MOISTURE by Mike Mehren Ph.D.

Moisture
BY MIKE MEHREN

The moisture in a feed seems to cause confusion at times, yet is very important when you compare feed, store it, harvest it, or buy it. Hopefully this column will provide you with a couple of pointers that improves your appreciation of its importance.

Moisture and dry matter always equal 100%. Therefore if a feed is 90% dry matter it has 10% moisture. Lush spring grass may have 18% dry matter, so its moisture is 82%. One that fools a lot of people is the moisture content of molasses. Beet molasses is 78% dry matter and 22% moisture, while cane molasses is 75% dry matter and 25% moisture. The dry matter in molasses is referred to as solids. Compare the dry matter of
either kind of molasses with a liquid supplement and you will find that the supplements generally have 65% moisture and 35% dry matter. This is because the liquid supplements have other kinds of carriers such as condensed solubles, lignin sulfonate, corn steep liquor, and yes, even water. Tub supplements also vary in their moisture content. Some are ‘cooked’ so that the moisture is quite low; approximately 5%. Other tubs are cured chemically, so the moisture content is higher; about 30-35%.

Let’s compare the moisture and value of two types of corn silage. One is corn cannery waste silage having a moisture content of 80%, while the other is field corn silage with a moisture content of 72%. The difference in moisture is not 8%! Corn cannery silage has 20% dry matter, so a ton of corn cannery silage has 400 lb of dry matter (2000 x 20%). A ton of corn silage has 28% dry matter, so there are 560 lb of dry matter (2000 x 28%). Corn cannery silage actually has 71% as much dry matter as field corn silage. Now lets do a cost comparison. Corn cannery silage is offered to you at $18.00/ton and corn silage is offered at $28.00/ton. Which is the better buy? The best way to compare these is to calculate the cost/lb of dry matter.

Corn cannery silage: 400 lb dry matter costs $18.00, so 1 lb of dry matter costs $.045 ($18 divided by 400).
Field corn silage: 560 lb dry matter costs $28.00, so 1 lb of dry matter costs $.05 ($28 divided by 560). In this instance, the corn cannery silage is a little better buy. You may want to take this calculation quite a bit further. A free-standing stack of corn cannery silage will shrink (or lose moisture) by abut 40%. If you buy 1000 tons you will have 600 tons available to feed. You will see this shrink as a river of moisture that runs out of the bottom of the pile. On the other hand, if you put the field corn silage into the same free-standing pile, it will only shrink by about 30%. By free-standing I mean that there is a cement slab, and possibly one cement side. Free-standing stacks aren’t usually covered with black plastic like those in a pit or trench. Covering the stack would make a huge difference in the amount of spoilage, and is definitely worthwhile. These differences in shrink can easily change the value of the two silages being compared. A calculation would show:

Corn silage, 1000 tons bought @ $28.00. 700 tons available to feed (1000 x 70%)
$28000 spent for 700 tons=$40/ton of silage at 28% dry matter ($28000 ÷700 tons). Cost/lb of dry matter available to feed = $.07. ($28000 ÷ 1,400,000 lb = .02 ÷ 28%= $.07/lb dry matter).

Corn cannery silage, 1000 tons bought @ $18.00. 600 tons available to feed (1000 x 60%). $18000 spent for 600 tons = $30/ton of silage at 20% dry matter. Cost/lb of dry matter available to feed = $ .075. ($18000÷1,200,000 = $.015 ÷ .20 = $.075 lb/dry matter). In this example we find that the field corn silage is a little better buy due to the difference in shrink (or loss) that occurs when it ferments.

The shrink mentioned has a significant impact on the amount of silage that you buy or put up. For instance, if you were going to feed 1000 calves an average of 50 lb/head/day of field corn silage for 100 days, this totals (1000 x 50 x 100 ÷ 2000 lb) = 2500 tons of silage. If you put 2500 tons of silage into your pit and it shrinks by 20%, you will only have 2000 tons available to feed (2500 ton x 80% = 2000 ton). You will run out of silage in 80 days and have to figure out what and how much feed will be needed for the last 20 days that the calves are in the lot. This gets kind of dicey when it occurs in the early spring when prices are high and feed is in short supply.

Moisture also plays a huge role in feed spoilage. I ran into a situation where silage was taken out of the pit on one day and fed over the next three days. The calves ate the silage fine the first day, feed intake went down on the second day, and really plummeted by the third day. The silage begins spoiling the minute it is removed from the pit. While in the pit there is no oxygen present. On day one there was no noticeable spoilage, but by the third day, the calves definitely detected objectionable smell and flavor.

When comparing feeds with different moisture, make certain you are comparing the same kind of feed. This means it has equal nutritional value whether wet or dry. You could compare:

alfalfa hay @ 88% dry	with alfalfa silage @ 40% dry
dry corn ground corn @ 85% dry	with high moisture corn @ 70% dry
dry rolled corn steam rolled corn @ 83% dry	with dry rolled corn @ 85% dry
grass hay @ 90% dry	with grass silage @ 30% dry

But if you compared cull carrots @ 10% dry with grass straw @ 90% dry all you would have is the cost/lb of carrot dry matter vs. grass straw dry matter. You would not have products of approximately equal nutritional value. The carrots have quite a bit of energy to produce gain or milk while the grass straw is best suited for maintenance, not gain or milk for a calf.

Speaking of carrots; I had a client that bought carrots at $12.00/ton delivered to his ranch. He was feeding some grass seed straw and then letting the cows eat as much carrots as they liked from the pile. He called me because he thought the carrot seller was cheating him regarding the weight of carrots that was being delivered. He was feeding 7 lb of straw and according to his calculations the cows were eating 230 lb of carrots per head per day. He didn’t think a cow could eat that many carrots. His cost was quite a bit more than his budget allowed. Let’s do some calculations.

Carrots @ 10% dry were costing $120/ton ($12÷0.10 = $120) of carrot dry matter. The cows were eating 23 lb of dry carrots each day. Their total lbs of feed was 29+ lb/cow/day. A 1200 lb cow could easily eat that amount of feed. The carrot part of the ration was costing him $1.38/cow/day. When we were done he realized that the carrots weren’t such a bargain after all.

Most of our fruit and vegetable waste products are very high in moisture. This presents a problem of storage. They will rot if just dumped on the ground. Sometimes they are stored in a large pit, others will mix them with a dryer feed and make a silage out of them. Let’s say you want to store carrots for future use and you have grass seed straw available. We want the final product to have 30% dry matter. We make a blend of 25% grass straw and 75% carrots; let’s check the dry matter of that mix:
.75 x 10% dry = 7.5 carrot
.25 x 90% dry = 22.5 grass straw
Total % dry = 30.0 dry mix

Moisture is a very important part of feed buying, hauling, storing, and feeding. It’s important to get an accurate measure of moisture. This can be done in feed lab or in a microwave oven. To use a microwave, put a sample of the feed in question in a micro-wave safe container. Weigh this. (An easy way is to add feed until the feed plus container weighs 1 lb. Put ½ glass of water in the microwave in addition to the feed sample. Heat on medium setting for 3 min.; remove and mix sample; heat again for 2 min.; remove and mix sample; heat again for 1 min. Sample should be crisp and dry; not burned to ashes.
Weigh sample and container. Heat for 30 seconds, weigh again. Continue heating and weighing for 30 sec. if the last weights are not the same. When the last 2 weights are the same, you have removed all the moisture. Dry matter is calculated by:
Weight of original sample: 1.0 lb
Minus Weight of final sample: 0.6 lb
Moisture removed 0.4 lb
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Therefore dry matter is 0.6 lb or 60% (0.6 lb ÷1 lb = 0.60 or 60%).

One last point for FFA and 4H folks, grain mixes or concentrates will spoil occasionally due to excess moisture or improper cooling. The feed may be out of date at the time
it is purchased, or it may develop mold before you finish feeding it. These problems may explain why your animals go ‘off feed’ just prior to fair or show.

Michael J. Mehren, Ph.D. is a livestock nutritionist who prefers moisture from a keg rather than from broccoli. He can be contacted by Email at mehrens@eotnet.net.