Tropical Grasslands-Forrajes Tropicales

Morpho-productive characterization of Tithonia diversifolia accessions collected in the state of Chiapas, Mexico

Jatnel Alonso — 2024-01-31

Tithonia diversifolia is widespread in animal production systems in Latin America; however, research results show high genetic variability among collected wild materials. The objective of this work was to characterize materials of T. diversifolia collected in the northeast of Chiapas (Mexico), in terms of morphology and production. The collections included seeds and cuttings. A germination bioassay was conducted with the seeds, and a field experiment run with the cuttings was evaluated at 90, 120 and 150 days of growth. In both cases, a completely randomized design with 3 and 13 repetitions, respectively, was used. Thirty-four materials were collected, and their localities of origin were georeferenced. Twelve materials had seeds at the time of collection. All seeds showed germination capacity. Material # 32 achieved the highest germination (32.7 %), while # 33 had the lowest value (0.7 %). Fifty percent of the materials had an emergence speed index (IVE) greater than 0.5; however, 5 of the materials did not reproduce in the field. Materials # 24 and # 29 were the tallest and had the highest number of leaves per plant. The group with the highest production of green matter/plant (10.29 kg) including materials # 14 and # 24. Morphological and production variables were used to identify 3 groups of materials which could be used in different animal production system options in Chiapas (Mexico).

Stem formation dynamics, yield and bromatological analysis of Mulato II grass (Urochloa hybrid) in the dry tropics of Mexico

Adelaido Rafael Rojas García — 2024-01-31

Forage in the dry tropics constitutes the most sustainable feed source for livestock, contributing the most to improving animal welfare, meat and milk quality. The objective was to evaluate the dynamics of stems, growth, yield and bromatological analysis of Urochloa hybrid variety Mulato II by varying the days of cutting and cutting height in the dry and rainy seasons. The variables evaluated were: stem dynamics, growth dynamics, structural characteristics, crude protein (CP), neutral detergent fiber (NDF) and acid detergent fiber (ADF), leaving a residual height of 10 and 15 cm in the dry and rainy seasons in an 8-week growth analysis. There were 8 experimental plots corresponding to each day of cutting, each plot measuring 3 × 3 m with 3 replicates distributed in a completely random design based on the slope of the irregular terrain. From the stage of 49 to 56 days, the highest density of stems was recorded, regardless of the season and cutting height, with an average of 360 stems/m2. The net growth of Mulato II grass showed the following trend from highest to lowest: 15 cm rain ˃15 cm dry ˃10 cm rain ˃10 cm dry with 209, 183, 155 and 133 cm/ stem, respectively (P≤ 0.05). Regardless of the cutting height and time of the year, the CP content in the leaves decreased from 19.8 to 7.9%, between 7 and 63 days of regrowth, respectively (P<0.05). Mulato II grass should be cut at 35 to 42 days after regrowth and at an intensity of 15 cm.

Mimosine concentration in giant leucaena (Leucaena leucocephala subsp. glabrata) fluctuates with age and plant part

Michael Honda — 2024-01-31

Giant leucaena is a multipurpose tree-legume found throughout the tropics and sub-tropics. Its foliage is used as animal fodder due to high protein and fiber. Giant leucaena has several other advantageous traits such as fast-growth, high yields and strong tolerance to environmental stresses. Despite having these desirable qualities, leucaena tissues contain an undesirable attribute, a toxic non-protein amino acid, mimosine, found in all parts of the plant including the foliage. The goal of this research was to determine mimosine concentrations in various tissues and life stages of giant leucaena plants to inform use of leucaena foliage as a fodder. Mimosine was extracted from different parts of giant leucaena at different ages and quantified using HPLC analysis. qRT-PCR was used to determine the relative expression of mimosine synthase in leucaena tissues. Mimosine was present in all parts of the leaf, stem and root of giant leucaena, and concentrations changed depending on the age of the plant. Green seeds had the highest expression level of mimosine synthase. Mimosine is ubiquitous and abundant in leucaena tissues with younger and immature plants and tissues containing more mimosine than older mature plants and tissues.

Application of two models based on remote sensing to estimate aerial net primary production in a pastoral system in the Colombian Altillanura

Raúl Alejandro Díaz Giraldo — 2024-01-31

The assessment of Net Above-ground Primary Production (NAPP), measured as accumulated dry matter (DM) by plants in above-ground biomass, is crucial for management decisions in cattle production systems based on pastures. This study aimed to compare two models for estimating NAPP using data collected via remote sensing: one empirical model using linear regression (ELR) between vegetation indices and plant biomass and another semi-empirical model based on plant radiation use efficiency (RUE). Fourteen pastures of Urochloa humidicola CIAT 6133 cultivar 'Llanero' (each 3.1 ha) managed under grazing with 30 days of resting period were monitored. Spectral information was obtained from a Sentinel 2 sensor to calculate the Normalized Difference Vegetation Index (NDVI), Enhanced Vegetation Index (EVI), and Land Surface Water Index (LSWI). Global radiation data were collected from a field meteorological station. The best-performing index was NDVI, with R2, root mean square error (RMSE), and relative prediction error (RE, %) of 0.68, 99.5, and 16.42 for ELR, and 0.79, 103.62, and 17.16 for RUE, respectively. Both ELR and RUE models demonstrated their potential for use as tools for NAPP estimation from Sentinel 2A images in tropical forage pastures.