The nutritional value of the lower maize stem cannot be improved by ensiling nor by a fungal treatment

Abstract

The effect of ensiling and fungal treatment on the chemical composition and on in vitro gas production, an indication of rumen degradability, of maize stems was studied. Stems from two maize cultivars (LG30211 and MZP8057) were separated into three parts: upper (above internode 12 up to and including internode 15), middle (above internode 8 up to and including internode 11), and lower stem (above internode 5 up to and including internode 7). The three parts of the stems were ensiled for 1, 2, 4, and 8 weeks and the lower stem was treated with the white-rot fungi Lentinula edodes and Pleurotus eryngii for 3, 6, and 9 weeks. The dry matter content decreased and the acid detergent fibre (ADF) and acid detergent lignin (ADL) content increased from the top to the bottom in the stem. Upon ensiling, the neutral detergent fibre, ADF and ADL content increased. The gas production between 3 and 20 h, a measure of cell wall degradability in rumen fluid, did not change after ensiling, but gas production within 3 h and within 72 h decreased after ensiling. The acetic acid content and the proportion of ammonia-N in total N increased, and pH decreased, after 1 week of ensiling and did not show a clear trend from 1 to 8 weeks. The ADL and cellulose content of the lower part of the stem of both maize cultivars increased after fungal treatment and the hemicellulose content decreased except for the lower stem of MZP8057 treated with P. eryngii. The ratio of syringyl to guaiacyl compounds increased after fungal treatment. The gas production between 3 and 20 h and within 72 h decreased after fungal treatment. Both ensiling and fungal treatment cannot improve the degradability of the investigated maize stems.