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INTRODUCTION
The Poaceae family is the most common group of forage species, comprising approximately 10 000 species and 651 genera. Among these is the genus Pennisetum (Giraldo-Cañas, 2010). Within this genus, there are notably large species with significant forage potential and rapid growth, such as Pennisetum purpureum (elephant grass), Pennisetum glaucum (pearl millet), and Pennisetum clandestinum (kikuyu grass) (Rengsirikul et al., 2013; Gómez et al., 2020). Biomass production in the genus Pennisetum depends on its management and the substantial accumulation of leaves and stems (Calzada-Marín et al., 2014; Maldonado-Peralta et al., 2019).
Pennisetum sp. is a palatable grass known for its considerable forage production and sweet flavour (Ramírez et al., 2008). It is distinguished by its high crude protein content, ranging between 16 and 20% (Ramírez et al., 2008; Vimos et al., 2020). These species are versatile and exhibit a wide range of adaptability, thriving at elevations ranging from 100 to 3000 m above sea level and in various climates (Tinini and Limache, 2017; Tenakwa et al., 2023). It thrives in soils with medium to high fertility and slightly acidic pH levels. Pennisetum sp. can also tolerate soils with elevated salinity levels and high organic matter content (Wangchuk et al., 2015; Li et al., 2016).
Currently, researchers have successfully developed numerous new and improved hybrid species within the Pennisetum genus. This resulted from crossing species characterized by high forage potential, adaptability, and hardiness (Pieterse and Rethman, 2002). To improve animal production, there is a current need for species with high biomass production, superior nutritional quality and optimal adaptability (Vargas and Carvajal, 2023). Notable Pennisetum hybrid grass cultivars include Cuba 22, Cuba 51, CT 115, CT 608, and CT 609, among others (Arias et al., 2019; Martínez and González, 2017). These hybrid grasses can achieve yields ranging between 70 and 180 tons of fresh forage per hectare (Martínez et al., 2010). Additionally, they are drought-resistant (Gonzáles et al., 2018). However, the performance and nutritional quality of these genera are influenced by the plant harvest age. As the age increases, the content of cell walls and other non-digestible fractions increases, and digestibility decreases (Costa et al., 2007). As grasses exhibit high nitrogen requirements, another factor that influences production and nutritional content is nitrogen fertilization (Pieterse and Rethman, 2002).
Aiming to replace grasses with lower productivity in Peru, these Pennisetum cultivars are being introduced on a large scale as forage resources due to their high yield and nutritional value. As part of this goal, the most promising approach involves assessing forage productivity per given area, which allows for improving availability in mixed systems (Nyambati et al., 2010; Rusdy, 2016; Hermitaño-Osorio et al., 2022; Rupay et al., 2023). However, in Peru, there has yet to be any previous research regarding these species’ productive performance and nutritional content. Therefore, this research aimed to evaluate the productive performance of dry matter and nutritional composition of three Pennisetum sp. cultivars (CT 115, Cuba 22, and Cuba 51) under two fertilization categories (with or without), harvested on five occasions.
MATERIALS AND METHODS
Study Area
The research was conducted in the pasture plots at the Chachapoyas Experimental Station of the Livestock and Biotechnology Research Institute, National University Toribio Rodríguez of Mendoza (UNTRM), located in Amazonas, Peru (6°14’04" S, 77°51’13" W; 2355 m altitude). Temperature and precipitation recorded during the experimental period are detailed in Figure 1A. Relative humidity is illustrated in Figure 1B. Temperature and precipitation data were sourced from the National Service of Meteorology and Hydrology of Peru SENAMHI (Ministry of the Environment of Peru [MINAM], 2024).
Experimental Design
Pennisetum sp. grass was planted at the Chachapoyas Experimental Station, where plots of 3 x 10 m (30 m2) were installed. Three cultivars (CT 115, Cuba 22 and Cuba 51) and two levels of nitrogen fertilization (with and without fertilizer) resulting in six treatments were evaluated. Each treatment consisted of three replicates, totalling 18 experimental units which were randomly distributed in the plots. The plants were installed in lines (3 plants/m2). Before the start of the experiment, the grasses were uniform cut (Day 0) to promote better regrowth. Urea fertilizer was applied at a 200 kg/ha rate as recommended by Cerdas-Ramírez et al. (2021) and applied on days 5 and 10 after the uniform cut.
Sampling and Post-Harvest Evaluations
Samples and evaluations were conducted on days 30, 45, 60, 75, and 90 after the uniform cut. (from October to December). Grass samples were collected by randomly placing 1 m2 squared frames and weighing them (fresh weight). Then, 1.5 kg of each sample was obtained and transported to the Laboratory of Animal Nutrition and Food Bromatology, UNTRM, to assess the dry matter yield and nutritional composition.
Dry matter (DM). To estimate DM per plot, a subsample of 250 g was dried in an oven (MMM Group, Venticell, Germany) at 105 °C for 24 h. The measurements were expressed in kilograms per hectare (kg/ha) (Barr et al., 1995), considering the fresh weight.
Nutritional composition. The remaining grass samples per plot (1.25 kg) were dried in an oven (MMM Group, Venticell, Germany) at 60 °C for 24 h, grounded and passed through a 2 mm sieve. Then, the nutritional composition was estimated following the methodology proposed by AOAC (2012). These included evaluations of crude protein (CP) content by the Kjeldahl method (N° 920.87), ash (As) content by the muffle ashing method (N° 923.03), and crude fibre (CF) by the enzymatic method (N° 962.09). Neutral detergent fibre (NDF) and acid detergent fibre (ADF) were analysed using the gravimetric method of Van Soest and Wine (Van Soest and Wine, 1967).
The gross energy (GE) was evaluated by combustion in an adiabatic calorimetric bomb (Parr 6200 Calorimeter, USA), following the method proposed by Terry and Osbourn (1980). Apparent in vitro digestibility was determined using a DaisyII® incubator (ANKOM Technology, D2001, USA), following the manufacturer’s protocol and the method proposed by ANKOM Technology (2014) and Giraldo et al. (2007).
Statistical Analysis
A completely randomized design (CRD) with a 3 x 2 factorial structure was used. The factors consisted of three cultivars (CT 115, Cuba 22, and Cuba 51) and two nitrogen fertilizations (with and without fertilizer), resulting in 6 treatments with three repetitions each. The experimental unit corresponded to a 3 x 10 m plot.
An analysis of variance (ANOVA) was employed at a significance level of 5% for the differences amongst measurements from the six treatment groups. When there was a significant interaction between factors, a Tukey’s test of mean comparisons (α≤5%) between treatments was applied. When there were only significant differences in the levels of at least one factor, a Tukey’s test of mean comparisons (α≤5%) was performed. Additionally, a Pearson correlation analysis (p<0.05) was conducted to explore the association between the study variables. All statistical analyses were executed using R4.3.3 software.
RESULTS AND DISCUSSION
Dry matter
Figure 2 illustrates the productive yield of dry matter of Pennisetum sp. The productive performance of each cultivar varied on all five days of harvest. Cultivar CT 115 and Cuba 22 exhibited higher dry matter yields compared to Cuba 51. An exception to this occurred on day 90, where CT 115 had the highest yield (73 578.5 kg/ha) and Cuba 51, the lowest (20 989.6 kg/ha) (p<0.05; Figure 2A). The application of nitrogen fertilizer did not significantly affect dry matter yield throughout all evaluation days (p>0.05; Figure 2B). Similarly, no significant interaction was observed between the factors. In all treatments, the cultivar increased the evaluated variables by more than 700% between days 30 and 90 after the uniform cut. Cultivar CT 115 had the highest increase, exceeding 900% during this period.
a,b,c Values with different superscripts are significantly different according to the Tukey test (p<0.05). Bars indicate standard error (n=3)
Figure 2. Dry matter yield (kg/ha) of Pennisetum sp. after the uniform cut. Values were assessed according to the cultivar (A) and nitrogen fertilizer inclusion (B)
The dry matter production varied, ranging from 2222.7 kg/ha to 73 578.5 kg/ha on days 30 and 90, respectively, indicating an increase of dry matter when the harvest time is delayed (Agza et al., 2013). This variation is due to the increase in tiller number, leaf elongation and stem growth (Maleko et al., 2019; Watanabe et al., 2023). The results align with similar studies, which reported a harvest yield of 27 000 kg/ha on day 90 (Dios-León et al., 2022) and between 4710 and 5750 kg/ha on day 45 (Nava et al., 2013).
The Cuba 22 cultivar yielded a dry matter of 6233.0 kg/ha on day 30 to 50 272.5 kg/ha on day 90. Similar results were obtained on this grass harvested on day 45 (13 005 kg/ha) (Vargas and Carvajal, 2023) and 60 (22 700 kg/ ha) (Samarawickrama et al., 2018). However, the results of this research (22 286 kg/ha) were higher than the 11 300 kg/ha sampled on day 56 by Cerdas-Ramírez et al. (2021). Likewise, dry matter values in this study were lower than the 55 710 kg/ha harvested on day 60 by Liman et al. (2022). The main differences could be due to the environmental characteristics required by each cultivar. These include the type of soil, altitude and agroclimatic conditions. Reports demonstrate that Pennisetum sp. cultivars can adapt up to 3000 m above sea level (Tinini and Limache, 2017). Fertilization is another crucial factor in dry matter production. Fertilization influences the root system of the plant and promotes nitrogen absorption, which consequently induces the plant to produce more leaves and stems (Cerdas-Ramírez et al., 2021).
Furthermore, increasing grass dry matter by applying inorganic nitrogen fertilizers is related to faster nutrient dilution than organic fertilizers that require microorganisms to make nutrients available (Kiliçalp et al., 2018). The highest dry matter yield is associated with the nitrogen fertilizer application, especially urea. This yield is attributed to the rapid urea mineralization, leading to nitrogen release, allowing plants to have a faster absorption of nutrients (Yalew et al., 2020, Del Aguila et al., 2023).
The results revealed that the CT 115 cultivar exhibited the highest dry matter yield. This behaviour is relevant to optimizing agricultural management practices and crop selection, particularly in Amazonian regions where Pennisetum sp. is the primary forage source. Furthermore, these findings can help future fertilization strategies to improve the yield and quality of these grasses (Fulkerson et al., 2007, 2008).
Nutritional composition
Pennisetum’s average crude protein values are shown in Figures 3A and 3B, respectively, according to the grass cultivar and nitrogen fertilization level. The type of cultivar did not affect the protein content on days 30, 45, and 60. However, significant differences were found in the protein concentration at days 75 and 90 (p<0.05). On these days, the Cuba 51 cultivar respectively exhibited 14.86% and 14.16%, compared to the other two cultivars which ranged between 12.77 and 14.03% (day 75) and between 10.64 and 10.77% (day 90) (Figure 3A).
a,b,c Values with different superscripts are significantly different according to the Tukey test (p<0.05). Bars indicate standard error (n=3).
Figure 3. Biweekly nutritional composition of Pennisetum sp. after the uniform cut. Values of crude protein percentage were assessed according to the cultivar (A) and nitrogen fertilizer inclusion (B). Values of ash percentage were assessed according to the cultivar (C) and nitrogen fertilizer inclusion (D). Values of crude fibre percentage were assessed according to the cultivar (E) and nitrogen fertilizer inclusion (F).
The addition of nitrogen fertilizer to the Pennisetum sp. crop did not influence the protein content of this grass on days 30, 45, and 90. However, a significant effect was observed at days 60 and 75. There was a higher protein percentage in the grasses receiving nitrogen fertilization than in the unfertilized group (p<0.05; Figure 3B). On the other hand, the crude protein content was not affected by the interaction of factors on all evaluation days. Likewise, a gradual reduction in CP content was observed over time, decreasing from 21% on day 30 to an average of 12% on day 90.
The CP of Cuba 22 grass showed a decline from day 30 (20.49%) to day 90 (10.64%). These findings surpass the recorded values of 19.48% on day 45 and 17.27% on day 60 reported by Mohamad et al. (2022). In podzolic soils, the Cuba 22 grass cultivars on day 45 and 65 respectively recorded 17.1 and 13.7% of protein (Samarawickrama et al., 2018).
Crude protein of the CT 115 cultivar on days 30 and 60 was 20.47 and 15.05%, respectively, whereas Dios-León et al. (2022) reported values of 12.5, 7.8 and 7.1% on days 30, 45 and 60, respectively. The differences among cultivars can be explained by the genetic improvement and the environmental conditions where Pennisetum sp. was cultivated. Also, climate change affects crop production by influencing various biophysical factors and their nutritional contents (Satyavathi et al., 2021). In this research, nitrogen fertilization did not affect the protein content of Pennisetum sp. on days 30 and 45. Nitrogen fertilization can be related to crude protein content because nitrogen in the plant is essential for its growth and development (Pieterse and Rethman, 2002). However, understanding the plant’s response to nitrogen fertilization and its true demand is important, to avoid nitrogen pollution and develop rational practices (Abedi et al., 2011; Kang et al., 2023).
Cultivar type did not affect the ash content of the grass on days 30 and 45 after the uniform cut. However, a significant difference was observed in the ash percentage at days 60, 75, and 90. Differences were dependent on the cultivar type, with the highest values for the cultivar CT 115 and the lowest for Cuba 51 (p<0.05; Figure 3C). On the other hand, the addition of nitrogen fertilizer (Figure 3D) and the interaction between factors did not alter the ash content in Pennisetum sp. on any evaluation day. Cultivar type and nitrogen fertilization, both showed a reduction in ash content over time, decreasing from an average of 19 to 12%.
The ash content shows similarities among Pennisetum cultivars on days 30 and 45 but diverged from day 60 onwards, varying from 19 to 10%. Mohamad et al. (2022) reported ash content ranging from 14.52% on day 45 to 16.50% on day 60, whereas Maleko et al. (2019) obtained 7.96% of ash content, values lower than those described in this research. Likewise, Martínez et al. (2010) reported 13.97% of ash on day 45 following 70 kg of nitrogen fertilization. For all grazed plants, the key factors influencing the mineral composition of forage include fertilizer application, the phenology stage, and environmental conditions (Mirzaei, 2012).
The ash content in the three cultivars evaluated was reduced as the harvest age of the Pennisetum was delayed. This is probably due because during the final phase of plant growth it is anticipated that a dilution and absorption of mineral nutrients will occur in various parts of the plant. Halgerson et al. (2004) support this observation by noting that concentrations of most minerals are higher in leaves than in stems; consequently, leaf reduction results in decreased mineral levels.
The type of Pennisetum sp. cultivar did not affect crude fibre content at days 30 and 60. However, on days 45 and 75, the Cuba 22 grass exhibited the highest values, reaching 28.9 and 31.6%, respectively. Contrary to this, Cuba 51 grass had the lowest values, with 25.4 and 29.0%, respectively. On day 90, CT 115 grass showed the highest content with 38.2%, while Cuba 51 had the lowest content with 31.4% (p<0.05; Figure 3E). On the other hand, the application of nitrogen fertilizer did not influence the crude fibre content (p>0.05; Figure 3F). Furthermore, the interaction between the factors did not affect this content. In general, more than a 10% nonsignificantly increase in crude fibre content was observed during the evaluation days.
The crude fibre (CF) of the Cuba 22 cultivars ranged from 24.9% (day 30) to 31.6% (day 75). Comparable results of crude protein include 25.62% (day 28), 28.36% (day 42) and 30.22% (day 56) (Jothirathna et al., 2022). In addition, CF values of 25.66% (day 45), 29.22% (day 60) and 32.40% were reported in hybrid crossings of Pennisetum purpureum with Pennisetum glaucum grass (Mohamad et al., 2022). CF increases with grass age; values of 37.30% (day 90) were reported in the Cuba 22 cultivar (Martínez and González, 2017). The increase in CF with grass age is consistent with previous findings; the cultivar CT 115 on days 30 and 90 recorded 25.22 and 38.15% of CF, respectively. Further, in a warm, humid climate with 1200 to 1300 mm rainfall and sandy loam soil, CT 115 recorded 32.28% of CF (Vivas-Carmona et al., 2019).
Nitrogen fertilization did not affect the crude fibre of the three cultivars of Pennisetum in days other than those after the uniform cut. However, reports are indicating that the nutritional content of grass is associated with soil fertility (Glowacz and Nixnikowski, 2018). Exploring alternative strategies, like organic-nitrogen fertilization and optimal harvest time for grasses like Pennisetum, could be promising for the sustainable improvement of natural grass yields (Yalew et al., 2020).
Neutral detergent fibre (NDF) content was similar between Pennisetum sp. cultivars on days 30, 45, 60, and 75 (p>0.05; Figure 4A). However, on day 90, the Cuba 22 cultivar recorded the highest NDF value (60%) compared to Cuba 21 (55.2%) and CT 115 (54.2%). Furthermore, no significant differences in NDF content were observed according to the nitrogen fertilization level (p>0.05; Figure 4B). Likewise, the interaction between factors did not affect this variable. Throughout the evaluation period, an increase of more than 13% in NDF content was evident.
a,b,c Values with different superscripts are significantly different according to the Tukey test (p<0.05). Bars indicate standard error (n=3).
Figure 4. Content of neutral detergent fibre (NDF) and acid detergent fibre (ADF) as percentages of DM of Pennisetum sp. after the uniform cut. NDF values were assessed according to the cultivar (A) and nitrogen fertilizer inclusion (B). ADF values were assessed according to the cultivar (C) and nitrogen fertilizer inclusion (D).
Acid detergent fibre (ADF) content was not affected by the Pennisetum sp. cultivar type during days 45 and 60 (Figure 4C). On day 30, the Cuba 51 cultivar exhibited a higher ADF content (25.1%) compared to CT 115 (23.5%) and Cuba 22 (22%) (p<0.05). On day 75, the Cuba 22 (35.8%) and CT 115 (36.2%) cultivars presented the highest ADF content, in contrast to Cuba 51 (32.8%). On day 90, the Cuba 22 cultivar showed a higher ADF content of 40.8%, compared to Cuba 21, which had the lowest value of 34.9% (p<0.05). On the other hand, nitrogen fertilizer levels affected ADF content on days 30 and 45. Unfertilized grasses respectively exhibited higher values of 24.2 and 29.7% compared to fertilized grasses, which showed the lowest values (22.9 and 26.9%, respectively). However, on days 60, 75, and 90, no significant differences were observed (Figure 4D). Furthermore, the interaction between factors did not affect the ADF content. During the evaluation days, an average increase of 18% in ADF content was observed for both study factors (fertilized and non-fertilized).
NDF varied until day 90 of evaluation. During the evaluation period, it increased from 45 to 60%. Similarly, the ADF varied from day 30 to day 75, increasing from 22 to 41%. In this sense, Retureta et al. (2019) reported 63.76% of NDF on day 56 and Tulu et al. (2022) 42.9% of ADF on Pennisetum cultivars. In the present research, the application of nitrogen fertilizer affected the NDF on day 75; however, Yalew et al. (2020) did not find differences on NDF content of grasses when applying inorganic nitrogen. Differences in NDF content could be due to the Pennisetum´s genetic features, soil properties, harvest time and climatic conditions (Yalew et al., 2020). Furthermore, in this research, on day 45 the unfertilized Pennisetum recorded the highest acid detergent fibre content. The increased acid detergent fibre content during advanced harvesting stages could be related to increased cell wall lignification as forage matures (McDonald et al., 2010).
In vitro digestibility (IVD) varied between Pennisetum sp. cultivars on days 30, 60, and 90 after the uniform cut (p<0.05; Figure 5A). On day 30, CT 115 and Cuba 22 exhibited higher digestibility (90.3%) compared to Cuba 51 (86.8%). However, on day 60, Cuba 51 showed a higher digestibility (86.3%) compared to Cuba 22 (82.1%). This trend was maintained until day 90, with Cuba 51 being the cultivar with the highest digestibility (80.4%), compared to Cuba 22 (74.6%). There were no differences in IVD on days 45 and 75 (p>0.05).
a,b,c Values with different superscripts are significantly different according to the Tukey test (p<0.05). Bars indicate standard error (n=3).
Figure 5. Biweekly in vitro digestibility (IVD) and gross energy (GE) content (as percentages of DM) of Pennisetum sp. after the uniform cut. IVD values were assessed according to the cultivar (A) and nitrogen fertilizer inclusion (B). GE were assessed according to cultivar (C) and to nitrogen fertilizer inclusion (D).
Nitrogen fertilization did not influence the IVD in all evaluation days after the uniform cut (p>0.05, Figure 5B), except on day 60, where fertilized grasses showed a higher IVD (85.2%) compared to the unfertilized grasses (82.3%; p<0.05). Furthermore, the interaction between the factors (cultivar-fertilization) did not affect the IVD on all evaluation days. Overall, a reduction in IVD from 90 to 75% was observed during the evaluation period.
The evaluation of forage quality is primarily determined by dry matter digestibility, a critical factor that directly impacts forage intake (Tenakwa et al., 2023). The results showed that the in vitro digestibility average on days 30 and 90 were 90.30 and 74.6%, respectively. Digestibility was reported in Pennisetum purpureum Schumach grass grown in the highlands of Tanzania (Maleko et al., 2019). On day 60 of age, the CT115 cultivar achieved a digestibility of 69.01% according to Ledea-Rodríguez et al. (2021). The Pennisetum digestibility results of this research are within the reported range in the literature (Maleko et al., 2019). High digestibility values in a pasture are generally associated with lower levels of NDF, since neutral detergent fibre represents the structural components of the plant (cellulose, hemicellulose, and lignin) that are less digestible. As plants mature, NDF tends to increase while digestibility decreases (Maleko et al., 2019).
The gross energy (GE) content in Pennisetum sp. was affected by the cultivar type on all days (p<0.05; Figure 5C). Cuba 51 showing the highest values and CT 115 the lowest. When evaluating the effect of nitrogen fertilization on GE, significant differences were found on days 30 and 60 (p<0.05; Figure 5D), with fertilized grasses exhibiting higher GE compared to unfertilized ones. However, no differences in GE were observed between fertilized and unfertilized grasses on days 60, 75, and 90 (p>0.05). Likewise, the interaction between factors did not influence GE.An increase in this variable was observed during the evaluation period, from 3400 to 4632 kcal/kg.
The gross energy average content on day 30 was 3454.6 kcal/kg. This was higher than the 2039.7 kcal/kg reported in Pennisetum glaucum at an altitude of 167 m above sea level (Tenakwa et al., 2023). Likewise, in Pennisetum purpureum grass, energy values were reported ranging from 1695.8 to 2030.2 kcal/kg DM (Turano et al., 2016). The minimum energy requirement for dairy cattle is 2388.5 kcal/kg of dry matter (NRC, 2001). This implies that, although the three cultivars of Pennisetum provide valuable energy content, additional evaluation of metabolizable energy is necessary to determine if supplemental energy sources are required to meet the nutritional demands for optimal milk production in dairy cattle (Weiss, 1993).
Correlations
On day 30, a positive correlation was observed between the IVD and the productive yield of dry matter (YDM). On the contrary, negative correlations were between the productive YDM and the ADF, as well as between the IVD and (NDF (p<0.05; Figure 6A).
YDM: productive yield dry matter, CP: crude protein, CF: crude fibre, As: Ash, NDF: neutral detergent fibre, ADF: acid detergent fibre, IVD: in vitro digestibility, GE: gross energy. Not significant: ns pe»0.05, significant: * p<0.05, ** p<0.01, ***p<0.001
Figure 6. Pearson correlation between productive yield of dry matter and nutritional composition of Pennisetum sp. Samples collected on days 30 (A), 45 (B), 60 (C), 75 (D) and 90 (E) after the uniformization cut.
On day 45, significant positive correlations were found between IVD and CP, YDM and IVD, CF and YDM, and NDF and GE (p<0.05; Figure 6B). Significant negative correlations were observed between NDF and IVD, NDF and YDM (p<0.05), GE and CF (p<0.01), and GE and YDM (p<0.001).
On day 60 (Figure 6C), a significant positive correlation was found betweenADF and As (p<0.05) and a significant positive correlation between YDM and As (p<0.01). Significant negative correlations were identified between As and GE, YDM and IVD (p<0.05) as well as between YDM and GE (p<0.01).
On day 74, both the positive and negative correlations increased (Figure 6D). Significant positive correlations were observed between ADF and As (p<0.05), ADF and CF, YDM and As, YDM and CF (p<0.01), and ADF and YDM (p<0.001). Variables showing significant negative correlations were GE and ADF, IVD and ADF, IVD and CF, CP and ADF, and CP and As (p<0.05), as well as GE and YDM and GE and CF (p<0.01).
On day 90 (Figure 6E), significant positive correlations were observed between CF and ADF (p<0.05), NDF and ADF, As and CF, and CP and IVD (p<0.01). In addition, significant positive correlations were also identified between YDM and CF and As and YDM (p<0.001). Significant negative correlations were found between YDM and GE, IVD and ADF, and CP and As (p<0.05). Significant negative correlations were also observed between IVD and NDF, CP and ADF, CP and YDM (p<0.01), and CP and CF (p<0.001).
CONCLUSIONS
Cultivar type (CT 115, Cuba 22, Cuba 51) significantly impacted dry matter, crude protein, ash, crude fiber, neutral and acid detergent fiber, in vitro digestibility, and gross energy (GE) in all evaluation days (30, 60, 75, and 90 after uniform cut). However, neither the level of nitrogen fertilization nor the interaction between the factors influenced the dry matter yield and nutritional composition of Pennisetum sp.
As the harvest time after the uniform cut increased, the crude protein content correlated negatively with the dry matter and crude fibre content; in vitro digestibility was negatively correlated with dry matter content.
