Composición nutricional de seis gramíneas tropicales del estado de Jalisco, México

El objetivo de este estudio fue evaluar la composición química de seis gramíneas forrajeras para el trópico húmedo y seco mexicano: Andropogon gayanus, Andropogon gerardii, Cenchrus ciliaris, Chloris gayana, Megathyrsus maximus y Urochloa brizantha. Las muestras se colectaron en noviembre de 2019, en Tonaya, Jalisco, México. Se determinaron: materia seca, cenizas, proteína cruda (total e insoluble), extracto etéreo, fibra detergente neutro, fibra detergente ácido, hemicelulosa, lignina y celulosa. La evaluación se realizó en el Laboratorio de Nutrición Animal del Departamento de Zootecnia, Universidad Autónoma Chapingo, Texcoco, Estado de México. Cada gramínea se evaluó por triplicado y cada repetición se consideró como unidad experimental. Las medias de composición química fueron separadas mediante la prueba de Tukey (p < 0.05). La correlación entre cada par de variables (p < 0.05) se estimó mediante el coeficiente de Pearson (p < 0.05). A mayor porcentaje de proteína total (p < 0.05) menor porcentaje de extracto etéreo y mayores porcentajes de cenizas y de proteína insoluble. Además, a mayor porcentaje de proteína insoluble, menor porcentaje de lignina (p < 0.05). Probablemente, la proteína se concentra en su fracción insoluble a expensas del extracto etéreo y la lignina. Consecuentemente, gran-tallo-azul (Andropogon gerardii) mostró porcentajes altos de proteína total (10.27%) y cenizas (7.88%), y bajos de lignina (5.23%) y extracto etéreo (1.37%); pero su proteína insoluble no fue tan elevada (2.06%) como la de guinea (Megathyrsus maximus) (6.08%). Por tanto, A. gerardii tuvo el mejor contenido nutricional a los 35 días de rebrote.

MORFOLOGI DAN PRODUKSI BIOMASSA Chloris gayana cv. Callide, DAN Megathyrsus maximus cv. Gatton PADA TAHUN PERTAMA PENANAMAN DI YOGYAKARTA

Penelitian ini bertujuan mengetahui karakter morfologi dan produksi biomasa Chloris gayana cv. Callidedan Megathyrsus maximus cv. Gatton yang diintroduksi di Yogyakarta pada tahun pertama penanaman.Tanaman tersebut ditanam dengan menggunakan biji dalam plot ukuran 2x2 m dengan cara menebar bijidan masing-masing spesies ditanam dengan 5 replikasi. Data yang diamati meliputi karakter morfologi,produksi biomasa, kadar bahan kering dan bahan organik. Data yang diperoleh dianalisis secara deskripsidan dengan metode t-test. Rumput yang diintroduksi merupakan tanaman perennial. Pertumbuhan tanamanmenunjukkan pertumbuhan yang baik. Morfologi tanaman normal sesuai karakter kedua tanaman ini. Chloris gayana cv. Callide memiliki produksi hijauan kering 25,21 ton/ha/ tahun pada tahun pertama (kadar BK 19,70% dan kadar BO 88,20%). Megathyrsus maximus cv. Gatton memiliki produksi hijauan kering 32,44 ton/ha/tahun pada regrowth kedua (kadar BK 19,85% dan kadar BO 88,18%). Berdasarkan penelitian dapat disimpulkan bahwa Megathyrsus maximus cv. Gatton memiliki produksi biomassa lebih tinggi dari Chloris gayana cv. Callide. Kata kunci: Chloris gayana, Megathyrsus maximus, morfologi, perennial, produksi biomassa, regrowth

Response to Climate Change: Evaluation of Methane Emissions in Northern Australian Beef Cattle on a High Quality Diet Supplemented with Desmanthus Using Open-Circuit Respiration Chambers and GreenFeed Emission Monitoring Systems

The main objective of this study was to compare the effect of supplementing beef cattle with Desmanthus virgatus cv. JCU2, D. bicornutus cv. JCU4, D. leptophyllus cv. JCU7 and lucerne on in vivo methane (CH4) emissions measured by open-circuit respiration chambers (OC) or the GreenFeed emission monitoring (GEM) system. Experiment 1 employed OC and utilized sixteen yearling Brangus steers fed a basal diet of Rhodes grass (Chloris gayana) hay in four treatments—the three Desmanthus cultivars and lucerne (Medicago sativa) at 30% dry matter intake (DMI). Polyethylene glycol (PEG) was added to the diets to neutralize tannin binding and explore the effect on CH4 emissions. Experiment 2 employed GEM and utilized forty-eight animals allocated to four treatments including a basal diet of Rhodes grass hay plus the three Desmanthus cultivars in equal proportions at 0, 15, 30 and 45% DMI. Lucerne was added to equilibrate crude protein content in all treatments. Experiment 1 showed no difference in CH4 emissions between the Desmanthus cultivars, between Desmanthus and lucerne or between Desmanthus and the basal diet. Experiment 2 showed an increase in CH4 emissions in the three levels containing Desmanthus. It is concluded that on high-quality diets, Desmanthus does not reduce CH4 emissions.

Genetic Diversity and Population Structure of a Rhodes Grass (Chloris gayana) Collection

Rhodes grass (Chloris gayana Kunth) is one of the most important forage grasses used throughout the tropical and subtropical regions of the world. Enhancing the conservation and use of genetic resources requires the development of knowledge and understanding about the existing global diversity of the species. In this study, 104 Rhodes grass accessions, held in trust in the ILRI forage genebank, were characterized using DArTSeq markers to evaluate the genetic diversity and population structure, and to develop representative subsets, of the collection. The genotyping produced 193,988 SNP and 142,522 SilicoDArT markers with an average polymorphic information content of 0.18 and 0.26, respectively. Hierarchical clustering using selected informative markers showed the presence of two and three main clusters using SNP and SilicoDArT markers, respectively, with a cophenetic correction coefficient of 82%. Bayesian population structure analysis also showed the presence of two main subpopulations using both marker types indicating the existence of significant genetic variation in the collection. A representative subset, containing 21 accessions from diverse origins, was developed using the SNP markers. In general, the results revealed substantial genetic diversity in the Rhodes grass collection, and the generated molecular information, together with the developed subset, should help enhance the management, use and improvement of Rhodes grass germplasm in the future.

Studies with Urochloa brizantha cv. MG5 Vitória in Okinawa, Japan: Vegetative propagation and a tractor tyre stress test

Feeding of high quality grass is critical to ensure breeding cows remain healthy with high reproductive rates and growing and fattening cattle achieve good growth rates. The Brazilian grass cultivar, Urochloa brizantha cv. MG5 Vitória, is highly nutritious and is known for its drought tolerance. In view of its low seed production potential in subtropical Japan and of phytosanitary problems (contamination with soil particles) of imported seed, a study was conducted in Okinawa to assess 2 methods of propagating this cultivar vegetatively. Cutting stems (culms) at about 10 cm from ground level and inserting them 3 cm into a 50:50 compost:soil mixture produced a 77% success rate in terms of rooted plantlets in a glasshouse compared with 67% for cutting the culm at 3 nodes from the base, subsequently allowing 2 weeks for adventitious roots to form on the lowest node, then cutting below the node where roots emerged and planting the rooted propagule in the same mixture. It seems that the simple process of cutting stems at about 10 cm from ground level and inserting them into a suitable mixture of soil and compost should result in an acceptable yield of plantlets for establishment of an MG5 forage crop. However, locating a source of high-quality seed free of phytosanitary problems seed would seem to be a better solution to increase the areas in Okinawa planted to MG5.In the tractor tyre stress trial conducted over 2 years, an MG5 forage crop established from seed showed depressed yields on the treatment subjected to tractor tyre pressure but performed as well as Chloris gayana, a much-used forage grass in Okinawa.

Genetic Diversity and Population Structure of a Rhodes Grass (Chloris gayana) Collection

Rhodes grass (Chloris gayana Kunth) is one of the most important forage grasses used throughout the tropical and subtropical regions of the world. Enhancing the conservation and use of genetic resources requires the development of knowledge and understanding about the existing global diversity of the species. In this study, 104 Rhodes grass accessions, held in trust in the ILRI forage genebank, were characterized using DArTSeq markers to evaluate the genetic diversity and population structure, and to develop representative subsets, of the collection. The genotyping produced 193,988 SNP and 142,522 SilicoDArT markers with an average polymorphic information content of 0.18 and 0.26, respectively. Hierarchical clustering using selected informative markers showed the presence of two and three main clusters using SNP and SilicoDArT markers, respectively, with a cophenetic correction coefficient of 82 %. Bayesian population structure analysis also showed the presence of two main subpopulations using both marker types indicating the existence of significant genetic variation in the collection. A representative subset, containing 21 accessions from diverse origins, was developed using the SNP markers. In general, the results revealed substantial genetic diversity in the Rhodes grass collection and the generated molecular information, together with the developed subset, should help enhance the management, use and improvement of Rhodes grass germplasm in the future.

Evaluación agronómica y nutricional de genotipos de Chloris gayana para la ganadería Colombiana

Introducción. Los forrajes de pastoreo son la principal fuente alimenticia del ganado. La variación climática reta a los productores a mantener una oferta constante de alimento, por lo que es necesario explorar otras alternativas forrajeras. Objetivo. Evaluar el comportamiento de veinte genotipos de Chloris gayana para explotaciones ganaderas. Materiales y métodos. El trabajo se desarrolló en el Centro de Investigación El Nus de la Corporación Colombiana de Investigación Agropecuaria (AGROSAVIA), San José del Nus, Antioquia, Colombia. Se empleó un diseño de bloques completos al azar, tres repeticiones y veinte tratamientos (genotipos Chloris gayana). En el análisis se utilizó un modelo mixto medidas repetidas en el tiempo, con el procedimiento GLIMMIX, cuyo efecto tiempo lo representó edad de corte. Las frecuencias de corte utilizadas fueron 21, 28, 35 y 42 días, entre agosto 2017 y octubre 2019 en época de baja y alta precipitación. Se evaluó vigor, cobertura de la especie, altura de planta, incidencia de plagas y patógenos, floración, rendimiento de materia seca (MS), proteína cruda (PC), fibra en detergente neutro y ácido (FDN, FDA), lignina (LIG), digestibilidad (DIG), hemicelulosa (HEM) y energía neta de lactancia (ENL). Resultados. Los caracteres que aportaron mayor variabilidad fueron MS, PC, FDN, FDA y DIG, se observó una asociación entre DIG, HEM y ENL. Se presentaron diferencias entre épocas y entre genotipos para la mayoría de las variables, a excepción de PC. La lignina fue la única que presentó diferencia en la triple interacción (genotipo*época*días de corte). La interacción genotipo*época mostró diferencias para FDA y LIG. El genotipo 13103 obtuvo el mayor rendimiento de MS (3032,2 kg MS ha-1). La B. Decumbens presentó el menor contenido de FDA y LIG, pero la mayor digestibilidad. Conclusiones. Los genotipos experimenales presentaron características de productividad y nutricionales similares e incluso mejores que los testigos.

Vegetation Response to Removal of Plant Groups and Grass Seeding in a Microphyllous Desert Shrubland: A 4-Year Field Experiment

Grazing is one of the most important land management activities worldwide, and cases of overgrazing increase erosion, land degradation, and plant invasion. The objective of this study was to assess the effect on individual species and species composition in response to groups of plants removals or grass seeding after four years of vegetation transformation in a microphyllous desert shrubland excluded from cattle grazing. Nine treatments involved (1) clearing of vegetation and seeding of Bouteloua curtipendula (BOCU), a native grass, (2) clearing and seeding of Chloris gayana (CHGA), an introduce grass from Africa, (3) clearing except for grasses (GRA), (4) clearing except for grasses and fodder shrubs (GRA-SHR), (5) free grazing by cattle (GRAZ), (6) clearing except fodder shrubs (SHR), (7) no modification (CON), (8) clearing of all plants (BARE), and (9) clearing except plants not eaten by cattle (UND). Treatments were replicated five times each in 10 m × 10 m experimental plots. Plots were surveyed for density, cover of all plants, and standing forage. Total plant cover was higher in CON and UND than the other treatments. Except for BOCU, where forage production was the highest, forage production ha−1 was low among all other treatments. Plant density was highest in SHR and lowest in CON. Results after four years of transformation indicate that seeded Chloris gayana failed to become established, but seeding of Bouteloua curtipendula was able to persist, and had the greatest influence on the vegetation restoration, which is what we consider the most appropriate restoration treatment.

Effect of Nitrogen Level on Herbage and Seed Yield of Rhodes Grass (Chloris gayana)

Nitrogen is the most important macronutrient for forage and food crop production. Currently, cultivable lands in Ethiopia undergo a deficiency of this element. Thus, this study was conducted to find an appropriate rate of nitrogen (N) fertilizer for the better agronomic performance of Chloris gayana Masaba. The experiment was carried out at Assosa Agricultural Research Center. The experiment was conducted using a randomized complete block design with three replications, and the treatments were five levels of nitrogen fertilizer (0, 23, 46, 69, and 92 kg N/ha). The collected data were analyzed using the general linear model procedure of SAS, and the least significance difference was used for mean separation. Plant height at forage harvesting, dry matter yield, leaf to stem ratio, leaf height, number of leaves per plant, number of tillers, and seed yield were significantly ( p < 0.001 ) influenced by the year of planting while nonsignificantly ( p > 0.05 ) by nitrogen fertilizer rate and interaction of planting year and fertilizer rate. The mean leaf to stem ratio was significantly ( p < 0.001 ) higher in 2017 and 2018 than in the 2019 planting year. However, forage dry matter yield was significantly ( p < 0.001 ) higher in 2019, followed by 2018 and 2017 planting years. Mean seed yield was significantly ( p < 0.001 ) different among the establishment years and the peak seed yield productivity attained during the third year of harvesting (1st = 2nd < 3rd year of harvesting). Generally, all measured agronomic traits were not significantly responsive to the different fertilizer rates, and in the economic point of view, 0 kg of N/ha is recommended.