No description available.

The reliability of genetic evaluations across separate management units (e.g. flocks) depends on the extent of genetic links or connections among animals in these units. Where poor connectedness exists, comparisons of estimated breeding values (EBV) across units may be biased. The objectives of this study were to identify breeding strategies to increase connectedness among units, to evaluate statistics that may reflect the reduction in bias as connectedness increases in such strategies, and to assess levels of connectedness in Suffolk and Targhee flocks participating in the National Sheep Improvement Program. Expectations of bias when production units have different genetic means were derived for a simple sire model. These expectations were applied to data involving two flocks of animals with three different types of connections: sharing of a common reference sire or use of either a full- or half-sibling sire in each flock. Bias decreased as numbers of progeny in each flock increased for all methods. Linking through a reference sire was most effective and was the only method that eliminated bias as progeny numbers became infinite. Pedigree and performance data on a single trait with heritability 0.25 were then simulated for 15 flocks with 40 to 140 ewes per flock. Each flock was simulated with a different founder genetic mean to introduce bias into the genetic evaluation. Flocks participated in sire referencing schemes by artificial insemination, with varying levels of participation, or by natural service. With sire referencing genetic gain was higher and inbreeding was lower than without, and bias was rapidly reduced to near-zero levels. Discontinuing the schemes led to lower genetic gain, but bias was not reintroduced. The prediction error correlation of flock genetic means was proposed as a connectedness measure because it was strongly associated with bias. Benchmarks of 0.05 and 0.10 for "good" and "superior" connectedness were established. Targhee flocks have increased connectedness across the breed by actively exchanging rams over 15 yr. In the Suffolk breed, connectedness has only improved within segregated clusters of flocks. Suffolk breeders need to engage in active ram exchange to decrease risk of biased across-flock EBV comparisons. / Ph. D.

In terms of numbers and volume of meat produced, the Chinese beef industry is one of the largest in the world. Development of the industry has only occurred within the last thirty years, and despite extensive cross-breeding programs with imported breeds, performance of Chinese cattle is low, and the industry is still subject to traditional farming methods. This study looks at the Australian-developed genetic evaluation system BREEDPLAN, which is regarded worldwide as one of the best systems for assisting with selection of beef cattle for increased performance by evaluating genetics and identifying superior animals, and asks if BREEDPLAN can be successfully applied to the Chinese beef industry. Issues discussed include the complementarity of BREEDPLAN to existing Chinese breeding programs and the benefits of BREEDPLAN if introduced, as well as opportunities for Australians to provide consultancy services to facilitate introduction. The marketing of Australian genetic material in China, and cross-cultural marketing issues are also considered. Field research was conducted in China using itinerant interviews and observational research, together with unstructured, informal interviews and discussions with Australian beef industry experts. It is found that breed improvement programs in China are controlled by the Ministry of Agriculture, and management practises within the government-run herds make them eminently suitable for the application of BREEDPLAN. The objective measurements of BREEDPLAN would provide observable genetic gain, resulting in increased industry productivity and profitability. In addition, it is found that a need exists within the Chinese beef industry for consultants not only with expertise and knowledge about BREEDPLAN, but also with an understanding of Chinese language and culture, which would be an advantage for dealing with cross-cultural difficulties. Market opportunities for Australian genetic material are considerable, but not unlimited, and further research is required to assess the size of the market. It is recommended that immediate steps be taken to introduce BREEDPLAN to the Chinese beef industry.

Detalesnių tyrimų Lietuvos baltalksnynuose niekas neatliko. Šiame darbe siekiama ištirti aukštos bonitetinės klasės baltalksnynų taksacinius parametrus ir įvertinti jų auginimo ekonominę vertę. Darbo objektas – Biržų miškų urėdijos baltalksnynai. Darbo tikslas – Įvertinti našiausių baltalksnynų augimo eigą Biržų miškų urėdijoje, bei atrinkti geriausius medynus ir rinktinius medžius Lietuvos miško sėklinės bazės sąvadui. Darbo metodai – Apibūdinant medyną buvo nustatyta: vidutinis aukštis, skersmuo ir amžius, aukštis iki žalių šakų, stiebo išreikštumas lajos dalyje, stiebo forma, skerspločių suma m2/ha, bonitetas, skalsumas, tūris m3/ha, medžių skaičius 1 ha, metinis tūrio prieaugis m3/ha. Iš viso buvo matuotas 21 sklypas. Kiekviename sklype buvo išskiriama po 3 barelius būdingose sklypo vietose. Darbo rezultatai – Intensyvus baltalksnynų retinimasis vyksta iki 35 metų amžiaus (nuo 3500 vnt/ha – 15 metų amžiaus, iki 1080 vnt/ha – 35 metų amžiaus), o vėliau amžiaus didėjimas medžių skaičiui vnt/ha esminės įtakos nebedaro. Didžiausią tūrio prieaugį m3/ha medynai pasiekia sulaukę 20 metų amžiaus. Vidutinį Lietuvos brandžių baltalksnynų tūrį 1 ha (191 m3/ha) (Lietuvos ..., 2010), našiausi Biržų miškų urėdijos baltalksnynai sukaupia sulaukę 17 metų amžiaus. Sparčiausiai baltalksnynai auga iki 15 metų amžiaus ir per metus į aukštį priauga vidutiniškai po 0,8 m, o nuo 30 iki 45 metų amžiaus per metus į aukštį priauga tik po 0,3 m. Įvertinant baltalksnynų kokybinius rodiklius... [toliau žr. visą tekstą] / Gray alder stands are not studied detailed in Lithuania. The goal of our work is to investigate the main taxation parameters of the most productive gray alder stands and assess the financial benefit of them. Object of the investigation: Gray alder stands in Biržai State Forest Enterprise. The aim of our investigation: to sort out the best gray alder stands in teritory of Biržai State Forest Enterprise and propose to include them in to the base of forests reproductive material. Methods: it was determined middle height, diameter, age, the distance to the vital branches, stem shape, radius (m2/ha), bonitet, stocking level, volume (m3/ha) , the density of trees (units per hectare), the annual growth rate (m3/ha) in order to characterize the gray alder stands. Results: it was determined that the most intensive decline process of gray alder stands continues to 35 years (from 3500 units per hectare in 15 years till 1080 units per hectare – 35 years) after that, increasing age has no significant effect on density. The greatest volume m3/ha is in 20 years. Middle volume of gray alder stands in Lithuania is 191 m3/ha. The most productive gray alder stands in Biržai State Forest Enterprise is in age of 17 years. The most rapidly growth continues to 15 years. Annual growth rate in height reaches 0.8 meter, whereas 30 – 45 years gray alder stands reaches only 0.3 meter annual growth in height. For the qualitative indicators, it was determined that the distance to the crown is 38 % in 15... [to full text]

Lic.-avh. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2006. / Härtill 2 uppsatser.

Licentiatavhandling (sammanfattning) Uppsala : Sveriges lantbruksuniverstet, 2007. / Härtill 2 uppsatser.

Licentiatavhandling Uppsala : Sveriges lantbruksuniversitet, 2006. / Härtill 2 uppsatser.

Resumo: O objetivo deste estudo foi investigar a existência de variabilidade genética aditiva sobre a variância residual do ganho de peso do nascimento à desmama (GND) de bovinos Nelore e as perspectivas de se explorar diferenças entre genótipos para variância residual para a obtenção de maior uniformidade de produção, por meio de seleção. Diferentes abordagens, implementadas em dois passos, foram estudadas: Inicialmente, avaliaram-se três modelos para análise de medidas de dispersão dos resíduos associados às observações de GND da progênie de touros Nelore. O modelo considerado mais promissor foi empregado em estudo subsequente, em que foi investigado o impacto do tamanho de progênie dos touros nas estimativas obtidas para variância aditiva sobre a dispersão residual e estimadores de dispersão em diferentes escalas foram comparados. A confiabilidade de tal abordagem foi verificada por meio de simulação de Monte Carlo. Um último estudo avaliou a possibilidade de se considerarem, simultaneamente, efeitos aditivos e ambientais sobre a variância residual de GND, empregando-se diferentes modelos para análise do logaritmo natural do quadrado do resíduo associado a cada observação. Concluiu-se que, ao se considerar famílias de grande tamanho, seria possível obter predições acuradas do mérito genético dos touros para a variância residual e alguma resposta em termos de uniformidade de produção, sendo a abordagem do último estudo considerada a mais adequada para este fim. Desconsiderar efeitos ambientais sobre a variância residual no segundo passo das análises pode levar a superestimação da variância aditiva sobre a dispersão residual, bem como da resposta esperada à seleção / Abstract: This study was carried out to investigate the existence of genetic variability on residual variance of beef cattle production traits and to evaluate the opportunity for improvement in uniformity of such traits by selecting for lower residual variance. Different two-step approaches were studied to address these questions: Firstly, three models were employed to analyze different measures associated with residual dispersion of weight gain from birth to weaning (GND) in the progeny of Nellore sires. The model that performed best was employed in a subsequent study to access the impact of progeny size on estimates of additive variance for residual dispersion, also aiming to compare dispersion estimators of different scales and to predict selection response in each situation. Reliability of this approach was verified by Monte Carlo simulation. The possibility of considering, simultaneously, additive and environmental effects on residual variance of GND was investigated by analyzing log squared residuals associated with each observation according to different models. It was concluded that, by considering large sire families, accurate estimates of genetic merit of sires for residual variance could be obtained as well as some improvement in uniformity of GND. Analyzing log squared residuals associated with each observation was considered the most promising approach for this task. Ignoring environmental effects at the level of residual variance could lead to inflated estimates of additive variance of residual dispersion, therefore implying in overestimation of response to selection / Orientador: Sandra Aidar de Queiroz / Coorientador: Roberto Carvalheiro / Banca: Vanerlei Mozaquatro Roso / Banca: Henrique Nunes de Oliveira / Mestre

Influence of chosen effects on efficiency of beef breeds Aberdeen Angus, Charolais, Limousine and meat-type Siemental, which were breeded in South Bohemia, was observed in this study. Impact of breed on average weight of calves in different ages, calving month and the serial number of the birth, influence of father´s relative breeding value, dependence of average age of pure bred female on reason of elimination and effect of stocking rate of a pasture on daily weight gain were evaluated.

A disponibilidade de informações baseadas nos marcadores genéticos surgiu como oportunidade de aprimorar os programas de melhoramento animal pela incorporação desses efeitos nas avaliações genéticas. Nesse contexto, o presente estudo teve como objetivos comparar modelos que consideraram ou não os efeitos dos marcadores para a estimação dos valores genéticos dos animais, bem como estimar os efeitos de substituição alélica dos marcadores por seis metodologias distintas (regressão múltipla bayesiana, regressão de cumeeira bayesiana, Bayes A, Bayes B, Bayes Cπ e LASSO bayesiano) e avaliar o impacto da inclusão desses efeitos na acurácia das estimativas dos valores genéticos e os conflitos de seleção existentes aos serem comparadas as classificações dos animais com base nos valores genéticos clássicos e nos valores genéticos assistidos por marcadores. Dados de 83.404 animais pertencentes a um programa de seleção de animas da raça Nelore, mensurados para peso na desmama, ganho de peso pós-desmama, perímetro escrotal e escore de musculosidade, que corresponderam a 116.652 animais na matriz de parentesco, foram utilizados. Do total de animais com informações fenotípicas e genealógicas disponíveis, apenas 3.160 foram genotipados para 106 marcadores do tipo SNP. Os resultados obtidos para a comparação de modelos não demonstraram vantagens claras da inclusão conjunta dos efeitos poligênicos e dos marcadores nos modelos de avaliação genética, entretanto, os modelos que incluíram apenas o efeito dos marcadores tiveram os piores ajustes e desempenhos preditivos. As diferenças observadas entre as estimativas dos efeitos de substituição alélica dos marcadores pelas diferentes metodologias analisadas se devem à maneira como cada método regulariza esses efeitos. A incorporação das informações dos marcadores nas avaliações genéticas proporcionou, no geral, um aumento na acurácia das estimativas dos valores genéticos, especialmente para os tourinhos de reposição. Ao serem comparados os 20% melhores animais classificados com base no valor genético clássico e no valor genético assistido por marcadores, os maiores conflitos de seleção foram observados para os touros e tourinhos genotipados. Em suma, o presente projeto demonstrou que, embora a utilização de painéis de marcadores de muito baixa densidade não altere a capacidade preditiva dos modelos de avaliação genética, esses têm impacto na acurácia das estimativas dos valores genéticos. / The availability of molecular markers information turned out to be an opportunity to improve animal breeding programs, by the inclusion of those effects in the estimation of breeding values. Under that perspective, the aims of present research were to compare genetic evaluation models that assumed or not markers effects on the estimation of breeding values, as well estimate the allelic substitution effects of SNP markers applying six different methodologies (Bayesian multiple regression, Bayesian ridge regression, Bayes A, Bayes B, Bayes Cπ and Bayesian Lasso) and evaluate the impact of these effects on the reliability of breeding values and the divergences on animals classification based on classical breeding values and marker assisted breeding values. Data of 83,404 animals belonging to a Nellore beef cattle (Bos indicus) selection program, measured for post-weaning gain, scrotal circumference and muscle score, corresponding to 116,562 animals on the relationship matrix, were used. From those animals, a set of 3,160 animals with phenotypic and genealogy data available, was genotyped for a panel of 106 SNP markers. Model comparison results did not demonstrate clearly the advantage of assuming polygenic and markers effects together in genetic evaluation models, however, models that considered only markers effects presented the worst global fit and predictive ability. Differences observed on the markers effects estimates were due the shrinkage process applied by each method. The incorporation of markers information on genetic evaluations provided, in general, increases on the reliability of breeding values, mainly for replacement young animals. Comparing the 20% best animals classified by classical breeding value and marker assisted breeding value, the highest divergences were observed to sires and young bulls that were genotyped. Summarizing, although this research showed that the inclusion of very low density SNP chip information was not able to improve the predictive ability of genetic evaluation models, they increased the reliability of breeding values estimates.