国内外奶牛良种繁育体系建设概况

奶牛良种繁育体系就是如何培育选择和使用优秀种公牛的一系列育种措施。本文主要简述了奶业发达国家奶牛良种繁育体系建设的发展历程及现状,指出我国奶牛良种繁育体系建设存在的主要问题,并对如何建设和完善我国奶牛良种繁育体系提出了建议。     

我国奶用公牛后裔测定中几个问题的探讨

后裔测定是当前验证奶用种公牛育种价值的常用有效方法。我国自1972年以来,在黑白花奶牛的培育研究中,广泛开展了公牛后裔测定工作,培育出一批优秀种公牛,也发现一些题题,现提出探讨. 一、采用何种繁育体系进行公牛后裔测定的问题当前全世界奶用公牛后裔测定所采用的繁育体系,大致可以分为四种。第一种是被测公牛采精配种一定数量以后,全部饲养于测定站     

西安市奶牛育种中心关于种公牛站寻求合作伙伴的公告

正西安市奶牛育种中心种公牛站依托西安市奶牛育种中心的技术团队支撑,历经40多年的发展,形成以西安为中心,辐射西北乃至全国的奶牛良种繁育体系。2011年完成新址新站建设,实现固定资     

中国奶业协会关于印发《中国荷斯坦母牛品种登记实施方案》等的通知

各省、自治区、直辖市、计划单列市畜牧(奶业)管理部门、奶业协会、育种组织、种公牛站,新疆生产建设兵团畜牧局:为进一步做好中国荷斯坦奶牛繁育和品种改良的基础性工作,加快我国奶牛良种繁育体系建设,中国奶业协会根据2004年第13次农业部常务会议精神,两年来先后组织专家对国     

北美与欧洲奶牛平衡育种概况及相关思考

世界各国的奶牛育种体系都是在漫长实践中逐步形成的。通过了解各国育种体系、各性状权重及公牛改良特点,借鉴国外平衡育种思路,有助于提高我国种公牛选择的精确度,完善我国公牛后裔测定体系,促进我国公牛自主选育工作。对于规模牧场,结合选种选配技术,能够更准确地选择适合自己牧场需求的国外优秀种公牛,从而达到提高奶牛生产性能、延长使用年限的目的。本文对美、加、荷、意、德五国奶牛平衡育种情况和综合性能指数进行了综述和分析,与同行分享一些关于育种的思考。     

北京奶牛中心

北京奶牛中心是我国重点奶牛繁育和推广中心,是国家级奶牛良种繁育和生产的龙头企业,主要任务是面向全国提供优良种牛精液,优质胚胎及配套技术服务。目前饲养从美国、加拿大等国家进口和胚胎移植培育的优秀荷斯坦种公牛140头,娟姗、瑞士褐种公牛10头,西门塔尔、利木赞、夏洛来等肉用种公牛22头,年产优质冷冻精液400万剂,优秀组合胚胎1万枚,主产品牛冷冻精液和胚胎推广面积覆盖了我国31个省、市、自治区;冻精产销量、市场占有率连续多年全国第一,在性控精液生产、胚胎性别控制、鉴定和切割以及转基因和克隆等方面开展研究,使中心育种工作达到了国际水平,对我国奶牛的改良和良种的繁育发挥着重大作用,每年带动全国农民增收10亿元,为我国新农村建设做出了巨大贡献。     

奶牛X性控冻精在应用中的技术要点

正性别控制繁育技术是继常规人工授精和胚胎移植之后,家畜繁育改良技术的第三次革命。目前,奶牛性控冻精人工授精技术是当前提高母牛繁殖最为先进、最为现实,而且是能够最大限度发挥奶牛繁殖潜力的一项高新技术。该技术有利于奶牛育种计划的实施,对改良奶牛的遗传性状发挥了积极的作用,能够提高种公牛的利用率。把握好奶牛X性控冻精在应用     

中国荷斯坦奶牛MOET育种体系的建立与实施

与世界大多数国家一样，迄今我国采用的奶牛育种方案，被称为“人工授精育种体系”即“AI育种体系”，其主要特点是：大规模使用种公牛的冷冻精液；在牛群中实施以获得优秀种公牛后代为目的的“定向选配”有计划地通过性能测定和后裔测定等育种措施，选育优秀种公牛；在育种群和生产群中全面使用“验证公牛”。这种育种体系的实施，可以在种子公牛即“公牛父亲”和种子母牛即“公牛母亲”的选择上实现一个较高的选择强度，在牛群的产奶性状和次级性状上获得较大的选择精确性。但AI育种体系最明显的缺点是：由于大规模的后裔测定，耗费大量…     

天津市荷斯坦奶牛种公牛培育体系建设研究初探

<正>根据农业部《中国奶牛群体遗传改良计划》中关于加快建立我国种公牛自主培育体系,提高种公牛自主培育能力的要求,适应国家奶牛良补工程建设需要,天津市奶牛发展中心(简称"中心")结合自身实际,近年来一直在荷斯坦奶牛种公牛自主培育体系建设方面进行大胆探索和认真实践,并取得了显著成效,培育出了一批顶级优秀种公牛。天津市奶牛发展中心是集奶牛育种科研、生产性能测定、外貌鉴定、品种登记和良种冻精推广等工作     

奶牛场选配方案的制定

本世纪50年代,美国、加拿大的奶牛育种专家曾指出,黑白花奶牛品种已成为世界性品种。在繁育方法上,主要采用同质选配和异质选配的方法。这些方法是在严格选择种公牛和母牛的基础上,通过制定选配方案即交配计划的手段来完成。制定选配方案的前提,是有明确的育种目标。育种目标应是结合群体实际情况,制定出在一定时间内奶牛群体主要的数量性状和质量性状预期达到的改进或改良指标。在制定奶牛选配方案时,可以借鉴以下的方法:     

Methods for measuring genetic progress in dairy traits

This article presents the results of Mr. Na's thesis (1972). A method to estimate genetic progress which Everett et al. (1967) applied to a simulated population of cows is tried on two real populations of cows. Data collected in 1963–1967 for the daughters and in 1948–1959 for the dams are used. The computed estimates are of little value because of the bias caused by the selection of sires. The reason why selection of bulls affects the estimation of genetic gain, which is not obvious, is described.The method seems to be appropriate for large quantities of data where adjustment for the influence of selection among sires is possible. In order to correct for age of dams, dams' performance, and selection of sires it is necessary to record the identification number of the dam of each cow and the number of daughters and their mean performance of each bull.Another method of estimation which requires a second “progeny test” for the old bulls is discussed. A fairly high number of bulls with two progeny tests would be necessary if a precise estimate of genetic progress is desired.     

Breeding aspects of embryo transplantation utilized in the bull dam path within a dual-purpose cattle population

The basic assumptions for applying superovulation and embryo transplantation to breeding plans are discussed.In a model simulation the superovulation—egg transfer technique was applied to elite cows (dams of bulls) in the breeding plan of a 500 000 cow population. The number of sons obtained per elite cow per year was varied from 0.5 (basis) to 10.0.The increase in genetic gain amounted to a maximum of 0.22 percentage units (from 1.51 to 1.73) per year and the extra returns to 44 000 D.Kr. per bull calf recruited, when the only factor allowed to change was the number of sons per elite cow.For all alternatives examined the optimum plan is also shown. In this case the maximum extra returns per bull calf recruited will be about 54 000 D.Kr., that is 10 000 D.Kr. more than in the basic plan.The results indicate that the utilization of a combined superovulation—egg transfer procedure might prove profitable when based on an efficient selection of dams of bulls.     

Approaches to the management of inbreeding and relationship in the German Holstein dairy cattle population

The aim of this study was to estimate the current level of inbreeding in the German cow population and for bull dams born in Germany, to find out sires most related to different subsets of their breed and to demonstrate the negative effect of homozygosity in the case of complex vertebral malformation (CVM). Further on, the application of optimum genetic contribution (OGC) theory for the selection of bull dams and bull sires in different breeding scenarios was investigated. Levels of inbreeding for the cow population were in a low range from 0.97% to 1.70% evaluating birth years from 1996 to 1999 in a total dataset of 244,427 registered Holstein cows. The inbreeding coefficient of 8030 bull dams was much higher, i.e. 3.71%, for the birth year 1999. Increases in inbreeding of 0.19% per year indicated an effective population size of only 52 animals. Individual sires like R.O.R.A. Elevation and Hannoverhill Starbuck were highly related to potential bull dams with coefficients of relationship of 13.4% and 12.9%, respectively, whereas P.F. Arlinda Chief (16.3%) and Carlin-M Ivanhoe Bell (16.1%) were highest related to the best available AI sires. Coefficients of relationship were calculated by classes of estimated breeding values (EBV) for production traits showing highest values above 7% in the two highest EBV-classes. The optimum genetic contribution theory using official EBVs and approximative, for zero inbreeding corrected EBVs, was applied for elite matings in a breeding program embracing 30 young bulls per year to find the optimal allocations of bull sires and bull dams. Compared with the actual breeding program applied in practice, OGC-theory has the potential to increase genetic gain under the same constraint for the increase of average relationship by 13.1%. A more relaxed constraint on increase in inbreeding allowed even higher expected genetic gain whereas a more severe constraint resulted in more equal contributions of selected bull sires. Contributions from 21 selected bull sires and 30 selected bull dams for a scenario at 5% constrained relationship were used to develop a specific mating plan to minimise inbreeding in the short term in the following generation applying a simulated annealing algorithm. The expected coefficient of inbreeding of progeny was 66.3% less then the one resulting from random mating. Mating programs can address inbreeding concerns on the farm, at least in the short term, but long-term control of inbreeding in a dairy population requires consideration of relationships between young bulls entering AI progeny test programs. Significantly better EBVs of CVM-free bulls compared with CVM-carriers for the paternal fertility justify the application of OGC for elite matings.     

Prospects and strategies for genetic improvement of the dairy potential of tropical cattle by selection

The import of genetic material and the use of crossbreeding to improve the dairy merit of tropical cattle has been criticized for eroding the livestock genetic resources of the tropics. An alternative is genetic improvement of the indigenous cattle through selection. The objective of the present paper is to examine the feasibility of this alternative.Constraints to genetic improvement of tropical cattle through selection are discussed. Low reproductive rates and high calf mortality reduce the intensity of selection. The generation interval, which is long in cattle, is further prolonged by the late sexual maturity and the long calving intervals in most tropical breeds. The most serious constraint is, however, that the extensive milk recording schemes which support dairy cattle breeding programmes in many temperate countries are almost non-existent in the tropics. In this situation, the most realistic approach to improvement through selection is to start with a single nucleus herd (or a group of cooperating herds).Two alternative selection programmes (with and without progeny testing) for a closed herd of 500 cows are outlined. The alternative which assumed no progeny testing, i.e. selection of bulls on pedigree information only, gave the fastest genetic improvement (predicted at 36 kg/year).By distributing breeding bulls from the herd the genetic progress can be disseminated to the outside population with a time lag of about two generations. A nucleus herd can supply about 15 selected bulls per 100 cows in the herd per year, enough for a population of several thousand cows.     

Effects of a breeding scheme combined by genomic pre‐selection and progeny testing on annual genetic gain in a dairy cattle population

The effectiveness of the incorporation of genomic pre‐selection into dairy cattle progeny testing (GS‐PT) was compared with that of progeny testing (PT) where the fraction of dam to breed bull (DB) selected was 0.01. When the fraction of sires to breed bulls (SB) selected without being progeny tested to produce young bulls (YB) in the next generation was 0.2, the annual genetic gain from GS‐PT was 13% to 43% greater when h² = 0.3 and 16% to 53% greater when h² = 0.1 compared with that from PT. Given h² = 0.3, a selection accuracy of 0.8 for both YB and DB, and selected fractions of 0.117 for YB and 0.04 for DB, GS‐PT produced 40% to 43% greater annual genetic gain than PT. Given h² = 0.1, a selection accuracy of 0.6 for both YB and DB, and selected fractions of 0.117 for YB and 0.04 for DB, annual genetic gain from GS‐PT was 48% to 53% greater than that from PT. When h² = 0.3, progeny testing capacity had little effect on annual genetic gain from GS‐PT. However, when h² = 0.1, annual genetic gain from GS‐PT increased with increasing progeny testing capacity.     

Genetic gain in dairy cattle populations is increased using sexed semen in commercial herds

Using stochastic simulation, the effect of using sexed semen to cow dams (CD) in a dairy cattle breeding scheme, with or without use of multiple ovulation and embryo transfer (MOET) to bull dams (BD), on annual genetic gain at the population level was examined. Three levels of sexed semen were combined with three levels of MOET: no sexed semen, sexed semen to the best CD and sexed semen to all heifers, combined with no MOET, MOET on all BD and MOET randomly on 20% of the BD. In total, nine scenarios were compared. The simulated population was monitored for 30 years and included 450 herds with 100 cows each. Each year 50 young bulls (YB), 10 active sires and 215 BD were selected on best linear unbiased prediction estimated breeding values by truncation selection across the simulated population, and the YB were tested within the population. Use of sexed semen alone gave a positive increase in the annual genetic gain of 2.1% when used on the best CD and 2.7% when used on all heifers, but only the latter was statistically significant. The increased annual genetic gain was caused by a larger contribution from the CD to the BD. Use of sexed semen together with MOET on BD increased the annual genetic gain by 1.8-2.5% compared with schemes without sexed semen and MOET on all BD. Performing MOET on all BD enables selection of offspring with high Mendelian deviations, which increase the annual genetic gain. Use of sexed semen decreased the genetic lag between the sires and the CD by 12-14% when used on the best CD and by 6% when used to all heifers. The decrease in the genetic lag is caused by the increased selection intensity of the cow dams.     

Reducing bias in the dairy cattle single‐step genomic evaluation by ignoring bulls without progeny

The number of genotyped animals has increased rapidly creating computational challenges for genomic evaluation. In animal model BLUP, candidate animals without progeny and phenotype do not contribute information to the evaluation and can be discarded. In theory, genotyped candidate animal without progeny can bring information into single‐step BLUP (ssGBLUP) and affect the estimation of other breeding values. We studied the effect of including or excluding genomic information of culled bull calves on genomic breeding values (GEBV) from ssGBLUP. In particular, GEBVs of genotyped bulls with daughters and GEBVs of young bulls selected into AI to be progeny tested (test bulls) were studied. The ssGBLUP evaluation was computed using Nordic test day (TD) model and TD data for the Nordic Red Dairy Cattle. The results indicate that genomic information of culled bull calves does not affect the GEBVs of progeny tested reference animals, but if genotypes of the culled bulls are used in the TD ssGBLUP, the genetic trend in the test bulls is considerably higher compared to the situation when genomic information of the culled bull calves is excluded. It seems that by discarding genomic information of culled bull calves without progeny, upward bias of GEBVs of test bulls is reduced.     

Prevalence of Tritrichomonas fetus in a bull population and effect on production in a large cow-calf enterprise

OBJECTIVE: To determine prevalence of infection with tritrichomonas fetus in a bull population; assess influence of age, breed, and grouping; assess effects on measures of cow performance (pregnancy rate, weaning percentage, weaning weight); and estimate test sensitivity. DESIGN: Epidemiologic study. ANIMALS: 1,383 bulls and records for 28,471 cows bred by these bulls in the immediate past breeding season. PROCEDURE: Bulls in 11 cattle units on a large ranch were tested for T fetus colonization by vigorous preputial scraping and protozoologic culture until no newly infected bulls were identified. Bull infection prevalence within units was calculated and correlated to production measurements reported for each cattle unit. RESULTS: Mean prevalence of T fetus-infected bulls was 11.9% (range, 0 to 35.9%). Significant difference was detected between mean age of infected bulls (5.5 years) and noninfected bulls (3.9 years). Difference in prevalence among breeds was found, although other factors may have influenced this finding. Cow performance measurements (weaning percentage, mean weaning weight, and adjusted mean weaning weight/exposed cow) for cows exposed by breeding to bull groups with the highest prevalence of infection (35.9%) were significantly different from mean values for the entire study population. Test sensitivity for this study (73%) was less than that reported in other studies. CLINICAL IMPLICATIONS: T fetus infection in a natural service beef herd has an adverse impact on several production measures: Severity of impact is related to prevalence of infection in the bull population, where prevalence is bull age and population dependent.     

Putative urinary pheromone of bulls involved with breeding performance of primiparous beef cows in a progestin-based estrous synchronization protocol

The objective of this study was to determine if factors associated with the biostimulatory effect of bulls alter breeding performance of primiparous, suckled beef cows using a progestin-based estrous synchronization protocol. We tested the hypotheses that the estrous synchronization response and AI pregnancy rates differ among cows exposed to bulls, continuously exposed to bull urine, and exposed to fence-line contact with bulls or cows not exposed to bulls or bull urine. Data were collected from 3 experiments performed over consecutive years. Cows were assigned to the following treatments: bull exposure (BE; n = 26) or no bull exposure (NB; n = 25) in Exp. 1, bull urine exposure (BUE; n = 19) or steer urine exposure (SUE; n = 19) in Exp. 2, and fence-line contact with bulls (BFL; n = 26) or no bull exposure (NB; n = 26) in Exp. 3. Synchronization protocols in each experiment included the use of a controlled internal drug release device (d -10), PGF(2alpha) (d -3), and GnRH and fixed-time AI (TAI; d 0). Cows that were observed in estrus by 60 h after PGF(2alpha) were inseminated 12 h later. Cows not observed in estrus by 60 h after PGF(2alpha) were TAI at 72 h and given GnRH (100 mug). Pregnancy was determined by ultrasonography 35 d after TAI. In Exp. 1, 2, and 3, cows were exposed directly to bulls, bull urine, or bull fence-line contact for 35, 64, and 42 d, respectively. Data were analyzed between treatments within each experiment. The proportion of estrous cycling cows did not differ between treatments at the beginning of each experiment; however, more (P < 0.05) BE and BFL cows were estrous cycling at the beginning of the estrous synchronization protocol than NB cows in Exp. 1 and 3. The proportion of cows that showed estrus and interval to estrus after PGF(2alpha) did not differ between treatments in Exp. 1 and 3. However, in Exp. 2, more BUE cows tended (P = 0.09) to have shorter intervals to estrus and to exhibit estrus after PGF(2alpha) than SUE cows. Overall, AI pregnancy rates were greater (P < 0.05) for BE and BUE cows than for NB and SUE cows in Exp. 1 and 2, respectively. There was no difference in AI pregnancy rates between BFL and NB cows in Exp. 3. The presence of bulls and exposure to bull urine appeared to improve breeding performance of primiparous beef cows using a progestin-based estrous synchronization protocol, whereas fence-line bull exposure was insufficient to cause this biostimulatory effect. We propose that a novel urinary pheromone of bulls may be responsible for the enhancement of fertility in the primiparous, postpartum cow.     

Stochastic simulation of dairy cattle nucleus breeding schemes: Influence of breeding strategy and biased breeding values in the population

SUMMARY: A stochastic simulation model of an open nucleus scheme was used to study the consequences of the breeding strategy and biased lactation records for population cows. Selection was for a single sex-limited trait with a heritability of 0.25 and based on animal model breeding value estimates. Selection of dams was across age classes while sires were required to have a progeny test before they could be selected as proven bull or bull sire. Dams to breed nucleus replacements and young bulls could be selected from the nucleus and the top population which contained 240 and 1600 replacement heifers annually. The first 15 years of the simulated period was used to reach a population with an equilibrium genetic progress for a progeny testing scheme. Comparisons were based on the 25 year period after an alternative breeding scheme was adopted. The annual genetic gain was calculated from the last 10 years of that period. The annual genetic gain in an open nucleus breeding scheme was .247 σ(a) . The annual genetic gain increased 5.4% when MOET was also used on cows selected to breed replacements for the top population. When, in addition the number of sires used on top population cows was reduced from 8 to 4, that being the number used in the nucleus, the annual genetic gain increased by another 2.8%. The reduction in annual genetic gain due to biased lactation records of top population cows ranged from 4.6 to 15.4%. The average bias in estimated breeding values of the top population dams selected to breed nucleus replacements ranged from 0.53 to 2,52 σ(a) . The regression coefficient of the EBV of the bull after progeny testing on the EBV of the dam at the time of selection was 0.55 without biased lactations and ranged from 0.10 to 0.27 with biased lactations. The reduction in genetic gain was especially related to the regression coefficient and to a lesser extent to the average bias. In practice, the expected reduction in annual genetic gain from biased lactation records of population cows is expected to be between 5 and 10 %. ZUSAMMENFASSUNG: Stochastische Simulation von Milchvieh-Nukleussystemen: Einflu? der Zuchtstrategie und verzerrter Zuchtwerte in der Population Eine stochastische Simulation eines offenen Nukleussystems wurde zur Untersuchung der Konsequenzen der Zuchtstrategie und verzerrter Laktationsabschlüsse für Populationskühe untersucht. Selektion bezog sich auf ein einzelnes weibliches Merkmal mit Heritabilit?t von 1/4 und gründete auf Tiermodell Zuchtwertsch?tzungen, Selektion von Muttertieren über Altersklassen, w?hrend Stiere vor der Selektion einen Nachkommenschaftstest haben mu?ten. Muttertiere für Nukleus- und Jungstiere kommen vom Nukleus und Spitzen der Population, die 240 und 1600 nachgestellte Kalbinnen umfa?ten. Die ersten 15 Jahre der simulierten Periode wurden zum Erreichen einer Population mit Gleichgewichtsfortschritt für ein Nachkommenschaftsprüfsystem verwendet. Vergleiche beruhten auf einer 25-Jahre-Periode nach Einrichtung des alternativen Zuchtsystems, und der j?hrliche Zuchtfortschritt wurde für die letzten 10 Jahre berechnet. Der j?hrliche Zuchtfortschritt im offenen Nukleussystem war 0,247 σ(a) und nahm um 5,4% zu, wenn MOETauch für Kühe zum Ersatz der Spitzenpopulation verwendet wurde. Wenn darüber hinaus die Zahl der Vatertiere in der Spitzenpopulation von 8 auf 4 reduziert wurde, die Zahl der im Nukleus verwendeten, konnte der j?hrliche genetische Fortschritt um weitere 2, 8% gesteigert werden. Die Verminderung des Zuchtfortschrittes auf Grund von verzerrten Laktationsabschlüssen der Spitzenkühe der Population variierte von 4,6 bis 15,4%. Die durchschnittliche Verzerrung der gesch?tzten Zuchtwerte der Populationsspitzenkühe für die Nukleusremonte bewegte sich von 0,53 bis 2,52 σ(a) . Der Regressionskoeffizient von EBV der Stiere auf Grund von Nachkommenschaftsprüfung auf EBV der Muttertiere beim Zeitpunkt der Selektion war 0,55 ohne verzerrte Laktationen und schwankte zwischen 0,10 und 0,27 bei verzerrten Laktationen. Die Verminderung des genetischen Fortschritts hing deutlich mit dem Regressionskoeffizient zusammen und weniger mit der durchschnittlichen Verzerrung. In der Praxis ist zu erwarten, da? die Reduktion des Zuchtfortschrittes durch verzerrte Laktationsabschlüsse der Population zwischen 5 und 10% liegt.