106 resultados para negative assortative mating
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Desenvolveu-se um estudo de simulação estocástica com o objetivo de verificar as consequências do uso combinado de acasalamento dirigido e sêmen sexado em uma população de bovinos de corte sob seleção. Simularam-se seis gerações de seleção para três cenários de acasalamento e uso de sêmen sexado. O primeiro cenário foi caracterizado por acasalamento aleatório e uso exclusivo de sêmen convencional. O segundo cenário caracterizou-se pelo uso de acasalamento associativo positivo nas 40% melhores vacas e acasalamento associativo negativo nas demais, sem uso de sêmen sexado. O terceiro cenário seguiu o mesmo procedimento de acasalamento do segundo, combinando-o com uso de sêmen sexado nas vacas submetidas a acasalamento associativo positivo. O acasalamento associativo positivo teve maior impacto no progresso genético que o uso de sêmen sexado, apesar de ter aumentado a incidência de endogamia na população. O uso de acasalamento associativo negativo foi ineficiente em reduzir a variabilidade dos animais destinados ao abate. O uso combinado de acasalmento associativo positivo e sêmen sexado aumentou a produção de animais geneticamente superiores.
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The objective was to evaluate the effect of nutritional density and season on the performance of young rabbit does before the first mating. Forty-eight females from the Botucatu Genetic Group were used in each season (warm or cool), starting at the age of 70 days, housed in groups of four per cage up to 119 days, and reared individually from 120 to 140 days of age. The high-density diet was formulated to contain, on a 90% DM basis, 18.4% CP, 16.5% ADF and 2,500 kcal DE kg-1; whereas the low-density diet was formulated to contain 14.7% CP, 24% ADF and 2,000 kcal DE kg-1. The experiment was conducted according to a 2x2 factorial design (two diets x two seasons) with repeated measures (weeks). The high-density diet promoted lower feed intake, higher final weight, and higher daily weight gain, adjusted for constant intake. But these facts alone do not warrant using a high-density diet for growing rabbit does, because it could have a negative impact during the reproductive phase. In the warm season, there was a reduction in feed intake and an improvement in feed efficiency. Along time, however, the mean body weight of does was similar in the two seasons.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Data comprising 53,181 calving records were analyzed to estimate the genetic correlation between days to calving (DC), and days to first calving (DFC), and the following traits: scrotal circumference (SC), age at first calving (AFC), and weight adjusted for 550 d of age (W550) in a Nelore herd. (Co)variance components were estimated using the REML method fitting bivariate animal models. The fixed effects considered for DC were contemporary group, month of last calving, and age at breeding season (linear and quadratic effects). Contemporary groups were composed by herd, year, season, and management group at birth; herd and management group at weaning; herd, season, and management group at mating; and sex of calf and mating type (multiple sires, single sire, or AI). In DFC analysis, the same fixed effects were considered excluding the month of last calving. For DC, a repeatability animal model was applied. Noncalvers were not considered in analyses because an attempt to include them, attributing a penalty, did not improve the identification of genetic differences between animals. Heritability estimates ranged from 0.04 to 0.06 for DC, from 0.06 to 0.13 for DFC, from 0.42 to 0.44 for SC, from 0.06 to 0.08 for AFC, and was 0.30 for W550. The genetic correlation estimated between DC and SC was low and negative (-0.10), between DC and AFC was high and positive (0.76), and between DC and W550 was almost null (0.07). Similar results were found for genetic correlation estimates between DFC and SC (-0.14), AFC (0.94), and W550 (-0.02). The genetic correlation estimates indicate that the use of DC in the selection of beef cattle may promote favorable correlated responses to age at first mating and, consequently, higher gains in sexual precocity can be expected.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)
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The objective was to evaluate a PCR assay for the detection of Brucella canis in canine semen, comparing its performance with that of bacterial isolation, serological tests and PCR assay of blood. Fifty-two male dogs were examined clinically to detect reproductive abnormalities and their serum was tested by the rapid slide agglutination test, with and without 2-mercaptoethanol (2ME-RSAT and RSAT, respectively). In addition, microbiological culture and PCR assays were performed on blood and semen samples. The findings of the semen PCR were compared (Kappa coefficient and McNemar test) to those of blood PCR, culture of blood and semen, RSAT, and 2ME-RSAT. Nucleic acid extracts from semen collected from dogs not infected with B. canis were spiked with decreasing amounts of B. canis RM6/66 DNA and the resulting samples subjected to PCR. In addition, semen samples of non-infected dogs were spiked with decreasing amounts of B. canis CFU and the resulting suspensions were used for DNA extraction and amplification. of the 52 dogs that were examined, the following tests were positive: RSAT, 16 (30.7%); 2ME-RSAT, 5 (9.6%); blood culture, 14 (26.9%); semen culture, 11 (21.1%); blood PCR, 18 (34.6%); semen PCR, 18 (34.6%). The PCR assay detected as few as 3.8 fg of B. canis DNA experimentally diluted in 444.9 ng of canine DNA (extracted from semen samples of noninfected dogs). In addition, the PCR assay amplified B. canis genetic sequences from semen samples containing as little as 1.0 x 10(0) cfu/mL. We concluded that PCR assay of semen was a good candidate as a confirmatory test for the diagnosis of brucellosis in dogs; its diagnostic performance was similar to blood culture or blood PCR. Furthermore, the PCR assay of semen was more sensitive than the 2ME-RSAT or semen culture. Examination of semen by PCR should be included for diagnosis of brucellosis prior to natural mating or AI; in that regard, some dogs that were negative on serological and microbiological examinations as well as blood PCR were positive on PCR of semen. (c) 2007 Elsevier B.V. All rights reserved.
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Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)