Leaf tensile strength, "in vitro" digestibility, and fiber component relationships in tall fescue

Em um programa de melhoramento de forrageiras, a identificação de plantas com elevado valor nutritivo, é um dos fatores importantes para melhorar o desempenho animal. Interrelações significativas entre características físicas e químicas talvez possam ser utilizadas como um critério para a seleção de novas cultivares de festuca-alta de maior valor nutritivo. Os objetivos deste experimento foram: a. avaliar a tensão foliar (TF) e a digestibilidade in vitro da matéria seca (DIVMS) e dos constituintes da parede celular; b. analisar as associações entre essas características com a TF e c. determinar a eficiência da TF como uma técnica para a seleção de novos germoplasmas de festuca-alta, com forragem de melhor qualidade. Setenta e um genótipos de festuca alta foram avaliados neste experimento. Foi encontrada uma variabilidade genética significativa para TF nesta população de festuca-alta. Geralmente, as correlações de TF com DIVMS e componentes da parede celular não foram significativas, enquanto que as correlações de DIVMS com os componentes da parede celular foram altamente significativas e negativas. Conforme esperado, houve baixa repetibilidade de correlações de caracteres nos dois anos. A "análise de coeficientes de trilha" demonstrou que a celulose e a lignina foram os caracteres com os maiores efeitos diretos na TF e na DIVMS.In a forage breeding program it is necessary to identify germplasms with high forage quality, able to positively influence animal performance. The interrelationships between leaf tensile strength (LTS) and chemical composition parameters may provide a useful criterion for screening tall fescue (Festuca arundinacea Schreb.) for herbage quality in a breeding program. Seventy-one genetically diverse genotypes of tall fescue were randomly selected from a broad-based population to evaluate LTS (leaf tensile strength), in vitro dry matter digestibility (IVDMD), acid detergent fiber (ADF), neutral detergent fiber (NDF), cellulose (CELL), lignin (ADL), hemicellulose (HEMI), ADL/ADF and ASH, to determine the associations among these traits with LTS, and the importance of LTS as a technique for screening tall fescue for herbage quality. Significant genetic variation was found in this gene pool for LTS. The majority of the correlations of LTS with IVDMD and with fiber components were not significantly different from zero while correlations of IVDMD with fiber components were highly significant and negative. As expected, character correlation repeatabilities between years were usually low. Path coefficient analysis showed that CELL and ADL were two important components with large direct effects on LTS and on IVDMD

Genetic characterization of type A enterotoxigenic Clostridium perfringens strains

Clostridium perfringens type A, is both a ubiquitous environmental bacterium and a major cause of human gastrointestinal disease, which usually involves strains producing C. perfringens enterotoxin (CPE). The gene (cpe) encoding this toxin can be carried on the chromosome or a large plasmid. Interestingly, strains carrying cpe on the chromosome and strains carrying cpe on a plasmid often exhibit different biological characteristics, such as resistance properties against heat. In this study, we investigated the genetic properties of C. perfringens by PCR-surveying 21 housekeeping genes and genes on representative plasmids and then confirmed those results by Southern blot assay (SB) of five genes. Furthermore, sequencing analysis of eight housekeeping genes and multilocus sequence typing (MLST) analysis were also performed. Fifty-eight C. perfringens strains were examined, including isolates from: food poisoning cases, human gastrointestinal disease cases, foods in Japan or the USA, or feces of healthy humans. In the PCR survey, eight of eleven housekeeping genes amplified positive reactions in all strains tested. However, by PCR survey and SB assay, one representative virulence gene, pfoA, was not detected in any strains carrying cpe on the chromosome. Genes involved in conjugative transfer of the cpe plasmid were also absent from almost all chromosomal cpe strains. MLST showed that, regardless of their geographic origin, date of isolation, or isolation source, chromosomal cpe isolates, i) assemble into one definitive cluster ii) lack pfoA and iii) lack a plasmid related to the cpe plasmid. Similarly, independent of their origin, strains carrying a cpe plasmid also appear to be related, but are more variable than chromosomal cpe strains, possibly because of the instability of cpe-borne plasmid(s) and/or the conjugative transfer of cpe-plasmid(s) into unrelated C. perfringens strains. © 2009 Deguchi et al

Association of insularity and body condition to cloacal bacteria prevalence in a small shorebird

Do islands harbour less diverse disease communities than mainland? The island biogeography theory predicts more diverse communities on mainland than on islands due to more niches, more diverse habitats and availability of greater range of hosts. We compared bacteria prevalences ofCampylobacter,ChlamydiaandSalmonellain cloacal samples of a small shorebird, the Kentish plover (Charadrius alexandrinus) between two island populations of Macaronesia and two mainland locations in the Iberian Peninsula. Bacteria were found in all populations but, contrary to the expectations, prevalences did not differ between islands and mainland. Females had higher prevalences than males forSalmonellaand when three bacteria genera were pooled together. Bacteria infection was unrelated to bird's body condition but females from mainland were heavier than males and birds from mainland were heavier than those from islands. Abiotic variables consistent throughout breeding sites, like high salinity that is known to inhibit bacteria growth, could explain the lack of differences in the bacteria prevalence between areas. We argue about the possible drivers and implications of sex differences in bacteria prevalence in Kentish plovers

Patterns of livestock activity on heterogeneous subalpine pastures reveal distinct responses to spatial autocorrelation, environment and management

BACKGROUND: In order to understand the impact of grazing livestock on pasture ecosystems, it is essential to quantify pasture use intensity at a fine spatial scale and the factors influencing its distribution. The observation and analysis of animal activity is greatly facilitated by remote tracking technology and new statistical frameworks allowing for rapid inference on spatially correlated data. We used these advances to study activity patterns of GPS-tracked cows in six summer-grazing areas in the Swiss Alps that differed in environmental conditions as well as livestock management. RESULTS: Recorded GPS positions were assigned to the activities of grazing, resting, and walking, and were discretized on a regular grid. Regression models with spatially structured effects were fitted to the spatial activity patterns using Integrated Nested Laplace Approximation. They indicated that terrain slope, forage quality, and stocking rate were the primary factors determining cow activity in the six study areas. Terrain slope significantly reduced livestock activity in five of the six areas and sparse forage availability significantly reduced grazing in all areas. In three areas, grazing pressure imposed by the pasture rotation was observable in the grazing pattern. Insolation, distance to the shed, and distance to water were less important for cow activity. In addition to the main factors identified across all study areas, we found effects operating only in individual areas, which were partly explained by specific environmental and management characteristics. In study areas with few paddocks, environmental variables exerted a stronger control on livestock activity than in areas with a short stocking period per paddock. CONCLUSIONS: The data demonstrated that a strict pasture rotation with short stocking periods is necessary to influence livestock activity, and hence potential effects on ecosystem processes. Without grazing management, livestock activity is primarily determined by the environment. Such insight is indispensable for studying relationships between grazing animals and ecosystem characteristics, and for developing management strategies to optimize ecosystem services. The analysis also highlighted the need for an appropriate statistical treatment of bio-logging data, since various estimates were biased if spatial autocorrelation was ignored. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s40462-015-0053-6) contains supplementary material, which is available to authorized users