Submitted to: Forage Focus
Publication Type: Popular Publication
Publication Acceptance Date: 12/14/2020
Publication Date: 3/12/2021
Citation: Coblentz, W.K. 2021. Summary of fermentation trends in round-bale silages. Forage Focus. p. 17. March 2021.
Technical Abstract: Over the last eight years, approximately 10 different research trials with baled silages have been conducted at the University of Wisconsin Marshfield Agriculture Research Station. While these research efforts have evaluated a wide variety of management issues, such as different plastic formulations, number of layers of plastic wrap, storage time, wrapping delays, use of bale-cutting mechanisms, forage species, and aerobic stability, a collective look at the relationship between fermentation acids and bale moisture is instructive. For this purpose, the total fermentation acids within 243 bales were regressed against bale moisture. A couple of points are worthy of emphasis: i) despite the differing experimental goals and conditions within these studies, bale moisture explained about 70% of the variability in the data set; ii) concentrations of total fermentation acids are highly variable, particularly across studies; iii) fermentation acids increase with bale moisture; and iv) relatively little fermentation occurs when bale moisture is <45%. Among fermentation acids, lactic acid is the most desirable because it is the strongest fermentation acid produced, and therefore drives the pH of the silage lower (more acidic). The relationship between lactic acid and bale moisture closely resembles the pattern observed for total fermentation acids; however, concentrations of lactic acid may be quite low, or even undetected, when bale moisture is < 45%. Producers may wonder why wetter bales might not be a better management strategy, since fermentation is enhanced by moisture. There are several reasons why bales exceeding 55% moisture may be problematic. These include obvious bale weight and associated safety issues, but also baler design, where balers still generally handle dry forages better than wetter ones. However, the main reason why moisture recommendations for baled silages are lower (drier) than chopped silages is the potential for clostridial fermentations. Typical products produced in this secondary fermentation type are ammonia and butyric acid; however, significant losses of dry matter and reduced voluntary intakes also result. Field wilting is an often recommended approach for controlling problematic clostridial activity in silages generally, and it is particularly important for baled silages, which are more susceptible. It also is important to note that all bales made at <45% moisture were well preserved and suitable for feeding, but the primary mode of preservation and stability in those bales was elimination of air, which requires good plastic integrity throughout storage.