Economic values and selection index in different Angus‐Nellore cross‐bred production systems

Bioeconomic models were developed to calculate economic values (EV) for economically important traits in beef cattle, to evaluate the impact of these traits on production profitability, to assess possible market changes with a payment system and to develop economic selection indexes for Angus cattle for two production systems. Two beef cattle production systems were simulated as follows: a cow‐calf cycle (CC) and a complete cycle (CoC). Following selection, positive changes in the EV were observed. In the CC, each 1.0% increment in weaning weight (WW), weaning rate (WR) and pregnancy rate (PR) resulted in increases in US$ 1.30, US$ 3.68 and US$ 3.55 per cow/year in profit, respectively. In the CoC, EV of US$ 1.01, US$ 1.79, US$ 1.19, US$ 1.34, US$ 6.84 and US$ 7.86 per cow/year were obtained for WW, year weight, yearling weight, final weight, WR and PR, respectively. The payment system for carcass quality showed that the scenario considering that 100% of the animals displayed uniform carcasses exhibited the highest EV and was considered optimal. Considering the sensitivity analysis, the price paid per animal was the factor that most affected the EV in both systems. The selection indexes obtained may be used in similar production systems, and the use of EV and selection indexes are important tools for any production system with positive change in profit after selection.     

Performance of genomic selection under a single-step approach in autochthonous Spanish beef cattle populations

This study evaluated different strategies for implementing a single-step genomic selection programme in two autochthonous Spanish beef cattle populations (Pirenaica—Pi and Rubia Gallega—RG). The strategies were compared in terms of accuracy attained under different scenarios by simulating genomic data over the known genealogy. Several genotyping approaches were tested, as well as, other factors like marker density, effective population size, mutation rate and heritability of the trait. The results obtained showed gains in accuracy with respect to pedigree BLUP evaluation in all cases. The greatest benefit was obtained when the candidates to selection had their genotypes included in the evaluation. Moreover, genotyping the individuals with the most accurate predictions maximized the gains but other suboptimal strategies also yielded satisfactory results. Furthermore, the gains in accuracy increased with the marker density reaching a plateau at around 50,000 markers. Likewise, the effective population size and the mutation rate have also shown an effect, both increasing the accuracy with decreasing values of these population parameters. Finally, the results obtained for the RG population showed greater gains compared to the Pi population, probably attributed to the wider implantation of artificial insemination.     

国内外肉牛遗传评估体系概况

种公牛的选育是肉牛育种工作的核心。传统选育肉用种公牛需要经过后裔测定进行选择,其优点是准确性高,但存在周期长、屠宰和肉质性状难以收集、成本高等问题,致其选择效率低。自2001年全基因组选择概念提出后,该技术迅速成为动植物育种领域研究的热点。利用全基因组选择进行肉用种公牛的选育,进行早期选择从而大幅度缩短世代间隔,可以提高繁殖性状等低遗传力性状的选择准确性,加快遗传进展,并大大降低育种成本。2014年,美国安格斯协会开始应用全基因组选择技术,其他欧美发达国家也陆续使用,肉牛育种进入基因组时代。中国自2017年开始使用全基因组选择技术选择青年肉用种公牛,并于2020年在全国范围内使用该技术进行基因组遗传评估。本文综述了国内外肉牛遗传评估现状,以期为我国肉牛育种工作提供参考和借鉴。     

皮埃蒙特牛改良南阳牛遗传育种研究进展

为了研究皮埃蒙特牛改良南阳牛遗传育种研究进展,本文综述了皮埃蒙特牛杂交改良南阳牛的历史进程,皮埃蒙特牛改良南阳牛杂交后代繁殖性能研究,皮埃蒙特牛改良南阳牛杂交后代肉用性能研究,并提出了产业化集群开发的合理化建议。     

奶牛育种中关注的新性状

各国奶牛群体的选育目标建立之后,选育目标一直在不断发展,选择指数中性状的组成、定义和权重等都在不断变化。奶牛的选育是从关注产奶性能而开始,随后增加了体型外貌性状。由于奶牛的健康和繁殖问题的增加以及社会对动物福利的不断关注,20世纪末,世界范围内平衡育种理念在奶牛育种中逐渐形成,一些重要的功能性状加入各国的选择指数中;进入21世纪后,随着奶牛养殖业和社会的发展,育种家们开始关注和研究更多的性状,部分新性状已经开始在育种实践中选育应用。本文通过整理奶牛育种中有关新性状的研究并收集各国奶牛选育方案中的相关信息,综述了近十年奶业发达国家在奶牛遗传选育中正在研究或已经开始应用的新性状,并将这些新性状分为生产效率相关的新性状、应对环境挑战的新性状、健康福利相关的新性状、产品和加工相关的新性状及管理相关的新性状五大类,总结了这些性状的选育背景、定义方法、遗传基础和选育应用情况等,最后还总结了奶牛育种中新性状的研究应用过程,以期为我国奶牛遗传育种研究和育种目标完善提供一定的借鉴。     

Review: optimizing genomic selection for crossbred performance by model improvement and data collection

Breeding programs aiming to improve the performance of crossbreds may benefit from genomic prediction of crossbred (CB) performance for purebred (PB) selection candidates. In this review, we compared genomic prediction strategies that differed in 1) the genomic prediction model used or 2) the data used in the reference population. We found 27 unique studies, two of which used deterministic simulation, 11 used stochastic simulation, and 14 real data. Differences in accuracy and response to selection between strategies depended on i) the value of the purebred crossbred genetic correlation (rpc), ii) the genetic distance between the parental lines, iii) the size of PB and CB reference populations, and iv) the relatedness of these reference populations to the selection candidates. In studies where a PB reference population was used, the use of a dominance model yielded accuracies that were equal to or higher than those of additive models. When rpc was lower than ~0.8, and was caused mainly by G × E, it was beneficial to create a reference population of PB animals that are tested in a CB environment. In general, the benefit of collecting CB information increased with decreasing rpc. For a given rpc, the benefit of collecting CB information increased with increasing size of the reference populations. Collecting CB information was not beneficial when rpc was higher than ~0.9, especially when the reference populations were small. Collecting only phenotypes of CB animals may slightly improve accuracy and response to selection, but requires that the pedigree is known. It is, therefore, advisable to genotype these CB animals as well. Finally, considering the breed-origin of alleles allows for modeling breed-specific effects in the CB, but this did not always lead to higher accuracies. Our review shows that the differences in accuracy and response to selection between strategies depend on several factors. One of the most important factors is rpc, and we, therefore, recommend to obtain accurate estimates of rpc of all breeding goal traits. Furthermore, knowledge about the importance of components of rpc (i.e., dominance, epistasis, and G × E) can help breeders to decide which model to use, and whether to collect data on animals in a CB environment. Future research should focus on the development of a tool that predicts accuracy and response to selection from scenario specific parameters.     

Comparison of genetic improvement for litter size at birth by direct and indirect selection in swine herd

Responses to selection for number of piglets born alive (NBA) by the total number of piglets born (TNB), the NBA, and the NBA plus number of piglets born dead (NBD) were compared using the accuracy of selection and expected genetic gain calculated from the selection index with family information and the real response to selection, using data generated by Monte Carlo computer simulation. The accuracy of selection for NBA selected by TNB was higher than that by NBA only if the genetic correlation between TNB and NBA was close to 1.0, or the value of heritability for the TNB was much larger than that for the NBA. The accuracy of selection for the NBA selected by the combination of the TNB and the NBA was generally highest in the three selection methods in each family structure. Selection by the TNB resulted in the greatest expected genetic gain for the TNB among the selection methods. In the best linear unbiased prediction (BLUP) selection, the genetic gain for the NBA accumulated by the NBA tended to be similar to that accumulated by the combination of the NBA and the NBD, and both genetic gains at generation 10 were significantly larger than that by the TNB (P < 0.001). The accumulated responses selected by the two‐trait animal model BLUP estimated from genetic parameters with errors were similar to those estimated from the true parameters, and there was no significant difference between them. These results indicate that selection by the NBA or by the NBA and the NBD gives more genetic improvement in the NBA than that by the TNB.     

德国黄牛改良南阳牛遗传育种研究进展

为了研究德国黄牛改良南阳牛遗传育种研究进展,本文综述了德国黄牛杂交改良南阳牛的历史进程,德国黄牛改良南阳牛杂交后代生产性能研究进展,并提出了德南牛产业化集群开发的合理化建议。     

我国肉用西门塔尔牛群体生长发育性状遗传参数估计及其遗传进展

旨在对我国国家肉牛遗传评估中心收集的于2000-2019年出生的6 837头肉用西门塔尔牛的各阶段体重和日增重数据进行遗传参数估计,并估计其在2007-2017年取得的遗传进展。本研究利用REML算法估计我国肉用西门塔尔牛各性状遗传力,通过ASREML软件计算所有个体的育种值,再估计各性状的遗传进展。结果显示,我国肉用西门塔尔牛初生重、6月龄重、12月龄重、18月龄重和24月龄重的遗传力估计值分别为0.44、0.42、0.35、0.38和0.46,初生至6月龄日增重、6~12月龄日增重、12~18月龄日增重、18~24月龄日增重的遗传力估计值分别为0.47、0.32、0.36、0.39。我国肉用西门塔尔牛在2007-2017年初生重、6月龄重、12月龄重、18月龄重和24月龄重的平均每年遗传进展为0.46、2.65、4.31、4.12和2.44 kg,初生至6月龄日增重、6~12月龄日增重、12~18月龄日增重、18~24月龄日增重的平均每年遗传进展为0.014、0.016、0.009和0.007 kg·d^-1。本研究对我国肉用西门塔尔牛群体生长发育性状的遗传参数做了系统评估分析,并评估了我国肉用西门塔尔牛取得的遗传进展,为下一步我国肉牛遗传改良计划的实施提供理论依据。     

Efficient selection against categorically scored hip dysplasia in dogs is possible using best linear unbiased prediction and optimum contribution selection: a simulation study

Breeding to reduce the prevalence of categorically scored hip dysplasia (HD), based on phenotypic assessment of radiographic hip status, has had limited success. The aim of this study was to evaluate two selection strategies for improved hip status: truncation selection based on phenotypic record versus best linear unbiased prediction (BLUP), using stochastic simulation and selection scenarios resembling those in real dog populations. In addition, optimum contribution selection (OCS) was evaluated. Two traits were considered: HD (as a categorical trait with five classes and a heritability of 0.45 on the liability scale) and a continuous trait (with a heritability of 0.25) intended to represent other characteristics in the breeding goal. A population structure mimicking that in real dog populations was modelled. The categorical nature of HD caused a considerably lower genetic gain compared to simulating HD as a continuous trait. Genetic gain was larger for BLUP selection than for phenotypic selection in all scenarios. However, BLUP selection resulted in higher rates of inbreeding. By applying OCS, the rate of inbreeding was lowered to about the same level as phenotypic selection but with increased genetic improvement. For efficient selection against HD, use of BLUP breeding values should be prioritized. In small populations, BLUP should be used together with OCS or similar strategy to maintain genetic variation.     

Post-Death Cloning of Endangered Jeju Black Cattle (Korean Native Cattle): Fertility and Serum Chemistry in a Cloned Bull and Cow and Their Offspring

To preserve Jeju black cattle (JBC; endangered native Korean cattle), a pair of cattle, namely a post-death cloned JBC bull and cow, were produced by somatic cell nuclear transfer (SCNT) in a previous study. In the present study, we examined the in vitro fertilization and reproductive potentials of these post-death cloned animals. Sperm motility, in vitro fertilization and developmental capacity were examined in a post-death cloned bull (Heuk Oll Dolee) and an extinct nuclear donor bull (BK94-13). We assessed reproductive ability in another post-death cloned cow (Heuk Woo Sunee) using cloned sperm for artificial insemination (AI). There were no differences in sperm motility or developmental potential of in vitro fertilized embryos between the post-death cloned bull and its extinct nuclear donor bull; however, the embryo development ratio was slightly higher in the cloned sperm group than in the nuclear donor sperm group. After one attempt at AI, the post-death cloned JBC cow became pregnant, and gestation proceeded normally until day 287. From this post-death cloned sire and dam, a JBC male calf (Heuk Woo Dolee) was delivered naturally (weight, 25 kg). The genetic paternity/maternity of the cloned JBC bull and cow with regard to their offspring was confirmed using International Society for Animal Genetics standard microsatellite markers. Presently, Heuk Woo Dolee is 5 months of age and growing normally. In addition, there were no significant differences in blood chemistry among the post-death cloned JBC bull, the cow, their offspring and cattle bred by AI. This is the first report showing that a pair of cattle, namely, a post-death cloned JBC bull and cow, had normal fertility. Therefore, SCNT can be used effectively to increase the population of endangered JBC.     

Genetic Evaluation of Reproductive Traits in Sanhe Cattle

This study was conducted on 20 949 reproductive records from 1998 to 2012 of 5 257 Sanhe cattle in Xiertala cattle farm,Inner Mongolia,which was a synthetic breed formed in China in 1986.Age at first pregnancy in heifer (AFPH),age at first calving in heifer (AFCH),gestation length in cow (GLC),days open in cow (DOC),and calving interval in cow (CIC) were considered for genetic evaluation.SAS 9.13 and DMU software were used for data processing,and AI-REML combined EM algorithm based on multiple traits animal model was employed for estimating variance components.The heritability for each trait were then calculated,and breeding value was used to analyze the genetic trends.The results showed that the estimated heritabilities of age at first pregnancy in heifer,age at first calving in heifer,gestation length in cow,days open in cow,calving interval in cow were 0.0552,0.0638,0.0527,0.1096 and 0.0844,respectively.The heritabilities were all less than 0.1 except days open (0.1096),indicating these were low inheritable traits.In general,trends of EBVs for each trait didn't show any defined progresses and indicating good reproductive performance maintained in Sanhe cattle.These results lay a theoretical foundation for optimizing breeding programs and improving the accuracy of selection in Sanhe cattle.     

陕西奶牛遗传改良策略探索

 奶牛作为陕西畜牧业的主导产业,为农民增收做出了巨大贡献。陕西奶牛经过多年的选育改良,品质明显提高,但要进一步发展,必须借鉴发达国家的成功经验,结合陕西省奶牛遗传育种实际,创造性地开展遗传育种工作。论文在对陕西省奶牛遗传改良历程、国外经验、目前奶牛改良存在问题等分析的基础上,探索我省奶牛遗传改良的策略。     

三河牛繁殖性状遗传参数的评估

本研究以1986年中国自主培育兼用牛新品种--三河牛,在内蒙古海拉尔谢尔塔拉种牛场核心群5 257头1998-2012年20 949条繁殖记录为研究材料,以青年牛首次妊娠日龄、青年牛首次产犊日龄、成母牛妊娠期、成母牛空怀期、产犊间隔为研究对象,用SAS 9.13、DMU软件对数据进行处理,采用AI-REML结合EM算法并配合多性状动物模型对各性状影响因素方差组分进行估计,估算出各性状遗传力,并利用各性状育种值分析其遗传趋势.结果显示,青年牛首次妊娠日龄、青年牛首次产犊日龄、成母牛妊娠期、成母牛空怀期、产犊间隔遗传力分别为0.0552、0.0638、0.0527、0.1096、0.0844,繁殖性状除成母牛空怀期遗传力为0.1096外,其余均小于0.1,属于低遗传力性状.青年牛首次妊娠日龄、青年牛首次产犊日龄、成母牛妊娠期、成母牛空怀期、产犊间隔育种值遗传趋势总体上无明显下降趋势,三河牛繁殖性能保持良好.该试验结果为三河牛优化育种方案、提高选种准确性提供重要理论依据.     

塑料暖棚养牛试验

本试验是在普通半坡式牛圈南侧覆盖聚乙烯塑料棚膜构成暖棚,冬春季节利用太阳能形成温室效应。在相同的饲料条件下,试验组肉牛日增重７３２±１０２ｇ,比对照组３０６．５±２１６ｇ多增加４２５．５ｇ,两者差异极显著（Ｐ＜０．０１）。经过１４０ｄ的饲养,试验组肉牛每头收入４３１．９３元,而对照组每头亏损４４．７元。     

张掖地区围栏育肥牛场防风墙后不同风速对肉牛场环境及肉牛生产性能的影响

本试验旨在研究防风墙在不同遮蔽距离的减风效果以及风速对牛生产性能的影响。选取初始体重差异不显著的40头牛随机平均分布在选定的4个牛栏中,根据牛栏距防风墙的远近分为2组,测定其日增重。同时根据牛场实际条件和天气状况布置测点,对测点的风速、温度等其他环境指标和肉牛的产热进行现场实测与计算分析。结果表明:安装防风墙的围栏育肥牛场在墙后1.2 m高度,水平遮蔽距离10倍墙高的范围内,可折减风速40%～70%;防风墙后的最佳遮蔽区域是在距离防风墙2～4倍墙高处、水平遮蔽距离6倍墙高距离范围内,风速折减效果明显,最大折减率可达70%左右;肉牛平均体重为480 kg,在外部风冷指数为-15.61的条件下,安装防风墙的围栏育肥牛场的风冷指数可以降低到-9.00,每头牛每小时可减少热量损失3.31 MJ;由于距离防风墙的远近不同,肉牛日增重相差0.15 kg/(头·d),但差异不显著(P>0.05)。     

肉牛遗传育种与繁殖技术应用现状

通过介绍我国肉牛遗传育种与繁殖技术方法,概述了数量遗传学、育种值估计、常规育种、分子育种技术等在肉牛育种、生产领域中的应用现状,并对人工授精技术、胚胎移植技术、胚胎分割技术、性别控制技术、体外授精技术和克隆技术等繁殖技术在肉牛科研与生产中的应用进行了介绍,以期为肉牛遗传育种与繁殖技术研究及生产提供参考.