Bovine gene polymorphisms related to fat deposition and meat tenderness

Leptin, thyroglobulin and diacylglycerol O-acyltransferase play important roles in fat metabolism. Fat deposition has an influence on meat quality and consumers' choice. The aim of this study was to determine allele and genotype frequencies of polymorphisms of the bovine genes, which encode leptin (LEP), thyroglobulin (TG) and diacylglycerol O-acyltransferase (DGAT1). A further objective was to establish the effects of these polymorphisms on meat characteristics. We genotyped 147 animals belonging to the Nelore (Bos indicus), Canchim (5/8 Bos taurus + 3/8 Bos indicus), Rubia Gallega X Nelore (1/2 Bos taurus + 1/2 Bos indicus), Brangus Three-way cross (9/16 Bos taurus + 7/16 Bos indicus) and Braunvieh Three-way cross (3/4 Bos taurus + 1/4 Bos indicus) breeds. Backfat thickness, total lipids, marbling score, ribeye area and shear force were fitted, using the General Linear Model (GLM) procedure of the SAS software. The least square means of genotypes and genetic groups were compared using Tukey's test. Allele frequencies vary among the genetic groups, depending on Bos indicus versus Bos taurus influence. The LEP polymorphism segregates in pure Bos indicus Nelore animals, which is a new finding. The T allele of TG is fixed in Nelore, and DGAT1 segregates in all groups, but the frequency of allele A is lower in Nelore animals. The results showed no association between the genotypes and traits studied, but a genetic group effect on these traits was found. So, the genetic background remains relevant for fat deposition and meat tenderness, but the gene markers developed for Bos taurus may be insufficient for Bos indicus.     

Genetic Diversity and Relationship of Yunnan Native Cattle Breeds and Introduced Beef Cattle Breeds

In this study, random amplified polymorphic DNA (RAPD) analysis was used to estimate genetic diversity and relationship in 134 samples belonging to two native cattle breeds from the Yunnan province of China (DeHong cattle and DiQing cattle) and four introduced beef cattle breeds (Brahman, Simmental, MurryGrey, and ShortHorn). Ten primers were used, and a total of 84 bands were scored, of which 63 bands (75.0%) were polymorphic. The genetic distance matrix was obtained by proportions of shared fragment. The results indicate that the Yunnnan DeHong cattle breed is closely related to the Brahman (Bos indicus), and the Yunnan DiQing cattle breed is closely related to the Simmental, ShortHorn, and MurryGrey (Bos taurus) breeds. Our results imply that Bos indicus and Bos taurus were the two main origins of Yunnan native cattle. The results also provide the basic genetic materials for conservation of cattle resources and crossbreeding of beef cattle breeds in South China.     

Association of a missense mutation in the bovine leptin gene with carcass fat content and leptin mRNA levels

Previously, we have shown that alleles of the BM1500 microsatellite, located 3.6 kb downstream of the leptin gene in cattle, were associated with carcass fat measures in a population of 154 unrelated beef bulls. Subsequently, a cytosine (C) to thymine (T) transition that encoded an amino acid change of an arginine to a cysteine was identified in exon 2 of the leptin gene. A PCR-RFLP was designed and allele frequencies in four beef breeds were correlated with levels of carcass fat. The T allele was associated with fatter carcasses and the C allele with leaner carcasses. The frequencies of the SNP alleles among breeds indicated that British breeds have a higher frequency of the T allele whereas the continental breeds have a higher occurrence of the C allele. A ribonuclease protection assay was developed to quantify leptin mRNA in a separate group of animals selected by genotype. Animals homozygous for thymine expressed higher levels of leptin mRNA. This may suggest that the T allele, which adds an extra cysteine to the protein, imparts a partial loss of biological function and hence could be the causative mutation.     

Back fat thickness and meat tenderness are associated with a 526 T→A mutation in the exon 1 promoter region of the MyF-5 gene in Chinese Bos taurus

Qualitative trait loci (QTL) for growth and meat quality traits in cattle (Bos taurus) have been previously mapped to three chromosome regions, 0 to 30, 55 to 70, and 70 to 80 cM on chromosome 5. We evaluated the allele frequencies and gene-specific single nucleotide polymorphisms (SNPs) of bovine myogenic factor 5 (MyF-5) in the QTL regions and their associations with live weight and meat characteristics in indigenous Chinese cattle breeds. PCR-SSCP methodology showed a T>A mutation at 526 bp. Least square analysis revealed a significant association of this SNP with backfat thickness and meat tenderness (P < 0.05), while no significant association was found with live weight, loin eye height, loin eye area, rib area, or water holding capacity. Allele frequencies of MyF-5-A/B in the five breeds were 0.760/0.239, 0.752/0.247, 0.629/0.370, 0.715/0.284, and 0.750/0.250, for JiaXian red, Luxi, Nanyang, Qinchuan, and XiaNan crossbreed, respectively. The genotype distributions for these alleles in two of the Chinese cattle breeds (Luxi and Qinchuan) were not in Hardy-Weinberg equilibrium (P < 0.05); while those for the other three breeds (JiaXian red, Nanyang, and XiaNan) were in agreement with Hardy-Weinberg equilibrium (P > 0.05). The genotypic frequencies among all five cattle breeds showed moderate diversity (0.25 < polymorphism information content < 0.5). Based on our findings, we suggest that the MyF-5 gene influences back fat thickness and meat tenderness in Chinese Bos taurus. This SNP could be useful for marker-assisted selection for meat quality traits in these cattle.     

Independent mitochondrial origin and historical genetic differentiation in North Eastern Asian cattle

In order to clarify the origin and genetic diversity of cattle in North Eastern Asia, this study examined mitochondrial displacement loop sequence variation and frequencies of Bos taurus and Bos indicus Y chromosome haplotypes in Japanese, Mongolian, and Korean native cattle. In mitochondrial analyses, 20% of Mongolian cattle carried B. indicus mitochondrial haplotypes, but Japanese and Korean cattle carried only B. taurus haplotypes. In contrast, all samples revealed B. taurus Y chromosome haplotypes. This may be due to the import of zebu and other cattle during the Mongol Empire era with subsequent crossing with native taurine cattle. B. taurus mtDNA sequences fall into several geographically distributed haplogroups and one of these, termed here T4, is described in each of the test samples, but has not been observed in Near Eastern, European or African cattle. This may have been locally domesticated from an East Eurasian strain of Bos primigenius.     

Origin and phylogeographical structure of Chinese cattle

Complete mitochondrial D-loop sequences of 231 samples were used to explore the origin and genetic diversity of Chinese cattle. Phylogenetical analysis of these sequences revealed both Bos taurus and Bos indicus mitochondrial types in Chinese cattle. Four of the previously identified mitochondrial DNA lineages (T1–T4) were identified in the Bos taurus type, including lineage T1, which was found for the first time in Chinese cattle. Two lineages (I1 and I2) were identified in the Bos indicus type. Our results support the suggestion that the Yunnan-Guizhou Plateau is the domestication site of Chinese zebu. We also found evidence that Tibetan cattle originated from taurine and zebu cattle. The distribution pattern of Chinese cattle breeds was closely related to the geographical and climatic background. It was possible to divide Chinese cattle in this study into two major groups: northern and southern cattle.     

中国黄牛mtDNA D-loop遗传多样性及起源

黄牛自古以来就是我国一个重要的畜种,其经济、文化价值很高。我国是世界上黄牛品种资源最丰富的国家之一。据《中国牛品种志》介绍,把一些地区同种异名的黄牛品种合并以后,尚有28个地方黄牛品种,按照其地理分布区域分为北方黄牛、中原黄牛和南方黄牛三大类型(邱怀,1986)。如果把中国地方黄牛品种分得更细,则有49个固有品种(常洪,1995)。关于中国黄牛的起源,历来有不同的观点。一般认为,中国黄牛是多元起源的,但究竟起源于哪几个牛种,观点不一(陈宏等,1993;于汝梁等,1993;Yu et al.,1999;陈幼春,1990)。主要的观点有:(1)中国黄牛主要起源于…     

Evidence for pleiotropism and recent selection in the PLAG1 region in Australian Beef cattle

A putative functional mutation (rs109231213) near PLAG1 (BTA14) associated with stature was studied in beef cattle. Data from 8199 Bos taurus, Bos indicus and Tropical Composite cattle were used to test the associations between rs109231213 and various phenotypes. Further, 23 496 SNPs located on BTA14 were tested for association with these phenotypes, both independently and fitted together with rs109231213. The C allele of rs109231213 significantly increased hip height, weight, net food intake, age at puberty in males and females and decreased IGF‐I concentration in blood and fat depth. When rs109231213 was fitted as a fixed effect in the model, there was an overall reduction in associations between other SNPs and these traits but some SNPs remained associated (P < 10^?4). Frequency of the mutant C allele of rs109231213 differed among B. indicus (0.52), B. taurus (0.96) and Tropical Composite (0.68). Most chromosomes carrying the C allele had the same surrounding 10 SNP haplotype, probably because the C allele was introgressed into Brahman from B. taurus cattle. A region of reduced heterozygosity surrounds the C allele; this is small in B. taurus but 20 Mb long in Brahmans, indicating recent and strong selection for the mutant allele. Thus, the C allele appears to mark a mutation that has been selected almost to fixation in the B. taurus breeds studied here and introduced into Brahman cattle during grading up and selected to a frequency of 0.52 despite its negative effects on fertility.     

Nucleotide Sequence and Variation of IGF2 Gene Exon 6 in Bos Taurus and Bos Indicus Cattle

The major assumption of this study is that polymorphism of a gene could be used to investigate its allele-specific expression as well as its methylation and imprinting status. Therefore, the aim of this study was to analyze the polymorphism of the coding region of the bovine IGF2 gene and to determine the sequence of its gene exon 6 in Bos taurus and Bos indicus cattle. A single nucleotide “C” deletion/insertion polymorphism was found in both cattle subspecies and a G/T transversion (RFLP-MboII) in the Bos indicus IGF2 gene. A 407-bp fragment of bovine IGF2 exon 6 was sequenced and the sequences (including variable nucleotides) were deposited in the GenBank database. A comparative analysis was performed for this fragment from different species; 99.5% identity was found between Bos taurus and Bos indicus cattle.     

Nucleotide sequence and variation of IGF2 gene exon 6 in Bos taurus and Bos indicus cattle

The major assumption of this study is that polymorphism of a gene could be used to investigate its allele-specific expression as well as its methylation and imprinting status. Therefore, the aim of this study was to analyze the polymorphism of the coding region of the bovine IGF2 gene and to determine the sequence of its gene exon 6 in Bos taurus and Bos indicus cattle. A single nucleotide "C" deletion/insertion polymorphism was found in both cattle subspecies and a G/T transversion (RFLP-MboII) in the Bos indicus IGF2 gene. A 407-bp fragment of bovine IGF2 exon 6 was sequenced and the sequences (including variable nucleotides) were deposited in the GenBank database. A comparative analysis was performed for this fragment from different species; 99.5% identity was found between Bos taurus and Bos indicus cattle.     

A comparison between cervical dimensions of pregnant and nonpregnant Santa Gertrudis and Bos taurus cows

Cervical measurements were recorded on palpation per rectum for 603 Bos taurus , Santa Gertrudis, and crossbred cattle. Postmortem cervical measurements were recorded for 77 of these cows. Antemortem measurements were positively correlated with those taken at postmortem examination (cervical diameter: r=0.75, P<0.01 and cervical length: r=0.29, P<0.06). Cervical diameters from antemortem and postmortem specimens were greater in Santa Gertrudis cattle than in Bos taurus and crossbred cattle (P<0.05). Cervical shape was different between Santa Gertrudis cattle and Bos taurus or crossbred cattle (P<0.01), with Santa Gertrudis cows having a higher incidence of conical shaped cervices than other breeds. Within Santa Gertrudis cattle, the incidence of conical cervical shape increased with age (P<0.05). Conical cervical shape was associated with a lower pregnancy rate in all breeds (P<0.01). Within Santa Gertrudis cattle, conical cervical shape was associated with a lower pregnancy rate in 1- to 4-year-old cows (P<0.05) but not in cows more than 4 years of age (P>0.05).     

Assignment of the growth hormone receptor gene to bovine chromosome 20 using linkage analysis and somatic cell mapping

A polymorphism was identified in the bovine growth hormone receptor ( GHR ) gene by digesting polymerase chain reaction (PCR) products with the restriction enzyme Alul. Two alleles were segregating in cattle of Bos indicus descent, but one allele appears to be fixed in Bos taurus cattle. GHR was localized to bovine chromosome 20 using bovine-rodent hybrid cell lines and linkage analysis.     

Genetic diversity and origin of Chinese cattle revealed by mtDNA D-loop sequence variation

To determine the origin and genetic diversity of Chinese cattle, we analyzed the complete mtDNA D-loop sequences of 84 cattle from 14 breeds/populations from southwest and west China, together with the available cattle sequences in GenBank. Our results showed that the Chinese cattle samples converged into two main groups, which correspond to the two species Bos taurus and Bos indicus. Although a dominant lineage was clearly discerned in both B. taurus and B. indicus mtDNAs, network analysis of the lineages in each of the two species further revealed multiple clades that presented regional difference. The B. taurus samples in China could be grouped into clades T2, T3, and T4, whereas B. indicus harbored two clades I1 and I2. Age estimation of these discerned clades showed a time range of 14,100-44,500 years before present (YBP). The phylogenetic pattern of Chinese cattle was consistent with the recently described cattle matrilineal pool from northeast Asia, but suggested that B. indicus contributed more to the cattle from south and southwest China. The genetic diversity of Chinese cattle varied among the breeds studied.     

Polymorphic regions affecting human height also control stature in cattle

Orthologous positions of 55 genes associated with height in four human populations were located on the bovine genome. Single nucleotide polymorphisms close to eight of these genes were significantly associated with stature in cattle (Bos taurus and Bos indicus). This suggests that these genes may contribute to controlling stature across mammalian species.     

中国地方黄牛的Y染色体遗传多样性及其进化起源

中国黄牛的进化起源与遗传多样性一直是国内外动物遗传学家感兴趣的课题之一.本文主要从Y染色体的形态多样性和Y染色体特异性微卫星标记遗传多态性两个方面对中国地方黄牛的遗传多样性和进化起源进行了综述.中国地方黄牛Y染色体具有中着丝粒、亚中着丝粒和近端着丝粒3种类型,这说明中国地方黄牛起源于普通牛和瘤牛.利用Y染色体特异性微卫星标记对中国地方黄牛Y染色体单倍型分布特征及Y染色体基因流模式的分析表明,北方种群中普通牛单倍型频率最高,瘤牛单倍型在南方种群中占优势;在中国不同地域,瘤牛Y染色体单倍型频率呈现自南而北、自东而西逐渐降低的趋势,这再次证实了中国黄牛主要来源于普通牛和瘤牛,这可能是这两类牛群在长期的历史进化过程中,分别从东南方向和西北方向进入我国,并在中原地区汇合的结果.本文为中国地方黄牛品种资源保护和杂交育种工作提供了参考依据.     

我国部分黄牛品种线粒体D-loop区遗传多样性与起源分化

为了解我国地方黄牛品种线粒体DNA的遗传变异情况, 文章测定了16个地方黄牛品种206个个体线粒体D-loop区的全序列, 共检测到101个变异位点; 99种单倍型, 其中73种是普通牛单倍型, 26种是瘤牛单倍型; 平均核苷酸差异为22.6920, 单倍型多样度为0.9320, 核苷酸多样度为0.0227, 表明我国黄牛品种遗传多样性非常丰富。构建的NJ进化树显示16个品种来源于两大母系: 普通牛和瘤牛; 构建的Network图表明73种普通牛单倍型可以分为3大单倍型群; 26种瘤牛单倍型分为5种单倍型群, 推测我国瘤牛在迁移过程中, 至少经历了4次群体扩张事件。通过分析比较地方黄牛品种与内罗门牛共有的 H3单倍型, 发现其中只有16%的序列与内罗门牛的H3单倍型非常相似, 其余84%的序列均发生了鸟嘌呤变异, 推测这些变异很可能是我国瘤牛固有的变异。     

Reproductive cycles in Bos indicus cattle

Several studies using transrectal ovarian ultrasonic scanning in Bos taurus (B. taurus) cattle and more recently in Bos indicus (B. Indicus) females evaluated the reproductive cycles of heifers and cows under different conditions. In general, B. indicus cattle have more follicles and more follicular waves during the estrous cycle and ovulate from smaller follicles than B. taurus. Consequently B. indicus females have smaller corpora lutea and it is assumed circulating concentrations of estradiol and progesterone are also less. However, these findings may vary depending on the nutritional status and regimen in which the animals are managed. Moreover, there are significant differences between B. taurus and B. indicus regarding follicle size at the time of deviation of the dominant follicle. These differences in ovarian function between B. indicus and B. taurus, e.g. greater antral follicle population are, probably, the main reasons for the great success of in vitro embryo production programs in Zebu cattle, especially in Brazil.