利用不同亲缘信息对奶牛产奶量进行遗传评定的效果分析

本研究采用选择指数法对假定的14头奶牛利用个体、母亲、半姐妹和女儿等4种不同信息来源进行个体产奶量育种值估计的基础上,系统地比较了利用不同亲缘信息对奶牛产奶量进行遗传评定的准确性。结果表明,利用不同亲缘信息估计个体育种值的准确性随着提供信息的记录次数(或个体数)的增加而提高;当提供信息的记录次数(或个体数)不大(n≤30)时,利用4种亲缘信息估计个体育种值的准确性高低顺序依次为:个体、女儿、母亲和半姐妹;而当提供信息的记录次数(或个体数)足够多(n30)时,利用女儿信息对奶牛产奶量进行遗传评定的准确性是最高的,其次为个体、半姐妹和母亲。     

猪遗传改良标准方案指南(续)

3.3猪群内EPD方案 在利用所有可用数据对群内所有猪计算EPD时则需要利用这些方案.除了个体的数据外,其它数据应包括全同胞、半同胞、双亲及定期更新的后裔数据.商业上常用电脑程序计算猪群内EPD值.猪群内遗传评估所使用的操作、模型及遗传参数都应当得到详细的记录,最好使用NSIF所推荐的记录.     

中国西门塔尔牛MOET育种体系

超数排卵和胚胎移植(MOET),不仅能提高西门塔尔牛的繁殖率,而且通过高强度的选择和缩短世代间距,还能提高选择反应加快其遗传进展。根据国外对MOET不同繁育体系的研究,成年型MOET(在第一次配种后)可获得中等的遗传进展(10—30％),而少年型MOET(在第一次配种前)可获得更高的遗传进展(30—100％),达到受胎家畜的效果。通过MOET改进现行的后裔测验体系,由常规的6年一个世代缩短为2—3年一个世代。但最高的遗传进展,通过MOET育种核心群选择方能实现,结合谱系,同胞测验和与生产性能有着密切相关的生理生化性状(标记性状)来增加在缩短世代间距,进行核心群选择的准确性,并以此为基础建立起西门塔尔牛MOET育种体系。选择来自同胞和半同胞组的250头泌乳牛组成育种核心群。其主要选择基础是,母牛的预选是谱系指数,组建核心群要依据乳肉性能而定,利用动物模型对其遗传值进行评定。公母牛的选择除考虑其谱系、同胞、本身性能外,还要结合与其生产性能有关的生理生化性状综合选择。每年从此核心群选择最好的32头母牛与来自130头公牛群中选择8头最好的公牛,用以为下一个世代产生512枚优质胚胎,最终每代可获得260头犊牛,其中130头母犊为核心群后备牛,另再从130头公犊中选8头最好的公牛作为供体的与配公牛,再产生下一代胚胎,形成周期性世代循环。通过两种途径尽可能提高选择强度,让优秀母牛产生更多的优秀后备母牛(CC),优秀母牛产生更多的优质种用公牛(CB),提高优秀母牛利用率。     

基于GBS简化基因组测序数据重建麦洼牦牛保种群系谱

旨在利用简化基因组测序技术(genotyping-by-sequencing, GBS)构建四川省龙日种畜场的3个麦洼牦牛保种群(全黑群、粉嘴群和弗洛群)系谱，为麦洼牦牛保种选育工作打下基础。本研究从3个保种群选取406头麦洼牦牛(全黑群211头、粉嘴群140头、弗洛群55头),采血提取DNA后进行GBS测序，利用获得的SNP对保种群亲缘关系展开研究，并初步构建系谱。结果：GBS测序后获得高质量SNP位点126 122个。PCA分析(principal component analysis, PCA)表明粉嘴群和全黑群有明显的分化趋势，弗洛群与全黑群、粉嘴群部分个体聚类紧密。本研究共计算出164 836个亲缘关系对，依据个体间的亲缘系数，判定出134个全同胞关系，912个半同胞关系，136个疑似亲子关系或全同胞关系，520个疑似半同胞关系或叔侄关系，205个疑似半同胞关系或叔侄关系或祖孙关系。结合群体进化树和亲缘关系分析，将保种群划分为12个家系(G1～G12)。家系遗传多样性分析结果表明，12个家系的观测杂合度(observed heterozygosity,Ho)为0.288 9～...     

蜂群分蜂行为研究进展

蜜蜂是多雄性真社会性昆虫,分蜂是这个庞大家族繁衍的重要手段,它们通过信息素和蜂舞来传递信息.群内工蜂是由不同亚家庭的全同胞姐妹和半同胞姐妹组成,它们在分蜂过程中扮演着不同的角色[1].它们自我组织如此有序,分工如此高效是十分值得我们深入研究的.     

动物模型BLUP选择效果的计算机模拟研究

在采用动物模型最佳线性无偏预测(BLUP) 方法对个体育种值进行估计的基础上, 模拟了在一个闭锁群体内连续对单个性状选择10个世代的情形, 并系统地比较了群体规模、公母比例和性状遗传力对选择所获得的遗传进展和群体近交系数变化的影响。结果表明, 扩大育种群规模不仅可以获得更大的持续进展, 同时还可有效缓解近交系数的过快上升; 育种群中公畜比例过低时, 不仅会降低遗传进展, 群体近交系数的上升速度也会加快, 实际中应保证育种群具有一定的规模和适宜的公母比例。对高遗传力性状进行选择时, 可望获得更大的遗传进展, 同时近交系数的上升速度也会快一些。     

家畜遗传抗性多基因效应预测的广义线性方法

在广义线性混合模型（GLMM）的框架内模拟研究了抗性性状的遗传分析方法，初步比较了GLMM方法与一般线性方法（LM）的育种值估计效果。模拟研究的抗性表型为单阈值和3阈值2种类型，选用的连接函数分别为logist连接和log连接，试验设计为全同胞一半同胞混合家系，参数估计采用Fisher迹法。研究结果表明，GLMM方法能较准确地估计公畜的个体育种值，在个体的遗传评定效果方面要明显优于LM方法，其预测的个体育种值排序结果与真实育种值的排序之间存在显著的秩相关。     

辽宁绒山羊联合育种工作进展及思路

联合育种，也叫分散核心群育种，是将多个中小型种畜禽选育场的遗传资源合并到一起，形成较大规模的核心群，进行统一遗传评定，选出最优秀的种公畜禽，供参与联合育种的各个种畜禽场共同使用。通过联合育种可以提高育种群群体规模，有利于提高公母畜禽选择强度；扩大育种资料来源，提高选种的可靠性；缩短育种群世代间隔，改善育种莉蛊等．     

内蒙古绒山羊毛长的遗传规律研究

内蒙古绒山羊是我国优良的品种资源,毛长作为内蒙古绒山羊重要的经济性状,其相关研究相对较少,本文通过对绒山羊毛长的研究,为内蒙古绒山羊育种提供了科学的理论依据。本研究利用ASREML软件分析内蒙古绒山羊毛长的表型遗传规律,然后,利用全同胞家系模型、父系半同胞模型、母系半同胞模型估计全同胞、父系半同胞和母系半同胞毛长的遗传力,以此研究亲本毛长对后代毛长的影响。研究结果表明,测定年份、群、个体年龄、母羊年龄为影响毛长的固定效应,毛长的全同胞遗传力为0.56、父系半同胞遗传力为0.26、母系半同胞遗传力为0.86,可以看出母系半同胞的遗传力显著高于父系遗传力。由此可以发现,对母羊毛长的选择可以加速毛长的遗传进展,提高毛长的生产性能。     

分子遗传技术在家畜遗传评定中的应用

基于表型信息和谱系信息估计基因加性效应值的种畜遗传评定方法在家畜遗传改良中发挥了很大作用,但因其无法真正了解控制经济性状的遗传本质,影响了家畜遗传改良的进一步进展。分子标记辅助选择可在一定程度上提高种畜遗传评定准确性,但在目前不能精确定位QTL或基因时,其效率受到很大影响。提高种畜遗传评定准确性的最有效途径应是直接利用控制经济性状的基因,后基因组时代的功能基因组研究的快速发展为实现这一目标提供了契机。同时,多个家畜品种基因组测序完成和大量SNP多态性的发现,使得利用覆盖全基因组多态性标记信息的基因组选择方法为家畜遗传评定开拓了又一条途径。     

法系夏洛来牛的引进繁育(上)

1986年后我站相继从国内、外引进法国夏洛来牛9头,在4头母牛基础上开始纯繁自育发展牛群。截至2003年6月,繁殖犊牛87头,存栏62头,其中成年公、母牛45头。4岁龄纯繁公、母牛平均体尺体重与同龄原种牛比,均有所提高。纯繁公牛20月龄采精调教,平均利用年限为61.73月龄,生产冻精71 074剂,淘汰年龄平均为84.6月龄。母牛平均初孕年龄为25.16月龄,平均淘汰年龄为95.71月龄,终生产犊4.8头。为社会创造巨大经济效益。     

Prevalence of trichomoniasis among California beef herds

Sixty cow-half herds of more than 50 cows each were randomly selected for a prevalence survey of bovine trichomoniasis in California. Herd size, as judged by the number of bulls, ranged from 1 to 210 bulls (median = 8; mean = 59 +/- 15.8). Preputial smegma was collected from 729 bulls (median = 6 bulls/herd) and cultured for Tritrichomonas foetus. Of 57 herds from which samples were collected, 9 (15.8%) had at least one infected bull. Of the 729 bulls from which samples were cultured, 30 (4.1%) were infected. Correcting for sensitivity of the diagnostic test yielded a prevalence of 5.0%. Infection rates for bulls greater than 3 years old and less than or equal to 3 years old were 6.7% and 2.0%, respectively (P less than 0.025). Median herd sizes were 14 bulls (range, 6 to 114) for infected herds and 7 (range, 1 to 210) for uninfected herds. These findings suggest that trichomoniasis is common in California beef herds. Because several bulls less than 4 years old were infected, we suggest that control measures stressing replacement of older bulls with younger ones should be combined with diagnostic procedures in those younger replacements, to ensure that they are not already infected.     

CEREBELLAR HYPOPLASIA OF GENETIC ORIGIN IN CALVES

Within 2 years, following the introduction of 2 Shorthorn bulls from the same stud into an Australian Illawarra Shorthorn (AIS) herd, 16 calves were born with cerebellar hypoplasia. All affected calves were the progeny of one bull mated to the daughters of the other. All other progeny of these bulls, most of which were from AIS dams, were normal. Affected calves exhibited severe ataxia, consistent head movement and abduction of the forelimbs. Microscopic changes in the cerebellum included sparsity of cells of the granular layer, loss of Purkinje cells and narrowing of the molecular layer. Observations on the frequencies of normal and abnormal calves are consistent with the hypothesis that the condition is caused by an autosomal recessive gene for which affected calves were homozygous and which was introduced into the herd in heterozygous condition by both of the Shorthorn bulls. Evidence is given for an unusually high frequency of the gene in the stud of origin of the Shorthorn bulls and a procedure for reducing its frequency is outlined. The possibility of a viral or toxic aetiology is discussed but is considered to be an unlikely explanation for the condition in this herd.     

荷斯坦公牛X和Y精子核形态差异及其影响因素分析

旨在分析荷斯坦公牛X和Y精子核形态(包括精子大小和形状)及其差异,探究流式分选及分选后冷冻对公牛X和Y精子核形态的影响.本研究使用荧光显微镜拍摄15头年龄相当、健康状况良好的荷斯坦公牛X和Y精子冷冻前后及新鲜精液分选前后共6类精子核图像,利用Image J插件Nuclear Morphology Analysis分析3...     

Efficacy of methods used to test fertility of beef bulls used for multiple-sire breeding under range conditions

A study was conducted during the 1982, 1983 and 1984 breeding seasons with 277 crossbred bulls, 1 to 3 yr of age, that were evaluated for physical soundness, testicular development, seminal quality, and both sexual and social behavior immediately before exposure to crossbred cow herds ranging in size from 89 to 329 cows. Crossbred cow herds were exposed to 4 to 24 bulls per breeding group (mean of 14) at a mean female: male ratio of 21.2 +/- .6:1 under extensive range conditions for 31 to 62 d (mean 46.6 d). All resulting calves were blood-typed to determine the number of calves sired by each bull as an estimate of his fertility. The mean number of calves sired by 1- (n = 116), 2- (n = 126) and 3-yr-old (n = 35) bulls was 4.7 +/- .1, 8.2 +/- .1 and 10.5 +/- .1, respectively. A regression model for predicting bull fertility under multiple-sire, range breeding conditions was selected that accounted for 29% of the total variance in fertility. Similar models accounted for a greater proportion of variance in fertility of 1-yr-old (37%) than of 2-yr-old bulls (22%). Due to the large amount of unexplained variation, the model could not predict individual bull fertility precisely. However, this study demonstrated that selection of herd sires with large scrotal circumference, low backfat thickness, low levels of primary sperm defects, and a low number of mounts in combination with a moderate number of services during libido testing would be expected to improve fertility of beef bulls used under extensive range conditions.     

A Working Model for the Evaluation of Different Immunological Traits as Indicators of Resistance to Infection in Dairy Cattle

In order to determine the relative value of different immunological traits as indicators of resistance to infection, an analysis was performed based on records of immunological traits in young bulls and “health card” records of clinical mastitis in their half sisters. The correlation analysis suggested that young bulls with high levels of serum immunoglobulin have half sisters with low mastitis frequency. A significant positive correlation was found between the antibody response peak against human serum albumin and susceptibility to mastitis. The results of this analysis should not be considered conclusive as the data were limited. Further work is required on a larger body of material. The model described here may be considered for future use as it enables immediate selection of animals.     

Assessment of impacts of tsetse and trypanosomosis control measures on cattle herd composition and performance in southern region, Ethiopia

This study was conducted to assess the impact of tsetse and trypanosomosis control measures on cattle herd size and composition, herd dynamics, and milk yield in Wolaita and Gamogofa Zones, southern Ethiopia. The study showed that the average number of cattle herd size in tsetse challenged areas was significantly higher than those in tsetse-controlled areas. The number of non-pregnant dry cows, bulls and oxen were significantly higher in tsetse challenged areas than the other two study areas. The rate of cattle addition to and disposal from the herd were significantly higher in tsetse challenged areas. Cows in Southern Tsetse Eradication Project (STEP) and community tsetse controlled areas were able to give 26-27?%, 25-29?% and 17-21?% more daily milk yield at the beginning, middle and end of lactation, respectively, than those in tsetse-challenged areas. In addition, cows in STEP and community tsetse controlled areas had lactation length longer by 1.20 to 1.35?months; age at first calving was shorter by 5.30 to 5.10?months; and calving interval was shorter by 4.20 to 3.20?months than cows in tsetse-challenged area, respectively. Hence, tsetse and trypanosomosis control both by the community and project would play key role in the improvement of cattle productivity.     

CONGENITAL AND DEVELOPMENTAL ANOMALIES OF THE GENITALIA OF SLAUGHTERED BULLS

The genital tracts of 968 slaughtered bulls (46% of which were young post-puberal animals) were examined for defects of a congenital or developmental nature. The overall occurrence of such lesions was 7%. These comprised persistent penile frenulum (0.5%), hypospadias (0.3%), detached urethral process (0.4%), testicular hypoplasia (0.2%), cryptorchidism (0.6%), mesonephric duct abnormalities (1.1%) and bulbourethral cysts, fusion and aplasia (3.6%). Segmental aplasia of the mesonephric duct, not previously recorded in the study area, was found in 4 Shorthorn bulls (0.4%); 2 affected animals were from one herd. In 3 cases of hypospadias (2 from one herd), the urethra communicated with the ventral surface of the penis at the junction of the body and glans through a slit-like orifice. The occurrence of defects observed was generally comparable to that found in bull populations elsewhere but elevated occurrence of several defects in particular herds emphasized the need for further study.     

Epidemiologic and economic analyses of an unusually long epizootic of trichomoniasis in a large California dairy herd

An epizootic of trichomoniasis in a large California dairy herd caused an estimated economic loss of $66,538 ($665/infected cow). Greatest losses were caused by infertility (about 50% of losses caused by excess days open). The disease continued in the herd, despite culling older bulls and replacing them with young uninfected bulls and despite institution of an artificial insemination (AI) breeding program for 2 high-production strings. The AI breeder's practice of checking for estrus by vaginal examination was implicated in the spread of the disease. Of 5 cows that became infected before or at conception, 1 had the infection throughout the gestation period and into the next lactation. The prevalence of trichomoniasis in the herd (estimated on the basis of culture results) was 10.67%. The culture method had a calculated sensitivity of only 58.7%. Of 940 cows in the herd, 132 aborted during the epizootic (8 aborted twice); 45 abortions would have been expected in a dairy herd of this size in the absence of trichomoniasis. In high-density mass-bred herds, conditions and/or management practices may be conducive for trichomoniasis transmission, and generally recommended control programs should be adjusted on such dairies. In particular, dairy operators should not assume that culling older bulls and replacing them with young uninfected bulls and that institution of an AI program will be effective in limiting the spread of the disease. Moreover, a diagnostic test with improved sensitivity would greatly assist in the identification of infected cows.