EFFECT OF EXPOSURE ON THE CHEMICAL-COMPOSITION AND IN-VITRO DRY-MATTER DIGESTIBILITY OF UNTREATED AND FORMALIN TREATED GREEN CHOP

Green chop, made from babala (Pennisetum typhoides) and forage sorghum (Sorghum bicolor sudanense) which were each harvested from six different rows at the pre-bloom and bloom stages of maturity, were exposed to the environment with and without formalin treatment (4.9 +/- 0.8 g formaldehyde per 100 g crude protein) for a period of 21 +/- 3 h. This was done at laboratory scale in a room at 27 degrees C. These treatments were compared in a complete randomized design with each other and with a corresponding non-exposed fresh green chop treatment. Exposure without formalin treatment caused a significant increase (P < 0.05) in the acid detergent fibre (ADF) content (41.0 vs. 38.3%) and a concomitant decrease (P < 0.05) in the in vitro dry matter digestibility (IVDMD) (63.1 vs. 66.6%) when compared with the non-exposed fresh material. This was accompanied by an increase (P < 0.05) in the non-protein nitrogen (NPN) fraction (41.6 vs. 32.4%). Exposed material treated with formalin had a higher (P < 0.05) total dry mass (58.6 vs. 51.6 g) and a lower (P < 0.05) ADF content (39.2 vs. 41.0%) than exposed untreated material. The decrease in IVDMD caused by exposure was totally prevented by formalin treatment. The IVDMD of exposed formalin-treated material was 67.8% in comparison with 63.1% (P < 0.05) and 66.6%, respectively, for the exposed untreated and the nonexposed fresh material. The NPN contents for exposed material being treated and untreated were the same (40.5 vs. 41.6%) while the nitrogen fraction appearing in ADF was higher (P < 0.05) for formalin-treated material (22.1 vs. 12.8%). It is concluded that the exposure of green chop led to some deterioration of forage quality, which was largely prevented by formalin treatment.