奶牛乳腺炎抗性的遗传学研究与应用

奶牛乳腺炎是威胁奶牛业健康发展的主要疾病之一,在世界范围内造成巨大损失,各国相继将乳腺炎抗性纳入奶牛育种目标。本文综述了奶牛乳腺炎抗性的表型特性、主要遗传参数及其与其它性状的遗传相关;总结了近年来关于奶牛乳腺炎抗性的分子遗传学研究成果及遗传工程的应用概况;对于未来的奶牛乳腺炎抗性选育,应实施完善表型标记、多分子标记聚合应用的研究;尽快建立我国牛奶测定系统、将乳腺炎抗性纳入奶牛育种目标应是当务之急。     

世界各国荷斯坦种公牛育种方法及选育方向的变化趋势

奶牛群体的生产水平在很大程度上取决于种公牛的遗传水平,因此种公牛的选育被认为是奶牛群体遗传改良工作的核心,而对于种公牛选育的目标也因国而异,并且随着育种的进程而不断变化。本文从种公牛选育的重要性、选育方法以及选育方向的变化趋势三个方面进行讨论,简述了世界各奶业强国在荷斯坦种公牛选育中采用的综合选择指数的算法、基因组选择的概况以及育种目标的变化趋势。     

保种和选育相结合的综合指数制订方法

保种与选育是动物育种中对立统一的两个方面 ,为现代育种学家所共识。解决这个矛盾的一个有效途径应该是将保种与选育结合起来 ,即在不断提高动物生产性能同时 ,兼顾那些有必要或值得保护的性状与性能。综合选择方法是动物多性状选择改良的一种有效方法 ,那么在育种工作中如何在不使保种特性丢失和性能下降的条件下制订综合选择指数呢 ?倘若保种性状就是选育性状 ,只需给该性状的遗传改进量施加一定的约束即可 ;当保种性状不是选育性状 ,并且与选育性状间存在着遗传相关时 ,如果将保种与选育性状的表型值放在一起制订综合选择指数 ,通过限制…     

提高产蛋母鸡健壮性和 产蛋持久性的策略

在商业性生产环境中,关注动物福利和环境与高生产效率同样重要,我们必须制定新的目标——蛋鸡的新育种目标以及饲养目标。蛋鸡的健壮目标需要通过遗传选育提高它们的健康和福利来实现。     

北京市黑白花奶牛主要数量性状遗传参数估测的结果与初步分析

<正> 数量性状遗传参数(遗传力、重复力和遗传相关)是家畜的重要的种性指标。黑白花奶牛育种工作中也作为重要依据。国外应用数量性状遗传参数指导黑白奶牛育种工作收到了显著效果。我们对北京市黑白花奶牛主要数量性状遗传参数进行了较全面深入地估测和研究,目的是揭示北京市黑白花奶牛主要数量性状的遗传规律,为北京市黑白花奶牛育种工作提供科学依据,不断提高种牛选择的科学性、计划性和预见性。     

北美奶牛育种指数变化及进展情况分析

总性能指数(Total Performance Index,TPI)和终身效益指数(Lifetime Profit Index,LPI)分别是美国和加拿大奶牛育种中对荷斯坦牛进行遗传评估的选择指数。本文主要通过分析TPI和LPI公式各性状指数变化及对美国TPI遗传增量的变化情况,来对北美奶牛育种目标的发展变化及遗传进展情况进行简述,为中国荷斯坦公牛及牧场奶牛育种工作提供一些参考和借鉴。     

综合选择指数在奶牛生产中的应用

选择指数是把所要选择的各方面的性状,按照遗传特点和经济效果综合成为一个指数,然后按指数高低进行选留。利用宁夏地区某牛场20头荷斯坦奶牛产奶量、乳脂率及外貌鉴定得分进行统计测定,对其选择指数进行了计算,并根据选择指数大小对牛进行了排序。结果表明,1号、2号牛选择指数最高,3号、8号、18号选择指数最低,其它居中。20头奶牛选择指数的排序与它们在实际生产中表现优劣情况相比较,所得结果两者基本一致。表明选择指数在奶牛选种选配方面能提供重要依据,在奶牛育种生产中有重要意义。     

荷斯坦牛性情研究进展综述

随着奶牛生产性能的不断改良提升,为实现平衡育种目标,实现最大改良经济效益,繁殖、长寿、行为学等性状也逐渐得到重视。本文介绍了奶牛性情性状相关研究与应用概况,简述了国内外奶牛性情评定方法与相关研究。奶牛性情与产量等主要经济性状存在关联,因此建立适用的、可行的、准确的奶牛性情评定标准,将奶牛性情逐步纳入我国奶牛群体遗传改良体系具备实践意义。     

奶牛繁殖性状占育种值评估体系权重分析

奶牛育种中相关的繁殖性状,如产犊难易、女儿怀孕率、公牛受胎率、母牛怀孕率等都是低遗传力性状,牧场育种工作环节须对牛群繁殖性状的改良加倍重视。本文对奶牛育种评估体系中可遗传的各繁殖相关性状作了简要介绍,对繁殖性状占育种体系权重、基因组对繁殖性状选育的影响以及体型性状对繁殖性状的影响进行了简要分析,供行业同仁参考。     

奶牛生长性状研究进展与展望

近年来,生长性状在奶牛育种中备受关注,随着对奶牛生长性状研究的日益深入,其与重要经济性状间的相关性逐渐凸显出来,对奶牛的育种工作也变得越来越重要。本文就奶牛生长性状定义、遗传参数、与经济性状的关联、生长性状QTL定位、GWAS分析等方面进行了综述,并明确了生长性状在奶牛未来育种中的地位。     

Genetic Improvement of Dairy Cow Reproductive Performance

The welfare of cow along with profitability in production are important issues in sustainable animal breeding programmes. Along with an intense/intensive selection for increased milk yield, reproductive performance has declined in many countries, in part due to an unfavourable genetic relationship. The largely unchanged genetic trend in female fertility and calving traits for Scandinavian Red breeds shows that it is possible to avoid deterioration in these traits if they are properly considered in the breeding programme. Today's breeding is international with a global selection and extensive use of the best bulls. The Nordic countries have traditionally recorded and performed genetic evaluation for a broad range of functional traits including reproduction. In recent years many other countries have also implemented genetic evaluation for these traits. Thus, the relative emphasis of dairy cattle breeding objectives has gradually shifted from production to functional traits such as reproduction. Improved ways of recording traits, e.g. physiological measures, early indicator traits, assisted reproductive techniques and increased knowledge of genes and their regulation may improve the genetic selection strategies and have large impact on present and future genetic evaluation programmes. Extensive data bases with phenotypic recordings of traits for individuals and their pedigree are a prerequisite. Quantitative trait loci have been associated to the reproductive complex. Most important traits, including reproduction traits are regulated by a multitude of genes and environmental factors in a complex relationship, however. Genomic selection might therefore be important in future breeding programmes. Information on single nucleotide polymorphism has already been introduced in the selection programmes of some countries.     

奶牛乳质性状相关基因及其单核苷酸多态性的研究进展

乳质性状为奶牛重要的经济性状,主要包括乳蛋白量、乳蛋白率、乳脂量和乳脂率等。乳质性状改良是当今遗传育种界的研究热点之一,利用候选基因策略寻找影响乳质性状的功能基因或功能性单核苷酸多态,并将其应用于奶牛乳质性状的分子育种实践已经成为后基因组时代的发展趋势。目前针对乳质性状的功能基因或功能性单核苷酸多态已经开展了大量的研究工作,作者就参与泌乳调控的乳质相关基因、脂肪合成与次生物质代谢通路,以及其他一些与乳质性状相关基因及功能性单核苷酸的研究现状进行简要综述。     

奶牛生物技术育种研究进展

奶业已成为我国农业战略产业的重要组成部分,与发达国家相比,我国奶牛在良种率、产奶量、乳品质等方面仍存在较大差距。面对日益增长的消费量和品质需求,加快奶牛育种显得尤为迫切。本文便针对我国奶业当前发展现状分析了我国奶牛产业发展存在的问题及利用生物技术进行育种的必要性和迫切性。从分子标记辅助选择、QTL 定位、全基因组关联分析、全基因组选择、转基因以及胚胎工程等方面阐述了近些年国内外奶牛生物技术育种研究现状和进展,讨论了目前奶牛生物技术育种过程中存在的问题,以期对我国奶业发展有所裨益。     

Genetics of resistance to mastitis in dairy cattle

Genetic variability of mastitis resistance is well established in dairy cattle. Many studies focused on polygenic variation of the trait, by estimating heritabilities and genetic correlation among phenotypic traits related to mastitis such as somatic cell counts and clinical cases. The role of Major Histocompatibility Complex in the susceptibility or resistance to intrammamary infection is also well documented. Finally, development from molecular genome mapping led to accumulating information of quantitative trait loci (QTL) related to mastitis resistance and better understanding of the genetic determinism of the trait. From economic and genetic analyses, and according to welfare and food safety considerations and to breeders and consumer's concern, there is more and more evidence that mastitis should be included in breeding objective of dairy cattle breeds. Many countries have implemented selection for mastitis resistance based on linear decrease of somatic cell counts. Given biological questioning, potential unfavourable consequences for very low cell counts cows are regularly investigated. Improvement of selection accuracy for mastitis resistance is ongoing and includes: advances in modelling, optimal combination of mastitis related traits and associated predictors, such as udder morphology, definition of global breeding objective including production and functional traits, and inclusion of molecular information that is now available from QTL experiments.     

牛催乳素基因及其单核苷酸多态性与产奶性状关系的研究进展

SNPs是目前遗传标记研究的一大热点,牛催乳素(prolactin,PRL)基因是与产奶性状相关的重要候选基因。PRL基因上的SNPs与牛的产奶量、乳脂量、乳蛋白量、乳脂率、乳蛋白率等性状存在某种关联,可用于牛的标记辅助选择(MAS)育种。笔者从PRL的结构与功能、基因的定位及作用机制、PRL上的SNPs与产奶性状关系的研究等几个方面进行了综述。     

Non-lactational traits of importance in dairy cows and applications for emerging biotechnologies

Dairy cattle have traditionally been selected for their ability to produce milk and milk components. The traditional single-minded approach to selection of dairy cattle has now changed and secondary traits are being included in selection indices by decreasing the emphasis on production. Greater emphasis on non-production traits reflects the industry's desire for functional dairy cattle. Six broad categories of non-lactational traits are discussed in this review. They are: type; growth, body size and composition; efficiency of feed utilisation; disease resistance, e.g. udder health as measured by somatic cell score; reproduction; and management. Most of these traits can be found within selection indices worldwide, although relative emphasis varies. The non-lactational traits mentioned above are quantitative, meaning that the phenotype in the whole animal represents the sum of lesser traits that cannot be easily measured. The physiological mechanisms that underlie quantitative traits are extremely complex. Genetic selection can be applied to quantitative traits but it is difficult to link successful genetic selection with the underlying physiological mechanisms. The importance that the bovine genome sequence will play in the future of the genetics of dairy cattle cannot be understated. Completing the bovine genome sequence is the first step towards modernising our approach to the genetics of dairy cattle. Finding genes in the genome is difficult and scanning billions of base pairs of DNA is an imperfect task. The function of most genes is either unknown or incompletely understood. Combining all of the information into a useable format is known as bioinformatics. At the present time, our capacity to generate information is great but our capacity to understand the information is small. The important information resides within subtle changes in gene expression and within the cumulative effect that these have. Traditional methods of genetic selection in dairy cattle will be used for the foreseeable future. Most non-lactational traits are heritable and will be included in selection indices if the traits have value. The long-term prognosis for genome science is good but advances will take time. Genetic selection in the genome era will be different because DNA sequence analysis may replace traditional methods of genetic selection.     

Non-lactational traits of importance in dairy cows and applications for emerging biotechnologies

Dairy cattle have traditionally been selected for their ability to produce milk and milk components. The traditional single-minded approach to selection of dairy cattle has now changed and secondary traits are being included in selection indices by decreasing the emphasis on production. Greater emphasis on non-production traits reflects the industry's desire for functional dairy cattle. Six broad categories of non-lactational traits are discussed in this review. They are: type; growth, body size and composition; efficiency of feed utilisation; disease resistance, e.g. udder health as measured by somatic cell score; reproduction; and management. Most of these traits can be found within selection indices worldwide, although relative emphasis varies.

The non-lactational traits mentioned above are quantitative, meaning that the phenotype in the whole animal represents the sum of lesser traits that cannot be easily measured. The physiological mechanisms that underlie quantitative traits are extremely complex. Genetic selection can be applied to quantitative traits but it is difficult to link successful genetic selection with the underlying physiological mechanisms. The importance that the bovine genome sequence will play in the future of the genetics of dairy cattle cannot be understated. Completing the bovine genome sequence is the first step towards modernising our approach to the genetics of dairy cattle.

Finding genes in the genome is difficult and scanning billions of base pairs of DNA is an imperfect task. The function of most genes is either unknown or incompletely understood. Combining all of the information into a useable format is known as bioinformatics. At the present time, our capacity to generate information is great but our capacity to understand the information is small. The important information resides within subtle changes in gene expression and within the cumulative effect that these have.

Traditional methods of genetic selection in dairy cattle will be used for the foreseeable future. Most non-lactational traits are heritable and will be included in selection indices if the traits have value. The long-term prognosis for genome science is good but advances will take time. Genetic selection in the genome era will be different because DNA sequence analysis may replace traditional methods of genetic selection.     

Farmer-preferred traits in smallholder dairy farming systems in Tanzania

Decisions of breeding schemes in many countries in sub-Saharan Africa tend to be either government or project driven, with a focus on upgrading local breeds. However, there is scant information on the individual animal traits that smallholder farmers prefer. The aim of this study was to examine farmers’ preferences of dairy cattle traits using a discrete choice experiment methodology. The study was conducted through visits to 555 randomly selected dairy farms in the sub-humid Eastern coast and temperate Southern highlands of Tanzania. Choices of animal traits were presented to farmers who were asked to evaluate choice alternatives based on attribute levels and finally select the alternative with the highest utility. The choice experiment data were analysed using a conditional logit model. Coefficients for milk yield, fertility, feed requirement, temperament and diseases resistance were overall statistically significant (p?<?0.05). In order of perceived importance, farmers were willing to keep a cow with high milk yield (coefficient?=?1.43?±?0.059), good fertility (0.85?±?0.050), easy temperament (0.76?±?0.066), low feed requirement (??0.56?±?0.092) and enhanced tropical disease resistance (0.48?±?0.048). The purchase price coefficient was negative (??0.001?±?0.0003), indicating that farmers would prefer improved dairy cattle at affordable prices. Farmers’ preferred traits were influenced by agro-ecological zone and type of production system (extensive vs intensive). The study provides an opportunity for breeding programme designers to take farmers’ preferred dairy traits into serious consideration.

     

Genetic and phenotypic parameters for conformation and yield traits in three Swiss dairy cattle breeds

This study presents genetic parameters for conformation traits and their genetic and phenotypic correlations with milk production traits and somatic cell score (SCS) in three Swiss dairy cattle breeds. Data on first lactations from Holstein (67 839), Brown Swiss (173 372) and Red & White breeds (53 784) were available. Analysed conformation traits were stature and heart girth (both in cm), and linear scores of body depth, rump width, dairy character or muscularity, and body condition score (only in Holstein). A sire model, with relationships among sires, was used for all breeds and traits and variance components were estimated using AS‐REML. Heritabilities for stature were high (0.6–0.8), and for the linear type traits ranged from 0.3 to 0.5, for all breeds. Genetic correlations with production traits (milk, fat and protein yield) and SCS differed between the dairy breeds. Most markedly, stronger correlations were found between SCS and some conformation traits in Brown Swiss and Red & White, indicating that a focus on a larger and more ‘dairy’ type in these breeds would lead to increased SCS. Another marked difference was that rump width correlated positively with milk yield traits in Holstein and Red & White, but negative in Brown Swiss. Results indicate that conformation traits generally can be used as predictors for various purposes in dairy cattle breeding, but may require specific adaptation for each breed.