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Search Results: 1 - 10 of 182317 matches for " Queiroz Sandra Aidar de "
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Modelos matemáticos utilizados para descrever curvas de crescimento em aves aplicados ao melhoramento genético animal
Tholon, Patricia;Queiroz, Sandra Aidar de;
Ciência Rural , 2009, DOI: 10.1590/S0103-84782009000700050
Abstract: the use of mathematical models to describe animal growth is not recent. they are able to summarize information on strategic dots of animal growth development and to describe the evolution of weight according to the animal age. it is also possible to compare different individuals in similar physiologic stages. the growth models most commonly used in poultry breeding are derived from richards function, and they present parameters that provide biological interpretation and knowledge to select a specific shape of growth curve in poultry. however, it is also possible to use segmented polynomials to describe trend changes during the animal growth. one needs to consider important variables affecting the growth curve parameters estimates, such as, production system, specie, sex and their interactions. model goodness-of-fit can be based on many criteria such as coefficient of determination (r2), residual mean squared error, (lse), estimated predicted mean error (pme), the easiness the analysis to reach convergence and the possibility of biological interpretation of parameters. studies involving modeling and description of growth curve and their components are described in literature, but, there is no selection programs applied to the growth curve shape. the importance of determinating the parameters of growth curve models is more relevant when considering that most of the genetic gains for growth traits are related to selection, on weights near to the inflexion point. often, selection to fast growth is important in all breeding programs, and could be based on genetic parameters of the growth curve parameters. these parameters are related to important productive and reproductive traits, and present different values, according to specie, sex and models used in evaluation. alternatively, other methodology used is random regression models, allowing graduation changes in (co) variances between ages during the time and predicting (co)variances during the studied trajectory. the us
Efeito da linhagem citoplasmática sobre o peso ao nascer e o ganho médio diário na pré-desmama em bovinos da ra?a Caracu
Pelicioni, Luciele Cristina;Queiroz, Sandra Aidar de;
Revista Brasileira de Zootecnia , 2001, DOI: 10.1590/S1516-35982001000100016
Abstract: the objective of this research was to evaluate the effect of cytoplasmic lineage on birth weight (bw) and pre weaning average daily gain (adg), respectively of 4,212 and 3,844 records of caracu cattle breed. the cytoplasmic lineage of each cow was traced back to the first female ancestor in the maternal line of its pedigree. the estimates of (co) variances and genetic parameters for bw and adg including or not the components of maternal and cytoplasmic lineage effects, performed by univariate analyses were evaluated according to six different models using the derivative-free restricted maximum likelihood method. the cytoplasmic lineage variance in the two models that included this effect was very low, 0.6172x10-5 and 0.1339x10-5, 0.62557x10-7 and 0.49502x10-7 for bw and adg, respectively. the cytoplasmic lineage effect could be neglected in the models of bw and adg of caracu cattle.
Efeito da linhagem citoplasmática sobre a produ??o de leite em bovinos da ra?a Caracu
Pelicioni, Luciele Cristina;Queiroz, Sandra Aidar de;
Revista Brasileira de Zootecnia , 2001, DOI: 10.1590/S1516-35982001000100017
Abstract: the objective of this research was to evaluate the effect of cytoplasmic lineage on milk yield of 11,163 records of caracu cattle breed. the cytoplasmic lineage of each cow was traced back to the first female ancestor in the maternal line of its pedigree. the estimates of (co) variances and genetic parameters for milk yield including or not the components of maternal and cytoplasmic lineage effects, performed by univariate analyses were evaluated according to six different models using the derivative-free restricted maximum likelihood method. the cytoplasmic lineage variance estimate in the two models that included this random effect was very low, 0.0025 and 0.0022. therefore, the inclusion of the random cytoplasmic lineage effect in the milk yield statistical model better explained the milk yield variation and also produced better estimates of genetic parameters for this trait.
Efeito da linhagem citoplasmática sobre a produ o de leite em bovinos da ra a Caracu
Pelicioni Luciele Cristina,Queiroz Sandra Aidar de
Revista Brasileira de Zootecnia , 2001,
Abstract: O objetivo do presente estudo foi avaliar o efeito da linhagem citoplasmática sobre a característica produ o de leite de 11.163 lacta es de vacas de um rebanho da ra a Caracu. A linhagem citoplasmática foi estudada tra ando-se o pedigree dos animais até as fêmeas fundadoras do rebanho. Com o intuito de apresentar estimativas de (co)variancias e parametros genéticos para a característica produ o de leite, incluindo-se ou n o os componentes de efeito materno e de linhagem citoplasmática, foram realizadas análises univariadas sob seis diferentes modelos. As análises estatísticas foram elaboradas pelo método de máxima verossimilhan a restrita livre de derivada. A estimativa da variancia de linhagem citoplasmática nos dois modelos que incluíram esse efeito como aleatório apresentou-se muito baixa, fornecendo estimativas praticamente nulas, 0,0025 e 0,0022. Apesar disso, a inclus o do efeito aleatório de linhagem citoplasmática no modelo estatístico de análise da produ o de leite proporcionou melhor ajuste dos dados, explicando melhor a varia o da produ o de leite e fornecendo melhores estimativas dos parametros genéticos.
Efeito da linhagem citoplasmática sobre o peso ao nascer e o ganho médio diário na pré-desmama em bovinos da ra a Caracu
Pelicioni Luciele Cristina,Queiroz Sandra Aidar de
Revista Brasileira de Zootecnia , 2001,
Abstract: O objetivo do presente estudo foi avaliar o efeito da linhagem citoplasmática sobre as características peso ao nascer (PN) e ganho médio diário pré-desmama (GMD) de, respectivamente, 4.212 e 3844 registros de bezerros de um rebanho da ra a Caracu. A linhagem citoplasmática (LC) foi estudada tra ando-se o pedigree dos animais até as fêmeas fundadoras do rebanho. Com o intuito de apresentar estimativas de (co)variancias e parametros genéticos para as características PN e GMD, incluindo-se ou n o os componentes de efeito materno e de linhagem citoplasmática, foram realizadas análises sob seis diferentes modelos pelo método de máxima verossimilhan a restrita livre de derivada. A variancia de linhagem citoplasmática nos dois modelos que incluíram esse efeito apresentou-se muito baixa, fornecendo estimativas praticamente nulas, 0,6172x10-5 e 0,1339x10-5; 0,62557x10-7 e 0,49502x10-7, para PN e GMD, respectivamente. O efeito de LC pode ser desconsiderado na modelagem das características PN e GMD de bovinos Caracu.
Optimum contribution selection using differential evolution
Carvalheiro, Roberto;Queiroz, Sandra Aidar de;Kinghorn, Brian;
Revista Brasileira de Zootecnia , 2010, DOI: 10.1590/S1516-35982010000700005
Abstract: a program to determine optimum contribution selection using differential evolution was developed. the objective function to be optimized was composed by the expected merit of the future progeny and the coancestry among selected parents. simulated and real datasets of populations with overlapping generations were used to validate and test the performance of the program. the program was computationally efficient and feasible for practical applications. the expected consequences of using the program, in contrast to empirical procedures to control inbreeding and/or to selection based exclusively on expected genetic merit, would be the improvement of the selection response and a more effective control of inbreeding.
Estimativas de efeitos genotípicos sobre os desempenhos pré e pós-desmama de popula??es Hereford x Nelore
Cardoso, Vania;Queiroz, Sandra Aidar de;Fries, Luiz Alberto;
Revista Brasileira de Zootecnia , 2008, DOI: 10.1590/S1516-35982008001000008
Abstract: the additive and non-additive effects on pre-weaning and post-weaning traits in hereford x nelore animals were estimated by multivariate linear regression analyses, including or not the ridge regression procedure. variance inflation factors (vif) estimates for all covariates were larger in the analysis without ridge regression. the estimates obtained in this study were used to predict the performances of successive generations of a ? crossbred braford population resulting from mating hereford bulls to nelore cows. high performance was observed in the f1 generation probably due to total individual heterosis and the maternal additive effects. the direct epistatic effects significantly reduced the performance in the f2 generation animals. the performance of pre-weaning traits in the f3 generation animals decreased due to full maternal epistatic effects of their f2 dams. predicted values for pre-weaning traits stabilized in the f4 generation and were close to those from the nelore breed. average performance of post-weaning traits in the f3 and f4 generations were similar or superior to those predicted for the f2 generation animals.
Profitability measures of dairy cows
Ribeiro, Anamaria Candido;McAllister, Alan Jackson;Queiroz, Sandra Aidar de;
Revista Brasileira de Zootecnia , 2008, DOI: 10.1590/S1516-35982008000900012
Abstract: this study was aimed at defining profitability measures designed for prediction of breeding values (ebv) in dairy cows. performance and economic data recorded in herds enrolled in the dhia (dairy herd improvement association) program in kentucky, usa, were used to evaluate economic functions which included the following profitability measures: lifetime net income (lni), efficiency (ef), milk income over feed costs (iofc), net income per day of productive life (nipl), net income at the end of the first lactation (ni1), and milk income over feed costs at the end of the first lactation (iofc1). the estimated averages for lni, ef, iofc, nipl, ni1 and iofc1 were respectively us$ 532.13, 1.04, us$ 3038.19, us$ -0.16, us$ -69.34 and us$ 1293.77. the heritability estimates for these traits ranged from 0.06 to 0.09. the ebv and spearman correlation estimates were positive, ranging from moderate to high values, suggesting a direct linear relationship among the profitability measures. lni was the best profitability measure and genetic correlation estimates between lni and economic measures recorded in first lactation (ni1 and iofc1) were moderate (<0.56). ni1 was the most efficient profitability measure, but it would be easier to record data to calculate iofc1. overall, results do not suggest any economic function measured in the first lactation as a selection criteria for lni. the profitability measures were affected by the short productive life of the animals in the herds. selection based on different profitability measures would not result in similar ranking of sires.
Efeito das taxas de descarte sobre medidas econ?micas de vacas leiteiras em Kentucky
Ribeiro, Anamaria Candido;McAllister, Alan Jack;Queiroz, Sandra Aidar de;
Revista Brasileira de Zootecnia , 2003, DOI: 10.1590/S1516-35982003000700025
Abstract: the aims of this research were to evaluate the effect of culling reasons on lifetime economic measures of dairy cows especially, lifetime net income (lni), lifetime efficiency (le), income over feed costs (iofc) and lifetime income per day of productive life (lipl) using 19,565 lifetime records from holstein cows. culling rate was calculated dividing the number of culled animals, yearly, by the number of all animals present in each year. data on reasons for disposal were used to calculate the culling rate distribution, dividing the number of animals in each class of culling reason by the total number of animals. the estimated culling rate was 31.39%. this value was high and could be a result from the short productive life of cows, 25.57 months. the main reasons for disposal were reproductive problems (21.57%), injuries and other causes (21.17%), and low production (17.20%). involuntary culling was responsible for the majority of culling, representing 75% of total. all traits were significantly affected by culling reason. cows culled for dairy purposes were more profitable to producers.
Efeito das taxas de descarte sobre medidas econ micas de vacas leiteiras em Kentucky
Ribeiro Anamaria Candido,McAllister Alan Jack,Queiroz Sandra Aidar de
Revista Brasileira de Zootecnia , 2003,
Abstract: Foram utilizadas 19.565 lacta es vitalícias de vacas da ra a Holandesa para avaliar o impacto dos motivos de descarte sobre a rentabilidade vitalícia de vacas leiteiras, mais especificamente sobre a receita líquida vitalícia (RLV), eficiência vitalícia (EF), receita do leite menos o custo de alimenta o (RLMA) e receita líquida por dia de vida produtiva (RLD). A taxa geral de descarte foi igual a 31,39%, valor que pode ser considerado alto e estaria diretamente relacionado com a vida produtiva curta encontrada para estes rebanhos, 25,57 meses. A principal causa de descarte foi problema reprodutivo (21,57%), seguido por injúrias e outras causas (21,17%) e baixa produ o (17,20%). Os descartes involuntários foram a grande maioria, representando 75% do total. As diferentes medidas econ micas estudadas sofreram impacto significativo do motivo de descarte, em que as vacas removidas por venda para fins leiteiros foram as mais rentáveis ao produtor.
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