Graduate Thesis Or Dissertation


The effect of various additives on nutritive value of ryegrass straw silage Public Deposited

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  • Observations were made on silage pH, chemical composition and 24hr in vitro dry matter digestion (IVDMD) to evaluate effects of various additives ensiled with annual ryegrass straw. Additives were compared in factorial designed trials utilizing .95 1 glass jar silos. Selection of additives used in each subsequent trial was based on results of preceding trials and then combined with other additives. All additives were used as a percent of straw on a dry matter basis and incorporated with water to give 22% dry matter in silages. Adding 4. 5% NaOH:KOH allowed greater (P<. 01) silage IVDMD than .5 g cellulase while this gave more (P<. 01) IVDMD than straw ensiled with water. Including 10% and 20% molasses lowered (P<. 01) silage pH to more desirable levels, with or without the other additives. Using 20% molasses resulted in more favorable silage aspects and the lowest (P <. 01) acid detergent fiber (ADF), acid detergent lignin (ADL) and cell wall constituents (CWC) for the silage. Adding 1% urea to silage having 20% molasses or 4. 5% hydroxide and 20% molasses increased (P<. 01) crude protein content and IVDMD. Adding 1.2% biuret to these silages raised (P<. 01) crude protein but did not affect IVDMD. Including . 1% elemental sulfur raised (P< 01) silage pH and a strong sulfur odor was present. Some spoilage occurred when sulfur was added to hydrooxide- treated ensilage and was more evident in material containing urea. Reduced (P<. 01) ADF and CWC values were observed in hydroxide silage having sulfur-biuret additives. Silage with 20% molasses and 1% urea had a lower (P<. 01) pH at 40 days than at 20 days ensilation. Adding .5% limestone lowered (P< . 01) pH further and improved (P<. 01) IVDMD at 40 days ensilation. Ensilage having 4. 5% hydroxide and the same molasses and urea additives resulted in a more elevated (P<. 01) p11 at 40 days. The addition of limestone to these additives lowered (P<. 01) silage pH while IVDMD was unaltered. Using . 5% formic acid in these silages lowered (P<. 01) pH while not affecting IVDMD. All silages had less (P<. 01) residual ash at 40 days than at 20 days ensilation. Ensiling straw with 20% molasses, 1% urea and . 5% limestone gave lower (P<. 01) pH values than for hydroxide-treated silage having the other additives at 0, 2, 4, 8, 16, 32 and 64 days ensilation. Decreased (P<. 01) ADF and CWC and increased (P<. 01) ADL values occurred in treated silage several days earlier (P<. 01) than untreated ensilage. Less (P<. 01) residual ash remained in either type silage after 32 days ensiling. Formation of organic acids during the 0-64 days ensiling by hydroxide-treated material gave peak (P<. 01) lactic acid at 16 days then dropped (P< 01) while acetic plateaued (P<. 01) at 16 days and butyric rose (P<. 01) sharply after 16 days. In contrast, untreated silage had a steady rise (P<. 01) of lactic to 64 days, acetic peaked (P<. 01) at 32 days, while butyric rose (P<. 01) at 8 days and declined at 32 days. Propionic acid was not detectable in untreated after 2 days ensilation while rises (P<. 01) occurred at 2 and 32 days in treated material. IVDMD was higher (P<. 01) with 2-64 day substrate from treated silage while digestion for untreated was increased after substrate had been ensiled for 32 days. In vitro rumen liquor following 24 hr fermentation of hydroxide-treated silage allowed greater (P<. 01) concentrations of acetate and butyrate than untreated silage while numerical differences for propionate were not significant. Lambs consumed more (P<. 05) dry matter and nitrogen from silage prepared in plastic barrels with 4.5% NaOH:KOH, 20% molasses, 1% urea and .5% limestone as compared to ensilage having these additives except hydroxide. Material ensiled with hydroxide resulted in higher (P<. 05) digestibility of dry and organic matter, ADF, ADL, CWC and crude protein. Also more (P<. 05) nitrogen was retained while urine volume and density was greater numerically. Rumen fluid of these lambs contained more (P<.05) acetic and propionic acids while butyric acid and C₂:C₃ ratio were not significantly different. Body weight gains during a 98 day trial were similar in heifers fed ryegrass silage, or straw ensiled with the molasses, urea, limestone and hydroxide additives, or the same straw silage without hydroxide when animals each received . 9 kg barleycottonseed meal supplement daily. Supplementing these silages with an equal amount of fat-molasses-urea mixture reduced (P<.05) gains and silage intake was depressed. An additional daily .9 kg grain supplement during the final 38 days of the trial stimulated intake of either type straw silage while consumption of ryegrass ensilage was lowered. Animals consumed the straw silage having hydroxide more readily than the untreated straw ensilage throughout the trial. Dry matter of these silages were 37 and 40%, respectively, and little spoilage was evident following 60 days ensilation in plastic lined trench silos.
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