Dr. Bill Weiss, Professor and Extension Dairy Specialist, The Ohio State University
If your cows are stranded in the middle of a desert, water may indeed be priceless; however, in most of the U.S., the water contained in feed has essentially no economic value, even though water is the most critical nutrient for milk production. We formulate diets on a dry matter (DM) basis because we assume cows can consume all the drinking water they need; we do not have to feed it. The economic value of feeds is derived from the amount of energy, protein, fiber, etc. in the feed. When pricing feeds, water is considered a diluent of nutrients and the higher the moisture concentration, the less you should pay for a particular feed on an as-fed basis. Two silages with identical nutrient composition on a DM basis have different dollar values on an as-fed basis if their DM concentrations differ. When buying or selling feeds, the DM concentration must be considered when deriving a price. For most concentrates, the DM does not vary greatly and can be ignored when pricing. For wet concentrates, such as wet brewers and wet distillers, DM should be considered when pricing. The DM concentration of hay can be variable, but generally, if hay is ‘wet’ it should not be purchased since it likely will spoil and have no economic value. If hay is baled at DM concentrations that results in a stable product, the variation in DM is not enough to greatly affect the price. Silage and balage vary greatly in DM concentration (ranges exceeding 30 percentage units of DM are not uncommon) and this variation will affect the economic value of the feed substantially.
To price wet feeds follow these steps:
The buyer and seller have to agree on a price on a 100% DM basis. This can be done using a program such as SESAME (see accompanying article on Nutrient Costs) or it can be done by using market prices of similar feeds. If you are considering buying wet distillers grains, you could use dried distiller grain prices. If you are buying haycrop silage or balage, you could use hay prices (make sure nutrient composition is similar).
- If using similar dry feeds to price the wet feed, convert market price of similar feeds to 100% DM basis: When using a dry concentrate: DM price = As-fed price/0.9; When using hay: DM price = As-fed price/0.85.
- Obtain an accurate value for the DM concentration of the feed of interest (see below).
- Convert the DM price to as-fed price for the feed of interest: DM price X (DM %/100) = As-fed price.
Dried distillers grains sell for $240/ton and wet distillers is 27% DM.
DM price/ton of dried distillers = 240/0.9 = $267/ton of DM.
Comparative price of wet distillers: 267 x 0.27 = $72/ton of as-fed wet distillers grains (this is the maximum value).
Alfalfa hay sells for $340/ton and a truckload of comparable balage has an average DM of 52%.
DM price/ton of hay = 340/0.85 = $400/ton of DM.
Comparative price for balage = 400 x 0.52 = $208/ton of as-fed balage (this is the maximum value).
In many cases, additional price discounts have to be applied to wet feed. Wet feeds are generally less stable than dry feed and undergo greater shrink or storage losses. If you are buying wet feed and will be storing it, then you should assume that you will lose about 10% of the feed to shrink and that should be considered in the price.
Moisture does not only dilute nutrients, it also is a good indicator of forage stability and overall quality. Silage or balage that is too wet (< 28% DM) may undergo a clostridial fermentation and have substantially less value than a well fermented silage. Silage or balage that was stored too dry (> 40% for a bunker silo and > 60% for balage) can suffer heat damage, which reduces energy and protein digestibility and it often becomes moldy. Moldy, heat-damaged silage has little economic or nutritional value. Corn silage that is too dry (greater than about 40% DM) has those problems plus the digestibility of the starch in the kernel is also usually reduced compared to normal corn silage. Be cautious when buying silages that are outside the acceptable range in DM concentrations; simply accounting for dilution may not adequately value the feeds.
Measuring Dry Matter of Feeds:
Because price depends so much on DM, you must obtain enough samples to get an accurate estimate of the DM concentration of the feed. If you a buying (or selling) chopped plants that are being put into a silo, we think you need to sample at least 4 truck (or wagon) loads (spread across the entire day) to get an accurate estimate of DM. Take 10 or more handful samples from each load (spread across the load) and place in a bucket, thoroughly mix the material and then take a subsample (smaller than a volleyball, larger than a softball). This process should be repeated for each load. Ideally, the 4 load samples should be assayed for DM (either by a lab or use of an accurate on-farm method) and then the average DM would be used to price the silage. Over compositing the sample (e.g., turning the 4 load samples into 1 sample) can increase sampling error and result in inaccurate values.
Bale to bale differences in DM can be substantial for balage. We think you need core samples from at least 10 bales to obtain an accurate average value for DM. The 10 core samples should be thoroughly mixed in a bucket and the entire sample sent to the lab or assayed on-farm for DM.