Diet and nutrition: forage analysis, mineral program, protein and more

Diet and nutrition: forage analysis, mineral program, protein and more

(Producer Questions prior to 2009)

When I look at a forage analysis, there are two columns of numbers, one column says "as is" and the other says "dry matter". Which one do I use?

Because nutrient requirements for beef cattle are reported on a "dry matter" basis, use this column to balance the ration. The percent moisture reported in the "as is" column will be used to determine the "dry matter" content and this number is used to convert the amount of hay that you calculated that was needed to balance the ration on a "dry matter" basis to the amount of hay that you will need to feed the cattle.

For example, you calculate that you need 25 lb of hay on a "dry matter" basis to meet the needs of a cow. The hay is 10% moisture, therefore, it is 90% "dry matter" (100 - 10% = 90%). You need to feed each cow 28 lb of hay (25lb divided by .9 = 27.7 lb of hay).

For more information, please see the "Understanding Feed Analysis" Learning Module.

Can you give me as much information as you have on chelated minerals and their importance?

You ask a very good question and one that is not easy to answer. Chelated minerals (usually these are trace minerals and not the macro-minerals) are minerals that have been, through a chemical reaction, bond to amino acids (amino acids are the building blocks of proteins) or protein complexes. Amino acids that reach the small intestine are very readily absorbed and are therefore, readily available to be used by the animal.

The thought is that minerals consumed by the animal are not absorbed very efficiently. So the theory would be that if minerals were tied to something that is readily absorbed naturally in the body, that the efficiency of absorption would be enhanced. So we know that amino acids are efficiently absorbed, so feed companies have "bound" minerals to amino acids to, in theory, increase their absorption, and therefore, their "bioavailability" to the animal. The data suggests that these mineral-amino acid complexes are more effectively absorbed by the animal.

As far as the data is concerned, results are all over the board with chelated trace minerals. What seems to be the most consistent in the data for chelated trace minerals is that there appears to be a positive response in young calves that have been stressed and it appears that you get an immune response.

We are trying to figure out a ration for dry second and third trimester range cows and yearling heifers. What would be a safe and or optimal level of WDGS to use with poor quality prairie hay and wheat straw? We are within 30 miles of an ethanol plant.

WDGS is a good choice in diets that includes medium to low quality forages. The amount will depend on the nutrient analysis of the forage. The WDGS can be both a source of energy and protein.

I would not feed over 7 lb/hd/day of WDGS on a dry matter basis. Typical WDGS is about 35% dry matter and 65% moisture. At a maximum of 7 lb/hd/day on a dry matter basis would calculate to 20 lb/hd/day (7 lb/hd/day divided by .35 = 20) on an as is basis when you include the water.

If you feed over 2 lb/hd/day on a dry matter basis, you will not need any phosphorus in the mineral supplement. You will need to add some calcium to the diet and that may be included either as limestone added directly to the mix or there are mineral blocks designed specifically for diets that are designed around corn by-products. Sulfur content can vary, but at the levels I described above, they shouldn't be a problem if you have a good mix and enough bunk space for all cows to get their share.

Which feeds are high in rumen degradable protein and which are high in rumen by-pass protein and how much of each is needed? What is acid detergent fiber?

The 1996 NRC for Beef Cattle contains a feed library that has an estimate of crude protein and then the portion of the crude protein that is degraded intake protein (DIP) and the portion that is un-degraded intake protein (UIP) or by-pass protein. As a general rule, forages would be 70% or above DIP and therefore 30% or less UIP. These values change based on maturity and type of forage. Corn is about 45% DIP and 55% UIP meaning if corn is 10% crude protein, that 45% of the 10% is DIP and 55% of the 10% is UIP. Urea is 100% DIP. Blood meal and feather meal are high is UIP, between 70% and 75% UIP. Not many feed companies carry feather meal and blood meal any more. Distillers grains can be 35% DIP and 65% UIP.

The amount of DIP and UIP needed in a diet depends on the class of livestock and the performance you are trying to achieve. Remember that is important to supply the rumen microbes with DIP as that is what's used for the microbes to make their own protein and it is important that this happens. Growing cattle likely need more UIP in their diets whereas mature cattle need less UIP. Again, the 1996 NRC would contain the requirements.

You may read the 1996 NRC Nutrient Requirements for Beef Cattle online for free at The National Academies Press website. The online book includes the Tables of Nutrient Requirements. You can also order a copy of the requirements in a paperback version and there is included a diagnostic model to check diets you develop.

Acid detergent fiber (ADF) primarily consists of cellulose, lignin, silica, insoluble crude protein and ash, which are the least digestible parts of the plant. Because ADF percentage in forages negatively relates to digestibility, it is used to calculate energy values. ADF is one of the most common analyses made, particularly on forages. Low ADF usually is preferred because it means higher net energy. As the plant matures, ADF increases.

Does by-pass protein still work to help the digestibility of roughage in beef animals if the protein (cotton seed meal) is diluted by salt (as self-fed supplement) to where the total ration is at 18% protein?

In forage diet for beef cows that consists of medium to low quality forage, there is usually a need for rumen degradable protein (DIP) and not so much of a need for by-pass protein. However, some of the bypass protein can be recycled to urea and be transported back into the rumen by salvia and be used as DIP. Calves and young lactating females have a greater need for by-pass protein compared to mature cows. Cottonseed meal is a good source of both DIP and by-pass protein. The protein is about 57% DIP and 43% by-pass. You can limit supplement intake in self-fed supplements using salt, it will take some experimenting. Our data would indicate that intake can be variable meaning that some cows will eat more than you calculated, some will eat about the right amount or less, and some won't eat any at all.

Can one feed a mixture of dicalcium phosphate and salt with free choice and meet requirements on good pasture?

When designing a mineral program, make sure you understand the class of livestock you are working with and what minerals and at what level the minerals will be supplied by the diet that is being consumed either in the grazed forage or feeds being fed. The 1996 NRC for beef cattle is a resource that will have nutrient needs of livestock and average nutrient compositions of feeds and forages. In addition, many times you can get information of nutrient content of forages in your state at the extension office. A mineral supplementation program should be simple, economical, and meet the needs of the cow herd as they change from one phase of production to another, and as they change diets (grazed pastures to harvested forages). These kinds of strategies have a good chance of being implemented. Calcium and P are probably the two minerals that most cow/calf producers should focus on especially when feeding harvested forages and before and during the breeding season. Phosphorus is the most expensive mineral that is supplemented.

A time tested, cost effective mineral program, has been a program that is ½ dicalcium phosphate (dical): ½ salt. Always have salt available for the cow herd. Some producers have included a trace mineralized salt in some situations when using dical. If the diet has a good phosphorus source, the formula may be 1/3 dical: 2/3 salt. DO NOT over feed phosphorus. If you are in a situation where trace minerals are needed, there are commercial mixes available. Feed only what is needed and not supplied by the diet. As micro-minerals are added to the mix, the cost will increase. In addition, as more of the minerals in the mix are in the chelated form versus the inorganic form, cost will go up. Read the tag for the levels that should be consumed by the cow on a daily basis. For most mineral supplements and the self-mixed mineral supplements mentioned above, 2 to 3 oz/head/day is a typical intake.

There are good commercial mixtures available. There may be a need for some micro-minerals and these needs can be ranch specific. Again, contact your extension person as they will have information on micro-minerals that may be deficient and need to be supplemented in your area.

The distillers plant gives me protein content (29%) and fat content (10%) along with moisture content (9.5%). Can I figure out TDN or energy with this information or do I need a sample test? I plan to use it in addition to prairie hay.

Excellent question. The simplest answer is to go to research data where they have compared the energy value of distiller grains with an energy source like corn. We have completed some of those experiments and continue to evaluate the energy value of distillers grains. Our data suggest that the dry or wet distillers grain plus solubles is 125% the energy value of corn in forage diets. So if corn is 90% TDN, then WDGS, MDGS, and DDGS will be 112.5% TDN. You might ask how a feed can be over 100% TDN. Part of the answer is the energy content of fat is 2.25 times the energy value of starch (the energy source in a feed like corn).

We are conducting experiments to determine the energy value of modified distiller grains plus solubles.

Sampling the DDGS or WDGS and sending it in for an NIR analysis will yield accurate number for moisture and percent crude protein. The energy value (TDN) will not be accurate because in an NIR analysis, TDN is estimated using ADF and ADF does not include fat content of a feed. If the lab did a chemical analysis for TDN, the number would be accurate as TDN is the sum of the digestible crude protein + crude fiber+ nitrogen-free extract + 2.25 x (ether extract or fat).

Bottom-line, use our research data.