Richard Ehrhardt, Michigan State University Extension Specialist, Small Ruminants
(Previously published on MSU Extension, Sheep & Goat: May 20, 2015)
Forms of silage
There are primarily two types of silage products fed to sheep: baled silage and precision-cut silage. Baled silage is simply large bales, round or square, baled when the forage is wilted and covered with stretch wrap plastic. As previously mentioned in Silage – Part 1, this means waiting much less than dry hay, only until the forage is around 40-60 percent moisture – under ideal drying conditions, this is often means cutting in the morning and baling at night. Silage makes it possible.
Precision-cut silage is forage chopped after wilting and stored either in plastic bags, covered bunks, or upright silos. Each has its pros and cons, with the choice of system depending largely on the cost of harvest and storage equipment relative to the farm income generation capacity (number of ewes, ewe productivity, farm size, etc.). In general, precision-cut silage is better suited to larger farms, as it requires larger and usually more expensive harvest and storage equipment. Baled silage is generally suited for smaller farms or for those wishing to market silage over longer distances. Both can be high quality products if made correctly. Precision-cut silage has advantages in feed mixing, as it is typically cut much shorter than baled silage, making it easier to mix with other silages or ingredients to create a total mixed ration. Baled silage can either be fed whole just like large round dry hay bales, split into sections with a bale slicer (what I use on my farm), or simply unrolled. All silage requires heavier handling equipment than dry hay, however, because of its extra water weight.
How many sheep do you need to feed silage?
An important consideration in feeding silage is to make sure it is fed before it spoils. Silage does have a limited shelf life after exposure to air, so it is critical to consume it quickly enough to prevent spoilage. Spoilage is first noted as heat production. Silage that has just started to heat is usually fine, but as it continues to rise in temperature it rapidly starts to mold and deteriorate, producing potentially poisonous end products. Cow dairy farmers would scoff at the notion of feeding silage that is not super fresh, since they see a drop in intake, and therefore milk production, with less than fresh silage. In sheep production, we can afford to be a little more forgiving, because the intake losses are not as dire for performance. However, we do not want spoilage. So there is a line to differentiate between these two situations. The time it takes silage to heat is a function of environmental temperature and air exposure. In broad and general terms, in temperatures less than 40 degrees Fahrenheit, silage may keep for four – five days before significant heating occurs, whereas at greater than 70 F it may start to heat after only 12 hours of air exposure. A good general rule would be four days of feeding for cold weather (less than 40 F) and two days for warm weather with intermediate temperatures in the three-day range.
A single bale of baled silage (4 feet by 4 feet) at 50 percent moisture may contain up to 600 pound of forage dry matter. Adult ewes commonly consume forage at 3 percent of their body weight, so it would take 20,000 pounds of ewe (600/0.03) to eat a bale in a single day and 5000 pounds to eat a bale in four days. If your ewes average 166 pounds, then it would take approximately 30 ewes to consume a bale before significant spoilage occurs in winter (all silage consumed in four days). In summer, a less common feeding time, you would need 60 ewes to minimize spoilage in the same scenario. Using the rationale described here, you can adjust these figures for your particular situation (size of animal, moisture content of silage, time of year fed) to determine if you have the minimum number of sheep to keep spoilage at bay.
Health concerns when feeding silage
It is important to understand the risks associated with feeding silage. Fortunately, most of the risk can be controlled at harvest with proper management. The greatest risk is presented by a common bacteria found in soil called Listeria monocytogenes, which can cause a disease known as listeriosis (a.k.a. “circling disease”). Unfortunately, sheep and goats are more prone to listeriosis relative to cattle, so silage quality is critical in disease prevention. As a result, it is important to minimize the amount of soil that is mixed with the forage, since most mistakes occurring either with procedures such as excessive tedding of forage during the drying process or baling during excessively muddy conditions. A more overt problem is the huge mistake of making a silage pile on the ground instead of on plastic or concrete. Additionally, it is also critical to ensure a good fermentation to prevent proliferation of any Listeria present and to also ensure the best possible silage product. Keys to good fermentation revolve around the exclusion of air during processing and storage: high density silage (dense bales for baled silage, dense packing for precision-cut silage), adequate moisture (less than 40 percent for all silage), air-tight storage (6 layers of stretch wrap plastic minimum for balage, tight impervious cover for precision cut), and protection of plastic from damage during storage. When soil content is minimized and good fermentation conditions are met, listeriosis is rare, and the risk is far lower than the reward of much higher quality forage.
This harvest system is an efficient 2-person program. This system allows capture of high quality forage during the relatively short growing season found in the Upper Peninsula. The quality of forage on this farm (grass, trefoil, clover mix) rivals that of alfalfa-based forage harvested in top dairy programs in more southern climes of Michigan, and is a great feeding option in a grain-poor climate.
What follows are the pros and cons of silage as compared to dry hay:
Advantages of feeding silage:
- Faster forage preservation process
- Greatly enhanced control of cutting date
- More tons harvested during tight harvest windows
- Flexible harvest – can fit into tight time schedules better
- High-quality forage
- Lower loss at harvest, storage and feeding
- Inexpensive storage – can leave outdoors since it is covered
- Huge variety of crops can be harvested
- Wider seasonal harvest window (can harvest early spring or late fall crops)
Disadvantages of feeding silage:
- Greater risk of listeriosis
- Greater equipment cost
- Heavier and more specialized handling equipment
- Heavier and more specialized baler
- Bale wrapping equipment (possible to rent or share)
- Plastic cost
- $6-12 per ton of forage dry matter
- Cost of handling, disposal/recycling