Relationships of sire scrotal circumference to offspring reproduction and growth

Reproductive and growth data were obtained on 779 and 564 yearling beef heifers and bulls, respectively, that had sires with yearling scrotal circumference data at the San Juan Basin Research Center, Hesperus, CO. Partial regression coefficients of reproductive and growth traits on inbreeding (FXC) and age of the individual and adjusted scrotal circumference of sire (SCSI) were obtained. Growth and reproductive traits of heifers and growth and breeding soundness traits of bulls were analyzed. Separate analyses for each sex were performed, but least squares models were similar. Models included fixed effects of breed, birth year (BY), age of dam (AOD) and the covariates FXC, age (day of birth in heifer analyses) and SCSI. Scrotal circumference of sire was adjusted for age, FXC, AOD and BY using values obtained in a separate analysis. Seminal traits improved as age increased, and there was a seasonal effect present for age of puberty. Inbreeding had a detrimental effect on reproductive traits. Partial regression coefficients for the reproductive traits on SCSI were: age of puberty, -.796 d/cm; age of first calving, -.826 d/cm; julian day of first calving, -.667 d/cm; julian day of second calving, .597 d/cm; most probable producing ability, .132 %/cm; percent sperm motility, -.74 %/cm; percent primary sperm abnormalities, .08 %/cm; percent secondary sperm abnormalities, .92 %/cm; percent normal sperm, -1.28 %/cm; total breeding soundness examination score, .28 units/cm and scrotal circumference, .306 cm/cm. A heritability of .39 was obtained for scrotal circumference.     

Association analysis of novel polymorphisms in 2′, 5′‐oligoadenylate synthetase gene with reproductive traits in indigenous and cross‐bred cattle of Indian Origin

2′, 5′‐Oligoadenylate synthetases (OAS) are important components of an interferon‐mediated antiviral pathway. No polymorphisms in exonic regions of bovine OAS1 gene have been identified and associated with reproduction traits. The objective of the study was to detect and evaluate the effects of mutations in exonic region of bovine OAS1 gene with reproduction traits in cattle. DNA samples collected from 250 individual cows of two Indian dairy breeds (Sahiwal and Frieswal) of cattle were used in the study. The genetic variants of the OAS1 gene were identified with polymerase chain reaction–single‐strand conformation polymorphism (PCR‐SSCP) and sequence analysis using seven set of primer pairs. The PCR‐SSCP analysis revealed polymorphism in the fragments comprising of exon 2, exon 5 and first fragment of exon 6 while the fragments of exons 1, 3, 4 and second fragment of exon 6 were monomorphic in Sahiwal and Frieswal cattle. The mutations in the amplified region comprising of exon 2 were found to have significant association with age at first breeding and calving, service period, dry period and pregnancy rate. Significant associations were found between SNPs in the exon 5 and service and dry periods of the animal, whereas the genetic variants in the first fragment of the exon 6 showed significant association with age at first breeding and calving. To our knowledge, this study demonstrated for the first time that the polymorphisms in OAS1 gene were associated with reproductive traits and it can be chosen as a candidate gene for improvement of reproductive performance of cattle.     

Identification of genomic regions related to age at first calving and first calving interval in water buffalo using single-step GBLUP

In Brazil, water buffaloes have been used to produce milk for mozzarella cheese production. Consequently, the main selection criterion applied for the buffalo genetic improvement is the estimated mozzarella yield as a function of milk, fat and protein production. However, given the importance of reproductive traits in production systems, this study aimed to use techniques for identifying genomic regions that affect the age at first calving (AFC) and first calving interval (FCI) in buffalo cows and to select candidate genes for the identification of QTL and gene expression studies. The single-step GBLUP method was used for the identification of genomic regions. Windows of 1 Mb containing single-nucleotide polymorphisms were constructed and the 10 windows that explained the greatest proportion of genetic variance were considered candidate regions for each trait. Genes present into the selected windows were identified using the UOA_WB_1 assembly as the reference, and their ontology was defined with the Panther tool. Candidate regions for both traits were identified on BBU 3, 12, 21 and 22; for AFC, candidates were detected on BBU 6, 7, 8, 9 and 15 and for first calving interval on BBU 4, 14 and 19. This study identified regions with great contribution to the additive genetic variance of age at first calving and first calving interval in the population of buffalo cows studied. The ROCK2, PMVK, ADCY2, MAP2K6, BMP10 and GFPT1 genes are main candidates for reproductive traits in water dairy buffaloes, and these results may have future applications in animal breeding programs or in gene expression studies of the species.     

Genetic association between different criteria to define sexual precocious heifers with growth,carcass, reproductive and feed efficiency indicator traits in Nellore cattle using genomic information

The aim of this study was to estimate genetic parameters for different precocious calving criteria and their relationship with reproductive, growth, carcass and feed efficiency in Nellore cattle using the single‐step genomic BLUP. The reproductive traits used were probability of precocious calving (PPC) at 24 (PPC24), 26 (PPC26), 28 (PPC28) and 30 (PPC30) months of age, stayability (STAY) and scrotal circumference at 455 days of age (SC455). Growth traits such as weights at 240 (W240) and 455 (W455) days of age and adult weight (AW) were used. Rib eye area (REA), subcutaneous fat thickness (SFT), rump fat thickness (RFT) and residual feed intake (RFI) were included in the analyses. The estimation of genetic parameters was performed using a bi‐trait threshold model including genomic information in a single‐step approach. Heritability for PPC traits was moderate to high (0.29–0.56) with highest estimates for PPC24 (0.56) and PPC26 (0.50). Genetic correlation estimates between PPC and STAY weakened as a function of calving age. Correlation with SC455, growth and carcass traits were low (0.25–0.31; ?0.22 to 0.04; ?0.09 to 0.18, respectively), the same occurs with RFI (?0.09 to 0.08), this suggests independence between female sexual precocity and feed efficiency traits. The results of this study encourage the use of PPC traits in Nellore cattle because the selection for such trait would not have a negative impact on reproductive, growth, carcass and feed efficiency indicator traits. Stayability for sexual precocious heifers (PPC24 and PPC26) must be redefined to avoid incorrectly phenotype assignment.     

Genetic (co)variances for calving difficulty score in composite and parental populations of beef cattle: II. Reproductive, skeletal, and carcass traits

There is limited genetic information relating calving difficulty and body weights to other productive and reproductive traits. Such information is useful for specifying selection criteria and for predicting economic consequences of selection. Genetic, maternal, and environmental covariances of six productive and reproductive measurements with calving difficulty, birth weight, 200-d weight, and 168-d postweaning gain were estimated in 12 experimental populations of cattle. Calf (direct) genetic effects resulting in longer gestation length were associated with increased calving difficulty and birth weight. Maternal genetic effects of increased gestation length and heavier birth weight were significantly associated. Lighter birth weight and reduced calving difficulty were associated with earlier heifer age at puberty. Increases in direct genetic effects of calving difficulty, 200-d weight, and postweaning gain were associated with a small increase in direct effect of scrotal circumference. Increased direct genetic effects of scrotal circumference were correlated with maternal effects decreasing calving difficulty and increasing 200-d weight. Direct effects of the skeletal measurements, yearling hip height, and heifer pelvic area were positively correlated with direct effects of calving difficulty, birth weight, 200-d weight, and postweaning gain, positively correlated with maternal effects for birth weight and 200-d weight, and negatively correlated with maternal calving difficulty. Percentage of retail product was positively associated with calving difficulty and negatively associated with 168-d gain. Predicted genetic change in calving difficulty resulting from one standard deviation of selection for either calving difficulty score or birth weight was much larger than for any other traits. Selection for 200-d weight, 168-d postweaning gain, hip height, pelvic area, or scrotal circumference was predicted to have opposite effects on direct and maternal calving difficulty. Estimated genetic correlations indicate some small to moderate relationships between calving difficulty and the measured productive and reproductive traits. However, selection for reduced calving difficulty should be based on calving difficulty score and(or) birth weight because of their superiority in predicted genetic change.     

中国肉用西门塔尔牛育种目标性状的选择及其经济权重的测算

为了选育中国西门塔尔牛肉用品系,本研究从中国肉用西门塔尔牛育种实践出发,确定了适应当前中国肉用西门塔尔牛的育种目标性状和选择性状。采用差额法计算出各目标性状的边际效益,并通过各目标性状表型值的遗传标准差校正边际效益,得到相应育种目标性状的经济权重。结果表明,中国肉用西门塔尔牛近期的育种目标性状主要包括生长发育性状（断奶重、育肥期日增重、18月龄体重）、胴体性状（胴体品质、屠宰率、净肉率）及繁殖性状（初产年龄、产犊间隔和留群时间）。在现有市场和生产条件下,上述育种目标性状的边际效益分别为17.93元/kg、16.2元/kg、7.17元/kg、297.99元/级、497.82元/%、594.46元/%、-3.62元/d、-26.55元/d、232.75元/y,3类性状中生长发育性状、胴体性状及繁殖性状的经济权重之比为31.49%：15.86%：52.65%,约为2：1：3,繁殖性状占总经济权重最高,其次是生长发育性状和胴体性状。综上所述,在中国肉用西门塔尔牛育种过程中,繁殖性状具有最重要的地位,需加强繁殖性状的选择力度。     

Selection of Objective Traits and Estimation of Economic Weights for Chinese Simmental Beef Cattle

In order to breed a beef line in Chinese Simmental cattle,this research defined breeding objective traits and selected traits according to real breeding condition of Chinese Simmental beef cattle.Using the balance method to calculate the marginal benefit of each objective trait and getting the corresponding economic weight of breeding objective traits through the standard value of the error corrected marginal benefit of breeding objective traits.The results showed that breeding objective traits mainly included growth traits (including weaning weight,fattening daily gain,18th month weight),carcass traits (including carcass quality,dressing percentage,pure meat percentage) as well as reproductive traits (including age at first calving,calving interval,stay group time).In the current market and production conditions,the marginal benefit of the breeding objective traits were 17.93 yuan/kg,16.2 yuan/kg,7.17 yuan/kg,297.99 yuan/grade,497.82 yuan/%,594.46 yuan/%,-3.62 yuan/d,-26.55 yuan/d and 232.75 yuan/y,respectively,and the ratio of relative economic weights of three kinds of traits was 31.49%:15.86%:52.65%,similar to 2:1:3,and reproductive traits occupied larger economic weight,was better than growth traits and carcass traits.The results indicated that reproductive traits played an important role in the process of breeding in Chinese Simmental beef cattle,and we needed to strengthen the selection of reproductive traits.     

Estimates of covariances between reproduction and growth in Australian beef cattle

Estimates of covariance components between scrotal circumference, serving capacity, days to calving, and yearling and final weight were obtained for Hereford, Angus, and Zebu cross cattle in temperate and tropical Australia. Analyses were carried out by REML employing a derivative-free algorithm and fitting bivariate animal models. Aspects of modeling and computational requirements related to the use of this method are discussed. Estimates of heritabilities agreed closely with those from univariate analyses, being low for female reproductive performance and moderate to high for male reproduction and growth. Estimates of genetic correlation between male and female fertility traits were low but favorable, being -.25, -.28, and -.41 between scrotal circumference and days to calving for Herefords, Angus, and Zebu crosses, respectively. Genetic correlations between male reproductive traits and weights ranged from .24 to .52 for the temperate breeds and were higher (.65 to .69) for Zebu crosses. Phenotypic correlations between scrotal circumference and weights were similar for all breeds, ranging from .32 to .47, whereas serving capacity and weights were phenotypically unrelated. Estimates of correlations between days to calving and weights were less consistent. Phenotypically, there was little association between the two traits. Genetic correlations for Zebu crosses were negative and low to moderate (-.36 to -.66) and estimates for Angus were close to zero.     

南阳牛生长性状相关基因组区域全基因组关联分析

本研究旨在筛选和鉴定与南阳牛生长性状相关的基因组区域和候选基因,从而更好地了解牛生长性状的遗传机制。试验共采集71头南阳牛母牛血样并提取基因组DNA,利用SLAF-seq（specific-locus amplified fragment sequencing）技术获得全基因组SNP标记并对试验个体基因型进行分型。对每头个体初生重及不同月龄（6、12、18、24、36）的体重、体高、体斜长、胸围和坐骨端宽及每6个月体增重等生长性状进行全基因组关联分析;获得显著相关的基因组区域后,对其中基因进行功能注释以筛选候选基因。结果显示,共获得141 755个筛选后的SNPs,通过全基因组关联分析鉴定出5个分别与12月龄体重（8号染色体：17 320 634~17 347 720 bp）、12月龄胸围（2号染色体：15 063 190~15 155 309 bp）、24月龄体斜长（11号染色体：60 727 342~81 425 987 bp）、36月龄坐骨端宽（14号染色体：15 635 762~15 643 272 bp）和12~18月龄体增重（26号染色体：40 456 192~40 456 477 bp）等生长性状显著相关的基因组区域（LOD≥6.35）。通过对5个基因组区域内的186个基因进行功能注释,共筛选得到11号染色体上的8个基因（BMP10、IFT172、SDC1、TCF23、TRIM54、RAB1A、VPS54和GDF7）与骨生长、肌肉发育和生长调控有关,建议其可优先作为牛生长性状相关候选基因进行进一步验证。     

牛繁殖性状候选基因研究进展

繁殖性状是牛（Bos taurus）重要的经济性状,与生产成本、经济效益密切相关。繁殖相关的主要性状包含精液品质、卵泡发生、排卵、胚胎发育、产犊难易、产犊间隔等,其表现通常受到基因的严格调控。对繁殖性状的重要基因功能深入挖掘和筛选对于牛的改良和选育、提高生产性能、节约生产成本至关重要。文章介绍了国内外关于牛繁殖性状基因的研究进展,如促黄体素受体（luteinizing hormone receptor,LHR）及牛精子鞭毛2（sperm flagella 2,SPEF2）与精液品质相关,促性腺激素释放激素（gonadotropin-releasing hormone,GnRH）、促卵泡素（follicle-stimulating hormone,FSH）、促黄体激素（luteinizing hormone,LH）及抗缪勒氏管激素（anti-Müllerian hormone,AMH）、骨形态发生蛋白15（bone morphogenetic protein 15,BMP15）、生长分化因子9（growth differentiation factor 9,GDF9）与卵泡发生、排卵相关,JY-1、尾型同源框2（caudal type homeobox 2,CDX2）及冠毛素2（pappalysin 2,PAPP-A2）与早期胚胎发育及产犊难易相关,唾液酸结合Ig样凝集素5（sialic acid binding Ig like lectin 5,SIGLEC5）、CXC基序趋化因子受体1（C-X-C motif chemokine receptor 1,CXCR1）及叉头转录因子O1（forkhead box O1,FoxO1）与产犊间隔相关,作者通过综述以上重要繁殖性状相关基因的研究,介绍了这些繁殖性状重要基因对牛生产性能的影响,以期为牛繁殖性状相关调控基因的研究提供参考依据。     

中国不同牛种DGAT1基因遗传多样性及经济性状关联分析研究进展

乙酰辅酯A∶二酰甘油酰基转移酶(DGAT1)是甘油三脂合成过程中唯一的关键酶,对动物机体脂肪代谢、沉积起重要作用,已成为研究奶牛泌乳性状和肉牛主要经济性状的重要候选基因之一。近年来,随着相关研究的不断深入,研究者普遍认为DGAT1基因对奶牛的产奶量、乳脂率、乳蛋白率、乳糖率、乳脂肪酸及空怀天数、输精次数、初配年龄等繁殖性状均有显著影响,且与肉牛体脂也存在相关性。作者主要介绍了DGAT1基因的遗传多态性及其与经济性状关联分析在中国各地区不同品种奶牛、肉牛、水牛和牦牛上的研究进展,指出该基因对奶牛的产奶性能及肉牛的肉质性状、生长性状具有重要的调控作用。但由于环境条件、品种及选育背景等因素影响,DGAT1基因遗传多态性对不同地区不同牛群体的经济性状影响不尽相同。因此,要将DGAT1基因实际应用在品种选育工作中还需明确该基因对研究群体的具体遗传效应,并结合其他候选基因进行综合分析。     

Genetic associations between accumulated productivity, and reproductive and growth traits in Nelore cattle

The total meat yield in a beef cattle production cycle is economically very important and depends on the number of calves born per year or birth season, being directly related to reproductive potential. Accumulated Productivity (ACP) is an index that expresses a cow's capacity to give birth regularly at a young age and to wean animals of greater body weight. Using data from cattle participating in the “Program for Genetic Improvement of the Nelore Breed” (PMGRN — Nelore Brasil), bi-trait analyses were performed using the Restricted Maximum Likelihood method based on an ACP animal model and the following traits: age at first calving (AFC), female body weight adjusted for 365 (BW365) and 450 (BW450) days of age, and male scrotal circumference adjusted for 365 (SC365), 450 (SC450), 550 (SC550) and 730 (SC730) days of age. Median estimated ACP heritability was 0.19 and the genetic correlations with AFC, BW365, BW450, SC365, SC450, SC550 and SC730 were 0.33, 0.70, 0.65, 0.08, 0.07, 0.12 and 0.16, respectively. ACP increased and AFC decreased over time, revealing that the selection criteria genetically improved these traits. Selection based on ACP appears to favor the heaviest females at 365 and 450 days of age who showed better reproductive performance as regards AFC. Scrotal circumference was not genetically associated with ACP.     

Estimation of (co)variance components for reproductive traits in Angus beef cattle divergently selected for blood serum IGF-I concentration

The objective of this study was to obtain estimates of (co)variance components for reproductive traits and insulin-like growth factor-I (IGF-I) concentration. Data were from a divergent selection experiment for blood serum IGF-I concentration in Angus beef cattle. Numbers of observations for mean IGF-I concentration of three blood samples taken at d 28, 42, and 56 of the 140-d postweaning test, scrotal circumference (SC), percentage of motile sperm cells (PMSC), percentage of morphologically normal sperm cells (PNSC), age of heifers at first calving (AFC), and calving rate (CR) were 1,848, 825, 596, 765, 294, and 2,092, respectively. Total number of animals in the numerator relationship matrix, including base animals, was 2,864, of which 1,861 were inbred. Estimates of direct heritability for IGF-I concentration of three blood samples collected at d 28, 42, and 56 of the postweaning test and for mean IGF-I concentration were 0.43+/-0.08, 0.51+/-0.09, 0.41+/-0.08, and 0.50+/-0.08, respectively. Estimates of direct heritability for SC, PMSC, PNSC, AFC, and CR were 0.51+/-0.13, 0.08+/-0.12, 0.47+/-0.07, 0.26+/-0.28, and 0.11+/-0.05, respectively. With the exception of age at first calving, estimates of maternal heritability and proportion of phenotypic variance that were due to permanent environmental effects of the dams were smaller than 0.21. Observations for calving rate were entered as either 1 (if calved) or 100 (if not calved). Estimates of additive genetic correlations of mean IGF-I concentration with SC, PMSC, PNSC, AFC, and CR were 0.35+/-0.11, 0.43+/-0.32, 0.00+/-0.03, -0.14+/-0.33, and -0.41+/-0.16, respectively. Environmental and phenotypic correlations for all of the traits with IGF-I measurements were smaller than 0.23. These results suggest that selection for increased serum IGF-I concentration should result in increased scrotal circumference, percent motile sperm cells, and calving rate.     

Selection signatures in Canchim beef cattle

Background: Recent technological advances in genomics have allowed the genotyping of cattle through single nucleotide polymorphism(SNP) panels. High-density SNP panels possess greater genome coverage and are useful for the identification of conserved regions of the genome due to selection, known as selection signatures(SS). The SS are detectable by different methods, such as the extended haplotype homozygosity(EHH); and the integrated haplotype score(i HS), which is derived from the EHH. The aim of this study was to identify SS regions in Canchim cattle(composite breed), genotyped with high-density SNP panel.Results: A total of 687,655 SNP markers and 396 samples remained for SS analysis after the genotype quality control. The i HS statistic for each marker was transformed into pi HS for better interpretation of the results.Chromosomes BTA5 and BTA14 showed pi HS 5, with 39 and nine statistically significant SNPs(P 0.00001),respectively. For the candidate selection regions, i HS values were computed across the genome and averaged within non-overlapping windows of 500 Kb. We have identified genes that play an important role in metabolism,melanin biosynthesis(pigmentation), and embryonic and bone development.Conclusions: The observation of SS indicates that the selection processes performed in Canchim, as well as in the founder breeds(i.e. Charolais), are maintaining specific genomic regions, particularly on BTA5 and BTA14. These selection signatures regions could be associated with Canchim characterization.     

三河牛繁殖性状遗传参数的评估

本研究以1986年中国自主培育兼用牛新品种--三河牛,在内蒙古海拉尔谢尔塔拉种牛场核心群5 257头1998-2012年20 949条繁殖记录为研究材料,以青年牛首次妊娠日龄、青年牛首次产犊日龄、成母牛妊娠期、成母牛空怀期、产犊间隔为研究对象,用SAS 9.13、DMU软件对数据进行处理,采用AI-REML结合EM算法并配合多性状动物模型对各性状影响因素方差组分进行估计,估算出各性状遗传力,并利用各性状育种值分析其遗传趋势.结果显示,青年牛首次妊娠日龄、青年牛首次产犊日龄、成母牛妊娠期、成母牛空怀期、产犊间隔遗传力分别为0.0552、0.0638、0.0527、0.1096、0.0844,繁殖性状除成母牛空怀期遗传力为0.1096外,其余均小于0.1,属于低遗传力性状.青年牛首次妊娠日龄、青年牛首次产犊日龄、成母牛妊娠期、成母牛空怀期、产犊间隔育种值遗传趋势总体上无明显下降趋势,三河牛繁殖性能保持良好.该试验结果为三河牛优化育种方案、提高选种准确性提供重要理论依据.     

Signatures of selection in Charolais beef cattle identified by genome‐wide analysis

Charolais cattle are one of the most important breeds for meat production worldwide; in México, its selection is mainly made by live weight traits. One strategy for mapping important genomic regions that might influence productive traits is the identification of signatures of selection. This type of genomic features contains loci with extended linkage disequilibrium (LD) and homozygosity patterns that are commonly associated with sites of quantitative trait locus (QTL). Therefore, the objective of this study was to identify the signatures of selection in Charolais cattle genotyped with the GeneSeek Genomic Profiler Bovine HD panel consisting of 77 K single nucleotide polymorphisms (SNPs). A total 61,311 SNPs and 819 samples were used for the analysis. Identification of signatures of selection was carried out using the integrated haplotype score (iHS) methodology implemented in the rehh R package. The top ten SNPs with the highest piHS values were located on BTA 4, 5, 6 and 14. By identifying markers in LD with top ten SNPs, the candidate regions defined were mapped to 52.8–59.3 Mb on BTA 4; 67.5–69.3 on BTA 5; 39.5–41.0 Mb on BTA 6; and 26.4–29.6 Mb on BTA 14. The comparison of these candidate regions with the bovine QTLdb effectively confirmed the association (p < 0.05) with QTL related to growth traits and other important productive traits. The genomic regions identified in this study indicated selection for growth traits on the Charolais population via the conservation of haplotypes on various chromosomes. These genomic regions and their associated genes could serve as the basis for haplotype association studies and for the identification of causal genes related to growth traits.     

Genetic Evaluation of Reproductive Traits in Sanhe Cattle

This study was conducted on 20 949 reproductive records from 1998 to 2012 of 5 257 Sanhe cattle in Xiertala cattle farm,Inner Mongolia,which was a synthetic breed formed in China in 1986.Age at first pregnancy in heifer (AFPH),age at first calving in heifer (AFCH),gestation length in cow (GLC),days open in cow (DOC),and calving interval in cow (CIC) were considered for genetic evaluation.SAS 9.13 and DMU software were used for data processing,and AI-REML combined EM algorithm based on multiple traits animal model was employed for estimating variance components.The heritability for each trait were then calculated,and breeding value was used to analyze the genetic trends.The results showed that the estimated heritabilities of age at first pregnancy in heifer,age at first calving in heifer,gestation length in cow,days open in cow,calving interval in cow were 0.0552,0.0638,0.0527,0.1096 and 0.0844,respectively.The heritabilities were all less than 0.1 except days open (0.1096),indicating these were low inheritable traits.In general,trends of EBVs for each trait didn't show any defined progresses and indicating good reproductive performance maintained in Sanhe cattle.These results lay a theoretical foundation for optimizing breeding programs and improving the accuracy of selection in Sanhe cattle.     

儋州鸡体尺性状全基因组关联分析

【目的】 挖掘影响地方鸡体尺性状的有效SNP位点及功能基因, 给儋州鸡育种工作提供有效的数据基础和理论支撑。【方法】 共采集200只儋州鸡血样并提取基因组DNA, 利用10×全基因组重测序技术获得全基因组SNP标记并对试验个体基因型进行分型。使用EMMAX软件基于混合线性模型对70日龄的儋州鸡体尺性状(胫长、胫围、体斜长、胸宽、髋骨宽、胸深、龙骨长)进行全基因组关联分析。【结果】 共发现与胫长性状和胫围性状基因组水平显著相关的SNPs位点有12和8个, 与胫长性状相关SNPs分别定位于1、2、4和8号染色体上; 与胫围性状相关的SNPs定位于2、4、8和13号染色体上。预测与胫长相关的候选基因为KCNA1、TPK1、EZH2、FSTL5和AMY2A基因, 与胫围相关的候选基因为TPK1、FSTL5、AMY2A、TGFBI、LECT2和IL-9。通过KEGG通路分析和GO注释发现, 8个基因参与钾离子跨膜转运、硫胺素新陈代谢、细胞增殖、钙离子结合、骨骼肌卫星细胞维持与骨骼肌再生、细胞受体相互作用、生长因子活性等生物学进程。【结论】 本研究发现了20个与儋州鸡体尺性状关联的SNPs位点, 并筛选到8个目标性状候选基因, 为儋州鸡育种提供候选的分子标记, 为地方鸡标记辅助选择提供新的思路。     

Genetic effects on beef heifer puberty and subsequent reproduction.

Significant genetic variation exists within and between breeds of beef cattle for age at puberty (AP). In general, faster-gaining breed groups of larger mature size reach puberty at a later age than do slower-gaining breed groups of smaller mature size; breeds selected for milk production reach puberty at younger ages than do those breeds not selected for milk production. Heterosis, independent of heterosis effects on weight, influences most measures of puberty in females and scrotal circumference (SC) in males. Crossbred heifers reach puberty at younger ages and heavier weights than their straightbred counterparts. Scrotal circumference has been shown to be an excellent indicator of AP in yearling bulls. Furthermore, a favorable genetic relationship exists between SC in bulls and AP of female offspring. Beef cattle breeders may take a direct approach to breeding for AP and subsequent reproduction by directly selecting for measures of fertility such as SC. However, an indirect approach, involving selection for an array of traits that provide an appropriate "genetic environment" for the expression of fertility (i.e., size, milk production, calving ease) may be preferred. Although seedstock producers are limited to making change through within-breed selection, commercial producers can take advantage of both within- and between-breed selection as well as crossbreeding to achieve the same goal.     

Additive genetic relationships between heifer pregnancy and scrotal circumference in Hereford cattle.

The objective of this study was to determine an appropriate method for using yearling scrotal circumference observations and heifer pregnancy observations to produce EPD for heifer pregnancy. We determined the additive genetic effects of and relationship between scrotal circumference and heifer pregnancy for a herd of Hereford cattle in Solano, New Mexico. The binary trait of heifer pregnancy was defined as the probability of a heifer conceiving and remaining pregnant to 120 d, given that she was exposed at breeding. Estimates of heritability for heifer pregnancy and scrotal circumference were .138+/-.08 and .714+/-.132, respectively. Estimates of fixed effects for age of dam and age were significant for heifer pregnancy and bull scrotal circumference. The estimate of the additive genetic correlation between yearling heifer pregnancy and yearling bull scrotal circumference was .002+/-.45. Additional analyses included models with additive genetic groups for scrotal circumference EPD for heifer pregnancy or heifer pregnancy EPD for scrotal circumference to account for a potential nonlinear relationship between scrotal circumference and heifer pregnancy. Results support the development of a heifer pregnancy EPD because of a higher estimated heritability than previously reported. The development of a heifer pregnancy EPD would be an additional method for improving genetic merit for heifer fertility.