Feedlot Management Primer

Chapter 7. Creating Diets or Balancing Rations

Computer Software: Methods do exist for balancing rations or creating feedlot diets with just a pencil and paper. However, given the complexity of feedlot diets, computer ration balancing software can reduce the time in looking at various ration options. Various universities and agriculture software companies have created such software for sale. The cost of such software can range from $40 to $4000, depending upon what you require. Universities and feed companies also offer such services. The only caution is that all this software can be "inherently stupid" and create a nutritionally balanced diet but which may be actually difficult, if not dangerous, to feed. A basic understanding of beef cattle nutrition and feedstuff characteristics is required to create feasible rations with computer software.

ENVIRONMENTAL ADJUSTMENTS FOR THE NUTRITION PROGRAM

The recommendations contained in most beef cattle production books are for cattle exposed to conditions relatively free of thermal stress or a temperature range of about 59 to 77 degrees Fahrenheit. Extremes in temperature influences the behavior and metabolic processes. All these changes go together to change returns to labor and management (profit/loss). Adjustments can be made to the diets so that we can predict performance and profits (Ames et al., 1981).

1. Adjust nutrient value of roughages

Roughages tend to be more highly digested during warm conditions than when the same diet is fed to cattle exposed to cold temperatures. Presently, no adjustment is recommended for concentrates fed to beef cattle. Adjustment for thermal effects on digestibility can be made to diet component values for feed or diets by the following general formula:

A = B + B((C_f (T-20))

A = Value adjusted for environment

B = Diet component value (TDN, NEg, NEm, CP)
    (NEg and NEm in Mcal/kg)

C_f = correction factor (0.001 for TDN, NEg, NEm) (0.0011 for CP)

T = Effective ambient temperature
The term ambient refers to other factors that affect temperature. An example would be "wind chill" if cattle are constantly exposed to cold wind and have no shelter.

     * Must do temperature calculations in Centigrade and not Fahrenheit:

F = 9/5(C) + 32       C = 5/9(F - 32)

Example: Adjust nutrient value for grass hay for 10° F

A = B + B((C_f(T - 20))

B = 1.21 Mcal/kg of NEm

C_f = 0.001 (correction factor for NEm)

T = -12^oC = 5/9(10 - 32)

A = 1.21 + 1.21((0.001(-12 - 20))
A = 1.17 Mcal/kg of NEm

2. Adjust for voluntary feed intake changes

In general, voluntary intake of feed tends to decrease as ambient temperature increases and intake increases when ambient temperatures decrease. Estimation of feed intake both within and among animals becomes more variable and less predictable as ambient temperature varies from 68 degrees Fahrenheit.

SUMMARY OF VOLUNTARY FEED INTAKE OF BEEF CATTLE IN DIFFERENT THERMAL ENVIRONMENTS

Example: Adjust voluntary feed intake for 10^oF (normal: 14 lbs)

Dry matter intakes stimulated 5 to 10%
14 lbs x 1.10 = 15.4 lbs

3. Increase available energy for maintenance energy requirements

Basal metabolic rates tend to be lower in animals with prior exposure to warm weather and elevated in animals with prior exposure to cold conditions. In beef cattle, adjustments based on seasonal changes in the thermal environment (mean monthly temperature) would be most appropriate, although it is likely that cattle never fully acclimate to the extremes in regions where there are marked seasonal fluctuations in ambient temperature. The estimates for net energy requirement for maintenance (NEm) is based on the relationship:

NEm = aW^.75

NEm = net energy for maintenance (Mcal/day)
a = 0.077 when no environmental stress incurred

W = live weight in kilograms

For each degree of prior exposure to ambient temperatures above or below 20^oC, 0.0007 should be subtracted or added respectively to "a" in the above equation. Thus for cattle with prior exposure to temperatures of 30, 20, 10 and 0^oC, the value "a" become 0.070, 0.077, 0.084, and 0.091, respectively.

FEED MIXING

The mixed ration should look the same throughout the bunk or in the self-feeder. While inadequate mixing can be a common problem, you can also mix too long in a vertical mixer. Sorting out can occur due to differences in particle size and weight of the various feedstuffs. Ingredients that are added in small amounts (for example: vitamins and minerals) should be mixed with one or two buckets of grain before being added to the mixer. The following is a recommended method of adding supplements to a vertical grinder mixer:

1. Add half the grain.

2. Add the supplement.

3. Add the rest of the grain.

4. Add the roughage.

5. Mix for five minutes at the feeding site to eliminate separation occurring during travel to the feeding location.

Rescheduling the use of selected equipment for peak demand periods to off-peak periods or manually shutting off some of the equipment with large motors, can save charges. However, be careful to avoid short cycling (i.e. frequent starts and stops) which can damage equipment. The feedlot operator should consult with the electric company to analyze the rate structure and identify when peak loads occur and how they can be reduced. An independent consultant or the electrical utility's representative can help choose the best system for load management.

FEED RESOURCE ECONOMICS

DETERMINING THE VALUE OF FEEDS

Nutrition cost accounts for 50% of the costs of maintaining a cow herd and 80% of the cost of feeding cattle. Therefore it is important to be able to determine how much your nutrition program is costing you.

Producers commonly ask which feeds are the best price. The first place to start is accurately pricing the feed that will be delivered to the animals. Price quotes on unprocessed feed may only be a starting point. Take into account delivery charges as well.

Market Price: Market price may be considered if the feed is already on the farm. Market price should be considered if you are trying to decide if the feed should stay on the farm and be fed or sold and another feed purchased for feeding. An example might be oats when it is relatively high priced on the market.

Cost of Production: Cost of production will be important when raising your own feed and you want to make sure you can maintain a cash flow. Actual cost of production will vary with the size of the operation and the amount of equipment used.

Based on Nutrients: When you supply feeds for livestock, you are actually supplying nutrients. These nutrients are usually energy (TDN, NE_l, NEg, and NEm), protein (CP, DP, or amino acid), and minerals (principally Ca and P). Prices vary with the same feedstuff depending on which nutrient value is used.

Pricing One Nutrient at a Time: We will initially review pricing one nutrient at a time. The following method demonstrates how to determine whether alfalfa hay or soybean meal is the best buy as a protein source.

*Soybean meal is the cheaper protein source

Price per unit of nutrient will not be the only determining factor in choosing which protein source to use. Method of delivery must also be considered. Feeding a meal form of protein supplement will require feed bunks versus just placing hay bales in a pasture or bale ring.

Nitrogen sources, such as urea, are an excellent supplement for high grain diets. Urea and biruet can be utilized in pasture situations but utilization will not be 100%. However, biuret has somewhat higher utilization values than urea on forage-based diets. The ideal way to use nonprotein nitrogen sources is to feed small amounts at frequent intervals.

Approximate Urea utilization (%)

The following example demonstrates the use of "cost per unit of protein" for comparisons of protein supplements when urea is fed once a day with a medium quality hay diet (approximately 50% utilization). We will use the information that is available on the feed tag.

Product A: 40% CP

Product B: 40% CP, not more than 20% nonprotein nitrogen crude protein equivalent.

NUTRIENT UTILIZATION

Many times supplements containing urea will still be the better buy even with the reduced utilization. Keep in mind, use the utilization level rather than the feed tag value when balancing diets.

Another method of pricing feeds based on nutrients is with ratios or what is sometimes called constants. One feed is used as a standard to price other feeds. We will use soybean meal ($230/tn) in the following example to price sunflower meal and dried distiller grain on protein.

There is a temptation to use the same ratios or constants all the time. This can become erroneous with feeds that vary in nutrient value such as hay, silage, barley, and oats. The relative prices of feeds also depends on the feeds selected as standards (in this case it was soybean meal).

The previous examples did not take into account by-pass protein potential. This is protein that is not digested in the rumen but rather in the intestine. By-pass protein, that is actually digested in the intestine, is more energy efficient for production. Certain feeding programs, such as dairy lactation diets, can take advantage of by-pass protein.

Calculating Value Based on Two Nutrients: Most feeds contain more than one nutrient. A common method is to use ratios or constants. Our standards in this example are corn and soybean meal.

Value of Oats: (.86 x $80) + (.27 x $200) = $122.80/ton

This method is simple but sometimes gives erroneous results. Is oats really worth $122.80? Probably not. Let's try another method.

Another method is to calculate what a nutritionally equivalent mixture of corn and soybean meal would cost compared to a ton of oats. We can make a corn-soybean meal mixture similar to the oats by the use of protein-energy ratios. We will use the feeds and prices from the previous example.

1. Determine mix of corn and soybean meal using a Pearson Square

2. Determine nutrient composition of corn-soybean meal mix

3. Determine Amount of Corn-SBM mix equal to ton of oats

Oats: 2000 lbs. x 68% = 1360 lbs. TDN

1360 lbs/78.4168% = 1734 lbs. of corn-SBM mix

Oats: 2000 lbs. x 12% = 240 lbs. CP

1734 lbs x 14.1030% = 244 lbs. CP supplied by corn-SBM mix

4. Determine value of oats

1734 lbs. of corn-SBM mix:

Therefore oats is worth $84.54 per ton

There are various software packages available that calculate the value of different feeds based on standard feeds such as corn and soybean meal. You might occasionally check the output with the previously demonstrated procedure to make sure it is giving you an accurate price.

Pricing Pasture: Pricing pasture may require other methods. The simplest method is to simply use what the neighbors are charging. Another consideration is land value. One could consider the cost of other feeds, such as a grain and hay diet, to get the same rate of gain.

Pricing Silage: The following are some methods for determining the value of silage. A rule of thumb is that silage is worth 1/3 the value of grass hay. If grass hay is worth $60/ton - Then silage (As fed) is worth $20/ton

This procedure assumes a constant between the energy value of silage and hay. It has been stated earlier to use caution in using constants, but it is a "quick and dirty" way of determining price of silage. Another "quick and dirty" formula can be used to determine the value of corn silage based on the price of corn grain:

Price of corn per bushel = A

Bushels of corn in a ton of silage = B

Storage & handling cost per ton of silage = C

Additive cost per ton of silage = D

Silage Price/ton = [(A x B) + C + D] x %Silage Dry Matter/35%

The bushels of corn grain per ton of corn silage varies between 5-7 bushels per ton. A storage and handling cost of $4 to $10 may be used if actual production data are not available. The following is an example

Example 1: [($2.00/bu x 5) + $8 + 0] x 30%/35% = $15.43/tn

Example 2: [($2.00/bu x 5) + $8 + 0] x 40%/35% = $20.57/tn

In the second example the increased dry matter increased the value of the silage. This formula can probably be used with dry matters between 30% and 40%. Silage quality and storage losses outside the range of 30% to 40% will override this method of calculating value.

One can figure approximately 10% loss of silage in a stave silo and 15 to 20% loss in a bunker silo. Government deficiency payments may alter the actual cost of production of corn silage.

Sampling Feed For Laboratory Analysis: It is still more accurate to take a sample of silage and have it analyzed by a laboratory. Don't take a sample until the silage has gone through the ensiling process. Silage is not silage until at least 3 weeks of storage time. Hay should be sampled in the fall since summer and early fall rains will decrease it's nutrient content if stored outside.

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