No abstract

Agronomic, nutritional, and environmental aspects are integrated to promote sustainable tropical grassland production. Biological nitrification inhibition (BNI) is a plant-based strategy to improve nitrogen use efficiency by grasses in which they suppress the pace of soil nitrification via exudation of inhibitory compounds. To evaluate the effect of BNI on the productive performance of Megathyrsus maximus under field conditions, we evaluated a collection of 27 germplasm accessions and commercial cultivars of the forage grass in the dry tropics of Colombia. We measured plant yield dry matter, nutrition quality parameters, and nitrification rates of soil at 22 months after pasture establishment. Our results highlighted germplasm accessions of superior agronomic performance (for dry matter production and nutrition quality) and high capacity to decrease nitrification. Although no relation was observed between agronomic aspects, nutritional aspects, and nitrification rates, we conclude that there is no agronomic or nutritional penalty on environmentally friendly grasses, and BNI could be adopted as a target trait in plant breeding programs toward the development of eco-efficient forages and contribute to the sustainable intensification of livestock systems.

The diversity and use of tropical forages for cattle feeding are the protagonists in livestock systems. The production and nutritional quality of forages represent a strategy of continuous research in animal feeding to help mitigate the environmental impact generated by tropical livestock. The objective of this study was to classify the nutritional behavior in contrasting seasons and the relationship with agronomic traits of a collection of 129 CIAT (Centro Internacional de Agricultura Tropical) accessions of Megathyrsus Maximus established in the Colombian dry tropics. By means of the near-infrared reflectance spectroscopy (NIRS) technique, crude protein (CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), and in vitro dry matter digestibility (IVDMD) were determined under rainy and dry seasons as fixed effects. We measured plant height, dry matter biomass (DMB) and flowering in field. Aspects such as plant height and DMB did not show correlation with nutritional aspects, whereas flowering was correlated with the content of structural carbohydrates. Despite genotype and precipitation affecting nutritional value, there is relative nutritional steadiness in NDF, ADF, and IVDMD between seasons for some accessions. According to the cluster analysis carried out for each season, it was evidenced that from the total collection, 51.2% of the accessions during the dry season and 19.4% of the accessions during the rainy season were classified with a better nutritional profile, thus, showing a higher number of materials with better nutritional behavior in the dry season. Both the genotypic characteristics of M. maximus and environmental conditions during contrasting seasons are factors that might influence the variability of the nutritional content, productive parameters, and flowering. Additionally, fodder material classification under Hotelling's T-squared test and Nutritional Classification Index suggests accessions that might be promising for resilient nutritional quality and adequate DMB, which proves that M. maximus could become an alternative for animal feeding and sustainable livestock production during critical dry periods in tropical agroecosystems.

Agronomic and nutritional parameters of a set of 28 accessions of Megathyrsus maximus established in Colombia during the rainy season were evaluated to identify accessions with differences in nutritional quality and characterize germplasm of M. maximus. ANOVA and multivariate analysis showed differences among accessions. Agronomic variables such as plant height, dry matter yield and green fresh weight were not correlated with nutritional variables. Flowering affected nutritional quality (neutral detergent fiber, acid detergent fiber and relative feed value). Flowering, fiber content, digestibility and crude protein content had the most influence on forage quality of M. maximus. The integral evaluation of biomass and nutritional parameters showed that the set of 28 M. maximus accessions contained 2 accessions with high nutritional quality and competitive biomass production. Heterogeneity of the collection in nutritional and agronomic assessments supports plant-breeding and offers alternatives for cattle producers in the tropics.

Background: Nutritional quality of forages is a strategy of continuous research in animal feeding to help mitigate the environmental impact generated by Tropical livestock. The aim of this study is to describe and classify the nutritional profile of the M maximus collection in Dry Tropics as a contribution to the selection of high-quality grassland for sustainable livestock production. The selection criteria were based in the potential of materials to mitigate climate change effects and to support plant breeding processes. For this, the nutritional composition of 129 CIAT accessions of Megathyrsus maximus was evaluated in representative cultivation conditions of Colombian Dry Tropical Forest by means of Near-Infrared Spectroscopy (NIRS) technique, Crude Protein (CP), Neutral Detergent Fiber (NDF), Acid Detergent Fiber (ADF), and in vitro Dry Matter Digestibility (IVDMD) was determined with rainy and dry seasons as fixed effects. Results: genotype and precipitation affect the nutritional value. However, there is relative nutritional steadiness in the NDF, ADF, and IVDMD among seasons for some accessions. According to the nutritional composition index (ICN), half of the evaluated collection had nutritional potential. From this group, 15 accessions showed higher values during rainy and dry seasons. Conclusions: M. maximus has an adequate nutritional profile for animal feeding in dry tropics agroecosystems. It generates alternative materials to project and sustain eco-efficient livestock production in the tropics.

ABSTRACT

The diversity and use of forages and grasslands for animal feeding are essential in tropical livestock systems. Seasonal changes are mainly marked by variations in precipitation patterns. Grasslands are managed as perennial crops and therefore must be resilient to tolerate both dry and rainy seasons. The integration of animal production with the genetic aspects of forages is important for helping to identify resilient alternatives for sustainability in livestock systems. This study developed a multivariate and multiharvesting trial (MHT) for plant height, green forage weight (GFW), and dry matter yield (DMY) in a diversity panel of 130 accessions of guineagrass [Megathyrsus maximus (Jacq.) B.K. Simon & S.W.L. Jacobs] established in the Patía Valley of Colombia. Our study aims to identify interactions among weather conditions and different genotypes for agronomic variables as well as identify outstanding accessions for their productivity and adaptability. The entry mean heritability values were .88, .47, and .39 for the traits plant height, GFW, and DMY, respectively. The genetic correlations among different harvests ranged .5–.9 for plant height and .2–.9 for GFW. Heritability and genetic correlations suggest that plant height and yield are largely influenced by plant genetic effects. The correlation among plant height and yield was .42 for GFW and .33 for DMY. Negative correlations were not found in the agronomic behavior of the materials among the harvests under rainy and dry conditions. The MHT analyzed under the methodology of factor analysis revealed that accessions 16062 and 6982 stood out consistently for plant height, GFW, and DMY across different harvests. These findings strengthen processes in the search for resilient forages in the transition toward eco‐efficient livestock production and provide knowledge on which agronomic variables and forage materials to select, according to criteria of interest to both producers and plant breeders.