Quantitative anatomy and in situ ruminal degradation parameters of elephant grass under different defoliation frequencies

Abstract

SUMMARY This study aimed to determine the area occupied by different tissues present in the leaf blade and the in situ degradability of leaf and stem of elephant grass (Pennisetum purpureum Schum.) under different defoliation frequencies (30, 45, 60, 75 and 90 days). Plants were classified into three levels of insertion in the tiller (apical, medial and basal). The results were presented as a proportion of the area of each tissue in relation to the total area of the leaf blade, namely, parenchyma tissue (PT), lignified vascular tissue (LVT) and non-lignified vascular tissue (NLVT). The proportion of tissue in the leaf blade is altered in accordance with the insertion in the tiller and increase in cutting age of the plant. PT has greater proportion at lower cutting ages, LVT increases with frequency and NLVT is higher at 60 days. The parameters of DM degradation in the two fractions evaluated decreased significantly with increasing maturity of the plant. The effective degradability of CP in leaf and stem decreased with the increase in the rate of passage (2, 5, and 8% h-1). The highest rate (c) of CP degradation for the leaf fraction was obtained with a frequency of 60 days, for the stem, with 45 days. The advance in plant maturity increases the proportion of lignified vascular tissue, thus influencing the ruminal degradation parameters of elephant grass. The defoliation frequency of 60 days offers an optimal point regarding the proportion of anatomical tissues correlated with the degradation of elephant grass.

Nutritive value and anatomical characterization from Pennisetum purpureum genotypes

“…The correlation between NDF and LIG (Table 4) was significant (r = -0.64) corroborating with Van Soest (1994) and Gallo, Moschini, Cerioli, and Masoero (2013), who demonstrated that there is an increase on the lignin content of fibrous portion. Sanchês et al (2018) analyzed the association of the degradability and their correlations with the anatomical components. The authors verified that the younger the forage, the higher the digestibility.…”

“…High significant correlations among the proportion of individual tissues (epidermis, ground and vascular tissues), or its combination, and the nutritional values suggested that, in general, plant tissues which digestion is rapid, such as the mesophyll tissue, display a positive correlation with the digestibility coefficients and the levels of CP, and a negative correlation with the levels of the cell wall (Sanchês et al, 2018). On the other hand, tissues resistant to digestion such as xylem vessels and sclerenchymatous tissue, or which digestion is partial and slow, as the parenchymatic bunches of the stems display a positive correlation with the lignin contents and a negative correlation with the digestibility (Table 4).…”

Light interception, chemical, and productive characteristics of elephant grass subjected to different cutting intervals

“…After the cutting of standardization, the plots were cut in accordance with the frequencies of preestablished cutoffs (30,45,60,75, and 90 days), on the day of completion of cutting, evaluation was conducted by the monitoring of light interception by the canopy, using the analyzer -AccuPAR Linear PAR/LAI ceptometer, Model . Readings were performed at four sampling points per plot, taking in each location one reading above and one below the canopy, using a reference height of 25 cm (SANCHÊS et al, 2018).…”

“…Analyzing the fractions within the frequencies, there was no significant difference (P > 0.05) in the NDF content at a frequency of 30 days; this result is explained by the high incidence of new material and material still in development. Sanchês et al (2018) observed that in plants of elephant grass, as the cells mature, the production of potentially digestible components tends to decrease, and the fiber content increases with advancing of the stage of maturation of the forage harvester, and natural senescence occurs, contributing to increased lignification.…”

“…Therefore, correlation of the harvest interval with light interception may define a method of more efficient management of this forage crop. In this sense, factors that interfere with the quality of forage grasses can involve anatomic origin, physics, and chemistry, in addition to those related to the structure of the vegetation, which are directly related to the management of pastures (SANCHÊS et al, 2018).…”