Silage inoculants for haylage: feasible?

Some authors define “haylage” as “… an alternative when weather conditions are not good enough for drying hay below 14 %...” (Kenney, 2001), “… a feed that is halfway between hay and silage (Saunders Comprehensive Veterinary Dictionary, 2007)” or “… ensiled forages, made up of grass, alfalfa and alfalfa- grass mixes (Wikipedia, 2008)”;
calendar icon 9 January 2009
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whereas “baleage”, also known as round bale silage, is “simply forage that is baled at a higher moisture content than dry hay and stored in sealed plastic wrap with 40 – 50 % DM” (Schroeder, 2004).

However, very often the terms are used indistinctly and there can be found affirmations like “round bale silage (a baleage) is also sometimes called haylage“. Mayer (1999) considered baleage, big bale haylage and round bale silage as different names given to the same preserved feedstuff. Both processes are anaerobic but the first one (haylage) is related to the DM content at ensiling; and the second one (baleage) is the procedure used to protect the material against spoiling (baling, wrapping). That is the reason why we fully agree with Schroeder (2004) when he writes “wrapped haylage bales”. Haylage may be preserved wrapped but also in other type of silos (bunker, trench, etc.).

Another controversial topic is the right DM content range for haylage. A review on this topic is shown in Figure 1.

The range varies from 35 to 60 % DM. Moreover, many companies produce haylage for horses and consider it as an especial feed type of wilted grass silage with 65 % DM.

For our purposes (use of silage inoculants in haylage for cattle) we will consider a range of 40 – 50 % DM, since below 40 % DM, it would be normal wilted silage, and over this range (55 % DM) the feed would be more adequate for horses due to the higher fiber content (see Figure 1) Two aspects are very important to be taken into account: a) the high DM content is out of the optimal values for LAB and b) the whole material, due to the high DM content, is difficult to compact.

The procedure for making haylage follows the same step as silage making, only the wilting lasts longer until reaching the desired DM content. The advantages of the use of haylage are given in the Figure 2.

The storage and harvest losses with different moisture contents are given in Figure 3. Note that the sum of losses at a level between 60 and 50 % of moisture (40- 50 % DM) are minimal, which represents a great advantage in the use of haylage.

While the stage of maturity increases, the crude protein (Figure 4a) decreases but the crude fiber (Figure 4b) content increases, which could be related with a lower feed intake and digestibility.

According to Pöllinger (2008), the quality parameters for haylage are not strictly enough determined. A major aim in haylage making should be a decrease in the pH value below 5, the best below 4.5 to diminish the risk of botulism (Kenney, 2001; Wright, 2001) and listeriosis (Ryser and Marth., 2007). Since the DM is higher compared with that in silages, the production of fermentation products will be lower. Common values for lactic and acetic acid contents in haylage would be from 15 to 50, and less than 20 g/ kg DM respectively. The butyric acid and ethanol are as undesirable as in the silages. Due to the commonly slower acidification, some amount of one/ both of these substances can appear.

The use of silage inoculants in haylages should fulfill the same role as in the silage: quicker and deeper acidification and/ or enlarged aerobic stability. It would improve animal performance. For example, Kent et al. (1988), found a tendency towards higher DM intake (20.4 vs. 18.1 kg/ day) of cows in early lactation fed treated haylage (alfalfa haylage of 45 % DM; P < 0.32). The use of inoculants decreased the pH value from 5.29 vs. 5.11 for the control and the treated haylage.

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