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close this book Animal traction
close this folder Appendix B: Animal nutrition
View the document Energy needs: bovine animals
View the document Energy needs: equine animals
View the document Nutrient needs of draft animals: protein, minerals, vitamins
View the document Feeds and feed composition
View the document Calculating a ration
View the document Recommended rations and feeding practices

Calculating a ration

Ration calculation can be demonstrated by the following examples using Table A (see page 188).

Example 1. To calculate the amount of Sudan Grass #1 needed to meet the U.F. maintenance requirement of a 300-kg bull. The value in Table A for digestible protein, phosphorous, calcium and U.F. are based on 100% dry matter. However, one kg of fresh roughage has less than 100% dry matter. Therefore, the first step is to adjust the amount of dry matter per kg of fresh roughage to 100% dry matter. For Sudan Grass #1, the percentage of dry matter per kg is 29.7%. One kg of fresh Sudan Grass #1 is adjusted to a 100% dry matter basis by the following calculation:

1/29.7% = 3.36 kg (100% dry matter basis)

This means that 3.36 kg of fresh Sudan Grass #1 contains one kg of dry matter. Step two is to locate the U.F. maintenance requirement of a 300-kg bull. The daily maintenance requirements of oxen chart shows the U.F. value of a 300-kg bull as 2.6. Step three is to calculate the amount of fresh Sudan Grass #1 needed for a 2.6 U.F. value. If 3.36 kg of fresh Sudan Grass #1 yields 0.57 U.F., then the needed calculation is:

3.36 x 2.6/0,57 = 13.3 kg.



Therefore, the bull requires 13.3 kg of green Sudan Grass #1 per day.

Example 2. To calculate the amount of Sudan cured hay to meet the U.F. maintenance requirement of a 300 kg bull, follow the same steps:

Step 1)

100/93.2 = 1.07

Step 2)

1.07 x 2.6/0.41 = 6.78 kg (U.F. value 1 kg dry matter)

Therefore the bull requires 6.78 kg of hay to meet its maintenance requirements. Calculation of protein and mineral contents of Sudan grass indicates that the fresh material meets nearly all of the animals' needs, but that the hay is deficient in every category. During the dry season, then, the stockowner would give the bull a grain supplement or mix a legume hay (high nutrient value) with the Sudan hay in order to balance the ration.

Feeds presented on an "as-fed" basis do not need adjustment for dry matter content.

To formulate a ration for a 300-kg bull:

1) Determine the animal's weight. Here, the weight is given as 300 kg.

2) Determine the maintenance requirements (per day basis).

U.F. (forage units) = 2.6 for a 300-kg bull

D.P. (digestible protein, or, in some charts "M.A.D." -- matière azoté digestible) = 80-130 g per U.F., or assuming a 300 kg bull needs and average 105 g/U.F., 2.5 x 105 = 273 g.

P (phosphorous) = 3-5 g per 100 kg live weight, or using an average of 4 g: live 300 kg weight x 4 = 12 g

Ca (calcium) = 5 g per 100 kg live weight, or 300 x 5 3 15 g

NaCl (sodium chloride; salt) = 5 g/100 kg live weight or 300/100 x 5 = 15 g.

3) Determine the energy value of the roughages the animal would normally consume. If left to graze freely, a bovine animal will consume between 10 and 20 kg of pasture (grass) per day. Since its digestive organs must process regular amounts of bulky material in order to function properly, it is reasonable to base the maintenance ration on roughages and the work or production ration on concentrate-supplements (grains and other low-fiber, high-energy feeds). It has already been established that 13.3 kg of green Sudan grass will furnish a 300-kg bull with its maintenance energy needs; in this example, this represents the average quality of mixed pasture grass that would be found early in the rainy season.

4) Determine the protein content of the roughage (maintenance) diet. Recall that for a work animal, protein, mineral and vitamin intake need not increase with production; only energy needs increase.

The following steps would be taken to find the number of grams of digestible protein contained in 13.3 kg of green Sudan grass:

a) One kg of 100% dry Sudan grass contains 4.2% protein, or 42 g of digestible protein per kg of dry matter.

b) In 13.3 kg of green Sudan grass there are 3.9 kg of dry matter:

*Ration consumed by bull

c) In 3.9 D.M., there are 164 g of digestible protein; in the 13.3 kg of fresh grass consumed by the bull, there are 164 g protein.

42 g x 3.9 kg = 164 g digestible protein

This ration is deficient in protein, since the requirement is 273 g (established earlier). However, in a wet season, free grazing situation, the animal would find a mixture of grasses that would meet all of its needs. The feeding of a protein supplement would be extremely important when the grasses begin to dry out, or if grazing time was limited to less than eight hours per day.

5) Determine the phosphorous value of the roughage.

a) One kg of 100% dry Sudan grass contains 0.12% phosphorous; or, 0.12% of 1000 g = 1.2 phosphorous per kg D.M.

b) 13.3 kg of green Sudan grass contains 3.9 kg D.M.; or, 3.9 x 1.2 = 4.7 g of phosphorous.

This ration is deficient in phosphorous, the requirement being 4 g per 100 kg live weight, or 12 g. The difference would probably be made up in the pasture mixture as long as grasses remained lush, but the stockman would be wise to furnish the animal with a mineral lick containing phosphorous year-round.

6) Determine the calcium value of the roughage.

a) One kg of 100% dry Sudan grass contains 0.34% Ca or 0.0034 x 1000 = 3.4 Ca per kg D.M.

b) 13.3 kg of green Sudan grass contains 3.9 x 3.4 g of Ca = 13.2 total Ca

The bull's Ca requirement is 5 g per 100 kg live weight, or 15 g total. Again, by providing them with a mineral lick, the owner ensures the animals' health regardless of fluctuations in grazing conditions.

7) Salt needs. While CEEMAT suggests that 5 g/100 kg live weight is sufficient for a working animal, it may be found that a bull consumes more if given free access to a block-especially during heavy work when salt is lost in sweat. Except in the case of salt-starved animals, the free-access system works well because animals will not normally consume more than they need. Phosphorous, Vitamin A and limited amounts of protein can be fed in a salt mix or block. The intake can be regulated by the feed formulation or texture of the block.

8) Calculate the work needs of the animal and determine the supplemental ration that will be fed.

A bull doing heavy work (plowing) needs 5/2 E, or 5/2 of its maintenance requirement. A 300-kg bull needs 5/2 x 2.6, or 6.5 U.F. per day.

In the example used, the bulky portion of the full ration consists of 13.3 kg of green Sudan grass; the grass has a U.F. value of 2.6. The supplemental work ration must provide about 4 additional U.F. if the animal is to get the required 6.5 U.F. These units can be supplied from any of the feeds listed in the table, but consideration would be given to these points:

a) Cost of feed. Grain is very expensive compared to grain by-products and other concentrate feeds. It is also in short supply during the work season; most of it has been used during the dry months.

b) Some feeds, particularly lush young pasture, legumes, and brans, have a laxative effect. Too much dry grain can also cause digestive trouble. It is generally advisable to feed a supplement made of a combination of various feeds.

c) Animals have individual preferences and may refuse to eat the supplemental ration as given. Precracking grains or adding salt, brewers' meal or bone meal to a ration may make it more palatable. The owner should make an effort to discover what the animal likes, what it digests easily, and when it will eat. Normally, an ox is fed its concentrate ration in the evening after it has grazed. However, a small portion of the ration may be given in the morning, or at noon if the animal has been allowed to graze and drink first. Animals do not work well when overly full and so it is preferable to have them eat at the end of the day.

d) Time of year determines the availability of certain feeds. Green corn or sorghum fodders are not available during the plowing season when they would be most useful. The farmer should store silage, hay and grain reserves for this heavy work period.

Suggested daily rations for a 300-kg bull doing heavy work (plowing) are given below. A 13 kg portion of mixed green pasture (early wet season grasses) has an approximate forage value of 2.5 U.F. and this quantity will be consumed if the bull is allowed 6-7 hours grazing time. In practice, 23 hours (grazing) would be given at mid-day (after the morning work session) and the remainder would be given in late afternoon/early evening.

Examples of Daily Rations for a 300-kg Bull:


(approximately equal to)

13 kg mixed green pasture

2.5 U.F.

2 kg mixed cracked corn and sorghum


1 kg peanut cake


2 kg legume hay (night fed at stable)



Total: 6.5 U.F.



a.m.-1 kg brewers' meal mixed in 4 liters water

1.0 U.F.

13 kg mixed green pasture


4 kg mixed green chop (night-fed cut past-ture)


2 kg cottonseed



Total: 6.5 U.F.



a.m.-1 kg peanut cake

1.0 U.F.

13 kg mixed green pasture


2 kg legume hay


2 kg mix wet brewers' meal and cracked corn



Total: 6.5 U.F.