Effects of forage length and bale chamber pressure on pearl millet silage

Pearl millet [Pennisetum americanum (L.) Leeke] is an annual warm season (C4) grass that has a high yield potential during summers when cool season species are heat-stressed and unproductive. In two field trials, 650 kg round bales were made from long (>100 cm) or short (chopped) (≈15 cm) forage and at bale chamber pressures of 421 or 842 × 10³ Pa. After 24 h of wilting, forage moisture concentrations at Trial 1 and Trial 2 were 771 and 583 g kg^-1, respectively. The higher baling pressure increased both mass and density of bales (P < 0.05). Length of cut had no effect on bale weight or density. Core temperatures were lower in higher density bales when the concentration of forage moisture was lower. Water-soluble carbohydrate concentrations were lower in silages made from the shorter forages (P = 0.013). Nutritive value of silage decreased during 8 mo of storage regardless of treatment. Baling chamber pressure and forage chopping treatments did not affect neutral detergent fiber (NDF) or in vitro dry matter digestibility (IVDMD) of post-storage silage. Acidity of silage ranged from pH 4.13 to 5.31. Lactic acid concentrations were lowest in silage in Trial 1 made from the wetter forage (771 g kg^-1) when chopped to 100 cm. Listeria was present in bales made from the wetter forage. Clostridium botulinum was detected in silage made from chopped forage when baled at low chamber pressure.