Repositorio Nacional

"Mexico has 159 species of Agave spp. In the agri-food industry stand out are Agave tequilana, A. angustifolia, and A. salmiana. A limitation to producing maguey seedlings is the low availability of organic substrates that favor plant adaptation in the field. The objective was to evaluate the effect of nitrogen (N), phosphorus (P) and potassium (K) found in substrates in response to vegetative and root growth of A. salmiana in agricultural areas of Huichapan, Hidalgo, Mexico. The treatment consisted of earthworm humus (EH) and leaf compost (LC) substrates with materials from the region with different percentages of EH (100, 75, 50%), LC (5, 10%), and sand (20, 40%). The treatments were applied with 14 random replications in two phases in seeds and 40-day-seedlings. The variables evaluated were NPK amount and pH in substrates. The physiological variables measured were plant height, leaf number, stem diameter, root length, and volume. Significant differences (P≤0.05) were observed in seedling physiology due to the effect of the treatment. The best agronomic responses (plant growth and root length/weight) of Agave seedlings were T5 (75% earthworm humus + 20% sand + 5% leaf-soil) and T6 (50% earthworm humus + 40% sand + 10% leaf-soil); in both treatments, the NPK percentages were different from the control (Haplic Phaeozem soil) group. The final concentration of NPK in T6 was N = 0.04%, P = 398.13 mg Kg-1 and K = 11.88 meq 100g-1 . The results infer that NPK availability in soil and progressive acidification (initial pH = 8.6, final pH = 7.4) of the substrate can favorably influence the plant response. The interactions between NPK availability in the substrate and their use for a better response in maguey seedling adaptability open up new lines of research on the productive systems in the región of Huichapan, Hidalgo, Mexico."

maguey, nutritional quality, plant physiology, productive soils, seedling BIOLOGÍA Y QUÍMICA CIENCIAS DE LA VIDA BIOLOGÍA VEGETAL (BOTÁNICA) FERTILIDAD DEL SUELO FERTILIDAD DEL SUELO

Protein retention assessment of four levels of poultry by-product substitution of fishmeal in rainbow trout (Oncorhynchus mykiss) diets using stable isotopes of nitrogen (δ15N) as natural tracers

DANIEL BADILLO ZAPATA (2014, [Artículo])

This is second part from an experiment where the nitrogen retention of poultry by-product meal (PBM) compared to fishmeal (FM) was evaluated using traditional indices. Here a quantitative method using stable isotope ratios of nitrogen (δ15N values) as natural tracers of nitrogen incorporation into fish biomass is assessed. Juvenile rainbow trout (Oncorhynchus mykiss) were fed for 80 days on isotopically distinct diets in which 0, 33, 66 and 100% of FM as main protein source was replaced by PBM. The diets were isonitrogenous, isolipidic and similar in gross energy content. Fish in all treatments reached isotopic equilibrium by the end of the experiment. Two-source isotope mixing models that incorporated the isotopic composition of FM and PBM as well as that of formulated feeds, empirically derived trophic discrimination factors and the isotopic composition of fish that had reached isotopic equilibrium to the diets were used to obtain a quantitative estimate of the retention of each source of nitrogen. Fish fed the diets with 33 and 66% replacement of FM by PBM retained poultry by-product meal roughly in proportion to its level of inclusion in the diets, whereas no differences were detected in the protein efficiency ratio. Coupled with the similar biomass gain of fishes fed the different diets, our results support the inclusion of PBM as replacement for fishmeal in aquaculture feeds. A re-feeding experiment in which all fish were fed a diet of 100% FM for 28 days indicated isotopic turnover occurred very fast, providing further support for the potential of isotopic ratios as tracers of the retention of specific protein sources into fish tissues. Stable isotope analysis is a useful tool for studies that seek to obtain quantitative estimates of the retention of different protein sources. © 2014 Badillo et al.

nitrogen 15, nitrogen, protein intake, animal behavior, animal experiment, animal food, animal tissue, aquaculture, Article, biomass, controlled study, energy metabolism, food composition, juvenile animal, nonhuman, poultry by product meal, protein a CIENCIAS FÍSICO MATEMÁTICAS Y CIENCIAS DE LA TIERRA CIENCIAS DE LA TIERRA Y DEL ESPACIO OCEANOGRAFÍA OCEANOGRAFÍA