牦牛和普通牛种间杂种公牛睾丸的组织学观测与研究

通过对牦牛和黄牛种间杂种公牛及未成年公牦掉睾丸的比较组织学观测，结果表明：杂种牛雄性不育的生殖隔离机制与生精小管及生精上皮细胞的发育状况、生精小管基膜的厚度、生精小管的间距、间质组织细胞的发育状况、间质组织与生精小管间形成大量组织液等因素有关。随种间杂交代数增加，睾丸组织的发育状况逐渐改善，精原细胞的死亡率相应降低，杂种3代（F3）已能完成减数分裂产生精子，并显示出精原细胞的死亡率的逐代减少与父本基因含量逐代增多有一定的相关性。     

“假黄牛”或“假牦牛”精母细胞减数分裂及精子发生的研究

黄牛与牦牛种间杂交的F3代杂种公牛，精母细胞减数分裂及精子发生的水平，与F1和F2代相比，呈现明显的渐进性改善。但个体间睾丸发育状况及减数分裂与精子发生水平仍有较大差异，且仍能观察到一些异常现象。F3代公牛虽能产生数量较多的精子，但大多仍是畸形或有缺损，这可能是其仍无生育力的主要原因。     

“尕里巴”或“牦渣子”公牛精母细胞减数分裂及精子发生的研究

本文观察研究了黄牛与牦牛的第二代种间杂种公牛减数分裂及精子发生。Ｆ２代杂种的染色体同源性及基因的同质性比Ｆ１代杂种提高，故减数分裂和精子发生状况有所改善，但仍存在许多异常，产生的精子畸形或有缺损，因而仍是不育的。     

“尕里巴”或耗渣子“公牛精母细胞减数分裂及精子发生的研究

本文观察研究了黄牛与牦牛的第二代种间杂种公牛减数分裂及精子发生。Ｆ２代杂种的染色体同源性及基因的同源性比Ｆ１代杂种提高，故减数分裂和精子发生状况有所改善，但仍存在许多异常，产生的精子畸形或有缺损，因而仍是不育的。     

种公牛睾丸周径大小与精液品质相关性的研究

公牛的睾丸大小对其繁殖力有十分重要的影响。本试验以青海省家畜改良中心13头荷斯坦和20头西门塔尔种公牛24月龄、36月龄睾丸周径实际测定数据为基础,分析研究种公牛睾丸周径大小与精液品质的相关关系。统计结果表明,荷斯坦种公牛阴囊周径与精液密度的相关系数r=0.835(P0.01);与射精量的相关系数r=0.569(P0.05);与精子活率的相关系r=0.900(P0.01);而西门塔尔种公牛阴囊周径与精液密度的相关系数r=0.745(P0.01);与射精量的相关系数r=0.360(P0.05);与精子活率的相关系r=0.041(P0.05);荷斯坦与西门塔尔两个不同品种间睾丸周径大小有差异但不显著(P=0.647;P0.05)。研究表明种公牛睾丸周径越长且质地坚硬,弹性越好,精子的产量就越高,精液品质就越好;睾丸过小的公牛不但精子产量低,而且精液品质也差。     

热应激对种公牛精液品质的影响

睾丸是种公牛产生精子的器官,虽然机体及阴囊对其生精温度有一定程度的调节,但是外界高温环境造成的热应激仍然会对精子的生成及其性状产生非常不利的影响,     

种公牛的夏季管理

种公牛耐怕热，高温对种公牛的造精机能影响很大。据资料显示，将种公牛放在30℃条件下，经数周后就会引起睾丸和阴囊皮温上升到34℃，这种高温的刺激常造成精了数目的减少，畸形精子的增加，精子活力下降。夏季，饲养管理种公牛，如何提高精子的活力和精率是至关重要的。所以夏季种公牛的饲养管理应注意以下要点。     

种公牛阴囊围度在肉牛育种中的应用

在肉牛生产中 ,高繁殖效率所产生的经济效益是增重速度和胴体品质的 5～ 10倍。因此 ,在肉牛育种工作中 ,对种公牛选择中最重要的一项就是性能力。性能力高的种公牛应具备以下三方面优秀品质 :性欲和交配能力强 ,体格健壮和良好的精液品质 ,其中任何一方面的不足都将会降低性能力甚至造成不育。在肉牛生产中 ,阴囊围度对青年公牛来说是一个有用的潜在生产性能指标 ,睾丸大小与精子产量和精液品质有很高的遗传相关性 ,睾丸越大 ,精子产量和精液品质越高 ,而阴囊围度的测量可以精确地估测睾丸容积。另一方面有证据表明 ,睾丸大的种公牛其女儿…     

种公牛睾丸周径与品种、体型性状及精液产量的相关性研究

本文以来自山西省家畜冷冻精液中心的荷斯坦、夏洛来和西门塔尔3个品种的32头种公牛为材料,研究了不同品种公牛睾丸周径（SC）之间的差异以及公牛体型对睾丸周径的影响,分析了公牛睾丸周径与射精量、精子密度之间的相关。结果显示,成年之后不同品种SC差异不显著;SC与体重、胸围呈高度正相关（P〈0.01）;SC与管围呈正相关（P〈0.05）;公牛睾丸周径与平均采精量的相关系数为0.11,与平均精子密度相关性为0.21,相关系数较低。此项研究结果可为选育种公牛提供一定的参考依据。     

免疫技术提高牦牛种间杂交受胎率

用黑白花公牛精液经皮下注射家兔或牦年犊,均可获得交高滴度的血清精子抗体;用分离纯化获得的精子抗体（ＩｇＧ）强化免疫异种莴种;家禽可获得血清精子抗抗体。精子抗体和精子抗抗均具有较强的专一性。有子抗体和精子抗抗体分别进行主动免疫或被动免疫防治母牦牛免疫不孕能显著提高牦牛种间杂交的台率（分别２７．９５％和２２．２１％）,获得显著的经济效益。     

Bos taurus Y chromosome of Africander cattle and the development of improved breeds for the tropics.

The Africander has anatomical and other characteristics of an animal of approximately 3/4 Bos indicus heredity. The fact that these cattle carry the Bos taurus Y chromosome supports this view and indicates that the local cattle in South Africa would have been crossed with one or more Bos taurus bulls. Droughtmaster and Braford cattle retain the Bos indicus Y chromosome because Bos indicus instead of Bos taurus bulls were used to establish these taurindicus breeds. Contrary to some assumptions, an approximate tenfold increase in productivity of cattle was made during the 18th and 19th centuries due to improvements in disease control, nutrition and genetic improvement. What is now needed is the development of taurindicus breeds combining to the maximum possible extent the disease resistance and hardiness of Bos indicus with the early maturity and productivity of Bos taurus cattle. In addition, the ravages of disease and the seasonal variations of food supply need to be overcome in tropical areas.     

中国黄牛Y-STRs遗传多样性与起源研究

[目的]研究中国黄牛Y染色体STRs的遗传多样性及父系起源。[方法]利用非变性聚丙烯酰胺凝胶电泳,选择2个牛Y-STRs位点INRA189和BM861,分析16个中国地方黄牛品种284头公牛与4头缅甸黄牛公牛的Y染色体遗传多样性。[结果]在中国16个黄牛品种中,2个Y-STR位点可以区分中国黄牛中的普通牛和瘤牛类型,表明中国黄牛有普通牛和瘤牛两种父系起源。4头缅甸黄牛均为瘤牛类型。在中国16个黄牛品种中,普通牛和瘤牛分布频率分别为57.0%和43.0%,其中普通牛频率在北方黄牛中占优势(98.3%),瘤牛频率在南方黄牛中占优势(76.1%),中原黄牛中普通牛频率较高为63.8%,瘤牛频率为36.2%。[结论]中国黄牛存在普通牛和瘤牛两种父系起源;普通牛频率自北向南逐渐减少,瘤牛频率自北向南逐渐增加,中原地区为普通牛和瘤牛的交汇处。     

Promoter region of the bovine growth hormone receptor gene: single nucleotide polymorphism discovery in cattle and association with performance in Brangus bulls

Expression of the GH receptor (GHR) gene and its binding with GH is essential for growth and fat metabolism. A GT microsatellite exists in the promoter of bovine GHR segregating short (11 bp) and long (16 to 20 bp) allele sequences. To detect SNP and complete an association study of genotype to phenotype, we resequenced a 1,195-bp fragment of DNA including the GT microsatellite and exon 1A. Resequencing was completed in 48 familialy unrelated Holstein, Jersey, Brown Swiss, Simmental, Angus, Brahman, and Brangus cattle. Nine SNP were identified. Phylogeny analyses revealed minor distance (i.e., <5%) in DNA sequence among the 5 Bos taurus breeds; however, sequence from Brahman cattle averaged 27.4 +/- 0.07% divergence from the Bos taurus breeds, whereas divergence of Brangus was intermediate. An association study of genotype to phenotype was completed with data from growing Brangus bulls (n = 553 from 96 sires) and data from 4 of the SNP flanking the GT microsatellite. These SNP were found to be in Hardy-Weinberg equilibrium and in phase based on linkage disequilibrium analyses (r(2) = 0.84 and D'= 0.92). An A/G tag SNP was identified (ss86273136) and was located in exon 1A, which began 88 bp downstream from the GT microsatellite. Minor allele frequency of the tag SNP was greater than 10%, and Mendelian segregation was verified in 3 generation pedigrees. The A allele was derived from Brahman, and the G allele was derived from Angus. This tag SNP genotype was a significant effect in analyses of rib fat data collected with ultrasound when bulls were ~365 d of age. Specifically, bulls of the GG genotype had 6.1% more (P = 0.0204) rib fat than bulls of the AA and AG genotypes, respectively. Tag SNP (ss86273136), located in the promoter of GHR, appears to be associated with a measure of corporal fat in Bos taurus x Bos indicus composite cattle.     

C- AND G- BANDING PATTERNS AND CHROMOSOMAL MORPHOLOGY OF SOME BREEDS OF AUSTRALIAN CATTLE

A cytogenetical study using metaphase chromosomes from cultured lymphocytes, was made of 2 Banteng (Bibos banteng) steers and 218 bulls representing 13 purebreeds (Bos taurus type, Bos indicus type and Sanga) and 7 cross-breeds. Studies were made of photographic karyotypes of Giemsa stained and C-banded chromosomes of bulls of each breed and of B-banded chromosomes from 3 breeds of Bos indicus and one cross-breed Australian Friesian Sahiwal) cattle. The relative lengths of chromosomes of Bos taurus and Bos indicus bulls were compared and significant difference in relative lengths of the X chromosomes were noted between these two species. There was a differences in morphology of the Y chromosomes; Sanga, Banteng and Bos taurus type breeds had a small submetacentric Y chromosome, except for the Jersey which had a metacentric Y chromosome. All Bos indicus type bulls had an acrocentric Y chromosome but the Droughtmaster breed had two forms of the Y chromosome (submetacentric and acrocentric). The C-banding patterns of the autosomes and X chromosomes were similar for all breeds while those of the Y chromosomes of Bos indicus type cattle allowed their accurate identification. G-banding patterns of Bos indicus resembled those of Bos taurus and enabled pairing of homologous chromosomes. Centromeres of the autosomes were unstained but those of the sex chromosomes were darkly stained.     

Genetic characterisation of the mithun (Bos frontalis) and studies of spermatogenesis, blood groups and haemoglobins of its hybrids with Bos indicus

The mithun (Bos frontalis) and its hybrids with Bos indicus were studied to provide further cytogenetic information which might throw light on the mechanisms of the male hybrid infertility and facilitate the establishment of a stable crossbreed. It was shown that compared with conventional cattle the mithun has a homozygous, species specific 2/27 centric fusion which reduced the diploid chromosome number from 60 to 58. This provided further proof that Robertson translocation-type rearrangements have been the major source of interspecies karyotype differences in the evolution of the Bovidae. In the mithun there was also significant polymorphism between centromeres of non-homologous chromosomes and there was heteromorphism between several homologous chromosomes which could possibly serve as useful genetic markers for breeding programmes. In F1 hybrids spermatogenesis progressed to a relatively advanced stage, without going so far as to produce spermatozoa. In back crosses to B indicus spermatogenesis progressed further so that spermatozoa could be seen, though not as numerous as in normal bulls. In most hybrids there were haemoglobin bands which corresponded either to Hb A or Hb B of cattle but were much wider. It was shown that these were a combination of Hb Mi derived from the mithun and Hb A or Hb B derived from B indicus. In a few hybrids there were only Hb Mi. In these cases Hb Mi had been present in both parents and proved that the dam was not a pure siri. The possible mechanism of hybrid male infertility is discussed including faults in the epistatic gene effect between chromosomes and changes in the degree of association of centromeric regions in interspecies hybrids. It is suggested that additional cytogenetic examination of blood lymphocytes and especially of testicles would help the understanding of the fertility barriers of hybrid males and would make a breeding programme for a stable crossbreed possible.     

南宁市肉牛的Y染色体遗传多样性分析

[目的]为了探究广西南宁市肉牛的父系遗传背景与遗传组成。[方法]利用PCR扩增、限制性酶酶切和生物信息学方法,对南宁屠宰场的73头肉牛Y染色体USP9Y基因的遗传多态性进行分析。[结果]发现73头公牛USP9Y基因的PCR产物具有多态性,2头牛显示471 bp带型,71头牛显示552 bp带型。在71个552 bp带型中,有28个可以被SspI酶切成2条带(338 bp和215 bp),表明这28头牛为Y3单倍型组(38.36%),而其余43个不能被SspI酶切,表明这43头牛为Y2单倍型组(58.90%)。仅有2头牛的PCR产物为471 bp,表明这2头牛为Y1单倍型组(2.74%)。屠宰牛群的单倍型多样度为0.5122±0.0309,表明屠宰牛群的Y染色体遗传多样度较高。[结论]南宁市屠宰牛群的来源比较复杂,有普通牛(Y1与Y2单倍型组)和瘤牛(Y3单倍型组)2个父系起源。     

中国黄牛Y-SNPs遗传多样性与起源研究

为了研究中国黄牛Y染色体SNPs的遗传多样性及父系起源,本研究利用PCR-SSCP与测序方法,选择4个牛Y-SNPs位点DDX3Y-7、UTY-19、ZFY-9和ZFY-10,分析了16个中国地方黄牛品种284头公牛与缅甸黄牛4头公牛Y染色体的遗传多样性.结果表明,在中国16个黄牛品种中,仅发现普通牛Y2和瘤牛Y3单倍型,表明只有Y2和Y3两种父系起源,尚未发现中国黄牛存在普通牛Y1单倍型的分子证据.4头缅甸黄牛均为Y3单倍型.在中国16个黄牛品种中,Y2和Y3单倍型频率分别为57.0％和43.0％,其中Y2单倍型频率在北方黄牛中占优势(98.3％),Y3单倍型频率在南方黄牛中占优势(76.1％),中原黄牛中普通牛Y2的单倍型频率较高,为63.8％0,瘤牛Y3的单倍型频率为36.2％.本研究证明,中国黄牛存在普通牛Y2和瘤牛Y3单倍型两种父系起源,Y2单倍型频率自北向南逐渐减少,Y3单倍型频率自北向南逐渐增加,中原地区为普通牛Y2和瘤牛Y3单倍型的交汇处.     

Normal DNA methylation status in sperm from a somatic cell cloned bull and their fertilized embryos

Epigenetic reprogramming confers totipotency even during somatic cell nuclear transfer (SCNT), which has been used to clone various animal species. However, as even apparently healthy cloned animals sometimes have aberrant epigenetic status, the harmful effects of these defects could be passed onto their offspring. This is one of the biggest obstacles for the application of cloned animals for livestock production. Here, we investigated the DNA methylation status of four developmentally regulated genes (PEG3, XIST, OCT4, and NANOG) in sperms from a cloned and a non‐cloned bull, and blastocysts obtained by in vitro fertilization using those sperms and SCNT. We found no differences in the methylation status of the above genes between cloned and non‐cloned bull sperms. Moreover, the methylation status was also similar in blastocysts obtained with cloned and non‐cloned bull sperms. In contrast, the methylation status was compromised in the SCNT blastocysts. These results indicate that sperm from cloned bulls would be adequately reprogrammed during spermatogenesis and, thus, could be used to produce epigenetically normal embryos. This study highlights the normality of cloned bull offspring and supports the application of cloned cattle for calf production.     

Prospects for increasing the utilization of cattle embryo transfer by small-scale milk and meat producers in tropical regions

Small community cattle farmers in the tropics are facing challenges to deliver quality products whilst under pressure to increase milk and beef yields per cow. These challenges could be partially met by crossbreeding Bos taurus with Bos indicus (F1) cattle utilizing embryo transfer (ET) technology. The Bos taurus infusion would increase milk production, whilst the Bos indicus influence can improve resistance to the harsh environment of the tropics. Here, individuals from existing herds can be used to produce F1 embryos which benefit from hybrid vigour. Resultant female offspring would in turn receive an F1 embryo on reaching breeding maturity. This approach would help to provide a cost-effective, systematic approach to improve productivity in dairy and beef cattle in the tropics. However, full usage of ET, including in vitro applications, in the tropics will require improvements in procedures, resources and education.     

秦川牛的染色体研究

对秦川牛(12♂,3♀)染色体的核型、G带、C带及Ag-NOR_s的研究表明:秦川牛品种内Y染色体存在多态现象,Y染色体有中、亚中和近端着丝点染色体。中和亚中着丝点Y染色体G带和C带与普通牛(Bos taurus)相同,近端着丝点Y染色体G带和C带与瘤牛(Bos indicus)相同。根据Y染色体多态性,讨论了秦川牛起源的多元性。统计了2002个细胞的Ag-NOR_s数目,每细胞Ag-NOR_s数变化范围3～10个,平均5.473±0.316。