The effects of genotype by environment interactions in dairy cattle open nucleus breeding schemes

SUMMARY: The evaluation of open nucleus breeding systems using progeny testing or adult or juvenile embryo transfer in the nucleus is extended to include genotype by environment interactions. Knowledge of the extent of such interactions can be used to design breeding schemes and to predict realistic rates of genetic gain in the commercial environment. Interactions between the nucleus and base (commercial) herds are assumed to be more important than those interactions within tiers (e. g., among base herds). The genetic selection differentials of animals born in the nucleus and evaluated for their performance under the base conditions are reduced by a factor equivalent to the genetic correlation for economic merit between the nucleus and base test environment. This leads to a lower asymptotic genetic gain per year and longer asymptotic genetic lag with regard to the genetic improvement in the base herds. The mean genetic merit in the commercial population at a given planning horizon (20 years) is also increased as the genetic correlation for economic merit between the nucleus and base environment decreases. The applies to all the breeding systems and so the genetic correlation is a critical parameter in evaluating open nucleus breeding schemes. ZUSAMMENFASSUNG: Wirkungen von Genotyp-Umweltinteraktionen in offenen Nukleuszuchtsystemen von Milchrindern Die Bewertung offener Nukleuszuchtsysteme mit Nachkommenschaftsprüfung oder adultem oder juvenilem Embryotransfer im Nukleus wird mit Berücksichtigung von Genotyp-Umweltinteraktionen erweitert. Kenntnis solcher Interaktionen sollen bei der Zuchtplanung und zur Voraussch?tzung realistischer genetischer Fortschrittsraten in praxisnahen Situationen Anwendung finden. Interaktionen zwischen Nukleus und Basis (kommerziell) Herden werden als wichtiger angenommen als Interaktionen innerhalb der Schichten (z.B. zwischen Basisherden). Genetische Selektionsdifferentiale von nukleusgeborenen Tieren, die ihre Leistung unter Bedingung der Praxis erbringen, werden proportional der genetischen Korrelation für Wirtschaftswert zwischen Nukleus und Basismilieu vermindert. Dies führt zum geringeren asymptotischen genetischen Fortschritt pro Jahr und einem l?ngeren asymptotischen, mit genetischer Verz?gerung in bezug auf genetische Verbesserung der Basisherden. Der mittlere Zuchtwert der kommerziellen Population bei gegebenem Planungshorizont (20 Jahre) wird ebenfalls proportional der genetischen Korrelation kleiner. Das bezieht sich auf alle Zuchtsysteme, so da? die genetische Korrelation ein kritischer Parameter zur Bewertung offener Nukleuszuchtsysteme ist.     

Deterministic genetic analysis of open nucleus breeding schemes for dairy cattle in developing countries

SUMMARY: A deterministic model is used to analyze the genetic properties of a two tier dairy cattle open nucleus breeding system proposed in developing countries. Theoretical selection response rates are adjusted to account for the effects of population size and structure, selection disequilibrium, sampling losses, inbreeding, and planning horizon. Optimized nucleus progeny testing, adult or juvenile multiple ovulation and embryo transfer in sib or pedigree testing schemes are used in the nucleus. All sires come from the nucleus. Females in the base herds may be recorded and selected as bull dams or donor cows in the nucleus. The predicted genetic means in the base after a given planning horizon (20 years) for a range of situations studied, is generally highest for adult sib testing, but is higher for nucleus progeny testing than for juvenile pedigree testing schemes. The genetic means are higher with more females in the nucleus and with higher reproductive and embryo transfer success rates. The genetic level of the base is higher with higher fractions of nucleus dams born in the base, but is little affected by the proportion of the total population included in the nucleus. The genetic responses are also reduced when heritability in the base is lower than in the nucleus. Policies on the formation and running of an efficient open nucleus breeding system are discussed. Key words: nucleus breeding schemes, nucleus progeny testing, multiple ovulation and embryo transfer, genetic improvement. ZUSAMMENFASSUNG: Deterministische genetische Analyse eines offenen Nukleussystems für Milchrinder in Entwicklungsl?ndern Ein deterministisches Modell wurde zur Analyse der genetischen Eigenheiten eines "Zwei-Stufen offenen Nukleuszuchtsystem" für Milchrinder für Entwicklungsl?nder verwendet. Theoretische Selektionserfolgsraten unter Berücksichtigung der Wirkungen von Populationsgr??e und Struktur, Selektionsungleichgewicht, Zufallsschwankungen, Inzucht und Planungszeitraum für optimierte Nukleusnachkommenschaftsprüfung, adulte oder juvenile multiple Ovulation und Embryotransfer mit Geschwister- oder Pedigreeprüfungspl?nen werden berechnet. Alle Vatertiere kommen von Nukleus, Muttertiere in den Basisherden z. T. leistungsgeprüft werden als Bullenmütter oder Spenderkühe im Nukleus verwendet. Das für die Basis gesch?tzte genetische Leistungsniveau eines gegebenen Planungshorizonts (20 Jahre) wird für eine Reihe von Situationen untersucht und ist im allgemeinen am h?chsten für adulte Geschwisterprüfungssysteme, aber h?her für Nukleusnachkommenschaftsprüfung als für juvenile Pedigreeprüfungspl?ne. Genetische Fortschritte sind h?her, wenn mehr weibliche Tiere im Nukleus und h?here Reproduktions- und Transfererfolgsraten existieren. Das genetische Niveau der Basis ist h?her, wenn ein h?herer Anteil von Nukleusmuttertieren aus der Basis stammt, aber es wird wenig vom Nukleusanteil der gesamten Population tangiert. Der genetische Fortschritt wird reduziert, wenn Rentabilit?t in den Basisherden niedriger als im Nukleus ist. Die Strategien zur Bildung und Management eines wirksamen offenen Nukleuszuchtsystems werden diskutiert.     

Top down preselection using marker assisted estimates of breeding values in dairy cattle

Top down preselection of young bulls before entering progeny testing has been proposed as a practicable form of marker‐assisted selection (MAS), especially in dairy cattle populations with large male paternal half‐sib families. Linkage phase between the superior (Q) and the inferior (q) QTL alleles of heterozygous sires (Qq at the QTL) with informative markers is established within each paternal half‐sib family and may be used for selection among grand‐progeny. If, additionally to sires, bulldams are also genotyped and data from consecutive generations are used, then a marker‐assisted best linear unbiased prediction (MA‐BLUP) model can be employed to connect the information of all generations and families of a top down design, and to select across all families. A customized ‘augmented’ sire model (with sires and dams of sires as random effects) is introduced for this purpose. Adapted formulae for the mixed model equations are given and their equivalence to a corresponding animal model and to a certain variant of previously proposed reduced animal models is shown. The application of the augmented sire model in MA‐BLUP estimation from daughter‐yield deviations and effective daughter contributions is presented.     

奶牛分子育种的研究进展

奶牛分子育种是将来奶牛品种改良的主要工具。奶牛主效数量性状基因座育种和转基因育种主要包括构建基因图谱 ,并据此定位主效数量性状基因座或与之连锁的DNA标记 ,通过转基因技术改良奶牛重要经济性状或研究开发乳腺生物反应器。     

奶牛繁殖障碍的防治

本文围绕引起奶牛繁殖障碍的3个主要因素(饲养管理不当、生殖器管疾病和繁殖技术失误),从奶牛繁殖障碍的发病原因、临床症状、诊断方法、治疗原则以及预防对策上进行了概述。     

Characterisation of the repeat breeding syndrome in Swedish dairy cattle

Repeat breeding (RB), defined as cows failure to conceive from 3 or more regularly spaced services in the absence of detectable abnormalities, is a costly problem for the dairy producer. To elucidate the occurrence of RB in Swedish dairy herds and to identify risk factors of the syndrome totally 57,616 dairy cows in 1,541 herds were investigated based on data from the official Swedish production-, AI- and disease-recording schemes. The characteristics of the RB syndrome were studied on both herd and individual cow level. The effects of risk factors on the herd frequency of RB were studied by logistic regression. A generalised linear mixed model with logit link, and accounting for herd-level variation by including a random effect of herd, was used to study the individual animal risk for RB. The total percentage of RB animals was 10.1% and the median proportion of RB animals in the herds studied was 7.5%. The proportion of RB cows in herds increased with decreased herd sizes with decreased average days from calving to first AI, with increased herd incidence of clinical mastitis, with decreased reproductive disorders, and increased other diseases treated by a veterinarian. On animal level, the risk factors were milk yield, lactation number, difficult calving or dystocia, season at first service, days in milk at first service and veterinary treatment for reproductive disorders before the first service. Cows being an RB animal in the previous lactation had a higher risk of becoming an RB animal also in the present lactation. In conclusion our results show that the repeat breeding syndrome is a multifactorial problem involving a number of extrinsic factors as well as intrinsic factors coupled to the individual animal.     

奶牛高效养殖生产技术

近几年,随着人们生活水平的不断提高,奶产品需求量逐年增加,我县城郊出现了以发展饲料转化率占第一位的奶牛养殖热.饲养奶牛的过程中,多数农户饲养管理粗放,在产乳技术的诸多环节上存在很多不合理性,影响了奶牛产奶性能的发挥,造成奶牛产乳量减少,效益不高.根据笔者在实际工作中的体会,简单谈一下实现奶牛高产高效的技术要点,供奶牛户参考.     

Background lead levels in dairy cattle: updated values for 1986

Lead poisoning continues to be a problem in cattle. The toxicologic significance of blood lead levels requires the differentiation of background blood lead from toxic levels. A ten-fold variation of background blood lead levels reported in previous studies has prompted us to conduct our own survey. Our results indicate significantly lower background blood lead levels in New York State cattle analyzed in 1986 than in those levels previously reported elsewhere.     

Methods and normal values for echocardiography in adult dairy cattle

ObjectiveThe objective of the study was to report normal ultrasonographic appearance and intra-cardiac dimensions in two dairy breeds and to calculate cardiac output (CO) using echocardiography.BackgroundIntra-cardiac dimensions, time indices and CO estimation have not previously been reported in adult cattle.Animals, materials and methodsEchocardiograms were obtained from healthy adult dairy cows (10 Jersey (J) and 12 Holstein Friesians (HF)) in the body weight range of 400 to 700 kg. Standard echocardiographic images were obtained from the left and right hemithoraces. Velocity time integrals were obtained in order to calculate CO using pulsed wave Doppler of aortic flow in the J cows. Measurements obtained included pulmonary artery and aortic diameters, left and right ventricular diameters (and calculated fractional shortening and left ventricular ejection fraction), left atrial size and time indices assessing valve function.ResultsHF cows had significantly (p < 0.05) larger pulmonary artery and aortic diameters, larger left atrial diameters and left ventricular internal diameters during diastole, but these were not different when corrected for body weight. Left and right ventricular dimensions, adjusted for body weight, were significantly larger (p = 0.02 and p = 0.035 respectively) in J cows when compared to HF cows. No differences were noted in the time indices between the two groups. No significant differences were noted in intra-operator variability and the only significant difference in inter-operator variability was in measurement of the pulmonary artery (p = 0.03; ICC = 0.63).ConclusionsIt is possible to obtain repeatable, reliable echocardiograms in order that meaningful intra-cardiac dimensions can be obtained in adult dairy cattle.     

The use of elite nucleus units in beef cattle breeding

Simple plans for the formation and continuation of elite nucleus breeding units utilizing multiple ovulation and embryo transfer for the genetic improvement of beef cattle were investigated. Three policies of forming nucleus units were considered, each in relation to conventional breeding herds with a possible rate of annual genetic change of .17 phenotypic standard deviation (SD) units and also to breeding herds with no genetic improvement. The genetic improvement (as a genetic lift) from the formation schemes ranged from .43 to 1.38 SD units. Three policies for the continuation of the nucleus units were outlined. The best scheme resulted in almost double the total genetic change possible from conventional breeding herds over a 20-yr period. Transfer of these gains from nucleus to breeding herds and to the commercial herds also was considered. Some advantages and limitations to nucleus breeding schemes were discussed. The opportunity exists for progressive breeders, or groups, to make use of improved genetic evaluation systems (expected breeding values) and embryo transfer to greatly accelerate rates of genetic change in economic efficiency of beef cattle.     

肉牛和奶牛家庭牧场发展现状与对策

为保证我国肉牛养殖业和奶牛养殖业的高速发展,经过多种养殖模式的对比,发现以家庭为主体集约化生产、商品化经营的家庭牧场更加适合未来畜牧业的发展趋势,我们认为肉牛和奶牛的家庭牧场式养殖已经成为我国畜牧业未来的发展方向之一。本文对我国肉牛和奶业发达国家的奶牛的家庭牧场发展现状进行了分析,并与畜牧业发达国家的家庭牧场进行对比,总结了我国家庭牧场在发展中存在的问题,并针对这些问题提出了未来我国家庭牧场的发展对策,以期促进我国肉牛和奶牛的家庭牧场持续健康发展。     

Optimized testing schemes using nucleus progeny, adult MOET siblings, or juvenile MOET pedigrees in dairy cattle closed populations

SUMMARY: Selection response rates are predicted for nucleus progeny testing, adult multiple ovulation and embryo transfer (MOET) sib testing, and juvenile MOET pedigree testing in closed populations. Deterministic models are adapted to adjust predicted genetic gains for the effects of population size and structure, selection disequilibrium, sampling losses, and inbreeding depression. The improvement schemes were optimized for different numbers of sires used and first lactation females recorded per year. The number of nucleus daughters tested per sire, and of females per MOET full sibship, that maximize the predicted response to selection per year, were determined. Annual genetic gains and inbreeding rates were interpolated to the same planning horizon (20 years) to compare the optimized schemes for a wide range of situations. The predicted maximum genetic gain per year is higher for adult MOET than for juvenile MOET (due to the proportional extra time to collect the embryos needed) and for nucleus progeny testing. Average annual inbreeding rates are much higher for MOET schemes than for nucleus progeny testing. The advantages of adult and juvenile over nucleus progeny testing are little affected by planning horizon, but are higher with more females recorded per year, higher heritability, and higher reproductive and MOET success rates. Comparison of the schemes at the same level of inbreeding is fairer for fixed testing resources. At the same inbreeding level, the genetic advantage of adult MOET was generally maintained, but juvenile MOET then lost its advantage over progeny testing in these closed populations. ZUSAMMENFASSUNG: Optimierte Prüfpl?ne für Nukleusnachkommen, adulte MOET Geschwister oder juvenile MOET Pedigrees in geschlossenen Milchviehpopulationen Selektionserfolge werden für Nukleusnachkommenprüfung, adulte multiple Ovulation (MOET) und Embryotransfer, Geschwisterprüfung und juvenile MOET Pedigreeprüfung geschlossener Populationen gesch?tzt. Deterministische Modelle werden modifiziert zur Berücksichtigung gesch?tzter genetischer Fortschritte für die Wirkungen von Populationsgr??e, Struktur, Selektionsungleichgewicht, Stichprobenungenauigkeit und Inzuchtdepression. Die Zuchtpl?ne werden für verschiedene Zahlen von Stieren und Erstlaktationskühe pro Jahr optimiert. Die Zahl der geprüften Nukleust?chter je Stier und Kühe je MOETVollgeschwistergruppe, die den gesch?tzten Erfolg maximieren, werden bestimmt. Um die optimierten Pl?ne über einen weiten Bereich zu vergleichen, werden j?hrlicher Zuchtfortschritt und Inzuchtzuwachs für den gleichen Planungshorizont von 20 Jahren interpoliert. Der gesch?tzte maximale Zuchtfortschritt pro Jahr ist für adultes MOET h?her als bei juvenilem (wegen zus?tzlicher Zeit zur Embryonengewinnung) und bei Nukleusnachkommenschaftsprüfung. Durchschnittliche j?hrliche Inzuchtraten sind viel h?her für MOET Pl?ne als für das Nachkommenschaftsprüfsystem. Die Vorteile des adulten und juvenilen MOET über Nukleusnachkommenprüfung werden durch den Planungshorizont nur geringfügig tangiert, werden aber h?her, wenn mehr weibliche Tiere je Jahr geprüft werden bei h?herer Heritabilit?t, h?herer Reproduktions- und Erfolgsrate. Der Vergleich der Pl?ne beim gleichen Inzuchtniveau ist für gegebene Testresourcen angemessener.     

Optimum contribution selection using traditional best linear unbiased prediction and genomic breeding values in aquaculture breeding schemes

The aim of this study was to compare genetic gain for a traditional aquaculture sib breeding scheme with breeding values based on phenotypic data (TBLUP) with a breeding scheme with genome-wide (GW) breeding values. Both breeding schemes were closed nuclei with discrete generations modeled by stochastic simulation. Optimum contribution selection was applied to restrict pedigree-based inbreeding to either 0.5 or 1% per generation. There were 1,000 selection candidates and a sib test group of either 4,000 or 8,000 fish. The number of selected dams and sires to create full sib families in each generation was determined from the optimum contribution selection method. True breeding values for a trait were simulated by summing the number of each QTL allele and the true effect of each of the 1,000 simulated QTL. Breeding values in TBLUP were predicted from phenotypic and pedigree information, whereas genomic breeding values were computed from genetic markers whose effects were estimated using a genomic BLUP model. In generation 5, genetic gain was 70 and 74% greater for the GW scheme than for the TBLUP scheme for inbreeding rates of 0.5 and 1%. The reduction in genetic variance was, however, greater for the GW scheme than for the TBLUP scheme due to fixation of some QTL. As expected, accuracy of selection increased with increasing heritability (e.g., from 0.77 with a heritability of 0.2 to 0.87 with a heritability of 0.6 for GW, and from 0.53 and 0.58 for TBLUP in generation 5 with sib information only). When the trait was measured on the selection candidate compared with only on sibs and the heritability was 0.4, accuracy increased from 0.55 to 0.69 for TBLUP and from 0.83 to 0.86 for GW. The number of selected sires to get the desired rate of inbreeding was in general less in GW than in TBLUP and was 33 for GW and 83 for TBLUP (rate of inbreeding 1% and heritability 0.4). With truncation selection, genetic gain for the scheme with GW breeding values was nearly twice as large as a scheme with traditional BLUP breeding values. The results indicate that the benefits of applying GW breeding values compared with TBLUP are reduced when contributions are optimized. In conclusion, genetic gain in aquaculture breeding schemes with optimized contributions can increase by as much as 81% by applying genome-wide breeding values compared with traditional BLUP breeding values.     

Economic evaluation of breeding strategies for improvement of dairy cattle in Kenya

Cost-benefit analysis using net present value (NPV) as the economic evaluation criterion was used to investigate the economic merits of four breeding strategies used for genetic improvement of dairy cattle in Kenya. The breeding strategies were evaluated over a 25-year period. The costs involved in setting up and running each strategy were obtained from large-scale dairy cattle farms, and government and private institutions involved in genetic improvement of dairy cattle. Only benefits from genetic improvement were considered. The impact on NPV due to changes in genetic and economic parameters was investigated. The ranking of the breeding strategies greatly differed with genetic ranking. Among the local selection programs, a strategy utilizing young bulls, sons of local bulls, was more profitable than one utilizing old progeny tested bulls. Continuous semen importation was not an economically viable alternative. The strategy utilizing young bulls progeny of imported bulls (PIB) was only viable if imports were from countries which are >2.00 SD in genetic merit above the local dairy cattle population. The ranking of strategies was not sensitive to changes in genetic parameters but to economic parameters. The use of local semen from young bulls progeny of local proven bulls is recommended. Alternatively, PIB can be utilized but the semen will have to be imported from countries which are >2.00 SD above the local dairy cattle population or the cost of imported semen should be?≤?US$40 per straw.     

Genetic evaluation of breeding strategies for improvement of dairy cattle in Kenya

Cost-benefit analysis using net present value (NPV) as the economic evaluation criterion was used to investigate the economic merits of four breeding strategies used for genetic improvement of dairy cattle in Kenya. The breeding strategies were evaluated over a 25-year period. The costs involved in setting up and running each strategy were obtained from large-scale dairy cattle farms, and government and private institutions involved in genetic improvement of dairy cattle. Only benefits from genetic improvement were considered. The impact on NPV due to changes in genetic and economic parameters was investigated. The ranking of the breeding strategies greatly differed with genetic ranking. Among the local selection programs, a strategy utilizing young bulls, sons of local bulls, was more profitable than one utilizing old progeny tested bulls. Continuous semen importation was not an economically viable alternative. The strategy utilizing young bulls progeny of imported bulls (PIB) was only viable if imports were from countries which are >2.00 SD in genetic merit above the local dairy cattle population. The ranking of strategies was not sensitive to changes in genetic parameters but to economic parameters. The use of local semen from young bulls progeny of local proven bulls is recommended. Alternatively, PIB can be utilized but the semen will have to be imported from countries which are >2.00 SD above the local dairy cattle population or the cost of imported semen should be ≤ US$40 per straw.