Forage conservation in the wet/dry tropics for small landholder farmers

  • Christopher Sean Regan

    Student thesis: Masters by Research - CDU


    This study investigates the use of 200 L steel drums, 120 L plastic drums and small round bales (800 mm lond x 450 mm diameter) wrapped in plastic film as silos when making silage from tropical legumes, (cavalcade, Cen'rosema pascuorum, and calopo, Calopogoniurn mucunoides), and tropical grasses (pangola, Digitaria eriantha, and elephant grass, Pennisetum purpureum). Using the above herbages silages were made at various DM contents and without additives.

    In addition, the nutritive value (and for silages, fermentation quality) of silages and hays made from cavalcade legume and pangola grass were compared. Nutritive value was assessed from measures of Dry Matter (DM) content, Digestibility (DDM), Energy content (Gross Energy, GE, and Metabolisable Energy, ME), andNitrogen content (total N, and Crude Protein, CP). The fermentation quality was assessed by the pH and by the relative proportions of lactic, acetic and butyric acids in the silages. Ammonia-N content was also determined for baled silages.

    Silage production from high DM forage in both steel and plastic drums was successful but dominant fermentation products varied. Wilted cavalcade legume and wilted pangola grass produced lactic acid dominant fermentations with minor acetic and zero butyric acid concentrations. Acetic acid dominated in wilted calopo silages preserved in plastic drums. Low DM elephant grass ensiled in plastic drums fermented poorly to produce high acetic, lower butyric, and zero lactic acid silages typical of a clostridial fermentation.

    Plastic drum silos had lower spoilage (p <0.01) than steel drum silos and were not affected by silage acids, whereas after three years of annual use steel drums were no longer suitable as silos due to corrosion.

    Small bales of lacerated cavalcade legume formed good quality silages which had dominant lactic, low acetic, minor butyric acid contents with low ammonia-N production (<5% total N) and low spoilage (11.5 ± 4.03%). Bales of unchopped pangola grass had ethanol dominant fermentations in which lactic acid content wasgreater than acetic acid, butyric acid production was minor, ammonia-N production <5% total N, and low spoilage (2.82 + 0.75%).

    The nutritive value of cavalcade legume and pangola grass pastures were low, and further reduced in both hays and silages (p <0.01). The silages were higher nutritive value than hays (p <0.01).

    Representative nutritive values for i) cavalcade legume and ii) pangola grass pasture v silage v hay were i) DM: 233, 553, 922 g kg-1 , DDM: 551, 527, 425 g kg -1DM, ME: 8.2, 7.7, 6.1 MJ kg-1DM, CP: 204, 161, 131 g kg-1DM, ii) DM: 221, 545, 920 g kg-1, DDM: 600, 578, 488 g kg-1DM , ME: 9.0, 8.5, 7.1 MJ kg-1DM, CP: 130, 110, 100 g kg-1DM.

    Nutritive values for bales of both silages and hays were maintained over a 7 month storage period. Silage fermentation and nutritive values were unaffected by silo storage location (inside / protected from weather v outside / unprotected from weather).

    In both species lower DM silages had higher ammonia-N contents. There was no significant relationship between bale bulk density and fermentation quality.

    It was concluded that i) good quality silage can be made from wilted tropical forage ensiled without additives, ii) cavalcade legume and pangola grass silages have higher nutritive values than hays made from the same pastures harvested at the same growth stage, iii) small bales wrapped in plastic film are more cost effective ($ kg-1DM) forsilage production than either 120 L plastic or 200 L steel drum silos, iv) small bale silage production has good potential as a wet season fodder conservation management strategy for small landholder farmers in tropical areas.
    Date of AwardAug 1997
    Original languageEnglish
    SupervisorJim Luong-Van (Supervisor) & David Parry (Supervisor)

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