Silage: A Vet’s Point Of View

As summer finally approaches after such a long wet winter, everyone’s thoughts turn to silage!  If silage is to form the basis of the diet, it’s vital that it’s of good quality since good nutrition underpins everything else – a well-fed herd is usually a healthy herd (or flock).

Silage: The Good, The Bad & The Ugly

As vets, we see a lot of silage on our travels, ranging from the very good, to the very bad, to the downright ugly.  We don’t tend to get involved in silage-making, but it does have a big impact on our work for the rest of the year, whether because of DAs due to inadequate intakes, ‘silage eye’ due to listeria contamination or milk fevers due to dry cows being fed on high potassium grass silage.

Carolyn’s Top 10 Clamp Silage Tips

Here are my ‘top ten clamp silage tips’, based on things we see commonly.  Some will also apply to big bale silage:

1. Take care at harvest – soil contamination can introduce clostridial bacteria into the silage. We’ve seen nasty blackleg outbreaks from silage that was heavily contaminated with soil due to flooding before a cut.
2. Don’t cut corners on consolidating the clamp or making it airtight. If air is allowed in, the silage will spoil, nutrients will be lost and palatability will suffer.  If you can easily push a thumb into the face, it probably isn’t compacted enough.
3. Avoid using tyres as ballast if possible, due to the risk of traumatic reticuloperitonitis (tyre wire disease).
4. Silage analysis is invaluable in predicting the nutrient and fermentative quality, but don’t over-rely on it. If samples are taken too early or incorrectly, DM and other calculations can be misleading and may have serious consequences for feeding. Especially don’t rely on just one analysis – characteristics will vary within a clamp.
5. Remove silage evenly and with clean, tidy cuts. Faces that have broken up as silage has been removed will have had air introduced deeper in, and will be more likely to suffer spoilage and reduced feeding value.  Even with a tidy face, it should take no longer than 3-5 days to go across it (even less for maize in summer conditions). After this, there will be excessive secondary fermentation and substantial nutrient losses.
6. If it doesn’t look, smell and feel good, it probably isn’t good. Very dark or black silage, indicating marked secondary fermentation, shouldn’t be fed. A vomit-like smell or a slimy feel indicates butyric fermentation and poor palatability and nutrient quality.
7. There are some unwanted organisms that grow well in poorly fermented silage, including moulds, clostridial bacteria and listeria. Visibly mouldy silage is obviously spoiled and should not be fed to animals, particularly if they are pregnant or lactating (moulds can cause abortions and milk drop, among other things).  Neither clostridial bacteria nor listeria can be seen with the naked eye, but both cause serious diseases.
8. The way you feed it is just as important as how you make it. Completely clear away leftovers before new silage is fed, rather than leaving them to rot at the bottom of the trough.  We’ve seen animals die from eating hot, black silage from troughs that were rarely cleaned out.
9. The chop length for grass silage to provide sufficient rumen ‘scratch factor’ must be less than 8cm (ideally 2-4cm). Any longer and cows will sort the ration. Watch out for cows making deep holes in silage as they eat – this can indicate sorting, or poor palatability as they search for something tastier further down.
10. Keep it free of rubbish – cattle can easily eat plastic or string along with silage. Keep it free of vermin, too.  There have been instances of badgers burrowing into the back of a clamp and setting up home – not what you want!