Silage is grass that has been conserved by fermentation. The grass is wrapped in plastic when the moisture content still exceeds 70%. Silage has a high protein content. The protein is partly broken down to ammonia, which burdens the liver and kidneys. It also disrupts the bacterial culture (intestinal flora) of the hind gut. In case you do choose to feed silage, use the same selection criteria as for hay:
- Coarse and stemmy
- Second or third cut
- High dry matter content
- Low in protein
- Low in non-structural carbohydrates.
The fermentation process converts a large portion of ESC and fructans. Further reduction of these WSC is not only unnecessary but also unwise. Chances are a secondary fermentation process will set in. This could lead to an increase of harmful bacteria.
When silage is made the old-fashioned way, grass is stored in a pit, in several layers on top of each other. This is called a ‘lasagna pit’. The different cuts of hay compensate for various nutritional values. Having silage analysed for NSC content is highly advisable. However, other types of roughage remain preferable over silage.
Haylage is baled in plastic when the moisture content of the grass is between 40% and 60%. Haylage therefor contains a higher dry matter percentage than silage. The grass has been given the opportunity to grow taller and which makes the protein content of haylage lower than of silage.
When making haylage, fermentation occurs like in the process of making silage, although to a lesser extent. The fermentation reduces the ESC and fructan levels compared to those in hay. Of course, for choosing haylage the same criteria apply as for selecting hay.
Silage and haylage may harbour a bacterium called Clostridium botulinum. This bacterium lives on the carcasses of small field animals and is dangerous for horses because it secretes a toxin that causes botulism. Especially in a high-protein and low-oxygen environment, such as silage or haylage, the bacterium thrives. Be sure to check for the presence of these animal carcasses.