Simulation study on the efficiencies of MOET nucleus breeding schemes applying marker assisted selection in dairy cattle

Advantages of breeding schemes using genetic marker information and/or multiple ovulation and embryo transfer (MOET) technology over the traditional approach were extensively evaluated through simulation. Milk yield was the trait of interest and QTL was the genetic marker utilized. Eight dairy cattle breeding scenarios were considered, i.e., traditional progeny testing breeding scheme (denoted as STANPT), GASPT scheme including a pre-selection of young bulls entering progeny testing based on their own QTL information, MOETPT scheme using MOET technology to generate young bulls and a selection of young bulls limited within the full-sib family, GAMOPT scheme adopting both QTL pre-selection and MOET technology, COMBPT scheme using a mixed linear model which considered QTL genotype instead of the BLUP model in GAMOPT, and three non-progeny testing schemes, i.e. the MOET, GAMO and COMB schemes, corresponding to MOETPT, GAMOPT and COMBPT with progeny testing being part of the system. Animals were selected based on their breeding value which was estimated under an animal model framework. Sequential selection over 17 years was performed in the simulations and 30 replicates were designed for each scenario. The influences of using QTL information and MOET technology on favorable QTL allele frequency, true breeding values, polygenetic breeding values and the accumulated genetic superiority were extensively evaluated, for five different populations including active sires, lactating cows, bull dams, bull sires, and young bulls. The results showed that the combined schemes significantly outperformed other approaches wherein accumulated true breeding value progressed. The difference between schemes exclusively using QTL information or MOET technology was not significant. The STANPT scheme was the least efficient among the 8 schemes. The schemes using MOET technology had a higher polygenetic response than others in the 17th year. The increases of frequency of the favorable QTL allele varied more greatly across the 3 male groups than in the lactating cows group. The accumulated genetic superiorities of the GASPT scheme, MOETPT scheme, GAMOPT scheme, COMBPT scheme, MOET scheme, GAMO scheme and COMB scheme over the STANPT scheme were 8.42%, 3.59%, 14.58%, 18.54%, 4.12%, 14.12%, 16.50% in active sires and 2.70%, 5.00%, 11.05%, 12.78%, 7.51%, 17.12%, 25.38% in lactating cows. Supported by Key Project for Introducing Advanced International Agriculture Science & Technologies (Grant No. 2006-G48), the National Key Basic Research and Development Program of China (Grant No. 2006CB102107) and National Key Technology Research and Development Program of China (Grant No. 2006BAD04A01).     

Productivity of pure- and crossbred cattle in a subtropical environment

The influence of different breeds of sire and dam types on cow productivity in an arid, subtropical environment was studied. Cows with calves sired by Simmentaler, Hereford and Bonsmara bulls were more (P<0.05) productive than those with calves sired by Afrikaner bulls. Simmentaler sires were superior (P<0.05) to Bonsmara sires. Crossbred cows of predominant (>50%)Bos taurus breeding were generally superior to crossbreds of predominantB. indicus breeding and purebreds. Crossbreeding systems to utilize breed effects to optimise cow productivity within environmental constraints are discussed.     

Production and breeding of transgenic cattle using in vitro embryo production technology

Transgenic technology permits major modifications of phenotype by introducing subtle changes in genotype. For domestic farm species, genetic modification may be used to enhance agricultural production or to generate novel genotypes capable of producing heterologous proteins for biomedical applications. The advent of in vitro embryo production techniques has facilitated the large-scale, commercial use of transgenic technology in cattle. Accordingly, we employed in vitro-produced zygotes and embryos in an effort to generate transgenic cattle. Overall, pronuclei in 36,530 in vitro matured and fertilized zygotes were microinjected with a construct designed to express human alpha-lactalbumin in the mammary gland. Of these, 1,472 developed and were transferred to recipients, including 148 twin transfers. Initial pregnancy rate on Day 30 of gestation was 28% (374/1,324). Subsequent calving rate was 17% (226/1,324). Eighteen calves (8%) were transgenic. In vitro produced embryos were used to facilitate breeding of transgenic bulls. Frequency of transgene transmission varied from 3 to 54% between bulls, indicating varying degrees mosaicism. Embryos produced in vitro by these bulls were biopsied and screened for transgenesis prior to transfer to recipients; so far all (6/6) calves born from screened, transgenic embryos were themselves transgenic.     

Applications of sexed semen in cattle production

Sexed semen will contribute to increased profitability of dairy and beef cattle production in a variety of ways. It could be used to produce offspring of the desired sex from a particular mating to take advantage of differences in value of males and females for specific marketing purposes. Commercial dairy farmers, those who produce and market milk, could use sexed semen to produce replacement daughters from genetically superior cows and beef crossbred sons from the remainder of their cow population. To increase the rate of response to selection, seedstock dairy cattle breeders could produce bulls for progeny testing from a smaller number of elite dams by using sexed semen to ensure that all of them produced a son. Using sexed semen could then reduce the cost of progeny testing those bulls, because fewer matings would be necessary to produce any required number of daughters. Commercial beef cattle farmers, producing animals for eventual slaughter, could use sexed semen to capitalize on the higher value of male than female offspring for meat production. They could also use sexed semen to produce specialized, genetically superior replacement heifers from as small a proportion of the herd as possible. This would allow the remainder of the herd to produce male calves from bulls or breeds with superior genetic merit for growth, feed conversion efficiency, and carcass merit. Single-sex, bred-heifer systems, in which each female is sold for slaughter soon after weaning her replacement daughter, would be possible with the use of X-chromosome-sorted semen. Use of sexed semen would make terminal crossbreeding systems more efficient and sustainable in beef cattle. Fewer females would be required to produce specialized maternal crossbred daughters, and more could be devoted to producing highly efficient, terminal crossbred sons.     

Bull selection and use in northern Australia. Part 2. Semen traits

Detailed semen evaluations were carried out on approximately 363 Santa Gertrudis, 5/8 Brahman and Brahman bulls on 12 different properties across northern Australia, as part of systematic breeding soundness examinations. A subset of bulls (n=245) were subsequently mated in groups, to cows and heifers at bull:female ratios of 2.5-6.0%, with the paternity of resulting calves being determined by microsatellite DNA testing. Motility traits of semen and spermatozoa were moderately repeatable and correlated with each other, but were unrelated to calf output. The percentage of morphologically normal spermatozoa in ejaculates was moderately to highly repeatable (e.g. r=0.10-0.64). The most common morphological abnormalities seen were mid-piece abnormalities, in particular, distal mid-piece reflex associated with a cytoplasmic droplet. Semen quality, particularly percent normal spermatozoa, was consistently related to calf output. In general, bulls with <50% normal spermatozoa sired few calves while bulls with the highest calf outputs had >70% normal spermatozoa. The presence or absence of heparin binding proteins in semen did not influence calf output. Semen from 93% of tested bulls was positive for heparin binding proteins. These results confirm that examination of semen, in particular, evaluation of percent morphologically normal spermatozoa, should be included in the breeding soundness examination of bulls.     

Paternity Tests in Multisired Beef Herds by Blood Grouping

The number of offspring sired by individual bulls in multisired beef herds was determined by blood grouping. Six series of tests, each having from 3 to 18 bulls as possible sires,, yielded from 35 to 114 dam-offspring pairs. The paternity was established for 45 to 90 % of the calves tested in each series. The rest were cases with either more than 1 bull not being excluded as the possible sire, or all bulls excluded from being the sire. The causes for the non-established paternities are discussed. Highly significant differences were found in the number of offspring sired by each bull. In each series, bulls ranking in the top third of the siring order sired 65–100 % of the calves with established paternities. Since a minority of the bulls sired the majority of the calf-crop, the generally recomended number of bulls for herds on the range can perhaps be reduced.     

Economic evaluation of genomic selection in small ruminants: a sheep meat breeding program

Recent genomic evaluation studies using real data and predicting genetic gain by modeling breeding programs have reported moderate expected benefits from the replacement of classic selection schemes by genomic selection (GS) in small ruminants. The objectives of this study were to compare the cost, monetary genetic gain and economic efficiency of classic selection and GS schemes in the meat sheep industry. Deterministic methods were used to model selection based on multi-trait indices from a sheep meat breeding program. Decisional variables related to male selection candidates and progeny testing were optimized to maximize the annual monetary genetic gain (AMGG), that is, a weighted sum of meat and maternal traits annual genetic gains. For GS, a reference population of 2000 individuals was assumed and genomic information was available for evaluation of male candidates only. In the classic selection scheme, males breeding values were estimated from own and offspring phenotypes. In GS, different scenarios were considered, differing by the information used to select males (genomic only, genomic+own performance, genomic+offspring phenotypes). The results showed that all GS scenarios were associated with higher total variable costs than classic selection (if the cost of genotyping was 123 euros/animal). In terms of AMGG and economic returns, GS scenarios were found to be superior to classic selection only if genomic information was combined with their own meat phenotypes (GS-Pheno) or with their progeny test information. The predicted economic efficiency, defined as returns (proportional to number of expressions of AMGG in the nucleus and commercial flocks) minus total variable costs, showed that the best GS scenario (GS-Pheno) was up to 15% more efficient than classic selection. For all selection scenarios, optimization increased the overall AMGG, returns and economic efficiency. As a conclusion, our study shows that some forms of GS strategies are more advantageous than classic selection, provided that GS is already initiated (i.e. the initial reference population is available). Optimizing decisional variables of the classic selection scheme could be of greater benefit than including genomic information in optimized designs.     

Non-random mating for selection with restricted rates of inbreeding and overlapping generations

Minimum coancestry mating with a maximum of one offspring per mating pair (MC1) is compared with random mating schemes for populations with overlapping generations. Optimum contribution selection is used, whereby ΔF is restricted. For schemes with ΔF restricted to 0.25% per year, 256 animals born per year and heritability of 0.25, genetic gain increased with 18% compared with random mating. The effect of MC1 on genetic gain decreased for larger schemes and schemes with a less stringent restriction on inbreeding. Breeding schemes hardly changed when omitting the iteration on the generation interval to find an optimum distribution of parents over age-classes, which saves computer time, but inbreeding and genetic merit fluctuated more before the schemes had reached a steady-state. When bulls were progeny tested, these progeny tested bulls were selected instead of the young bulls, which led to increased generation intervals, increased selection intensity of bulls and increased genetic gain (35% compared to a scheme without progeny testing for random mating). The effect of MC1 decreased for schemes with progeny testing. MC1 mating increased genetic gain from 11–18% for overlapping and 1–4% for discrete generations, when comparing schemes with similar genetic gain and size.     

Age- and tactic-related paternity success in male African elephants

Information on age- and tactic-related paternity success isessential for understanding the lifetime reproductive strategyof males and constitutes an important component of the fitnesstrade-offs that shape the life-history traits of a species.The degree of reproductive skew impacts the genetic structureof a population and should be considered when developing conservationstrategies for threatened species. The behavior and geneticstructure of species with large reproductive skew may be disproportionatelyimpacted by anthropogenic actions affecting reproductively dominantindividuals. Our results on age- and tactic-specific paternitysuccess in male African elephants are the first from a free-rangingpopulation and demonstrate that paternity success increasesdramatically with age, with the small number of older bullsin the competitive state of musth being the most successfulsires. However, nonmusth males sired 20% of genotyped calves,and 60% of mature bulls (>20 years old) were estimated tohave sired offspring during the 5-year study period. The 3 mostsuccessful males sired less than 20% of the genotyped offspring.Hence, contrary to prediction from behavior and life-historytraits, reproduction was not heavily skewed compared with manyother mammalian systems with a similar breeding system. Nevertheless,these results indicate that trophy hunting and ivory poaching,both of which target older bulls, may have substantial behavioraland genetic effects on elephant populations. In addition, theseresults are critical to the current debate on methods for managingand controlling increasing populations of this species.     

The relationship between breeding soundness evaluation and fertility of beef bulls under group mating at pasture

The relationships between natural service fertility of beef bulls and the components of breeding soundness evaluation, age, preweaning average daily gain, yearling weight and scores of two libido tests were studied in two seedstock herds. In one of the herds (YBH), 15 yearling bulls were rotated during six-week breeding season so that each group of five bulls served the cows for a period of one week and rested for two weeks before the next exposure. Five older bulls (one 3-year old and four 2-year old) were assigned to the other herd (MBH) during the entire breeding season (six weeks). The progeny of each bull were identified by blood typing.Calf crop was 6.4% higher (P=0.14) in the MBH compared with that in the YBH. There were large differences in fertility between the bulls in the MBH. The 3-year old bull sired 40.9% of the calves, presumably due to his high social dominance order. The third group of yearling bulls, which served the herd during the third and sixth weeks of breeding, sired the highest number of calves (49.4%) compared with the other two groups (28.4% and 22.2%). In each of the groups one and two of the yearling bulls, one bull did not produce any progeny, while another one sired 44% of the calves. The correlation coefficients between fertility of the bulls and the traits used to predict their fertilizing capacity were generally small and inconsistent in different groups, when the effect of age in the mixed age group was removed. The correlation coefficients of bull fertility with scrotal circumference and reproductive system score were higher and more consistent in different groups as compared with the other traits studied.     

Incidence and inheritance of the 1/29 and 14/20 Robertsonian translocations in Canadian beef cattle

Metaphase chromosomes were prepared from peripheral leukocyte cultures of 253 beef animals representing 21 breeds. A total of 10 Robertsonian translocations were identified. Nine were 1/29 fusions and one was a stable 14/20 fusion identified in several Simmentals. To our knowledge, the only other case of this translocation reported was also in the Simmental breed, suggesting that this fusion may be unique to the breed. A further 54 relatives of known 1/29 and 14/20 carriers were examined, revealing that both fusions were inherited by 50% of offspring of the heterozygous carrier. Heterozygous male 1/29 carriers left fewer calves than karyotypically normal bulls when used in natural service.     

Zootechnical performance of cloned cattle and offspring: preliminary results

This paper presents information on the evolution of sets of cloned heifers of Holstein breed in comparison to that of control heifers derived from artificial insemination (AI) in the same farm, as well as data on a set of cloned bulls and their semen characteristics. Preliminary observations on a group of calves sired by a cloned bull and offspring of cloned females are reported. Mean birth weight in the clone group (50 females) was statistically higher than that of 68 contemporary female controls obtained by AI (49.27 +/- 10.98 vs. 40.57 +/- 5.55 kg, respectively, p < 0.05). Growth rate was within normal values for Holstein heifers (from 0.7 to 0.8 kg/day) and daily gain was not influenced by the high or low birth weight of clones. Within animals of the same clone, variability of daily gain was reduced compared to their control counterparts. Semen production from three cloned bulls was within the parameters expected for young bull of the same age. A direct comparison of morphological analysis was made between the frozen thawed semen of the donor bull and of his three clones collected at the same age. The overall semen picture appeared within acceptable limits and the clones presented similar percentages of sperm abnormalities (80% of morphologically normal spermatozoa) as the donor. These preliminary results suggest no deleterious effect of cloning on the semen picture of cloned sires. Frozen semen from one clone bull was used for an AI trial, resulting in 65% pregnancies, 25 live calves were naturally delivered. Concerning the offspring of both female and male clones, the phenotypical and clinical observation of the calves in the first week of age did not reveal any clinical abnormality, suggesting that the deviations observed in clones are not transmitted to the progeny.     

Repeat superovulation, non-surgical embryo recovery, and surgical embryo transfer in transgenic dairy goats

We investigated the capability of repeat superovulation and non-surgical embryo retrieval, coupled with surgical embryo transfer, to expedite the production of transgenic progeny from transgenic founder dairy goat does. In addition, we compared embryo yields, number of embryos transferred per recipient, pregnancy rates, and offspring born during both the traditional (September-December) and non-traditional (January-May) breeding seasons. Although there were no significant differences, there were numerically more transferable embryos recovered per flush (3.5+/-0.9 vs. 2.4+/-0.9 embryos; mean+/-S.E.M.) and increases in both the proportion of recipients that were pregnant (83 vs. 69% pregnant) and offspring born from total embryos transferred (67 vs. 53% offspring) during the traditional versus the non-traditional breeding season. The transfer of one, two or three embryos did not significantly affect the proportion of pregnant recipients during either season. However, there was a difference (P<0.05) in the proportion of offspring produced for one versus two embryo transfers (89 vs. 44% offspring, respectively) during the non-traditional breeding season. Overall, 14 transgenic offspring were produced from 54 total offspring born, and the kidding interval was reduced to <3 months for six of the seven transgenic does. In summary, repeat superovulation and non-surgical embryo retrieval, coupled with surgical embryo transfer, expedited the production of progeny from transgenic founder does.     

Normal telomere lengths of spermatozoa in somatic cell-cloned bulls

Interesting questions have been raised regarding cloned animals, including whether cloning restores cellular senescence undergone by donor cells, and how long cloned animals will be able to live. In this study, focusing our attention on the fact that telomere lengths of spermatozoa are longer than those of any somatic cells and that telomere length is maintained throughout aging in humans, we compared the telomere lengths of spermatozoa in normal and two somatic cell-cloned cattle. The telomere lengths of the spermatozoa in the normal cattle (22.42+/-0.32 kb) were maintained throughout aging as in humans. In the cloned cattle, telomere lengths of the spermatozoa (25.8 and 20.9 kb) were the same as or longer than those found in normal cattle. Considering that telomere lengths of the donor cells, which had been derived from the muscle tissue of an old bull, were reported to be 20.1 kb, the results suggested that the telomere lengths of the germ cell line had extended from nucleus transfer to spermatogenesis. Moreover, we produced offspring (nine calves) from a somatic cell-cloned bull and measured the telomere lengths of their leukocytes. In all of the offspring, the telomere lengths of leukocytes were normal, too. These results indicate the possibility that somatic cloned bulls could be used as breeding sires.     

Improving reproductive efficiency in range cattle: An application of the O'Connor Management System

One group of 125 Hereford cows from a range herd served as a control, while five management techniques were utilized to determine if reproductive performance could be maximized in another similar group from the same ranch. These five techniques were 60-d calving season, cows in moderate body condition at calving time, calf removal for 48 h at the start of breeding season, cows gaining weight near breeding time, and cows bred by bulls predicted to have high fertility (O'Connor Management System). Under the O'Connor Management System, 6% more cows became pregnant, 14% more weaned calves and calves were born 24 d earlier in the calving season. Consequently, calves weighed 14 kg more at weaning and net profit was increased approximately $39 per cow for cows in the O'Connor system.     

Response to genomic selection: The Bulmer effect and the potential of genomic selection when the number of phenotypic records is limiting

Background

Over the last ten years, genomic selection has developed enormously. Simulations and results on real data suggest that breeding values can be predicted with high accuracy using genetic markers alone. However, to reach high accuracies, large reference populations are needed. In many livestock populations or even species, such populations cannot be established when traits are difficult or expensive to record, or when the population size is small. The value of genomic selection is then questionable.

Methods

In this study, we compare traditional breeding schemes based on own performance or progeny information to genomic selection schemes, for which the number of phenotypic records is limiting. Deterministic simulations were performed using selection index theory. Our focus was on the equilibrium response obtained after a few generations of selection. Therefore, we first investigated the magnitude of the Bulmer effect with genomic selection.

Results

Results showed that the reduction in response due to the Bulmer effect is the same for genomic selection as for selection based on traditional BLUP estimated breeding values, and is independent of the accuracy of selection. The reduction in response with genomic selection is greater than with selection based directly on phenotypes without the use of pedigree information, such as mass selection. To maximize the accuracy of genomic estimated breeding values when the number of phenotypic records is limiting, the same individuals should be phenotyped and genotyped, rather than genotyping parents and phenotyping their progeny. When the generation interval cannot be reduced with genomic selection, large reference populations are required to obtain a similar response to that with selection based on BLUP estimated breeding values based on own performance or progeny information. However, when a genomic selection scheme has a moderate decrease in generation interval, relatively small reference population sizes are needed to obtain a similar response to that with selection on traditional BLUP estimated breeding values.

Conclusions

When the trait of interest cannot be recorded on the selection candidate, genomic selection schemes are very attractive even when the number of phenotypic records is limited, because traditional breeding requires progeny testing schemes with long generation intervals in those cases.     

杂交群体动物基因聚合

基因聚合是通过优化设计杂交方案,选择利用目标基因或与其紧密连锁的分子标记,通过世代选择实现将来源于多个不同群体的优势目标基因或基因型聚合到同一个理想个体中,进而达到生产出超级经济性状个体的目的。针对聚合不同目标基因个数,设计4类杂交方案——两群体、三群体、四群体级联、四群体对称。在相同的杂交方案中,比较基因型选择和表型选择策略,分析不同杂交组合、性状遗传力、初始基因频率、基础群体规模对聚合设计的影响,并筛选出最佳的聚合方案。研究结果表明,在较大的基础群体规模和较高初始群体基因频率下,获得聚合多个目标基因的理想个体的可能性较大。在四群体杂交方案中,亲本的杂交次序对于级联杂交比对称杂交的影响较大。模拟结果表明,运用基因型选择进行聚合育种优于表型选择。文章所开发设计的聚合模拟育种的统计分析方法和相应软件为指导杂交育种方案和选择策略的设计提供理论参考,同时,为进一步设计开发聚合设计模拟育种平台奠定基础。     

Estimation of relatedness among non-pedigreed Yakutian cryo-bank bulls using molecular data: implications for conservation and breed management

Background

Yakutian cattle, the last remaining native cattle breed in Siberia, are well adapted to the extreme sub-arctic conditions. Nowadays only ca. 1200 purebred animals are left in Yakutia. The semen of six Yakutian bulls was stored in a cryo-bank without any pedigree documentation because of the traditional free herding style of the population.

Methods

To clarify the genetic relatedness between these bulls and to provide recommendations to use their semen in future conservation and breed management programs, we have analysed 30 autosomal microsatellites and mitochondrial DNA sequences in 60 individuals including the six for which semen has been stored. Four relatedness estimators were calculated. In addition, we assessed the value of the cryo-bank bulls for the preservation of genetic variation of the contemporary Yakutian cattle by calculating allelic and gene diversity estimates and mean molecular coancestries.

Results

On the basis of microsatellite variability, including the Yakutian cryo-bank bulls increases the allelic variation in the contemporary population by 3% and in the male subpopulation by 13%. In terms of the mean molecular coancestries, they are less related to the contemporary cow population than the breeding bulls and therefore could be used to reduce inbreeding in the living population. Although 30 loci are insufficient to resolve definitely their relatedness categories, the data suggest four pairs of cryo-bank bulls as possible half-sibs.

Conclusions

Our results show that even relatively limited cryo-bank storage of semen can carry allelic variation through a bottleneck. We propose a breeding scheme based on the rotation of breeding females and the division of cryo-bank bulls into three groups. Thus, if molecular data (e.g. autosomal microsatellite genotypes) for the contemporary population are available and based on relatively small-scale laboratory analyses, it is possible to avoid serious mistakes in their use for breeding applications. The approach suggested here based on the use of Yakutian cryo-bank semen can be easily extended to cryo-bank materials of other animals in future breeding programs.     

Abnormal segregation of alkaline ribonuclease genes in cattle1

Polymorphism of alkaline ribonuclease in the leucocytes of 76 bulls, 554 cows and their progeny of 556 calves was investigated. All possible genotype matings were examined. Observed offspring genotypes were compared with the expected ratios. Abnormal genotype distribution was noticed: homozygous calves of RNase^B/RNase^B genotype were significantly fewer than expected.     

SEXUAL SELECTION IN AMERICAN TOADS: A TEST OF A GOOD-GENES HYPOTHESIS

Adaptive mate choice in species lacking male resource control and/or paternal care might be maintained by selection because preferred males sire genetically superior offspring. For such a process to occur, some male phenotypic trait(s) must both reliably indicate male genetic quality and influence the pattern of mate choice by females. In American toads, Bufo americanus, male body length has been documented to influence female mating patterns: females usually mate with males that are larger than average. However, the relationship between male size and male genetic quality is unknown. We conducted a controlled breeding experiment using 48 sires and 19 dams to determine if larger males sire offspring with superior larval performance characteristics (greater survival to metamorphosis, larger mass at metamorphosis, and earlier metamorphosis). We also aged each sire to test the hypothesis that older males are, on average, genetically superior to younger males. We crossed each female with three sires representing three body size categories (mean and 1 SD ± mean snout-ischium length). Hatchlings (500 from each cross) were reared to metamorphosis in seminatural ponds in the field. Metamorph weight (log transformed) and age at metamorphosis showed significant heritability and were genetically correlated with each other. Hence, sires differed in genetic quality. However, none of the three measures of offspring performance was correlated with sire body size or age. Thus, we obtained no support for the prediction that sire body size or age is related to genetic quality.