Fermentative characteristics of Digitaria eriantha subsp. eriantha silage harvested at different stages of maturity

Abstract

An experiment was conducted to investigate the influence of stage of growth at harvest on fermentative characteristics of Digitaria eriantha subsp. eriantha silage. The treatment included three different growth stages (early vegetative, boot stage and full-bloom stage). The materials were ensiled either directly (unwilted) or after wilting for a period of 5–6 h prior to the ensiling. Samples of silage were taken from three bottles at 0, 7, 21 and 120 d for analysis of fermentative characteristics. Within the directly cut silage, stage of harvesting had no effect on pH on day 7, but on days 21 and 120 there were differences. Lower pH was recorded consistently for the boot stage silage. Within the prior-wilted groups, lower pH was recorded on day 7 for the boot growth stage while the difference between the growth stages in terms of pH was not significant on day 21. Within the directly cut silage, lactic acid concentration was consistently higher for the boot stage as compared to the early or full-bloom stage. Similarly, within the prior-wilted group, silages harvested at the boot growth stage resulted in higher lactic acid concentration on days 7 and 21, but on day 120 lactic acid concentration was higher for the early vegetative stage. In directly cut silages, harvesting at the boot growth stage resulted in a higher acetic acid concentration than that of the early vegetative growth stage or the full-bloom growth stage. For wilted silage, however, lower acetic acid concentration was recorded for the boot stage silage. In directly cut silage, the total nitrogen (N) concentration of boot-stage silage on day 120 was higher compared to the rest, but within the wilted silage the N value for boot-stage silage was not significantly different compared to the early vegetative stage. At day 120 the ammonianitrogen concentration increased for the early vegetative growth stage and full-bloom growth stage, while it was either reduced or remained similar for the boot-stage harvest when compared to the control. Under the current set of experiments, harvesting at the boot growth stage seems beneficial as the silage is lower in pH, higher in lactic acid concentration and able to retain most of the nitrogen in the silage for later use by the target animal.

Keywords: growth stage, moisture level, preservation, silage

African Journal of Range & Forage Science 2008, 25(3): 141–145