Aptitud forrajera de hojas de mandioca (Manihot esculenta) y su aporte nutricional a microsilos de caña de azúcar

The objective of this research was to evaluate the forage productivity of different cassava cultivars and their nutritional contribution to sugarcane microsilages. For this, an essay was carried out in Corrientes, Argentina, on seven cultivars (Amarilla, Palomita, Tapó Joá, Rocha, Clon 60, Clon 30, EC-9). The characterization of the materials was carried out through the measurement of different foliar variables: foliar retention, dry leaf biomass, dry matter (DM), nitrogen (N), gross protein (PB), phosphorus (P), and potassium (K) foliar percentage. The cultivar Amarilla was highlighted for its forage production that reached 23.160 kg/DM but presented only 4.62% PB. Another five cultivars showed lower leaf productivity but protein concentration higher than 11%. About nutritional characteristics of microsilages, the treatment consisted of combining two proportions of cassava foliage and sugarcane T1 (30% cassava + 70% sugarcane) and T2 (15% cassava + 85% sugarcane). For each treatment six sampling units were made, from which three were evaluated at 30 days of silage and the remaining at 60 days. In microsilages samples were evaluated pH, %MS, N, PB, neutral (NDF) and acid detergent fiber (ADF) in each instance. In T1 pH stabilized at 60 days and in T2 at 30 days. The PB (%) was significantly higher in T1 at both times. The ADF and NDF (%) were established over time. Cassava leaves proved to be a valuable protein resource, which can be successfully ensiled to supplement nutritional deficiencies of cattle from Northeastern Argentina.El objetivo de este trabajo fue evaluar la aptitud forrajera de hojas de diferentes cultivares de mandioca y el aporte nutricional a microsilos de caña de azúcar. Los ensayos se efectuaron en Corrientes, Argentina y consistieron en dos experimentos. El primero indagó la productividad y calidad forrajera de hojas de mandioca, para lo cual se caracterizaron siete cultivares (Amarilla, Palomita, Tapó Joá, Rocha, Clon 60, Clon 30 y EC-9) a través de la medición de las variables: retención foliar, biomasa seca, porcentaje de materia seca (MS), de nitrógeno (N), proteína bruta (PB), fósforo (P) y potasio foliar (K). El cultivar Amarilla se destacó por su producción forrajera, la cual alcanzó 23.160 kg de MS/ha, pero presentó sólo 4,62% de PB. Otros cinco cultivares, presentaron menor productividad foliar pero mayor concentración proteica, superior al 11%. El segundo experimento investigó las características nutricionales de microsilos al evaluar dos tratamientos que consistieron en combinar dos proporciones de follaje de mandioca y caña de azúcar: T1 (30% mandioca + 70% caña) y T2 (15% mandioca + 85% caña). En cada tratamiento se hicieron seis unidades de muestreo, de las cuales tres fueron evaluadas a los 30 días y las restantes a los 60 días de ensilado (dde), determinándose en cada instancia: pH, %MS, N, PB, fibra detergente neutra (FDN) y fibra detergente ácida (FDA). En T1 el pH se estabilizó a los 60 dde y en T2 a los 30 dde. La PB (%) fue significativamente superior en T1 en ambos momentos. Los % de FDA y FDN fueron estables en el tiempo. Las hojas de mandioca demostraron ser un valioso recurso proteico, que puede ensilarse exitosamente para suplementar deficiencias nutricionales de la ganadería del nordeste argentino

Condición de un pastizal del este del Chaco

The aim of this study was to assess the condition of a grassland of Eastern Chaco. The work was done on a livestock ranch in Makalle (Chaco). Vegetation is characterized by herbaceous plants dominated by warm season grasses. Proportion of preferred, intermediate and undesirable species was determined, based on their forage attributes. Quantity of annuals and weed species, percent bare soil, vigour of best species and dry matter yield (Kg DM/ha) were also determined. The grassland had 40.4% preferred species with good vigour, low percentage of weeds (2%) and low bare soil (2%). Dry matter yield was 1639.1 kg DM/ha (seasonal mean). Condition was rated good to excellent. No deterioration was detected.El objetivo del presente trabajo fue establecer la condición de un pastizal del este de la provincia del Chaco. El trabajo se realizó en un establecimiento ganadero ubicado en la Localidad de Makallé. Se caracteriza por la presencia de un estrato herbáceo con predominio de gramíneas, de ciclo de crecimiento primavero-estival. Se determinó la proporción de especies clasificadas como preferidas, intermedias y/o indeseables, según sus características forrajeras; la cantidad de plantas anuales o malezas; la proporción de suelo desnudo; el vigor de las mejores especies y la producción estacional de materia seca. Teniendo en cuenta que el pastizal evaluado está integrado por un 40,4% de forrajeras preferidas que tuvieron un vigor alto; la cantidad de malezas fue baja (2%) al igual que la proporción de suelo desnudo sin cobertura vegetal (2%) y la producción forrajera fue de 1.639,1 kg/ha (promedio estacional). Se puede inferir en que la condición del pastizal es buena a excelente. No hay indicios en la vegetación y la producción del pastizal que manifiesten el comienzo de su deterioro

Collective and independent-particle motion in two-electron artificial atoms

Investigations of the exactly solvable excitation spectra of two-electron quantum dots with a parabolic confinement, for different values of the parameter R_W expressing the relative magnitudes of the interelectron repulsion and the zero-point kinetic energy of the confined electrons, reveal for large R_W a remarkably well-developed ro-vibrational spectrum associated with formation of a linear trimeric rigid molecule composed of the two electrons and the infinitely heavy confining dot. This spectrum transforms to one characteristic of a "floppy" molecule for smaller values of R_W. The conditional probability distribution calculated for the exact two-electron wave functions allows for the identification of the ro-vibrational excitations as rotations and stretching/bending vibrations, and provides direct evidence pertaining to the formation of such molecules.Comment: Published version. Latex/Revtex, 5 pages with 2 postscript figures embedded in the text. For related papers, see http://www.prism.gatech.edu/~ph274c

Ambientes pastoriles de un establecimiento foresto-ganadero de la localidad de Chavarría (Corrientes).

El objetivo del presente trabajo fue establecer la condición de ambientes pastoriles de la Localidad de Chavarría - Corrientes. El establecimiento Toro Cuaré está situado en el Departamento San Roque, provincia de Corrientes, localidad de Chavarría. El ecosistema predominante en el área de estudio es de lomadas y planicies arenosas. Se realizaron censos para determinar la composición florística de la comunidad vegetal. Para establecer la homogeneidad del pastizal se determinó la cobertura de cada especie expresada en porcentaje. También se agruparon las especies según la categorización en pastos ordinarios, duros, finos y tiernos. Se determinó la producción de forraje disponible, mediante el mé- todo de corte y pesada en 12 jaulas de exclusión del pastoreo. Para la caracterización de los ambientes se utilizó una metodología que considera tanto aspectos cualitativos como cuantitativos propuesto por Martín (2004). En el área de estudio se consideraron los valores de la comunidad Espartillar o pastizal. Para el bajo se tomaron como referencia los de la comunidad hidrófila ó praderas húmedas. Los mayores valores de presencia y cobertura corresponden a Andropogon lateralis Nees, Cyperus rotundus y Axonopus argentinus Parodi. En el sitio de estudio los pastos dominantes son incluidos dentro de la clasificación de ordinarios (A. lateralis) y duros (Cyperus spp.). Los pastos finos y los tiernos, como Axonopus argentinus y Paspalum spp., alcanzan un 30% de cobertura. El rendimiento de materia seca obtenido en el pastizal fue de 2498 y 867 Kg MS ha-1en verano y otoño respectivamente. En la comunidad hidrófila en verano alcanzó los 2760 y en otoño 1850 Kg MS ha-1. La condición del pastizal es muy buena y buena para la comunidad hidrófila o pradera húmeda

The application of a mechanistic model to analyze the factors that affect the lactation curve parameters of dairy sheep in Mexico

Pollott́s mechanistic model has been designed to describe lactation curve parameters based on the known biology of milk production and can be useful for analyzing the factors that affect this process. A total of 553 lactations (9956 weekly test-day records) of crossbred dairy sheep from four commercial farms located in Mexico, were analyzed to investigate environmental factors that influenced lactation curve parameters, using Pollott’s 5-parameter additive model. This model was fitted to each lactation using an iterative nonlinear procedure. The estimated parameters were maximum milk secretion potential (MSmax), relative rate of increase in cell differentiation (GR), maximum secretion loss (MSLmax), relative rate of decline in cell numbers (DR) and the proportion of parenchyma cells dead at parturition. A general linear model procedure was used to determine the effect of type of lambing, lambing number, flock and lambing season on total lactation milk yield (TMY), lactation length and estimated parameters of the Pollott model. Ewes had an average milk yield of 74.4 L with an average lactation length of 140 days. Flock had a significant (P < 0.05) effect on most of the analyzed traits, which can be explained by the different farmś management practices. The TMY were significantly (P = 0.005) higher for twin-lambing than single-lambing lactations. Sheep in their first lambing had lower TMY than those in their fourth lambing (P = 0.01), possibly explained by the lower values of MSmax (2.85 vs. 5.3 L) and the decrease in DR throughout life (P = 0.03). However, the relative GR was greatest (P = 0.04) during first lambing and then decreased as lambing number increased. Both lambing number and type of lambing also affected milk yield. The parameters of the Pollott model can be useful to explain, with a biological approximation, the dynamics of differentiation, secretion and death of mammary cells in dairy sheep

Effect of tannins from tropical plants on methane production from ruminants: A systematic review

Methane (CH4) is a greenhouse gas generated during the feed fermentation processes in the rumen. However, numerous studies have been conducted to determine the capacity of plant secondary metabolites to enhance ruminal fermentation and decrease CH4 production, especially those plants rich in tannins. This review conducted a descriptive analysis and meta-analysis of the use of tannin-rich plants in tropical regions to mitigate CH4 production from livestock. The aim of this study was to analyse the effect of tannins supplementation in tropical plants on CH4 production in ruminants using a meta-analytic approach and the effect on microbial population. Sources of heterogeneity were explored using a meta-regression analysis. Final database was integrated by a total of 14 trials. The ‘meta’ package in R statistical software was used to conduct the meta-analyses. The covariates defined a priori in the current meta-regression were inclusion level, species (sheep, beef cattle, dairy cattle, and cross-bred heifers) and plant. Results showed that supplementation with tropical plants with tannin contents have the greatest effects on CH4 mitigation. A negative relationship was observed between the level of inclusion and CH4 emission (−0.09), which means that the effect of CH4 mitigation is increasing as the level of tannin inclusion is higher. Therefore, less CH4 production will be obtained when supplementing tropical plants in the diet with a high dose of tannins

Haemonchus contortus Acetylcholine Receptors of the DEG-3 Subfamily and Their Role in Sensitivity to Monepantel

Gastro-intestinal nematodes in ruminants, especially Haemonchus contortus, are a global threat to sheep and cattle farming. The emergence of drug resistance, and even multi-drug resistance to the currently available classes of broad spectrum anthelmintics, further stresses the need for new drugs active against gastro-intestinal nematodes. A novel chemical class of synthetic anthelmintics, the Amino-Acetonitrile Derivatives (AADs), was recently discovered and the drug candidate AAD-1566 (monepantel) was chosen for further development. Studies with Caenorhabditis elegans suggested that the AADs act via nicotinic acetylcholine receptors (nAChR) of the nematode-specific DEG-3 subfamily. Here we identify nAChR genes of the DEG-3 subfamily from H. contortus and investigate their role in AAD sensitivity. Using a novel in vitro selection procedure, mutant H. contortus populations of reduced sensitivity to AAD-1566 were obtained. Sequencing of full-length nAChR coding sequences from AAD-susceptible H. contortus and their AAD-1566-mutant progeny revealed 2 genes to be affected. In the gene monepantel-1 (Hco-mptl-1, formerly named Hc-acr-23H), a panel of mutations was observed exclusively in the AAD-mutant nematodes, including deletions at intron-exon boundaries that result in mis-spliced transcripts and premature stop codons. In the gene Hco-des-2H, the same 135 bp insertion in the 5′ UTR created additional, out of frame start codons in 2 independent H. contortus AAD-mutants. Furthermore, the AAD mutants exhibited altered expression levels of the DEG-3 subfamily nAChR genes Hco-mptl-1, Hco-des-2H and Hco-deg-3H as quantified by real-time PCR. These results indicate that Hco-MPTL-1 and other nAChR subunits of the DEG-3 subfamily constitute a target for AAD action against H. contortus and that loss-of-function mutations in the corresponding genes may reduce the sensitivity to AADs