NUTRIENTS IN DIFFERENT FEEDS by Mike Mehren Ph.D.

At a meeting recently a gentleman in the audience was concerned about how protein supplements were compared. He noted that cost per head day was most important.
This is true, but each supplement must supply the same amount of protein for the comparison to be accurate.

Here’s an example: We are feeding a group of cows meadow hay. We have determined that they need more protein, and want to compare several different sources of protein.
The amount needed is ½ lb of protein daily, no matter what form the protein comes from.

A 32% protein block costs $500/ton. It takes 1.6 lb/cow/day to provide 0.5 lb protein, So the cost/head/day is $.40 ($500 divided by 2000 x 1.6 lb =.40)

A 32% Liquid protein supplement costs $370/ton. It takes 1.6 lb/cow/day to provide the same amount of protein. So the cost/head/day is $.29.

A 22% Protein Tub costs $770/ton. It takes 2.49 lb/cow/day to provide the same amount of protein. So the cost/head/day is $.97.

18% Protein Alfalfa Hay costs $200/ton. It takes 2.8 lb/cow/day to provide the same amount of protein. So the cost/head/day is $.28.

Of course you must include cost of labor and equipment to figure total cost.

Some supplement manufacturer’s reps want you to compare sources of protein when the cattle only consume a certain amount of their supplement, such as 1 lb. This is like comparing rutabagas and steak! Make certain that your comparison is for an equal amount of protein.

Now to get dirty. Every feedstuff contains a small amount of dirt (or ash). When an excessive amount of dirt is present, it dilutes the amount of other nutrients that can be used by the animal to produce milk or meat. Don’t get me wrong, ash is important. All minerals are in the ash fraction of the feed. A mineral source such as limestone (a source of calcium) or mono-dicalcium phosphate (a source of calcium and phosphorus) is virtually all ash. Excess ash can explain reduced performance, reduced intake, and poor silage quality. Years ago a cattle feeder and I were talking about his potato slurry. I mentioned that it was almost one half dirt. He looked at the as fed portion of the analysis and noted that it only showed 6% ash. However the slurry was only 15% dry matter. Six percent ash of the 15% dry matter equals 40% ash on a dry basis. Fortunately we were able to work with the potato processor and they were able to remove a large portion of the dirt from the slurry. Excess ash can also come from the way a feed is harvested. Feeds that are laid in a windrow will have a higher ash content than a product that is cut and delivered directly to the cattle or a silage pit. Lots of gophers in the field also can be a source of dirt. A while back I could almost guarantee which particular person was harvesting corn silage and putting it in bags. His silage had much more ash than anyone else’s. He might have been cutting too low to the ground. Here’s a table that shows the average ash content of different feeds on a 100% dry matter basis.

Feed	Percent Ash
Alfalfa Hay	9
Corn	2
Corn distillers w/ solubles	5
Corn Silage	5
Barley	3
Bluegrass straw	6
Grass Hay	6
Grass seed screenings	12
Wheat Straw	8
Molasses	14
Orchard grass pasture	8

Feeds that I have encountered high ash content include Canadian grain screenings, grain screenings, grass seed screenings, pea vine silage, beet top silage, and potato waste.. Feeds having 25% or more ash above average should be considered ‘dirty’. As long as you recognize that it is there and take it in to account, excess ash doesn’t usually cause a major problem.

One area that has caused some confusion is the amount of ash in supplements. Mineral supplements better be high in ash or there isn’t enough mineral in the product to matter. An ash content of 75% or more would be common for free choice minerals and mineral premixes. Salt is about 97% ash. Protein and Energy supplements should have more ash than a grain or vegetable protein because most have added minerals such as calcium, phosphorus, magnesium, salt, and trace minerals.

Finally, the energy content of feed is measured in several different terms. Energy is measured in calories no matter what term is used. The terms used are TDN, Net Energy for Maintenance, and Net Energy for Gain. The gross energy of wheat straw and corn is about the same! However cattle are able to get more energy out of corn than they can wheat straw. Without the bugs in the paunch, cattle would get almost no energy from the wheat straw. This is why some folks ammoniate straw and researchers continue to work on a means of releasing the energy in straw.

Energy is not measured directly in a feed testing laboratory. Formulas are used to calculate the energy of a feed. Since a formula is used, there are also formulas that provide you with values that express energy of your feed in terms that you like to use.
Examples would be:

Feed	TDN	NEm	NEg
	%	…..Mcal/cwt……
	……100% dry matter basis…….
Corn, whole	88	98	65
Corn, steam rolled	93	104	71
Alfalfa Hay, Hi quality	60	62	31
Corn Silage	72	75	47
Orchard Grass Pasture	65	66	37
Wheat Straw	42	43	0

This table shows us several things. Processing corn increases the energy of the corn. The question you need to answer is ‘at what cost’? Also when corn is steam rolled, moisture is added, so it doesn’t have the same shelf life. This may not be a big deal in cold weather, but can allow mold growth and spoiling during warm weather. Feedlots don’t store steam rolled grain; it is fed up within 2 days. Note the energy of orchard grass pasture. Many pasture grasses have more energy than high quality hay. This is why cattle do so well when on high quality pasture.

Nutrients that can be converted to usable energy by cattle include fat, sugars, starch, protein, cellulose, and hemicellulose. The last two nutrients are part of the fractions known as crude fiber, acid detergent fiber, and neutral detergent fiber. These fractions are the least available source of energy. Fat is the most concentrated source of energy. One pound of fat has as much energy as about 2.5 lbs. of grain. Most common feedstuffs have some fat in them. Feeding fat doesn’t make an animal fat any more than feeding an animal sugar makes an animal’s meat taste sweet.

Making a good comparison of alternatives is important whether it’s a protein supplement, ash content of a feed, or energy content.

Mehren’s politically incorrect dictionary defines election as a misspelling of a biological term for an event of short duration but one that may have lasting consequences.

Michael J. Mehren, Ph.D. is a livestock nutritionist whose loss of hearing and memory make each day a delight. Here’s hoping that you and yours enjoy good health and happiness during the coming year.