The main difference between hay and silage is that the hay is grass cut and dried to use as animal fodder whereas silage is the fermented, green forage fodder stored in a silo. The moisture content of hay is not more than 12% while that in the silage is 40-60%.
Hay and silage are two types of crops used to feed livestock in winter as they are unable to graze the filed during this time period. Both crops are made up of grass. They can be considered as preservation methods of forage.
Key Areas Covered
1. What is Hay
– Definition, Facts, Processing
2. What is Silage
– Definition, Facts, Processing
3. What are the Similarities Between Hay and Silage
– Outline of Common Features
4. What is the Difference Between Hay and Silage
– Comparison of Key Differences
Key Terms
Fermentation, Grass, Hay, Microbes, Moisture Content, Silage 
What is Hay
Hay is a form of preserved forage made up of grass that has been mown and dried for use as fodder. Generally, the moisture content of fresh grass is around 80%. So, the dry matter (DM) value is 20% or less. The cut forage is subjected to drying in the fields itself to have a moisture level of 12%. Also, the DM value of grass becomes 88%. Finally, the hay is baled. The baled hay is heavy due to its less moisture content.
Figure 1: Baled Hay
However, baled hay is at a risk of heating and mold. Hay can be heated due to the continued metabolic activity, which is facilitated by the presence of water in it. This heat can become very high even to induce spontaneous combustion and barn fires.
What is Silage
Silage is the other form of preserved forage; it contains grass compacted and stored in airtight conditions in a silo without being dried first. In addition, grass, silage can be made of other green fodder as well. The wilted or fresh grass is packed, forming an anaerobic environment. On that account, the ensiling process allows the natural sugars of grass to be fermented by the activity of microbes. Fermentation of water-soluble carbohydrates results in organic acids such as lactic acid and acetic acid. As acids accumulate within the packed forage, the pH of the mixture drops until it becomes unfavorable for the growth of microbes. At this point, the forage is ready for storage. Generally, the process takes around 21 days to be completed. The bales are wrapped in plastic to prevent air from entering.
Figure 2: Silage
The moisture content of the silage should be 40-60%. Too wet silage may be subjected to spoilage and nutrient loss. Too dry silage is called haylage and its moisture content is 12-40%.
Similarities Between Hay and Silage
- Hay and silage are the preservation methods of forage.
- They are produced mainly from the grass.
- Both serve as fodder for livestock in the winter.
Difference Between Hay and Silage
Definition
Hay: Grass that has been mown and dried for use as fodder
Silage: Grass compacted and stored in airtight conditions in a silo without being dried first.
Moisture Content
Hay: 12%
Silage: 40-60%
DM Value
Hay: 82%
Silage: 40-60%
Preparation
Hay: Grass is cut and dried in the field
Silage: Grass is cut and tightly packed to induce microbial activity
Storage
Hay: As bale
Silage: Bales are covered with plastic wraps
Digestion
Hay: Not digested
Silage: Partially digested; easy to digest by the animal
Conclusion
Hay is the dried grass with a moisture content up to 12% while silage is the fermented grass with a moisture content up to 40-60%. Therefore, the main difference between hay and silage is the moisture content.
Reference:
1. “Hay, Haylage and Silage: What’s the Difference?” Horse Journals, 27 Oct. 2017, Available Here
Image Courtesy:
1. “Roundbale1” By I, Montanabw (CC BY-SA 3.0) via Commons Wikimedia
2. “Diets-Silage-Total-2753627″(CC0 Public Domain) via MAx Pixel
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