Taurine and zebu admixture in Near Eastern cattle: a comparison of mitochondrial, autosomal and Y-chromosomal data

Eight Bos taurus cattle breeds from the Near East region were screened with a Bos indicus (zebu)-diagnostic Y-specific microsatellite (INRA124) to estimate the proportion of zebu Y chromosomes in each population. This value was compared with previously published values for zebu introgression for both the mitochondrial and autosomal gene pools of the same breeds. All breeds revealed considerable levels of introgression from B. indicus cattle when the autosomal data were taken into consideration; this was particularly apparent in cattle populations from Iraq in the east, and declined in the populations further west towards Anatolia. This non-random pattern of introgression and admixture is suggestive of the introduction of zebu cattle from the region corresponding to present-day Iran and northern Pakistan. In addition, the maternal and paternal markers demonstrate that the movement of cattle into and within the Near East was complex.     

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.     

Complete mitochondrial genomes of Bos taurus and Bos indicus provide new insights into intra-species variation, taxonomy and domestication

The taurine and zebuine cattle breeds comprise the majority of the world cattle population but their taxonomic status is still controversial. The two forms of cattle are currently classified as Bos taurus and Bos indicus species and are differentiated primarily by the presence or absence of a hump. However, these two species hybridize readily, producing fully fertile offspring. We have determined and analyzed complete B. taurus and B. indicus mitochondrial genome sequences to investigate the extent of sequence divergences and to study their taxonomic status by molecular dating. The sequences encompassed 16,338 and 16,339 nucleotides, respectively, and differed at 237 positions. Estimated divergence times indicated that the two cattle lineages separated 1.7-2.0 million years ago. Combined phylogenetic analyses of 18 new and 130 previously reported extant B. taurus and B. indicus control region sequences with data from 32 archaeological specimens of the extinct wild aurochs (Bos primigenius) identified four major maternal lineages. B. primigenius haplotypes were present in all but the B. indicus lineage, and one B. taurus sequence clustered with B. primigenius P haplotypes that were not previously linked with domestic cattle. The B. indicus cluster and a recently reported new B. primigenius haplotype that represents a new lineage were approximately equidistant from the B. taurus cluster. These data suggest domestications from several differentiated populations of B. primigenius and a subspecies status for taurine (B. primigenius taurus) and zebuine (B. primigenius indicus) cattle.     

Comparative analysis of GDF 8 (myostatin) in Bos indicus and Bos taurus.

We report the myostatin gene sequence of Bos indicus cattle in comparison to Bos taurus. B. indicus genomic sequence was obtained by overlapping PCR amplification of genomic DNA. Exon splice sites were confirmed by mRNA sequencing. There were 5 exonic single nucleotide polymorphisms (SNP) only one of which was a non-synonymous mutation that resulted in a serine to asparagine (S214N) amino acid substitution. The B. indicus gene has two insertions of 16 and 12 bases in the first intron. In addition, SNPs in the 3' UTR and intronic regions are also reported.     

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.     

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.     

Importance of sperm genotype (indicus versus taurus) for fertility and embryonic development at elevated temperatures

Heat stress has negative effects on bovine reproduction, particularly for European breeds (Bos taurus taurus) that are less thermotolerant than zebu cattle (Bos taurus indicus). Here, the evidence that spermatozoa and oocyte both contribute to early embryonic resistance to heat shock is demonstrated. In addition, the use of reproductive biotechnologies to improve bovine thermotolerance, are outlined by comparing data from taurus, indicus and crossbred genotypes.     

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…     

Pattern and manipulation of follicular development in Bos indicus cattle

Bos indicus cattle are widespread in tropical regions due to their adaptation to these environments. Although data on reproductive performance have indicated both inferior and superior results for B. indicus cattle, there is little doubt that B. indicus cattle are superior than Bos taurus cattle when they are both kept in tropical or subtropical environments, where stressors like hot temperatures, humidity, ectoparasites and low quality forages are greater. Reproductive endocrinology and oestrus behaviour of the B. indicus cattle have been studied for over 30 years; however, the application of technologies such as real time ultrasonography and Heat-Watch systems has expanded our knowledge on the ovarian follicular-wave dynamics during the oestrous cycle and the time of ovulation. Ovarian follicular dynamics in B. indicus cattle is characterised by the occurrence of two, three or sometimes four waves of follicular development. While dominance is similar to that in B. taurus cattle, maximum diameters of the dominant follicle and CL are smaller than those reported in B. taurus and are probably due to a lower capacity for LH secretion than in B. taurus. Duration of oestrus is approximately 10 h and the interval from oestrus to ovulation is about 27 h. However, the variability in response to prostaglandin F2alpha (PGF) treatments and the difficulty for oestrus detection in B. indicus cattle have limited the widespread application of artificial insemination (AI) and emphasizes the need for treatments that control follicular development and ovulation. Follicular-wave development in B. indicus cattle can be controlled mechanically by ultrasound-guided follicle ablation, or hormonally by treatments with GnRH or oestradiol and progestogen/progesterone in combination. Treatments with GnRH plus PGF and a second GnRH (synchronization protocol known as Ovsynch) or oestradiol benzoate (known as GPE) have resulted in acceptable pregnancy rates after fixed-time AI (FTAI) in cycling cows, but results were lower in heifers and cows in postpartum anoestrus. Alternatively, treatments with oestradiol and progestogen/progesterone releasing devices resulted in synchronous emergence of a new follicular wave, and a second oestradiol or GnRH treatment after device removal resulted in synchronous ovulation and acceptable pregnancy rates to FTAI. Furthermore, oestradiol and progesterone treatments combined with eCG (given at the time of device removal) increased pregnancy rates in suckled B. indicus cows and may be useful for the treatment of cows in postpartum anoestrus. In summary, exogenous control of luteal and follicular development facilitates the application of assisted reproductive technologies in B. indicus cattle by offering the possibility of planning AI programs without the necessity of oestrus detection and without sacrificing the overall results.     

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.     

Superovulation and embryo transfer in Bos indicus cattle

Compared to Bos taurus breeds, Bos indicus breeds of cattle present several differences in reproductive physiology. Follicular diameter at deviation and at the time of ovulatory capability are smaller in B. indicus breeds. Furthermore, B. indicus breeds have a greater sensitivity to gonadotropins, a shorter duration of estrus, and more often express estrus during the night. These differences must be considered when setting up embryo transfer programs for B. indicus cattle. In recent studies, we evaluated follicular dynamics and superovulatory responses in B. indicus donors with the objective of implementing fixed-time AI protocols in superstimulated donors. Protocols using estradiol and progesterone/progestrogen releasing devices to control follicular wave emergence were as efficacious as in B. taurus cattle, allowing the initiation of superstimulatory treatments (with lower dosages of FSH than in B. taurus donors) at a self-appointed time. Furthermore, results presented herein indicate that delaying the removal of progesterone/progestogen-releasing devices, combined with the administration of GnRH or pLH 12 h after the last FSH injection, results in synchronous ovulations, permitting the application of fixed-time AI of donors without the necessity of estrus detection and without compromising the results.     

Expressed sequenced tags profiling of resistant and susceptible Gyr x Holstein cattle infested with the tick Rhipicephalus (Boophilus) microplus

Tick resistance in cattle is mainly found in zebu (Bos indicus) animals, although it is also present in some taurine (B. taurus) breeds. In order to characterize functional genes involved in tick resistance/susceptibility in cattle, two cDNA libraries were generated using skin tissues of selected Holstein x Gyr animals. A total of 2700 high-quality reads from both resistant and susceptible cDNA were assembled into 458 sequences (contigs) and 834 singletons, with a mean size of 447.7 nucleotides. Assignment of homologous proteins by BLASTX revealed 790 (61.1%) and 300 (23.2%) hits in resistant and susceptible cDNA, respectively; 121 of these hits matched bovine proteins. A total of 502 (38.9%) unique sequences were found to have no significant homology with known sequences and were classified as novel sequences. In general, the most abundant sequences consisted of those coding for hypothetical proteins whose function had not yet been determined, in addition to ribosomal proteins, binding proteins and structural proteins, such as keratin and collagen. The most abundant protein found was collagen type III alpha, although ribosomal proteins accounted for half of the 40 most frequent hits. In addition, five matches within the top 40 best hits corresponded to immune response proteins. These sequences could be used for future studies on functional genomics of cattle tick resistance as well as for genomic sequencing projects.     

Growth and reproductive development from weaning through 20 months of age among breeds of bulls in subtropical Florida

To determine the effect of breed on growth and reproductive development, weaned bulls in each of 2 yr were managed as a single group for approximately a year. In Year 1, the study group consisted of 24 Angus, 24 Brahman, 20 Hereford and 14 Senepol bulls, while in Year 2, it contained 25 Angus, 17 Brahman. 13 Romosinuano and 9 Nellore x Brahman bulls. Body and testicular growth measurements were recorded at 6-wk intervals. At approximately 1 yr of age and quarterly thereafter (4 periods), bulls were evaluated for libido, pubertal status, and GnRH-induced LH and testosterone secretion. Significant breed-by-age interactions occurred for most growth measurements. Brahman bulls (Bos indicus ) were (P < 0.05) older and heavier at puberty than Angus, Hereford, Senepol and Romosinuano bulls (Bos taurus ). Libido scores were lowest for Brahman and Nell ore x Brahman bulls (Bos indicus ). highest for Angus and Hereford bulls (temperate Bos taurus breeds) and intermediate for Senepol and Romosinuano bulls (tropical Bos taurus breeds; P < 0.05). Differences were not consistent among breeds or between years for GnRH-induced LH secretion. In both years, basal testosterone concentrations and areas under the GnRH-induced testosterone curve were higher (P < 0.05) for Angus and Hereford bulls (temperate breeds) than for Brahman, Senepol, Romosinuano and Nellore x Brahman bulls (tropical breeds). In conclusion, reproductive development of Senepol and Romosinuano bulls (tropical Bos taurus breeds) was more similar to Angus and Hereford bulls (temperate Bos taurus breeds) than to Brahman and Nellore x Brahman bulls (Bos indicus ).     

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。     

Estimation of taurindicine hybridization of American Zebu cattle in Brazil

Our objective was to estimate Bos primigenius taurus introgression in American Zebu cattle. One hundred and four American Zebu (Nellore) cattle were submitted to mtDNA, microsatellite and satellite analysis. Twenty-three alleles were detected in microsatellite analysis, averaging 4.6 ± 1.82/locus. Variance component comparisons of microsatellite allele sizes allowed the construction of two clusters separating taurus and indicus. No significant variation was observed when indicus and taurus mtDNA were compared. Three possible genotypes of 1711b satellite DNA were identified. All European animals showed the same restriction pattern, suggesting a Zebu-specific restriction pattern. The frequencies of B. primigenius indicus-specific microsatellite alleles and 1711b satellite DNA restriction patterns lead to an estimate of 14% taurine contribution in purebred Nellore.     

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.     

Breeding soundness evaluation of extensively managed bulls in Costa Rica

This paper describes the results of single breeding soundness evaluations (BSE) in 898 Bos indicus, Bos taurus and B. indicus x B. taurus bulls, 1 to 12 yr old, extensively reared in different climatic regions of Costa Rica and representing approximately 2% of the total breeding bull population. Thirty-three percent (n = 296) of the bulls were classified as unsound for breeding owing to clinical problems (9.1%, n = 82), low scrotal circumference (SC) being the most common finding, followed by unsatisfactory sperm morphology (23.9%, n = 214). The prevalence of bulls unsound for breeding was lowest in Bos indicus (29%, P < 0.01), intermediate in B. taurus (41%), and highest in B. indicus x B. taurus (48%). The percentages of abnormal sperm heads, acrosomes and midpieces tended to be higher in the ejaculates of bulls with softer testicular consistency (P < 0.001), a long scrotum (P < 0.01) or a low SC (P < 0.05), and such bulls were more often classified as being unsound for breeding (P < 0.05). Frequencies of sperm abnormalities were higher in bulls < 2 yr of age than in older males (P < 0.01) and were highest in B. indicus x B. taurus bulls (P < 0.001). The results confirm differences between species in their adaptability to a tropical environment and support earlier evidence of an association between SC, testicular consistency and scrotal length clinical parameters, and testicular function in bulls.     

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.     

Karyotype analysis of mithun (Bos frontalis) and mithun bull x Brahman cow hybrids

We examined the cytogenetics of mithun (Bos frontalis), a domesticated version of the Asian gaur, and hybrids (F(1) generation) produced by artificial insemination of Brahman cows (Bos indicus) with mithun semen. Reproductive potential was also examined in the F(1) generation and a backcrossed heifer for utilization of heterosis. Metaphase chromosome spreads were examined by conventional staining and fluorescence in situ hybridization hybridized with the entire chromosome 1 of mithun as a specific probe. Chromosome 1 of mithun was found to be equivalent to Bos taurus chromosomes 2 and 28. The karyotype of the female mithun (N = 4) comprised 58 chromosomes, including 54 acrocentric and four large submetacentric chromosomes, without the four acrocentric chromosomes found in the domesticated species B. indicus. However, one of the four female mithuns with a normal mithun phenotype had an abnormal karyotype (2n = 59), indicating introgression from B. taurus or B. indicus. The F(1) karyotypes (N = 6, 3♂3♀) of the mithun bull × Brahman cow cross had 2n = 59, intermediate between their parents; they were consistent heterozygous carriers with a centric fusion involving rob(2;28), as expected. Two pronounced red signals were seen in the mithun karyotypes, three red signals in the mithun × Brahman hybrids, and four red signals in the Brahman cattle, in good agreement with centric fusion of bovine rob(2;28). The female backcross hybrid (N = 1) with 2n = 59 had a similar chromosome configuration to the F(1) karyotypes and had rob(2;28). Such female backcross hybrids normally reproduce; however, the F(1) bulls (N = 3) had not yet generated normal sperm at 24 months.