Keywords:

Season

Pastures

Defoliation frequency

Nutritional value

Bromatology

Regrowth

Chemical composition of Urochloa and Megathyrsus maximus cultivars under tropical humid

forest conditions

Composición química de cultivares de Urochloa y Megathyrsus maximus bajo condiciones de

bosque húmedo tropical

Composição química de cultivares de Urochloa e Megathyrsus maximus sob condições de oresta

úmida tropical

Fabio Daniel Garrido-Ricoveri

María José Román Villasmil

Rover Enrique Maldonado-Cruz

Luis Enrique Cordero Contreras

Alonso José Fossi Medina

Juan Argenis Vergara López

Rosa Razz

Jorge Ortega

Rev. Fac. Agron. (LUZ). 2026, 43(1): e264306

ISSN 2477-9407

DOI: https://doi.org/10.47280/RevFacAgron(LUZ).v43.n1.VI

Animal production

Associate editor: Dr. Jorge Vilchez-Perozo

University of Zulia, Faculty of Agronomy

Bolivarian Republic of Venezuela

University of Zulia, Faculty of Agronomy, Maracaibo, Venezuela.

El Guayabo Local Station, National Institute for Agricultural

Research (INIA), Venezuela.

Animal Nutrition Laboratory, Faculty of Agronomy, University of

Zulia, Maracaibo, Venezuela.

Department of Animal Science, Faculty of Agronomy, University

of Zulia, Maracaibo, Venezuela.

Department of Statistics, Faculty of Agronomy, University of

Zulia, Maracaibo, Venezuela.

Received: 09-09-2025

Accepted: 28-11-2025

Published: 08-01-2026

Abstract

Urochloa and Megathyrsus maximus comprise the most widely

sown grasses in Venezuela, and their composition is inuenced by

management practices and the rainfall regime in the region. The

chemical composition of seven grass cultivars (CV) was evaluated

during the dry and rainy seasons (SE) under two (4 and 6 weeks)

defoliation frequencies (DF) in tropical humid forest conditions

of the Catatumbo municipality, Zulia state, Venezuela. Dry Matter

(DM), Ash (ASH), Ether Extract (EE), Crude Protein (CP) and

Crude Fiber (CF) were measured. A randomized complete block

design with a split-plot arrangement and four replications per

cultivar was used. Highly signicant eects (p<0.01) of SE were

observed on ASH, EE and CF contents. Defoliation frequency

signicantly aected (p<0.01) all evaluated variables, with notable

CP contents in cultivars BR02/0465 (10.36 %) and CIAT 606

(10.17 %). Considering SE, CV and DF together, highly signicant

eects (p<0.01) were determined on EE contents of M. maximus cv.

Tanzania (2.59 %) and CIAT BR02/0465 (2.39 %) during the dry SE

at DF 4 weeks. Regarding CF, signicant decreases (p<0.01) were

recorded as the age advanced from 4 to 6 weeks in cultivars Tanzania

(26.87 % to 26.66 %), BR02/0465 (25.03 % to 21.68 %) and Mulato

II (24.81 % to 20.46 %). From a bromatological perspective, the

evaluated cultivars demonstrated high nutritional value, particularly

CIAT BR02/0465, identifying it as a promising option for the

tropical humid forest of El Guayabo.

This scientic publication in digital format is a continuation of the Printed Review: Legal Deposit pp 196802ZU42, ISSN 0378-7818.

Rev. Fac. Agron. (LUZ). 2026, 43(1): e264306 January-March ISSN 2477-9409.

2-6 |

Resumen

Urochloa y Megathyrsus maximus agrupa a los pastos más

sembrados en Venezuela y su composición está inuenciada por

el manejo y el régimen pluviométrico de la zona. Se evaluó la

composición química de siete cultivares (CV) de pastos en época (EP)

seca y lluviosa, bajo dos (4 y 6 semanas) frecuencias de defoliación

(DF), en condiciones de bosque húmedo tropical del municipio

Catatumbo del estado Zulia, Venezuela. Se evaluó la Materia Seca

(MS), Cenizas (CEN), Extracto Etéreo (EE), Proteína Cruda (PC) y

Fibra Cruda (FC). Se utilizó un diseño de bloques completos al azar con

arreglo de parcelas subdivididas con cuatro repeticiones por cultivar.

Se constataron efectos altamente signicativos (p<0,01) de EP sobre

los contenidos de CEN, EE y FC. La FD afectó signicativamente

(p<0,01) los contenidos de todas las variables evaluadas, destacando

los contenidos de PC de los cultivares BR02/0465 (10,36 %) y

Basilisk (10,17 %). Al considerar EP, CV y FD, se determinaron

efectos altamente signicativos (p<0,01) en los contenidos de EE

de M. maximus cv. Tanzania (2,59 %) y CIAT BR02/0465 (2,39 %)

durante EP seca en la FD 4 semanas. Respecto a FC, se registraron

disminuciones (p<0,01) en sus contenidos conforme avanzó la edad

desde las 4 hasta las 6 semanas en los CV Tanzania (26,87 a 26,66

%), BR02/0465 (25,03 % a 21,68 %) y CIAT Mulato II (24,81 a 20,46

%). Desde el punto de vista bromatológico, los cultivares evaluados

presentan un alto valor nutricional, destacando a CIAT BR02/0465

como cultivar promisorio en el bosque húmedo tropical de El

Guayabo.

Palabras claves: época, pastos, frecuencia de defoliación, valor

nutricional, bromatología, rebrote

Resumo

Urochloa e Megathyrsus maximus agrupam as pastagens mais

cultivadas na Venezuela e sua composição é inuenciada pelo manejo

e pelo regime pluviométrico da região. Foi avaliada a composição

química de sete cultivares (CV) de pastagens na época (EP) seca e

chuvosa sob duas (4 e 6 semanas) frequências de desfolhação (FD),

em condições de oresta úmida tropical do município de Catatumbo,

estado Zulia, Venezuela. Foram avaliados o Material Seco (MS),

Cinzas (CEN), Extrato Etéreo (EE), Proteína Bruta (PB) e Fibra

Bruta (FB). Utilizou-se um delineamento em blocos completos ao

acaso com arranjo de parcelas subdivididas e quatro repetições por

CV. Foram constatados efeitos altamente signicativos (p<0,01) da

EP sobre os teores de CEN, EE e FB. A FD afetou signicativamente

(p<0,01) os teores de todas ases variáveis avaliadas, destacando-se os

teores de PB dos cultivares BR02/0465 (10,36 %) e Basilisk (10,17

%). Ao considerar a EP, o CV e a FD, foram determinados efeitos

altamente signicativos (p<0,01) nos teores de EE de M. maximus

cv. Tanzania (2,59 %) e CIAT BR02/0465 (2,39 %) durante a EP seca

na FD 4 semanas. Em relação à FB, foram registradas diminuições

(p<0,01) em seus teores conforme avançou a idade de 4 para 6

semanas nos cultivares Tanzania (26,87 a 26,66 %), BR02/0465

(25,03 % a 21,68 %) e CIAT Mulato II (24,81 a 20,46 %). Desde o

ponto de vista bromatológico, os cultivares avaliados apresentam alto

valor nutricional, destacando-se o CIAT BR02/0465 como cultivar

promissor na oresta úmida tropical de El Guayabo.

Palavras-chave: época, pastagens, frequência de desfolhação, valor

nutricional, bromatologia, rebrote

Introduction

Over the last few decades, various cultivars of the genus Urochloa

have been developed to generate eective responses to global

production constraints (Morales-Velasco, 2016), taking advantage

of the natural diversity of this genus (Rodríguez et al., 2013).

Currently, there are around 400 ecotypes of Urochloa brizantha

and 83 of Urochloa decumbens (formerly Brachiaria brizantha and

Brachiaria decumbens) preserved in germplasm banks around the

world (Enríquez et al., 2005), which has provided a solid basis for the

development of new cultivars in recent decades (Miles, 2005).

In Venezuela, species of the genus Urochloa predominate due

to their lower nutritional requirements compared to other genera,

such as Megathyrsus and Cynodon. Specically, in 2003, there were

3,675,000 ha of Urochloa spp. planted throughout Venezuela, of

which 949,000 were in the state of Zulia (Espinoza et al., 2012).

Despite the abundant literature on the chemical composition of

grasses worldwide, there are few studies on the specic climatic

conditions of Zulia State and how these inuence yield and chemical

composition. For these reasons, the objective of this research was to

evaluate the chemical composition of seven grass cultivars in the dry

and rainy seasons, with two defoliation frequencies, in the tropical

rainforest of the Catatumbo municipality, Zulia State, Venezuela.

Materials and methods

The study was conducted using samples from the El Guayabo

Local Station, of the Instituto Nacional de Investigaciones Agrícolas

(INIA), located in the Catatumbo municipality of Zulia State,

Venezuela (8°33’55.99‘N; 72°19’54.90’W). The climate and

vegetation correspond to tropical humid forest (Ewel and Madriz,

1968), average rainfall 2,278.43 mm over 10 years and average

annual temperature of 27.24 °C, with peak rainfall occurring in the

months of April-June and September-November.

The soil is heavy in texture with low phosphorus and medium

potassium content. It was classied as Vertic Hapludepts, isp, with

a pH of 5.6, a slope of 0.5 % in northeast-southeast direction, no

stoniness either on the surface or within the prole, and severe

drainage limitations.

Management of experimental plots

The pastures were cultivated under rainfed conditions and without

fertilization, using the methodology of Toledo and Schultze-Kraft

(1982). Sowing was carried out directly, using sexual seed with

distances of 0.80 m between furrows and 0.50 m between rows. The

plots measured 5 × 3.2 m, reaching a total size of 16 m² per plot, with

distances of 2 m between plots.

Each plot consisted of four rows of plants, separated by distances

of 0.5 m. There were 10 plants per row, for a total of 1,120 individuals.

Each plot was divided into two subplots of 8 m² each, corresponding

to the two defoliation frequencies (4 and 6 weeks). For the evaluation,

1 m² was harvested in the centre of the plot in each repetition. A

total of 10 samples were taken, considering the identication of the

periods of minimum and maximum precipitation for the years 2016-

2017 through the average monthly precipitation during the evaluation

period (September the rst 2016 to November 23, 2017), covering a

minimum of two samples of both frequencies. Thus, 10 samples were

used, of which 5 corresponded to the 4-week frequency and 5 to the

6-week frequency.

This scientic publication in digital format is a continuation of the Printed Review: Legal Deposit pp 196802ZU42, ISSN 0378-7818.

Garrido-Ricoveri et al. Rev. Fac. Agron. (LUZ). 2026, 43(1): e264306

3-6 |

Canchila et al. (2008) reported that defoliation at advanced

stages of growth generates higher DM contents due to the longer

period available for accumulation within the plant cell, while

frequent defoliation reduces stem density, so that by prolonging the

intervals between cuts, favours intraspecic competition for sunlight,

accelerating the metabolic processes of plants due to this competition,

given that as the plant ages, the apical meristems become less active,

decreasing the biosynthesis of compounds such as proteins and

nucleic acids, which favour the accumulation of compounds in the

form of structural carbohydrates.

Cedeño et al. (2022) observed increases in DM from 25 to 50

days in U. decumbens (14.10 % to 20.43 %), U. brizantha (14.19 %

to 21.54 %), U. hybrid (13.43 % to 23.51 %) and M. maximus cv.

Tanzania (16.76 % to 28.19 %). Similarly, Núñez-Arroyo et al. (2022)

determined increases in DM levels in the Diamantes cultivar (18.90 %

to 20.40 %) of U. decumbens during the dry season.

Ashes

Highly signicant eects (p<0.01) of SE and CV were observed,

as well as signicant eects (p<0.05) of DF related to ASH contents.

The highest ASH contents increased from the rainy SE (10.28 %)

to the dry SE (12.00 %), possibly due to greater synthesis of organic

nutrients during this period (Contreras-Jácome et al., 2025).

At the same time, a trend towards increased ASH levels (p>0.05)

was observed during the rainy SE, possibly due to an increase in

the solubility of minerals in the soil, which is consistent with Vega

Espinosa et al. (2006), who observed a decrease during the rainy

season from 30 (6.70 %) to 45 days (5.82 %).

The CVs with the highest ASH contents were BR02/0465, Cobra,

and Mulato II, averaging 11.43 %, with no dierences (p>0.05)

between them, and higher (p<0.05) than those observed in Cayman,

with 10.53 %, as shown in Table 1. The levels obtained in Cayman

were higher than the values (9.4 %) reported by Ventura-Ríos et al.

(2023) in the humid tropics of Mexico. The results in Mulato II were

higher than those of Muinga et al. (2016), with 6.7 %, while the

contents of Basilisk and Marandú CVs are close to those reported

by Nguku et al. (2016) in the establishment phase, with 12.10 % and

13.90 % at 22 weeks after planting.

The ASH contents were higher (p<0.05) at DF 4 weeks with 11.30 %

than at 6 weeks with 10.98 %. This eect corresponds to the dilution

of ASH in DM due to the progress of plant development, since the

concentration of mineral content in the tissue decreases as the age

of the plant increases, because these elements are found in greater

proportions in younger and growing organs (Ramírez et al., 2014),

since the DM content increases at a faster rate than the absorption and

transport of minerals to the leaves (Steinberg et al., 2012).

Crude protein

Highly signicant eects (p<0.01) were observed for CV and DF,

as well as for the SE × DF and DF × CV interactions related to the CP

content of the cultivars evaluated.

The cultivars with the highest CP contents were BR02/0465 (10.36

%), followed by Basilisk (10.17 %) and Mulato II (9.92 %) (Table 1). In

general, the CVs showed high CP contents. Hare et al. (2015) obtained

7.47 % in BR02/0465, which is lower than the results obtained in this

study. Hare et al. (2023) reported CP values for the cultivars Cobra

(10.1 %), Mulato II (9.4 %), Cayman (9.95 %) and Marandú (8.72 %)

in the third year of evaluation, similar to those obtained in this study.

Ventura-Ríos et al. (2023) obtained 6.5 % in the Cayman cultivar,

considering four defoliation frequencies (30, 60, 90 and 120 days).

Experimental design

A randomised block design with a split-plot arrangement was

used, considering the season eect (SE) as the main plot, while the

cultivars (CV) and defoliation frequencies (DF) were considered

subplots.

Laboratory analysis

The samples used were dried in a forced-ventilation oven at 65 °C

for 48 hours and ground in a Wiley mill (Thomas Scientic), using a

1 mm sieve, and then stored in pre-labelled, airtight plastic bags. The

analyses are expressed as percentages based on dry matter.

Physical and chemical analysis was carried out at the Animal

Nutrition Laboratory of the Faculty of Agronomy of the University

of Zulia, using the methods described in AOAC (1990) for the

determination of dry matter (DM), ash (ASH), crude protein (CP),

ether extract (EE) and crude bre (CF).

Statistical analysis

Physical and chemical variables data were recorded in MS-Excel

spreadsheets. The data were subjected to analysis of variance using

the General Linear Model (GLM) of the InfoStat software version

2008 (Infostat, 2008). When signicant eects of any of the factors

evaluated were detected, a Tukey test was applied to detect possible

dierences in means. When interaction eects between the factors

evaluated were detected, a minimum signicant dierence test was

applied.

Results and discussion

Dry matter

Analysis of variance showed a highly signicant eect (p<0.01)

of CV, as well as the eect of DF and the SE × DF interaction on the

DM content of the cultivars evaluated.

The highest DM levels (p<0.05) were observed in M. maximus cv.

Tanzania, followed by U. brizantha cv. Marandú and U. decumbens

cv. Basilisk, which did not dier from each other (p<0.05), as shown

in Table 1. DM contents increased (p<0.05) with increasing plant age

from 21.98 % at 4 weeks DF to 23.12 % at 6 weeks DF.

Regarding the SE × DF interaction, the lowest DM contents (21.03 %;

p<0.01) were obtained in the rainy SE at 6 weeks (23.35 %), the dry SE at

4 weeks (22.93 %) and the dry SE at 6 weeks (22.90 %).

Table 1. Dry matter, ash and crude protein contents of cultivars

of the genus Urochloa and Megathyrsus maximus

cv. Tanzania, growing in the tropical humid tropic

conditions of El Guayabo, Catatumbo municipality,

Zulia State, Venezuela.

Cultivar

DM ASH CP

Megathyrsus maximus cv. Tanzania 24.91

11.31

9.15

Urochloa brizantha cv. Marandú 23.42

11.10

9.86

Urochloa decumbens cv Basilisk 23.29

10.74

10.17

Urochloa híbrido CIAT BR02/0465 22.90

11.45

10.36

Urochloa híbrido cv. Mulato II 22.00

11.41

9.92

Urochloa híbrido cv. Cayman 21.12

10.53

9.30

Urochloa híbrido cv. Cobra 20.23

11.44

9.75

Standard error 0.39 0.18 0.07

a, b, c, d, e

Means with dierent letters within the same column are statistically dierent (Tukey,

p<0.05).

This scientic publication in digital format is a continuation of the Printed Review: Legal Deposit pp 196802ZU42, ISSN 0378-7818.

Rev. Fac. Agron. (LUZ). 2026, 43(1): e264306 January-March ISSN 2477-9409.

4-6 |

Regarding the eect of the SE × DF interaction, CP contents were

higher (p<0.01) during DF 4 weeks, regardless of the SE, with 11.16 % in

dry SE and 10.20 % in rainy SE, followed by DF 6 weeks, with 9.23

% in dry SE and 8.56 % in rainy SE.

Regarding the SE × CV interaction, with the exception of CVs

BR02/0465 and Basilisk, CP contents were higher (p<0.01) during

the rainy SE (Table 2). The CIAT BR02/0465 and Basilisk cultivars

obtained the highest CP contents (p<0.01) during the rainy season

(10.83 % and 10.45 %), while during the dry SE, the Mulato II and

Cobra cultivars obtained higher CP contents (10.21 % and 10.00 %,

respectively).

Table 2. Crude protein contents of cultivars of the genus Urochloa

and Megathyrsus maximus cv. Tanzania during the dry

and rainy seasons in the tropical rainforest of El Guayabo,

Catatumbo municipality, Zulia State, Venezuela.

Cultivar

Season

Rainy Dry

Urochloa híbrido CIAT BR02/0465 10.83

9.90

cde

Urochloa decumbens cv Basilisk 10.45

9.90

cde

Urochloa brizantha cv. Marandú 9.79

def

9.93

cde

Urochloa híbrido cv. Mulato II 9.64

def

10.21

Urochloa híbrido cv. Cobra 9.50

10.00

Urochloa híbrido cv. Cayman 9.10

9.50

Megathyrsus maximus cv. Tanzania 8.70

9.61

Standard error 0.10

a, b, c, d, e, f, g

Means with dierent letters are statistically dierent (LSD, p<0.01).

Ether extract

Highly signicant eects (p<0.01) were detected on SE, CV and

DF, as well as on the DF × CV and SE × DF × CV interactions.

Regarding the SE × CV × DF interaction, the highest EE contents

were obtained in the Basilisk cultivar during the rainy SE at DF 6 weeks

(2.60 %) and in Tanzania during the dry SE at DF 4 weeks (2.59 %).

On the other hand, Basilisk at DF 4 weeks during the rainy SE obtained

the lowest (p<0.01) EE contents, followed by CV Cobra at DF 6 weeks

and Marandú at DF 4 weeks under the same SE, with no dierences

between them (p>0.01), as shown in Table 3.

A trend (p>0.01) towards a decrease in EE during the dry SE was

observed as age increased, because young plants have a high EE content

since lipids are hydrolysed by lipase to glycerol and fatty acids (FA) in

active cells to be used in the synthesis of phospholipids and glycolipids

for organelles formation; thus, FA form part of the EE and are present as

compounds in the protective layer of the epidermis, stems, leaves and

fruits (Umami et al., 2018), functioning as a response to water stress.

Table 3. Ether extract content of seven cultivars of the genus Urochloa and Megathyrsus maximus at two defoliation frequencies during

the dry and rainy seasons in the tropical humid forest of El Guayabo, Catatumbo municipality, Zulia State, Venezuela (Mean

± Standard Error).

Cultivar

Dry season Rainy season

DF4 DF6 DF4 DF6

M. maximus cv. Tanzania 2.59 ± 0.14

2.08 ± 0.17

abcdef

1.67 ± 0.14

efghi

1.89 ± 0.17

cdefgh

CIAT BR02/0465 2.39 ± 0.14

abc

2.19 ± 0.17

abcde

1.65 ± 0.14

efghi

1.80 ± 0.17

defgh

U. híbrido cv. Mulato II 2.08 ± 0.14

abcdef

2.15 ± 0.17

abcde

1.44 ± 0.14

gihj

2.19 ± 0.17

abcde

U. brizantha cv. Marandú 2.38 ± 0.14

abc

2.08 ± 0.17

abcdef

1.34 ± 0.14

hij

1.97 ± 0.17

cdefg

U. híbrido cv. Cobra 2.35 ± 0.14

abcd

2.51 ± 0.17

1.73 ± 0.14

efgh

1.12 ± 0.17

U. híbrido cv. Cayman 2.01 ± 0.14

defgh

2.13 ± 0.17

abcdef

1.58 ± 0.14

fghi

2.07 ± 0.17

abcdef

U. decumbens cv. Basilisk 1.85 ± 0.14

bcdef

2.60 ± 0.17

1.01 ± 0.14

1.52 ± 0.17

fghij

DF: Defoliation frequency (weeks).

a, b, c

Means with dierent letters between lines are statistically dierent (LSD, P<0.01).

Thus, Khan et al. (2015) consider that management practices that

avoid prolonged ripening and a decrease in the leaf:stem ratio may

favour the concentration of FA in the plant and, therefore, the EE.

During the rainy SE, and with the exception of the Cobra CV, a

tendency (p>0.01) towards an increase in EE content was observed,

which could be due to a lower dilution of EE per fresh mass, as well

as a decrease in photosynthetic activity due to lower respiration and

photoassimilate production caused by excess water in the soil prole

(Del Pozo, 2002).

Crude bre

Highly signicant eects (p<0.01) were observed for SE, CV and

DF, as well as eects of the DF × CV interaction.

During the dry SE, the CF contents were higher (p<0.05), at 25.24

%, compared to the rainy SE (p<0.05), at 22.84 %. The highest CF

contents (p<0.01) were observed in M. maximus cv. Tanzania (26.76

%), followed by Marandú (24.39 %), as shown in Table 4. The latter

contrasts with the results of Combat Caballero et al. (2018), who

reported CF contents in B. decumbens of 38 %. Similarly, the CF

contents of Mulato II and Marandú were lower than those reported by

Balseca et al. (2015) (41.9 % and 45.4 %, respectively). In general,

the CF contents of the CV were lower than those reported by Macas

Giler et al. (2024) in B. hybrid Sabia AIG-3303 J (28 % at 30 days).

Table 4. Crude bre contents of cultivars of the genus Urochloa

and Megathyrsus maximus cv. Tanzania, growing in

the tropical humid forest conditions of El Guayabo,

Catatumbo municipality, state of Zulia, Venezuela.

Cultivar Crude bre (%)

Megathyrsus maximus cv. Tanzania 26.76

Urochloa brizantha cv. Marandú 24.39

Urochloa decumbens cv Basilik 24.02

Urochloa híbrido cv. CIAT BR02/1794, Cobra 23.83

Urochloa híbrido cv. CIAT BR02/1752, ayman 23.37

Urochloa híbrido CIAT BR02/0465 23.35

Urochloa híbrido cv. Mulato II 22.64

Standard error 0.07

a, b, c, d, e

Means with dierent letters dier statistically (Tukey, p<0.05).

This scientic publication in digital format is a continuation of the Printed Review: Legal Deposit pp 196802ZU42, ISSN 0378-7818.

Garrido-Ricoveri et al. Rev. Fac. Agron. (LUZ). 2026, 43(1): e264306

5-6 |

Regarding the DF × CV eect, the highest CF contents (p<0.01)

were exhibited by M. maximus cv. Tanzania, regardless of DF,

followed by CIAT BR02/0465 (Table 5). The higher values for

Tanzania are attributed to its lower tolerance to ooding, an eect

observed by Smith et al. (2025).

Table 5. Crude bre contents of cultivars of the genus Urochloa

and Megathyrsus maximus cv. Tanzania at two defoliation

frequencies, growing in the conditions of the tropical

humid forest of El Guayabo, Catatumbo municipality,

Zulia State, Venezuela.

Cultivar

Defoliation frequency

4 weeks 6 weeks

Megathyrsus maximus cv. Tanzania 26.87

26.66

Urochloa híbrido CIAT BR02/0465 25.03

abc

21.68

Urochloa híbrido cv. Mulato II 24.81

20.46

Urochloa brizantha cv. Marandu 24.60

24.18

Urochloa decumbens cv Basilisk 24.27

23.77

Urochloa híbrido cv. Cobra 24.18

23.48

Urochloa híbrido cv. Cayman 23.69

23.06

Standard error 0.53 0.65

a, b, c, d, e, f, g

Means with dierent letters dier statistically (LSD, p<0.01).

Umami et al. (2018) observed decreases in both stems and leaves

of U. brizantha, U. ruziziensis, U. decumbens, and U. humidicola

during the dry SE. Likewise, a decrease (p<0.01) in CF was observed

as the age of the plant increased (24.99 % to 23.56 %). In early stages,

grasses are usually in the vegetative phase, with a high proportion

of young stems and leaves where CF accumulates. On the other

hand, at DF 6 weeks, during the transition to the reproductive phase,

there may be a temporary increase in non-brous components in

new leaves, thus diluting the CF content in the DM. In addition, as

physiological maturity approaches, the FC concentration depends on

the metabolic pathways, given that C4 plants are more ecient than

C3 plants, allowing to increase photosynthetic eciency and water

use by modifying its primary and secondary structural walls at a faster

rate than C3 plants (Ventura-Ríos, 2024).

Low CF levels could in turn be associated with the eect of soil texture

class, rainfall volume and proximity to the Zulia River (770 m), which

determines the presence of sucient moisture in the soil to sustain the

plant’s metabolic needs. The behaviour is similar to that of CP content,

which could be associated with the C4 metabolism type, which overcomes

the limitations of photorespiration and increases photosynthetic eciency

under stress conditions (Reyes-Pérez et al., 2022).

Conclusions

The season was a determining factor in the nutritional quality of

Urochloa and Megathyrsus maximus grasses in tropical rainforest

conditions, inuencing the DM, ASH, CP, EE and CF contents. In

contrast, DF proved to be a less inuential management factor on most

nutrients (DM, ASH, EE), but critical for PC and CF accumulation.

The Urochloa and Megathyrsus grass cultivars evaluated have

an adequate physical-chemical prole. Within this group, U. hybrid

BR02/0465 is established as the most promising species for El Guayabo

region due to its excellent bromatological balance (23.22 % DM, 10.42

% CP, 2.03 % EE, 24.15 % CF), suggesting high nutritional quality

and sustained animal performance potential.

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