Fermentative characteristics and in vitro gas production of Pennisetum purpureum hybrid grass silage as influenced by manure type and age at harvest

The nutritive quality of Pennisetum purpureum hybrid grass silage as influenced by manure types and age at harvest were evaluated by their fermentative characteristics and in vitro gas production. The study was a factorial arrangement in a randomized complete block design which comprised four manure types (cattle, poultry, swine, goat) and no manure (control) and two harvesting times (4 and 8 weeks after cutback (WAC)) with three replicates. Results showed that the mean pH (4.70) of silage made from grass fertilized with cattle manure was significantly (p<0.05) different from the value of 5.20 in silage of unfertilized grass at 4WAC. Lactic acid contents of the silage ranged from 4.32 % to 6.99 %, with silage made from swine manure fertilized grass being highest (p < 0.05). Crude protein (CP) contents of the silage ranged from 6.30 % in silage made from unfertilized grass at 8WAC to 9.10 % in silage from grasses that were fertilized with goat and poultry manures at 4WAC. Neutral detergent fibre (NDF) contents ranged from 54 % to 66 % in silage made from grass that was harvested at 8WAC having the highest (p < 0.05) NDF contents. The highest in vitro gas production of 43.33 ml/200mg DM was recorded in silage from grass that was harvested at 4 WAC and fertilized with cattle manure. The silage with highest in vitro dry matter digestibility (56.67 %) was from poultry manure fertilized grass harvested at 4WAC with lowest value (49.67 %) in silage from unfertilized grass, harvested at 8WAC. The study showed that the silage of Pennisetum purpureum hybrid grass fertilized with swine manure and harvested at 4 WAC have higher quality above other manure types as well as unfertilized grass harvested at later stage.Keywords: manures, digestibility, regrowth, Pennisetum purpureum, silag