Total Teat Number Research Articles

Genome-wide detection of multiple variants associated with teat number in French Yorkshire pigs

BackgroundTeat number is a vital reproductive trait in sows, crucial for providing immunity and nutrition to piglets during lactation. However, “missing heritability” in Single Nucleotide Polymorphism (SNP)-based Genome-Wide Association Studies (GWAS) has led to an increasing focus on structural variations in the genetic analysis of complex biological traits.ResultsIn this study, we generated a comprehensive CNV map in a population of French Yorkshire pigs (n = 644) and identified 429 CNVRs. Notably, 44% (189 CNVRs) of these were detected for the first time. Subsequently, we conducted GWAS for teat number in the French Yorkshire pig population using both 80K chip and its imputed data, as well as a GWAS analysis based on CNV regions (CNVR). Interestingly, 80K chip GWAS identified two SNPs located on Sus scrofa chromosome 5 (SSC5) that were simultaneously associated with Total Teat Number (TTN), Left Teat Number (LTN), and Right Teat Number (RTN). The leading SNP (WU_10.2_5_76130558) explained 3.33%, 2.69%, and 2.67% of the phenotypic variance for TTN, LTN, and RTN, respectively. Moreover, through imputed GWAS, we successfully identified 30 genetic variants associated with TTN located within the 73.22 -73.30 Mb region on SSC5. The two SNPs identified in the 80K chip GWAS were also located in this region. In addition, CNVR-based GWAS revealed three significant CNVRs associated with TTN. Finally, through gene annotation, we pinpointed two candidate genes, TRIM66 and PRICKLE1, which are related to diverse processes such as breast cancer and abnormal vertebral development.ConclusionsOur research provides an in-depth analysis of the complex genetic structure underlying teat number, contributing to the genetic enhancement of sows with improved reproductive performance and, ultimately, bolstering the economic benefits of swine production enterprises.

Genome-wide association analysis revealed new QTL and candidate genes affecting the teat number in Dutch Large White pigs.

Teat number (TNUM) is an important reproductive trait of sows, which affects the weaning survival rate of piglets. In this study, 1166 Dutch Large White pigs with TNUM phenotype were used as the research object. These pigs were genotyped by 50K SNP chip and the chip data were further imputed to the resequencing level. The estimated heritabilities of left teat number (LTN), right teat number (RTN) and total teat number (TTN) were 0.21, 0.19 and 0.3, respectively. Based on chip data, significant SNPs for RTN on SSC2, SSC5, SSC9 and SSC13 were identified using genome-wide association analysis (GWAS). Significant SNPs for TTN were identified on SSC2, SSC5 and SSC7. Based on imputed data, the GWAS identified a significant SNP (rs329158522) for LTN on SSC17, two significant SNPs (rs342855242 and rs80813115) for RTN on SSC2 and SSC9, and two significant SNPs (rs327003548 and rs326943811) for TTN on SSC5 and SSC6. Among them, four novel QTL were discovered. The Bayesian fine-mapping method was used to fine map the QTL identified in the GWAS of the imputed data, and the confidence intervals of QTL affecting LTN (SSC17: 45.22-46.20 Mb), RTN (SSC9: 122.18-122.80 Mb) and TTN (SSC5: 14.01-15.91 Mb, SSC6: 120.06-121.25 Mb) were detected. A total of 52 candidate genes were obtained. Furthermore, we identified five candidate genes, WNT10B, AQP5, FMNL3, NUAK1 and CKAP4, for the first time, which involved in breast development and other related functions by gene annotation. Overall, this study provides new molecular markers for the breeding of teat number in pigs.

Genome-wide association study using a single-step approach for teat number in Duroc, Landrace and Yorkshire pigs in Korea.

We investigated the genetic basis of teat number in sows, which is an important factor in their reproductive performance. We collected genotyping data from 20 353 pigs of three breeds (Duroc, Landrace and Yorkshire) using the Porcine SNP60K Bead Chip, and analyzed phenotypic data from 240 603 pigs. The heritability values of total teat number were 0.33 ± 0.02, 0.51 ± 0.01 and 0.50 ± 0.01 in Duroc, Landrace and Yorkshire pigs, respectively. A genome-wide association study was used to identify significant chromosomal regions associated with teat number in SSC7 and SSC9 in Duroc pig, SSC3, SSC7 and SSC18 in Landrace pig, and SSC7, SSC8 and SSC10 in Yorkshire pig. Among the markers, MARC0038565, located between the vertnin (VRTN) and synapse differentiation-inducing 1-like (SYNDIG1L) genes, showed the strongest association in the Duroc pig and was significant in all breeds. In Landrace and Yorkshire pigs, the most significant markers were located within the apoptosis resistant E3 ubiquitin protein ligase 1 (AREL1) and latent transforming growth factor beta-binding protein 2 (LTBP2) genes in SSC7, respectively. VRTN is a candidate gene regulating the teat number. Most markers were located in SSC7, indicating their significance in determining teat number and their potential as valuable genomic selection targets for improving this trait. Extensive linkage disequilibrium blocks were identified in SSC7, supporting their use in genomic selection strategies. Our study provides valuable insights into the genetic architecture of teat numbers in pigs, and helps identify candidate genes and genomic regions that may contribute to this economically important trait.

Genetic Parameter Estimates for Teat and Mammary Traits in Commercial Sows.

The objective was to evaluate the genetics of sow teat and mammary traits at farrowing and at weaning. Data were recorded on 3099 Landrace × Large White F1 sows. Underline traits included the total teat number (TT), the functional teat number (FT), the non-functional teat number (NFT), the damaged teat number (DT), and the number of functional mammary glands (FMG). Variance components were estimated using AIREMLF90. Means for TT, FT, and NFT at farrowing were 14.93, 13.90, and 1.03, respectively. Heritability estimates for TT, FT, and NFT ranged from 0.18 to 0.37, 0.16 to 0.28, and 0.14 to 0.18, respectively. Estimates of heritability for DT and FMG at weaning were 0.03 and 0.06, respectively. Estimated genetic correlations between FT with TT and NFT were 0.68 to 0.78 and -0.19 to -0.57, respectively. Genetic correlation estimates between TT, FT, and NFT with the number weaned were 0.25, 0.50, and -0.38, respectively. An increase of one TT and FT enhanced (p < 0.05) the number weaned by 0.14 to 0.16 and 0.18 to 0.27 piglets, respectively. The results suggest that genetically increasing the number of functional teats on a sow at farrowing would improve the number of piglets at weaning.

Genome-Wide Association Study Identifies the Crucial Candidate Genes for Teat Number in Crossbred Commercial Pigs.

The number of teats is a crucial reproductive trait with significant economic implications on maternal capacity and litter size. Consequently, improving this trait is essential to facilitate genetic selection for increased litter size. In this study, we performed a genome-wide association study (GWAS) of the number of teats in a three-way crossbred commercial Duroc × (Landrace × Yorkshire) (DLY) pig population comprising 1518 animals genotyped with the 50K BeadChip. Our analysis identified crucial quantitative trait loci (QTL) for the number of teats, containing the ABCD4 and VRTN genes on porcine chromosome 7. Our results establish SNP variants of ABCD4 and VRTN as new molecular markers for improving the number of teats in DLY pigs. Furthermore, the most significant noteworthy single nucleotide polymorphism (SNP) (7_97568284) was identified within the ABCD4 gene, exhibiting a significant association with the total teat number traits. This SNP accounted for a substantial proportion of the genetic variance, explaining 6.64% of the observed variation. These findings reveal a novel gene on SSC7 for the number of teats and provide a deeper understanding of the genetic mechanisms underlying reproductive traits.

The impact of functional teat number on reproductive throughput in swine.

The objective was to evaluate the impact of functional teat number on reproductive throughput in swine. Data included 735 multiparous Landrace × Large White F1 females. Sow underlined traits consisted of total teat number (TT), functional teat number (FT), nonfunctional teat number (NFT), and number of functional mammary glands (FMG). Weaning traits were calculated for both the biological and the nurse dam. For the biological dam, litter size at weaning (LSW) included a sow's biological piglets regardless of cross-fostering. For nurse dam, number weaned (NW) included the piglets a sow weaned. For the biological dam, piglet survival (PS) was calculated as litter size at weaning / (total number born × 100). Linear regression estimates were calculated in RStudio v. 1.1.456 and variance components were estimated using GIBBS3F90. Average total number born, number born alive, TT, FT, NFT, and FMG were 14.22, 13.12, 14.43, 13.96, 0.42, and 10.7, respectively. An increase in one FT enhanced (P < 0.05) LSW by 0.32 piglets and NW by 0.33 piglets. Similarly, an increase in one FT improved (P < 0.05) PS by 1.63% and reduced (P < 0.05) preweaning mortality by 2.73%. However, an increase in one FT reduced (P < 0.05) average piglet weaning weight (WW) for biological and nurse dams by 35 and 94 g, respectively. Yet an increase in one FT enhanced (P < 0.05) litter weaning weight (LWW) for biological and nurse dams by 1.3 and 1.5 kg, respectively. Heritability estimates for TT, FT, NFT, FMG, WW, LWW, LSW, and PS were 0.25, 0.22, 0.53, 0.18, 0.21, 0.22, 0.16, and 0.18, respectively. Genetic correlation estimates between FT with TT, NFT, and FMG were 0.79, 0.09, and 0.28, respectively. Estimated genetic correlations between TT with WW, LWW, LSW, and PS were 0.37, 0.38, 0.11, and -0.19, respectively. Genetic correlation estimates between FT with WW, LWW, LSW, and PS were 0.44, 0.49, 0.39, and 0.35, respectively. Results suggest increasing functional teat number would enhance both piglet survival and reproductive throughput.

Genomic evaluation and genome-wide association studies for total number of teats in a combined American and Danish Yorkshire pig populations selected in China.

Joint genomic evaluation by combining data recordings and genomic information from different pig herds and populations is of interest for pig breeding companies because the efficiency of genomic selection (GS) could be further improved. In this work, an efficient strategy of joint genomic evaluation combining data from multiple pig populations is investigated. Total teat number (TTN), a trait that is equally recorded on 13,060 American Yorkshire (AY) populations (~14.68 teats) and 10,060 Danish Yorkshire (DY) pigs (~14.29 teats), was used to explore the feasibility and accuracy of GS combining datasets from different populations. We first estimated the genetic correlation (rg) of TTN between AY and DY pig populations (rg = 0.79, se = 0.23). Then we employed the genome-wide association study to identify quantitative trait locus (QTL) regions that are significantly associated with TTN and investigate the genetic architecture of TTN in different populations. Our results suggested that the genomic regions controlling TTN are slightly different in the two Yorkshire populations, where the candidate QTL regions were on SSC 7 and SSC 8 for the AY population and on SSC 7 for the DY population. Finally, we explored an optimal way of genomic prediction for TTN via three different genomic best linear unbiased prediction models and we concluded that when TTN across populations are regarded as different, but correlated, traits in a multitrait model, predictive abilities for both Yorkshire populations improve. As a conclusion, joint genomic evaluation for target traits in multiple pig populations is feasible in practice and more accurate, provided a proper model is used.

A Whole Genome Sequencing-Based Genome-Wide Association Study Reveals the Potential Associations of Teat Number in Qingping Pigs.

Simple SummaryTeat number is important for the mothering ability of a sow, but this trait has seldom been investigated by high-depth genomic data-based genome-wide association study (GWAS). Here, we performed GWAS for the teat number-related traits in 100 Chinese native Qingping pigs by recording their left and right teat numbers and analyzing their genetic variations through 10-fold whole-genome sequencing. T-Box Transcription Factor 3 (TBX3) on Sus scrofa chromosome (SSC) 14 and Wnt signaling pathway are revealed to be associated with teat number-related traits, with important roles in mammary gland morphogenesis and development.Teat number plays an important role in the reproductive performance of sows and the growth of piglets. However, the quantitative trait loci (QTLs) and candidate genes for the teat number-related traits in Qingping pigs remain unknown. In this study, we performed GWAS based on whole-genome single-nucleotide polymorphisms (SNPs) and insertions/deletions (Indels) for the total number of teats and five other related traits in 100 Qingping pigs. SNPs and Indels of all 100 pigs were genotyped using 10× whole genome resequencing. GWAS using General Linear Models (GLM) detected a total of 28 SNPs and 45 Indels as peak markers for these six traits. We also performed GWAS for the absolute difference between left and right teat number (ADIFF) using Fixed and random model Circulating Probability Unification (FarmCPU). The most strongly associated SNP and Indel with a distance of 562,788 bp were significantly associated with ADIFF in both GLM and FarmCPU models. In the 1-Mb regions of the most strongly associated SNP and Indel, there were five annotated genes, including TRIML1, TRIML2, ZFP42, FAT1 and MTNR1A. We also highlighted TBX3 as an interesting candidate gene for SSC14. Enrichment analysis of candidate genes suggested the Wnt signaling pathway may contribute to teat number-related traits. This study expanded significant marker-trait associations for teat number and provided useful molecular markers and candidate genes for teat number improvement in the breeding of sows.

Genome-Wide Association Study for Body Length, Body Height, and Total Teat Number in Large White Pigs

Body length, body height, and total teat number are economically important traits in pig breeding, as these traits are usually associated with the growth, reproductivity, and longevity potential of piglets. Here, we report a genetic analysis of these traits using a population comprising 2,068 Large White pigs. A genotyping-by-sequencing (GBS) approach was used to provide high-density genome-wide SNP discovery and genotyping. Univariate and bivariate animal models were used to estimate heritability and genetic correlations. The results showed that heritability estimates for body length, body height, and total teat number were 0.25 ± 0.04, 0.11 ± 0.03, and 0.22 ± 0.04, respectively. The genetic correlation between body length and body height exhibited a strongly positive correlation (0.63 ± 0.15), while a positive but low genetic correlation was observed between total teat number and body length. Furthermore, we used two different genome-wide association study (GWAS) approaches: single-locus GWAS and weighted single-step GWAS (WssGWAS), to identify candidate genes for these traits. Single-locus GWAS detected 76, 13, and 29 significant single-nucleotide polymorphisms (SNPs) associated with body length, body height, and total teat number. Notably, the most significant SNP (S17_15781294), which is located 20 kb downstream of the BMP2 gene, explained 9.09% of the genetic variance for body length traits, and it also explained 9.57% of the genetic variance for body height traits. In addition, another significant SNP (S7_97595973), which is located in the ABCD4 gene, explained 8.92% of the genetic variance for total teat number traits. GWAS results for these traits identified some candidate genomic regions, such as SSC6: 14.96–15.02 Mb, SSC7: 97.18–98.18 Mb, SSC14: 128.29–131.15 Mb, SSC17: 15.39–17.27 Mb, and SSC17: 22.04–24.15 Mb, providing a starting point for further inheritance research. Most quantitative trait loci were detected by single-locus GWAS and WssGWAS. These findings reveal the complexity of the genetic mechanism of the three traits and provide guidance for subsequent genetic improvement through genome selection.

Accelerated deciphering of the genetic architecture of agricultural economic traits in pigs using a low-coverage whole-genome sequencing strategy.

BackgroundUncovering the genetic architecture of economic traits in pigs is important for agricultural breeding. However, high-density haplotype reference panels are unavailable in most agricultural species, limiting accurate genotype imputation in large populations. Moreover, the infinitesimal model of quantitative traits implies that weak association signals tend to be spread across most of the genome, further complicating the genetic analysis. Hence, there is a need to develop new methods for sequencing large cohorts without large reference panels.ResultsWe describe a Tn5-based highly accurate, cost- and time-efficient, low-coverage sequencing method to obtain 11.3 million whole-genome single-nucleotide polymorphisms in 2,869 Duroc boars at a mean depth of 0.73×. On the basis of these single-nucleotide polymorphisms, a genome-wide association study was performed, resulting in 14 quantitative trait loci (QTLs) for 7 of 21 important agricultural traits in pigs. These QTLs harbour genes, such as ABCD4 for total teat number and HMGA1 for back fat thickness, and provided a starting point for further investigation. The inheritance models of the different traits varied greatly. Most follow the minor-polygene model, but this can be attributed to different reasons, such as the shaping of genetic architecture by artificial selection for this population and sufficiently interconnected minor gene regulatory networks.ConclusionsGenome-wide association study results for 21 important agricultural traits identified 14 QTLs/genes and showed their genetic architectures, providing guidance for genetic improvement harnessing genomic features. The Tn5-based low-coverage sequencing method can be applied to large-scale genome studies for any species without a good reference panel and can be used for agricultural breeding.

PSI-10 The Relationship Between Litter Size and Functional Teat Number at Farrowing on Litter Size at Weaning

Abstract Sow functional teat number (FTEAT) is positively associated with piglet preweaning survival and litter throughput. The objective was to estimate the value of FTEAT in relationship to litter size to optimize the number of pigs weaned. Number of pigs born alive (NBA) and total teat number (TTEAT) were counted at farrowing on 836 multiparous purebred sows between March and September, 2020. Teats were evaluated by trained staff at farrowing and considered functional based on visual appraisal of teat morphology. Litter size at weaning (LSW) was recorded after a 26.5 d lactation length (LL). Sow was the experimental unit and all data were analyzed as a function of the biological sow. Number born alive was categorized by quartile: Q1 ≤ 10 NBA (n=185; µ=8.2); Q2 = 11 to 12 NBA (n=194; µ=11.6); Q3 = 13 to 14 NBA (n=238; µ=13.5); Q4 ≥ 15 NBA (n=219; µ=16.3). Data were analyzed in PROC GLM of SAS with farm, breed, and NBA quartile as categorical effects and LL and FTEAT as linear terms. The interaction of NBA quartile and FTEAT was also included. Mean TTEAT, FTEAT, LSW and preweaning survival were 15.4, 14.5, 11.3 and 89.4%, respectively. As a linear term, a one teat increase in FTEAT improved (P&amp;lt; 0.01) LSW by 0.3±0.1 pigs. Yet the value of an additional functional teat increased with increasing NBA. A one teat increase in FTEAT improved (P&amp;lt; 0.01) LSW in Q1, Q2, Q3, and Q4 by 0.12, 0.27, 0.33, and 0.38 pigs, respectively. The analysis demonstrates the impact of FTEAT on sow performance increases with increasing litter size, and highlights the importance of functional teats to optimize litter throughput and maximize the genetic potential of a maternal line.

57 The Impact of Functional Teat Number on Piglet Survival and Sow Efficiency

Abstract Pre-weaning mortalities have become a pressing issue in modern swine production. Litter size at birth has greatly increased through direct genetic selection. Unfortunately, little emphasis was placed on improving functional teat number, resulting in a nutrient access shortage. Therefore, a total of 750 sows consisting of three genetic lines in a commercial barn in Nebraska, USA, were used to evaluate the impact of functional teat number on piglet survival. Teat traits recorded at farrowing included total teat number (TT), functional teat number (FT), and non-functional teat number (NFT); with population means of 14.84 (1.21), 14.55 (1.30), and 0.28 (0.56), respectively. Production traits recorded included total number born (TNB), wean number (WN), total pre-weaning mortality (PWM), and post-cross foster mortality (CFPWM). The lm function within RStudio was used to estimate regressions, with parity and piglets placed (PP) used as covariates for WN and CFPWM, and parity, PP, and TNB for PWM. One additional FT increased WN (P &amp;lt; 0.01; 0.33), and reduced PWM (P &amp;lt; 0.01; -3.04%) and reduced CFPWM (P &amp;lt; 0.01; -3.71%). A subset of 274 sows were used to determine the effects of increasing functional teats on sow and piglet efficiency. Additional traits recorded included sow average daily feed intake (ADFI), backfat loss (BF) and average piglet weaning weight (WW). Parity, ADFI, backfat-entry, and WN were used as covariates for BF; parity, backfat-entry, and WN for ADFI; and parity, PP, ADFI, and WN were used for estimating WW. Regression estimates showed that an additional functional teat had no significant impact (P &amp;gt; 0.05) on ADFI, BF, or WW. Taken together, these results suggest that improving functional teat number does not impact ADFI or BF for sows and does not influence average piglet weaning weight, but it does decrease PWM resulting in more pigs weaned per litter.

A genome-wide association study for the number of teats in European rabbits (Oryctolagus cuniculus) identifies several candidate genes affecting this trait.

In the European rabbit (Oryctolagus cuniculus), a polytocous livestock species, the number of teats indirectly impacts the doe reproduction efficiency and, in turn, the sustainable production of rabbit meat. In this study, we carried out a genome-wide association study (GWAS) for the total number of teats in 247 Italian White does included in the Italian White rabbit breed selection program, by applying a selective genotyping approach. Does had either 8 (n=121) or 10 teats (n=126). All rabbits were genotyped with the Affymetrix Axiom OrcunSNP Array. Genomic data from the two extreme groups of rabbits were also analysed with the single-marker fixation index statistic and combined with the GWAS results. The GWAS identified 50 significant SNPs and the fixation index analysis identified a total of 20 SNPs that trespassed the 99.98th percentile threshold, 19 of which confirmed the GWAS results. The most significant SNP (P=4.31×10-11 ) was located on OCU1, close to the NUDT2 gene, a breast carcinoma cells proliferation promoter. Another significant SNP identified as candidate gene NR6A1, which is well known to play an important role in affecting the correlated number of vertebrae in pigs. Other significant markers were close to candidate genes involved in determining body length in mice. Markers associated with increased number of teats could be included in selection programmes to speed up the improvement for this trait in rabbit lines that need to increase maternal performances.

PSIII-11 Effect of Breast cancer metastasis-suppressor 1-like (BRMS1L) genotype on teat number traits in Jeju native pigs (JNP) and Landrace

Abstract The purpose of this study was to compare the changes of teat number traits of Jeju native pig (JNP) and Landrace varieties according to the breast cancer metastasis-suppressor 1-like (BRMS1L) genotype. The number of teat varies according to the single-base polymorphism with a G or A base 1,087 from the start codon ATG in the exon 1 region of the BRMS1L gene. The total teat number was examined at birth for 28 JNPs and 72 Landraces, and the BRMS1L genotype was analyzed by Pyrosequencing. As a result, the genotyping frequency of JNP was 1 A / A type, 9 A / G type, and 18 G / G type, whereas, on the contrary, Landrace had 70 A / A type, 2 A / C type, and C / C was identified as 0 heads. The total teat number was between the two varieties was 13.32 ± 0.95 and 14.51 ± 1.03, respectively (P &amp;lt; 0.001). According to genotypes in Jeju native pig breeds, the total number of nipples was 15 A / A, 14.0 ± 0.82 A / G, and 12.89 ± 0.74 G / G (P &amp;lt; 0.018). Conversely, Landrace was 14.54 ± 1.02 A / A and 13.5 ± 0.5 A / G. As a result of the above study, the frequency of varieties and genotypes was found to have a significant effect on the difference in nipple count. Based on the results of this study, if the improvement of Jeju native pigs is to be carried out, it is expected that the number of nipples will increase and the mammalian capacity will increase.

Genome-wide association studies for the number of teats and teat asymmetry patterns in Large White pigs.

The number of teats is a morphological trait that influences the mothering ability of the sows and thus their reproduction performances. In this study, we carried out GWASs for the total number of teats and other 12 related parameters in 821 Italian Large White heavy pigs. All pigs were genotyped with the Illumina PorcineSNP60 BeadChip array. For four investigated parameters (total number of teats, the number of teats of the left line, the number of teats of the right line and the maximum number of teats comparing the two sides), significant markers were identified on SSC7, in the region of the vertnin (VRTN) gene. Significant markers for the numbers of posterior teats and the absolute difference between anterior and posterior teat numbers were consistently identified on SSC6. The most significant SNP for these parameters was an intron variant in the TOX high mobility group box family member 3 (TOX3) gene. For the other four parameters (absolute difference between the two sides; anterior teats; the ratio between the posterior and the anterior number of teats; and the absence or the presence of extra teats) only suggestively significant markers were identified on several other chromosomes. This study further supported the role of the VRTN gene region in affecting the recorded variability of the number of teats in the Italian Large White pig population and identified a genomic region potentially affecting the biological mechanisms controlling the developmental programme of morphological features in pigs.

PSII-30 The genetics of functional teats in swine

Abstract The objective of this study was to evaluate the genetics of functional teats in swine. Piglet survival is of great importance for swine producers throughout the world due to its relationship with animal well-being and farm profitability. Availability and accessibility of functional teats on a sow during lactation is essential for enhancing piglet livability. Teat traits including total teat number (TT), functional teat number (FT), and non-functional teat number (NFT), were observed and recorded on 3,249 Landrace × Large White F1 sows. Damaged teat number (DT) and functional mammary gland number (FG) were also observed on sows prior to weaning. Variance components were estimated using AIREMLF90, with parity and farm as fixed effects. Means for TT, FT and NFT at farrowing were 14.94, 13.91 and 1.03, respectively, and 14.43, 13.02 and 1.15, respectively at weaning. Means for TT and FT were greater (P &amp;lt; 0.01) at farrowing than at weaning. Heritability estimates for TT, FT and NFT ranged between 0.19 and 0.30, 0.17 and 0.24, and 0.12 and 0.16, respectively. Total teat number and functional teat number had positive genetic correlation estimates ranging from 0.74 to 0.77. Functional mammary glands had a negative linear relationship of -1.16 with DT, and genetic correlations of 0.87 and -0.83 with FT and NFT, respectively. Linear regression models relating TT and FT to number of piglets weaned revealed that an increase of one functional teat at farrowing increased number weaned by 0.26. Overall, there was sufficient genetic variation for total teat number and functional teat number signifying that genetic gains from selecting for these traits is possible. Results also suggest that by focusing selection on functional teat number, an increase in non-functional teat number can be avoided. Therefore, utilizing functional teat number in the breeding goal should improve the general teat quality and sow performance.

Genome-wide detection of genetic loci and candidate genes for teat number and body conformation traits at birth in Chinese Sushan pigs.

Body conformation at birth and teat number are economically important traits in the pig industry, as these traits are usually explored to evaluate the growth and reproductive potential of piglets. To detect genetic loci and candidate genes for these traits, we performed a GWAS on 269 pigs from a recently developed Chinese breed (Sushan) using 38 128 informative SNPs on the Affymetrix Porcine SNP 55K Array. In total, we detected one genome-wide significant (P=1.31e-6) SNP for teat number on chromosome X and 15 chromosome-wide significant SNPs for teat number, body weight, body length, chest circumference and cannon circumference at birth on chromosomes 1, 3, 4, 6, 7, 9, 10, 13, 14, 15, 17 and 18. The most significant SNP had an additive effect of 0.74 × total teat number, explaining 20% of phenotypic variance. Five significant SNPs resided in the previously reported quantitative trait loci for these traits and seven significant SNPs had a pleiotropic effect on multiple traits. Intriguingly, 12 of the genes nearestto the significant SNPs are functionally related to body conformation and teat number traits, including SPRED2, MKX, TMSB4X and ESR1. GO analysis revealed that candidate genes proximal to the significant SNPs were enriched in the G-protein coupled receptor and steroid hormone-mediated signaling pathway. Our findings shed light on the genetic basis of the measured traits and provide molecular markers especially for the genetic improvement of teat number in Sushan and related pigs.

Genome-wide association study and genomic predictions for exterior traits in Yorkshire pigs1.

The objectives of this study were to identify informative genomic regions that affect the exterior traits of purebred Korean Yorkshire pigs and to investigate and compare the accuracy of genomic prediction for response variables. Phenotypic data on body height (BH), body length (BL), and total teat number (TTN) from 2,432 Yorkshire pigs were used to obtain breeding values including as response variable the estimated breeding value (EBV) and 2 types of deregressed EBVs-one including the parent average (DEBVincPA) and the other excluding it (DEBVexcPA). A final genotype panel comprising 46,199 SNP markers was retained for analysis after quality control for common SNPs. The BayesB and BayesC methods-with various π and weighted response variables (EBV, DEBVincPA, or DEBVexcPA)-were used to estimate SNP effects, through the genome-wide association study. The significance of genomic windows (1 Mb) was obtained at 1.0% additive genetic variance and was subsequently used to identify informative genomic regions. Furthermore, SNPs with a high model frequency (≥0.90) were considered informative. The accuracy of genomic prediction was estimated using a 5-fold cross-validation with the K-means clustering method. Genomic accuracy was measured as the genomic correlation between the molecular breeding value and the individual weighted response variables (EBV, DEBVincPA, or DEBVexcPA). The number of identified informative windows (1 Mb) for BH, BL, and TTN was 4, 3, and 4, respectively. The number of significant SNPs for BH, BL, and TTN was 6, 4, and 5, respectively. Diversity π did not influence the accuracy of genomic prediction. The BayesB method showed slightly higher genomic accuracy for exterior traits than BayesC method in this study. In addition, the genomic accuracy using DEBVincPA as response variable was higher than that using other response variables. Therefore, the genomic accuracy using BayesB (π = 0.90) with DEBVinPA as a response variable was the most effective in this study. The genomic accuracy values for BH, BL, and TTN were calculated to be 0.52, 0.60, and 0.51, respectively.

Relationship between Number of Teats and Litter Size in Eutherian Mammals

Mammals are vertebrates with hair and mammary glands, which produce milk for nursing their young. Mammals may be divided into two groups Prototheria and Theria. Prototherian are oviparous and Therian are viviparous. Theria is a subclass of mammals. It includes Eutherians (placental mammals) and metatherians (marsupial mammals). Mammals have a wide variety of skin glands, but all seem to be variations of two major glands, Sudoriferous (sweat) and Sebaceous (oil) glands. Mammary glands appear to be modified sebaceous glands. A teat is the projection from the breast or dug or udder or mammary glands of mammals. A litter is the live birth of multiple offspring at one time in animals from the same mother and usually from one set of parents. In this research we test the hypothesis of Gilbert’s ''one-half rule''. According to one half-rule, the average number of young in a litter is one half the typical numbers of teats and the maximum litter size is equal to the total number of teats. To find relationship between number of teats and litter size, various examples of mammalian species are considered and a comparison and correlation was drawn. In this research we also introduced teat formula (Tf) in mammals for the first time.

Joint linkage and linkage disequilibrium mapping reveals association of BRMS1L with total teat number in a large intercross between Landrace and Korean native pigs

Previously, we reported a quantitative trait locus (QTL) that affects total teat number (TTN) on pig chromosome 7 (SSC7) in a large F2 intercross population between Landrace and Korean native pigs. The aim of this study was to refine the QTL associated with TTN and to identify positional candidate gene(s) within the refined genomic region. TTN was recorded in 1105 F2 progeny. All experimental animals were genotyped using 980 informative single nucleotide polymorphism (SNP) markers located on SSC7. A haplotype-based linkage and association analysis using the PHASEBOOK programme was applied to refine the QTL region. Additionally, linear mixed-effect models were used to assess the effect of a positional candidate gene on TTN and other economically important traits [i.e., thoracic vertebrae number (THO), carcass body length (CBL) and weight (CW), back fat thickness (BFT) and intramuscular fat content (IMF) in loin muscles]. Joint linkage and association analysis refined the critical region to a 4.50 Mb region that included a novel positional candidate gene, BRMS1L that encodes the breast cancer metastasis-suppressor 1-like protein, which could possibly be implicated in normal mammary gland development. Significant association of an SNP marker (g. −1087 G > A) in the 5′-flanking region of BRMS1L with TTN (P = 1.10 × 10−8), THO (P = 5.80 × 10−4), and CBL (P = 0.038) was observed. Based on these data, we propose BRMS1L as a positional candidate gene for TTN in pigs. After validation of the association in other independent populations, these results could be useful in optimizing breeding programmes that improve TTN and other economically important traits in swine.