Parâmetros genéticos para características de carcaça avaliadas por ultrassonografia em bovinos da raça Guzerá Genetic parameters for body weight and real-time ultra sound carcass traits of Guzera cattle

A partir das observações de 1.325 animais (90,4% de machos e 9,6% de fêmeas) e do pedigree de 6.642 animais da raça Guzerá foram estimados os parâmetros genéticos para o peso corporal e as características área de olho de lombo e espessura de gordura na costela e na garupa, avaliadas por meio da técnica de ultrassonografia. Os componentes de (co)variância foram estimados pelo método da máxima verossimilhança restrita, utilizando-se o aplicativo MTDFREML. Foram utilizados, para as estimativas de repetibilidade e herdabilidade, modelos unicaracterística e, para as correlações genéticas e fenotípicas entre as características, modelos bicaracterísticas. As estimativas de repetibilidade (erros-padrão) foram 0,44(0,10) para peso corporal, 0,39(0,10) para área de olho de lombo, 0,75(0,06) para espessura de gordura na costela e 0,49(0,08) para espessura de gordura na garupa. As estimativas de herdabilidade, respectivamente a partir de modelos uni e bicaracterísticas, foram 0,42(0,11) e 0,41(0,11) para peso corporal, 0,35(0,09) e 0,34(0,09) para área de olho de lombo, 0,20(0,08) e 0,32(0,02) para espessura de gordura na garupa e 0,05(0,06) e 0,10(0,08) para espessura de gordura na costela. As estimativas de correlações genéticas foram 0,79(0,09) entre o peso corporal e a área de olho de lombo; 0,20(0,08) entre o peso corporal e a espessura de gordura na garupa; 0,05(0,06) entre a área de olho de lombo e a espessura de gordura na costela; 0,02(0,27) entre a área de olho de lombo e a espessura de gordura na garupa; e 0,64(0,22) entre as duas medidas de espessura de gordura. Os resultados indicam que é uma mensuração suficiente para a adequada avaliação das características área de olho de lombo e espessura de gordura na carcaça e que a seleção direta para essas características pode resultar em carcaças mais musculosas e de melhor acabamento. Indica, ainda, ausência de antagonismo genético entre a seleção para peso corporal e características área de olho de lombo e espessura de gordura na carcaça.<br>Genetic parameters were estimated for body weight and real-time ultra-sound loin-eye area, rump fat thickness, and back fat thickness using data from 1,325 yearling Guzera cattle (90.4% bulls and 9.6% heifers) and pedigree structure with 6,642 animals. Variance and covariance components were estimated using REML methodology and MTDFREML software. Single trait animal models were used to estimate repeatability and heritability for the four traits. Multiple traits animal models were used to estimate genetic correlations among the traits. Repeatability estimates (standard errors) were 0.44(0.10) for body weight, 0.39(0.10) for loin-eye area, 0.75(0.06) for rump fat thickness, and 0.49(0.08) for back fat thickness. Heritability estimates were 0.42(0.11) and 0.41(0.11) for body weight, 0.35(0.09) and 0.34(0.09) for loin-eye area, 0.20(0.08) and 0.32(0.08) for back fat thickness, and 0.05(0.06) and 0.10(0.08) for rump fat thickness, respectively from single and multiple traits models. Genetic correlation estimates were 0.79(0.09) between body weight and loin-eye area, 0.20(0.08) between body weight and back fat thickness, 0.05(0.06) between loin-eye area and rump fat thickness, 0.02(0.27) between loin-eye area and back fat thickness and 0.64(0.22) between the two measurements of fat thickness. In order to evaluate carcass traits, results suggested that repeated real-time ultra-sound measurements are not needed and that direct selection for these traits might be effective. In addition, there is no genetic antagonism between selection for body weight and carcass traits

Selection for higher body weight in Nelore cattle is effective in achieving an increase of longissimus muscle area without reducing subcutaneous fat thickness

The objectives of this study were to estimate heritabilities and genetic and phenotypic correlations between carcass traits measured by ultrasound and other economically important traits generally used as selection criteria in beef cattle and to estimate the genetic changes in the carcass traits as a result of selection for post-yearling weight. Carcass traits measured by ultrasound at two ages (12 and 18 months) and the correlation of these traits with weight, hip height and body condition score of males (yearling) and females (post-yearling) were analyzed. Multi-trait analysis was performed using the restricted maximum likelihood method under an animal model. To demonstrate the effect of selection for growth, phenotypic and expected breeding value means of the carcass traits and weights according to selection line (Nellore control line, selection line and traditional line) were estimated using records from animals born in the last 3 years (2006 to 2008). The heritability estimates were high for longissimus muscle area (LMA) at 12 and 18 months of age (0.47 and 0.40, respectively). For fat thickness measures, heritabilities ranged from 0.37 to 0.29. Genetic correlations of the same trait between the two ages were high for LMA (0.95). The Nellore breed shows medium to high genetic variability in carcass traits measured by ultrasound at 12 and 18 months of age, and a greater response is expected if selection for backfat thickness is performed at about 12 months of age. Selection for higher body weight will lead to an increase of LMA at the two ages without reducing subcutaneous fat thickness

Relação entre heterogeneidade ambiental e distribuição de espécies em uma floresta paludosa no Município de Cristais Paulista, SP, Brasil Floristic composition and relationship between environmental heterogeneity and species distribution in a swamp forest from Cristais Paulista, São Paulo State, Brazil

Neste estudo foi caracterizada a composição florística e fitossociológica de uma floresta paludosa no nordeste do Estado de São Paulo, onde variações no padrão de drenagem ocorrem principalmente no sentido perpendicular ao curso d'água, em função da topografia. Nosso objetivo foi investigar a distribuição das espécies em relação ao substrato e a entrada de luz na comunidade. Foram alocadas 60 parcelas de 10×10 m, distribuídas em seis grupos de 10 parcelas cada. Em cada parcela foram medidos e identificados os indivíduos com PAP > 10 cm, avaliadas as propriedades químicas e granulometria do solo, o desnível topográfico, a drenagem e a abertura do dossel. Foram registradas 88 espécies, das quais 61 foram observadas nas parcelas. Uma análise de correspondência canônica (CCA) indicou correlações entre a distribuição das 29 espécies mais abundantes e drenagem, desnível topográfico e Fe no eixo 1 e abertura do dossel no eixo 2. O coeficiente de Spearman indicou correlações significativas entre 66% das 29 espécies e profundidade do lençol freático ou abertura do dossel. Como exemplo, Calophyllum brasiliense e Xylopia emarginata prevaleceram em solos mal drenados; Siphoneugena densiflora e Virola sebifera em solos bem drenados; Myrcia laruotteana e Xylopia sericea em parcelas com maior abertura de dossel. A heterogeneidade ambiental foi um importante fator na determinação da distribuição e a coexistência de espécies, resultando em um incremento na diversidade local.<br>In the present study, we characterized the floristic composition and tree structure of a swamp forest in northeast of São Paulo State, Brazil, where the drainage pattern changes mainly across the watercourse due to the topography. We aimed to investigate the species distribution in relation to substrate and light entrance in the community. Sixty quadrats (10×10 m) were divided into six groups of 10 plots. In each quadrat, individuals with PBH > 10 cm were measured and identified. We also evaluated soil chemical properties, granulometry, topographic unevenness, drainage, and canopy openness. Eighty-eight species were recorded, from which 61 were detected in the quadrats. Canonical correspondence analysis (CCA) indicated correlations between the distribution of the 29 most abundant species and drainage, topographic unevenness and Fe in the axis 1, and canopy openness in the axis 2. Spearman's rank correlation coefficient indicated significant correlations between 66% from the 29 species and water table depth or canopy openness. As examples, Calophyllum brasiliense and Xylopia emarginata were predominant in poorly-drained soils; Siphoneugena densiflora and Virola sebifera, in the drained ones; and Myrcia laruotteana and Xylopia sericea, in the quadrats presenting higher canopy openness. Environmental heterogeneity showed to be an important factor in determining the species distribution and coexistence, which increases local diversity

Giants of the Amazon: How does environmental variation drive the diversity patterns of large trees?

For more than three decades, major efforts in sampling and analyzing tree diversity in South America have focused almost exclusively on trees with stems of at least 10 and 2.5 cm diameter, showing highest species diversity in the wetter western and northern Amazon forests. By contrast, little attention has been paid to patterns and drivers of diversity in the largest canopy and emergent trees, which is surprising given these have dominant ecological functions. Here, we use a machine learning approach to quantify the importance of environmental factors and apply it to generate spatial predictions of the species diversity of all trees (dbh ≥ 10 cm) and for very large trees (dbh ≥ 70 cm) using data from 243 forest plots (108,450 trees and 2832 species) distributed across different forest types and biogeographic regions of the Brazilian Amazon. The diversity of large trees and of all trees was significantly associated with three environmental factors, but in contrasting ways across regions and forest types. Environmental variables associated with disturbances, for example, the lightning flash rate and wind speed, as well as the fraction of photosynthetically active radiation, tend to govern the diversity of large trees. Upland rainforests in the Guiana Shield and Roraima regions had a high diversity of large trees. By contrast, variables associated with resources tend to govern tree diversity in general. Places such as the province of Imeri and the northern portion of the province of Madeira stand out for their high diversity of species in general. Climatic and topographic stability and functional adaptation mechanisms promote ideal conditions for species diversity. Finally, we mapped general patterns of tree species diversity in the Brazilian Amazon, which differ substantially depending on size class