Submitted to: International Grasslands Congress
Publication Type: Abstract only
Publication Acceptance Date: 2/11/2005
Publication Date: 6/26/2005
Citation: Muck, R.E., Holmes, B.J. 2005. Factors affecting bag silo densities and losses. In: O'Mara, F.P., Wilkins, R.J., 't Mannetje, L., Lovett, D.K., Rogers, P.A.M., Boland, T.M., editors. XX International Grassland Congress: Offered Papers, XX International Grassland Congress, June 26 - July 1, 2005, Dublin, Ireland. p. 480. Interpretive Summary:
Technical Abstract: Our objective was to measure densities and losses in bag silos at three farms, looking for causes of variation in both. All bag silos made on these farms over the course of two years were monitored at filling and emptying. All loads of forage entering the bags were weighed and sampled. Average density was calculated based on bag length and nominal bag diameter. At emptying, the weight of all silage removed from a bag was recorded. Any spoiled silage not fed was weighed, sampled and specifically identified on the emptying log. A grab sample from the face of each silo was taken periodically, one per filling load. Over two years, 47 bag silos were made at the three farms, 23 of alfalfa, 23 of corn and 1 of red clover. Density ranged from 160 to 280 kg dry matter (DM)/m^3. Density increased as DM content increased. The operator and how the bagging machine was set were important factors affecting density. The same bagging machine was used at the Arlington (Arl) and West Madison (WM) farms, and Arl consistently got higher densities. The Prairie du Sac (PDS) farm had higher densities the second year after training from a manufacturer's representative. Density declined with longer particle size. Kernel processing in corn silage reduced density at PDS where there was a planned comparison. Dry matter losses were measured on 39 of the bag silos and ranged from 0 to 40%. Average DM losses were 9.2% invisible plus uncollected losses and 5.4% spoilage losses for a total loss of 14.6%. Six silos had excessive spoilage losses (>15%) due to damaged plastic or overly dry silage (>40% DM) being fed out in warm weather. In contrast, 11 silos had no spoiled silage, and 15 bags had less than 5% spoilage loss, representing bags with spoilage largely at the ends. Invisible losses were reduced in high porosity silages (where spoilage losses were exacerbated), greater in warm weather, and affected by emptying procedures (reduced at WM where bag silos were emptied in 2 to 3 one-day periods as opposed to daily removal for cattle at PDS and Arl). Spoilage losses in bags without damaged plastic were greater in dry, porous silages, from emptying silos in warm weather, and at lower feed out rates. Both invisible and spoilage losses were not affected by crop or bagging machine. These results indicate that low DM losses (<10%) are regularly achievable in bag silos. However, deviations from good management (harvesting between 30 and 40% DM, operating the bagging machine to get a smooth bag of high density, monitoring routinely for and patching holes, and feeding out at a minimum of 300 mm/d) can result in substantial (>25%) losses. Because higher losses occur during warm weather, silage from the best preserved bags should be reserved for summer use.