Chemical composition of Taiwan grass (Pennisetum purpureum Schum.) at different harvesting intervals

Abstract

Objective: To evaluate the effect of the harvesting interval on the quality of Taiwan grass (Pennisetum purpureum Schum.).

Design/Methodology/Approximation: Crude protein (CP), in vitro dry matter digestibility (IVDMD), crude fiber (CF), neutral detergent fiber (NDF), acid detergent fiber (ADF), lignin, ether extract, and ashes were determined. Samples were collected from the Papaloapan experimental site of the Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias, Isla, State of Veracruz (18° 01’ 45’’ N, 95° 31’ 35’’ W). Treatments consisted of five harvesting intervals (30, 60, 90, 120, and 150 days). Data were analyzed under the general linear model and means were separated using Tukey’s test (P<0.05).

Results: The nutritional value decreased (P<0.05) as the harvesting interval increased from 30 to 150 days. The following elements decreased: CP (leaves, from 12.3 to 3.7%; stems, from 8.9 to 2.1%), IVDMD (leaves, from 66.5 to 43.5%; stems, from 62.7 to 32.5%), ether extract (leaves, from 2.4 to 1.4%; stems, from 1.4 to 0.6%), and ashes (leaves, from 10.3 to 6.1%; stems, from 10.9 to 2.9%). On the contrary, the following elements increased: CF (leaves, from 28.4 to 41.1%; stems, from 33.4 to 44.5%), NDF (leaves, from 60.4 to 72.5%; stems, from 63.8 to 74.3%), ADF (leaves, from 36.7 to 46.8%; stems, from 34.6 to 50.7%), and lignin (leaves, from 9.7 to 15.3%; stems, from 11.0 to 18.3%).

Study Limitations/Implications: Neither ˂30 days harvesting intervals nor yields (tons) per hectare were taken into account.

Findings/Conclusions: Taiwan grass should be harvested at 60 days, when its nutritional value has not decreased too much.