THE EFFECT OF A PROPIONIC-ACID BACTERIAL INOCULANT APPLIED AT ENSILING, WITH OR WITHOUT LACTIC-ACID BACTERIA, ON THE AEROBIC STABILITY OF PEARL-MILLET AND MAIZE SILAGES

The effect of applying a new strain of Propionibacterium shermanii (PS ), alone or with lactic acid bacteria inoculants (LAB) at ensiling, on the aerobic stability of pearl millet and maize silages was studied u nder laboratory conditions. The LAB inoculants comprised of Pediococcu s pentosaceus (PP) in the experiments with millet, and PP + Lactobacil lus plantarum (LP) in various combinations in the experiments with mai ze. The inoculants (made by Lallemand, France) were applied each at 0. 5 x 10(6) cfu g(-1). Silages with no additives served as controls. The pearl millet used was either fresh, or wilted for 2 or 4 d (at 201, 2 68 and 448 g DM kg(-1), respectively). There were two experiments with maize (at 401 and 353 g DM kg(-1)). After treatment, the chopped fora ges were ensiled in 1.5-1 anaerobic jars. Three jars per treatment wer e sampled on days 2, 5, 10 and 90. At the end of the experiments, the silages were subjected to an aerobic stability test lasting 6 d, in wh ich CO2 production was measured along with chemical and microbiologica l parameters, to evaluate aerobic deterioration. The PS inoculant resu lted in improvement in the aerobic stability as compared with the cont rol, only in the fresh and 2-d wilted pearl millet silages. The amount s of CO, (g kg(-1) DM) produced were 8.5 +/- 7.7 and 6.8 +/- 1.1 vs 18 .8 +/- 22.7 and 27.0 +/- 18.5 in the PS treated and control of the fre sh and 2-d-wilted pearl millet, respectively. All silages of the Cd-wi lted millet were stable upon aerobic exposure. In the first maize expe riment the PS treatment and the control were more stable than the LAB inoculated silages. In the second experiment with maize, none of the s ilages were stable upon aerobic exposure; they showed increased pH val ues and CO2 production around 20 g kg(-1) DM. The propionic acid bacte ria inoculant had only a marginal effect on the aerobic stability of t he pearl millet and maize silages, probably because it could not susta in under silage conditions.