990 resultados para taxa líquida de reprodução


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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Pós-graduação em Zootecnia - FCAV

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

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The Cerrado is home to important biodiversity areas in the state of Sao Paulo. Therefore, research on the reproduction of species of this biome are essential to help conservation programs. Pollination is the main mechanism by which outcrossing plants perpetuate their populations, and the attractive, such as nectar, are of vital importance to many anthophilous animals and essential to the maintenance of interactions with pollinators. In this context, the objective of this study was to investigate the ecological dynamics of secretion and sugar composition of floral nectar in Zeyheria montana, an ornithophilous exclusive Cerrado species, visited preferentially by Colibri serrirostris, also exclusive to this biome. This dynamic was assessed in isolated flowers in pre-anthesis, using microsyringes to collect nectar and manual refractometer to measure the concentration. Experiments were carried out to evaluate production throughout anthesis, including the assessment of total daily production, the effect of successive removal, the rate of production during the day and night and changes in concentration and composition of sugars, which was performed in HPLC (High Performance Liquid Chromatography). The rate of nectar production was about three times greater at night with a concentration two times lower, resulting in a supply of large amounts of dilute nectar in the early morning hours, peak of visitation for hummingbirds. Moreover, the production of nectar was more pronounced before the anthesis, and is available to visitors already in newly opened flowers, which are preferentially visited by C. serrirostris. There was an increase in the nectar production of flowers in the group with successive manual removal upon the control group, suggesting that the withdrawal by visitors stimulates the production, ensuring the availability of the resource including flowers previously visited... (Complete abstract click electronic access below)

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Climate change in tropical countries, like Brazil, causes major problems in dairy production due to an increase of heat stress effects. In recent years, milk production in Brazil increased 36.07%. The Southeast region remains a leader in production with herds of high producing Holstein cattle (mostly), which is more susceptible to heat stress. Thermal stress decreases fertility in direct and indirect ways. Conception rates are reduced of 40-60% during cooler months of the year and 10-20% in the warmer months. Negative effects of heat stress involve changes in reproductive hormones, follicular development, oocytes, and embryos, and decreased dry matter intake. Several studies discuss change in reproductive hormones, such as reduction in plasma concentration of GnRH, LH, and oestradiol, which lead to decreased detection of estrus and ovulation. Various methods are being studied to bypass these negative effects and increase the fertility of dairy cows under heat stress. Cooling systems are the most advantageous and can be associated with technologies such as ET and TAI

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Infertility is directly related to chromosomal abnormalities in germ cells. Among them, the aneuploidies are the most frequent chromosomal abnormalities and responsible for embryo implantation failures, miscarriages, fetal losses and newborns with congenital malformations, mental disability and neuropsychomotor developmental delay. Male patients with normal somatic karyotype may present different rates of aneuploidies in sperm, resulting in abnormal embryos. This study aimed to correlate the frequency of chromosomal aneuploidies in spermatozoa with embryo implantation rate in couples undergoing assisted reproductive techniques. The methodology has included chromosomal analysis by GTG banding and molecular cytogenetic study using Fluorescent In Situ Hybridization technique for evaluation of chromosomes 9, X and Y in germ cells of 22 patients referred to the Human Reproduction Service of the Clinical Hospital FMRP-USP. Embryo implantation rates were determined by hormonal evaluation in maternal peripheral blood and ultrasound confirmation. Two patients presented abnormal karyotype, characterized by polymorphism of the heterochromatic region of the long arm of chromosome 9 and a satellite in the short arm of chromosome 22. Both alterations, usually considered variants of normality, have been related to infertility phenotype and miscarriages. Significant differences were detected between couples who presented pregnancy (group 1) and couples with embryo implantation failure (group 2), with higher frequency of aneusomy and diploidy of chromosome 9, as well as total aneuploidy in sperm of group 2 patients. Our results suggest a correlation between aneuploidy and embryo implantation rates, since the infertile group with reproductive failure has showed higher frequency of aneuploidy. Screening for aneuploidies detection in male germ cells should be included in order to decrease embryo implantation failures, miscarriages and fetuses with chromosomal ...

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Pós-graduação em Zootecnia - FCAV