Use Of Progeny Testing Research Articles

Fatores genéticos e de meio na produção de leite de caprinos leiteiros

Objetivou-se, no presente estudo, avaliar a produção de leite de caprinos leiteiros da região sudeste do Brasil, com intuito de verificar os fatores de meio e estimar os parâmetros genéticos pelo método dos mínimos quadrados (MMQ). Os controles de 1336 lactações foram inicialmente ajustados pela função multifásica (difásica) e calculou-se a produção de leite total (PLT). Os dados foram provenientes de sete propriedades e três raças (Parda Alpina, Saanen e Toggenburg). A média e o erro-padrão da PLT estimados pelo MMQ foram de 635,31 ±39,75 kg. A interação ano x estação do parto influenciou a PLT. Em um dos anos estudados, a PLT foi menor para as cabras paridas no final da estação. Nas três estações de parto, observou-se comportamento quadrático da PLT, em função dos anos de parto. Para as três estações, a PLT aumentou de 1986 até meados de 1990, decrescendo em seguida. A idade de máxima PLT foi observada aos 46,65 meses. Das três raças estudadas, observou-se que as raças Parda Alpina e Saanen apresentaram alternância de superioridade na PLT em algumas fazendas, porém maiores que a Toggenburg. Os coeficientes de herdabilidade e repetibilidade da PLT estimados pelo MMQ foram de 0,296 ± 0,079 e 0,277 ± 0,033, respectivamente. Estes resultados revelam baixa confiabilidade em poucas observações dessas características ou na inconsistência das estimativas da função multifásica. Como a PLT é uma característica limitada ao sexo, sugere-se o teste de progênie como método de seleção mais eficiente para os reprodutores e uso de inseminação artificial como processo de disseminação do material genético selecionado.

Linkage disequilibrium in two‐stage marker‐assisted selection

Linkage disequilibrium in two‐stage marker‐assisted selection

Artificial Insemination and Livestock Improvement

Publisher Summary Artificial insemination (A.I.) has now an accepted role in the dairy industry of many countries. It has attained this position as a cheap and efficient way of getting cows in calf. The existence of large breeding groups in the A.I. centers is a magnificent opportunity for the rational use of progeny testing, in which, after finding good bulls, their successors should be bred from within the unit and progeny-tested in their turn. The exact organization of such a breeding unit still remains to be worked out, and tentative efforts are now being made in several countries. The problems that such schemes involve are often sociological and psychological, and possible solutions will have to be judged on these, as well as on genetic grounds.

The Use and Interpretation of Progeny Tests in Livestock Improvement

This paper will in the main deal with the possibilities of the use of progeny testing for the improvement of livestock, in particular under British conditions. Before dealing with individual species, it will perhaps be of value to consider the problem generally and create a framework in which the practical discussion may more fruitfully be carried on.Let us consider first then an ideal case in which we are dealing with a large population of animals all kept under the same general conditions of management. In such a situation, it is possible to predict, using recent advances in population genetics, the probable genetic improvement that could be achieved by different selection programmes. The basic factor that needs to be known for such a calculation is the heritability of the character for which selection is practised—the accuracy with which the breeding value can be predicted from the performance. From the heritability, the accuracy of a progeny test in measuring the breeding value of a sire can be calculated and by this means the probable rate of advance in a progeny testing programme can be evaluated.

Relation of Age of Parents to Mortality and Sex Ratio of Chicks at Eight Weeks

PHYSIOLOGICAL characters are very important in breeding poultry for egg production, viability, and disease resistance. For the most part these characters have a low degree of heritability necessitating the use of progeny testing which requires old parents for reproduction. Longevity also offers something of a measure of viability, and family mortality rate affords a useful tool to guide the breeder.This study was undertaken first to discover possible relations between age of parents and the viability of their offspring to eight weeks of age. It was desirable also to learn whether age of parents has any effect on the sex ratio of chicks at eight weeks of age. Observations on the effect of this early mortality on the sex ratio at the age of eight weeks would also be useful.LITERATURE REVIEWPearl (1940) reported the mortality rate in infants from 20 countries during the first year of life as .

Selection for economic characters in Australian Merino sheep. II. Relative efficiency of certain aids to selection.

Theoretical consequences of the use of progeny testing, sib testing, and mass selection are examined in a flock of 1,000 ewes producing 700 progeny of breeding age each year. Selection based on a combination of individual merit and merit of half-sibs should result in approximately the same annual improvement as that achieved by optimum use of progeny-tested sires. In large flocks extensive use of outstanding sires by artificial insemination may increase progress for traits with heritability of about 0.3 by a factor of about 1.2 as compared with mass selection. The advantages to be gained by progeny testing and artificial insemination may be outweighed by the dangers of inbreeding, and the cost involved would have to be considered. As most of these advantages should be achieved by combination or even by mass selection, which avoid inbreeding and much of the cost, progeny testing with wide use of progeny-tested sires is unlikely to be the most economical road to flock improvement.

The use of progeny testing with artificial insemination in dairy cattle

The problem of the use of progeny testing in conjunction with artificial insemination in dairy-cattle breeding has been considered from the viewpoint of statistical genetics.