 and 34.50%), E (13.61 and 34.10%) and F (3.40 and 38.1%) were observed for Zel and Lori-Bakhtiari breeds, respectively. Comparison of banding pattern frequencies by Chi-square test showed significant difference between two breeds (P<0.01). One sample from each banding patterns were sequenced. The alignment and motif analysis of sequences by BioEdit and DNASIS MAX software showed incidence of 11 single nucleotide polymorphism (SNP) and 18 DNA motifs in EDG1 marker site. According to different SNPs, the paternal and maternal haplotypes were determined by phase software. The association study showed significant association between EDG1 gene haplotypes and banding patterns with fat-tail traits in Lori-Bakhtiari sheep except for height of fat-tail. This study was the first effort for evaluate of these genes in sheep. Therefore, more studies on other breeds of sheep and on coding sequence of these genes are recommended.

Genetic diversity of Iranian Lori-Bakhtiari sheep assessed by pedigree analysis

In this study a pedigree analysis was conducted to characterize the genetic structure and diversity of the closed nucleus of Iranian Lori-Bakhtiari sheep. Herdbook information collected between 1992 and 2014, was used to estimate generation interval, pedigree completeness level, inbreeding and its evolution during the studied years. Animals born between 2011 and 2014 were selected as a reference population for estimating parameters derived from probability of gene origins. The mean generation interval was 3.42 year in the studied period. Average inbreeding coefficient of the animals in the reference population was 1.02%. The rate of inbreeding was 0.17% per generation (P<0.01) in the studied period. Realized effective population size estimated from individual increase in coancestry was 101. The effective number of founders, effective number of ancestors and founder genome equivalent of the reference population were 77, 43 and 21 respectively. The results indicated that population under study has fairly good genetic diversity. However, population has lost a part of its genetic diversity due to unbalanced contribution of founders, bottlenecks and genetic drift. For continued genetic gain, enlarging the selection basis and implementation of methods that maximize the selection response at an acceptable level of inbreeding are recommended.