|Akins, Matthew - University Of Wisconsin|
Submitted to: Journal of Dairy Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/26/2017
Publication Date: 4/20/2018
Citation: Coblentz, W.K., Akins, M.S. 2018. Recent advances and future technologies for baled silages. Journal of Dairy Science. 101:4076-4092.
Interpretive Summary: The use of stretch polyethylene film to preserve baled silages has increased in popularity during the last two decades, especially with small and mid-sized dairy or beef producers. In this article, we review recent research that will help producers understand the unique properties, and improve the quality, of baled silages. Most core principles for making high-quality precision-chopped silages also apply to baled silages; among these, the exclusion of air (oxygen) and subsequently maintaining anaerobic conditions within the wrapped bale or other silo types is a management priority. While most core management principles are the same for baled and precision-chopped silages, a major difference between silage types is the slower and less-extensive fermentation of baled silages. This difference occurs for a number of reasons that include: i) a lower recommended moisture concentration (45 to 55%); ii) the long-stemmed nature of baled forages that restricts plant sugars from contacting lactic-acid-producing bacteria; and iii) generally lower densities in baled silages compared to well-packed chopped silages. To date, research evaluating inoculants and/or other additives designed to improve aerobic stability or the fermentation of particularly problematic forages has been limited, but should not be discontinued. Development of plastic wraps embedded with an oxygen-limiting barrier have yielded mixed results, with most differences between these novel plastic formulations and reputable commercial products related to more desirable counts of yeasts and molds at the surface layer, rather than improved fermentation or nutritive value on a whole-bale basis. Baled silages can be produced successfully by adhering to straightforward management principles, where the exclusion of oxygen is the highest priority. As such, this form of silage production is likely to remain popular for the foreseeable future.
Technical Abstract: Although the concept of ensiling large-round or large-square bales dates back to the late 1970’s, there have been many refinements to both equipment and management since that time, resulting in much greater acceptance by small or mid-sized dairy or beef producers. There are several reasons this silage preservation technique is attractive to producers, but the primary advantage is a reduced risk of weather damage to valuable forage crops compared to preservation as dry hay. Most core principles for making high-quality precision-chopped silages also apply to baled silages; among these, establishing and subsequently maintaining anaerobiosis are priorities. For baled silages, these priorities are critical, in part because recommended moisture concentrations (45 to 55%) are drier, and particle-length is much longer. These factors act to restrict the rate and extent of silage fermentation, often resulting in less production of desirable fermentation acids and a greater (less-acidic) final pH. Within this context, preservation of baled silages can be improved by applying polyethylene (PE) film wraps promptly, using an appropriate number of PE film layers (6 to 8), selecting a storage site free of sharp objects or other debris, and by monitoring wrapped bales closely for evidence of puncture, particularly by birds or vermin. Under certain conditions, such as those in which the bale moisture of highly buffered forages exceeds the recommended range, the heterogeneous nature of baled silages coupled with a restricted rate and extent of fermentation may increase susceptibility to clostridial activity compared to precision-chopped forages ensiled at comparable moisture concentrations. To date, research evaluating inoculants and/or other additives designed to improve the fermentation of challenging forages or aerobic stability has been limited, but should be discontinued. Development of PE film embedded with an oxygen-limiting barrier has yielded positive results in some trials; however, most differences between these novel formulations and reputable commercial PE film have been related to decreases in yeast and mold counts at the surface layer. Related assessments of fermentation or nutritive value determined on a whole-bale basis have been less conclusive. Baled silages can be produced successfully by adhering to straightforward management principles; as such, this form of silage production is likely to remain popular for the foreseeable future.