ASSESSING THE IMPACT OF SEX-SPECIFIC MICROSATELLITE VARIANTS ON PHENOMICS OF INBRED SWISS ALBINO MICE

An inbred strain limits the segregating variance and provides more power and requires fewer experimental animals to produce good reproducibility. This study was undertaken with the aim to assess the impact of sex of offsprings and sex specific microsatellite variants on performance and fitness traits in F4 inbred Swiss albino mice. The phenomics of different performance and fitness traits were estimated on 506 F4 inbred mice population. Two ‘X’ chromosome specific microsatellite loci (DXMit187 and DxMit172) were used for PCR-Microsatellite genotyping of 102 F4 inbred population. PIC estimates showed that both the loci were informative for the population. In the current population, with the increasing level of “F” a declining trend was observed for Body weight at birth (BWB), Body weight at weaning (BWW), Litter size at weaning (LSW) and Litter weight at weaning (LWW). In F4 inbred population, BWW and ABW for males (17.32±0.32g and 30.81±0.31g) were significantly (p<0.05) higher than females (16.39±0.30g and 27.83±0.28g). The significant (p<0.05) impact of sex of offspring on performance traits revealed that less magnitude of inbreeding depression was observed in male as compared to female. There were 3 alleles and 5 genotypes at the DXMit172 locus, and 3 alleles and 4 genotypes at the DXMit187 locus. The highest and lowest allelic frequencies were found at DXMit172 locus for 142 (0.422) and 154 (0.226) alleles, respectively, and at DXMit187 locus for 126 (0.588) and 146 (0.093) alleles, respectively. Genotype 142/142 (0.382) and 154/148 (0.059) had the highest and lowest genotypic frequency at the DXMit172 locus, respectively, and at DXMit187 locus for 126/126 (0.588) and 146/146 (0.039) genotypes, respectively. In the current study, only the DXMit172 loci had significant genotypic associations with fitness traits (p<0.05). The average FIS based on X- specific microsatellite markers was 0.790 in the F4 inbred population. These results indicate that rate of inbreeding depression is more in females than in males

Analysis of selection signatures reveals important insights into the adaptability of high-altitude Indian sheep breed<i>Changthangi</i>

AbstractChangthangiis a high-altitude sheep breed of India that is adapted to cold and hypoxic climate of Himalayas. In the present study, we analysed population structure ofChangthangiand contrasted it with selected Indian and European commercial sheep breeds to detect genomic regions under positive selection. The studied domesticated sheep breeds includedChangthangi, Indian Garole, Deccani, Tibetan, RambouilletandAustralian Merino. While the PCA results revealedChangthangiclustered withTibetansheep; TREEMIX and ADMIXTURE results also detected the introgression of lowland Indian sheep inheritance inChangthangi. Cross-population comparisons ofChangthangiusing XP-EHH showed multiple functional regions present on OAR 7, 15 and 16, to be under selection inChangthangisheep. These regions are related to adaptation to climatic and hypoxic stressors, nervous system and mitochondrial functioning. The genes present in these regions are suitable candidates for future studies on the genetic mechanisms underlying high-altitude adaptation.</jats:p

Gene

Not AvailableChangthangi is a high-altitude sheep breed of India that is adapted to cold and hypoxic climate of Himalayas. In the present study, we analysed population structure of Changthangi and contrasted it with selected Indian and European commercial sheep breeds to detect genomic regions under positive selection. The Illumina OvineSNP50v1 genotype data on 292 animals from seven different sheep breeds i.e., Changthangi (n = 29), Garole (n = 26), Deccani (n = 24), Tibetan (n = 37), Rambouillet (n = 102) and Australian Merino (n = 50) was used. European Mouflon (n = 24) was used as an out-group for studying the stratification and phylogenetic lineage. While the principal component analysis (PCA) revealed Changthangi to cluster with Tibetan sheep; TREEMIX and ADMIXTURE results also detected the introgression of lowland Indian sheep inheritance in Changthangi. Changthangi sheep were compared with other breed groups as reference i.e., commercial (Australian Merino and Rambouillet), Indian (Deccani, Garole and Tibetan) and breeds inhabiting plains (Australian Merino, Rambouillet, Deccani and Garole). Genomic comparisons of Changthangi using cross population extended haplotype homozygosity (XP-EHH) showed multiple functional regions present on Ovis aries (Oar) chromosomes 2, 3, 6 and 18 to be under selection in Changthangi sheep. These regions were related with adaptation to climatic and hypoxic stressors, fleece characteristics and functioning of immune and reproductive systems. UCP genes, associated with adaptation to cold and hypoxic conditions, were the main loci under positive selection in Changthangi sheep population. The selection signals in Indian and European commercial sheep breeds were mainly associated with body weight and carcass traits. Furthermore, selection signals found in different comparisons were found to be part of different quantitative trait loci (QTLs) associated with important traits in different breed classes. The genes present in these regions are suitable candidates for future studies on the genetic mechanisms underlying high-altitude adaptation

Lifetime reproductive performance of Chokla sheep at an organized farm in semi-arid conditions

The Chokla sheep, renowned as the finest carpet wool producer of India, plays an important role in supporting the rural economy of the arid and semi-arid regions of its native state of Rajasthan. This study was carried out to assess the lifetime reproductive efficiency of Chokla ewes by analyzing the records of 1,001 ewes bearing 3,541 lambs over a period of 22 years (1994–2016) to assess five traits, namely total lambs born (TLB; 3.38±0.11 lambs), total lambs weaned (TLW; 2.97±0.11 lambs), cumulative lamb weights at birth (TLBW; 9.59±0.37 kg), weaning (TLWW; 39.59±1.68 kg) and 12 months of age (TLAW; 50.15±2.51 kg) produced by an ewe in her lifetime. Period of birth of ewe had a significant effect on all the traits whereas season of birth, inbreeding coefficient and birth weight of ewe had no influence. REML procedures were employed to estimate the genetic parameters through an animal model. Analysis revealed low heritability estimates for the lifetime reproductive traits (TLB; 0.06±0.04, TLW; 0.05±0.04, TLBW; 0.09±0.05, TLWW; 0.05±0.04 and TLAW; 0.02±0.04), suggesting greater role of environmental and managemental factors. Positive correlation among cumulative lamb weights (0.51–0.92) suggested selection for birth weights would result in higher weights at subsequent life stages of lambs. The low heritability estimates and high CV% for all the traits suggest the suitability of a management focussed approach for improvement of lifetime reproductive performance of ewes.</jats:p

Evaluation of reproductive traits of Chokla sheep under semi-arid conditions of Rajasthan

The study analysed the records of 1,172 ewes maintained at ICAR–Central Sheep and Wool Research Institute at Avikanagar and Bikaner, Rajasthan over a period of 22 years (1994-2016). Eight reproductive traits were assessed, namely age at first service (AFS; 572.39±6.59 days), age at first successful service (ASS; 635.71±9.36 days), age at first lambing (AFL; 773±8.77 days), weight at first service (WFS; 25.16±0.11 kg), weight at first successful service (WSS; 25.85±0.16 kg), weight at lambing (WL; 28.61±0.21 kg), lambing interval (LI;371±6.87days) and service period (SP; 228.31±6.62 days). The effects of period of birth of ewe, ewe’s birth weight and sire were significant for all the traits except LI and SP with an improvement of 17.47% –37.6% observed over the period of study. Season of birth of ewe had significant effect on AFL. AFS, ASS and AFL were significantly influenced by their respective covariates (WFS, WSS and WL). The statistically significant improvement over the periods suggest that through suitable selective breeding policy and good managemental measures, the reproductive performance of the flock can be enhanced. The optimization of ewe weights could reduce the age of sexual maturity and the ewe’s weight at birth may serve as an indicator for future performance in this regard. Selection of superior sires may improve the genetic potential of the flock with respect to the reproductive traits.</jats:p