A580
Nutrition For Beef Cattle - Calculating Beef Cow Rations

hand calculating ration

Least Cost Analysis: Least cost rations utilize linear functions to determine the cheapest formulation for all nutrients desired. The least cost ration will consider as many questions asked or will find the combination of ingredients that will deliver the lowest cost for the nutrient specified. Usually it will be in order of the most expensive nutrient such as energy, then to protein and so on until all requirements are met. It will consider as many feeds as desired. This would include feeds on hand and feeds that could be purchased. Nutrition consultants, especially feedlot nutrition consultants, will utilize nutritional balancing software in their services. Most good software packages not only will provide the ration balancing component but will also estimate performance the ration will provide for a given animal, estimate intake of a specified group of cattle, will print out feed truck "feed sheets," provide for supplement building plus other features such as communicating with their client.

This ration balancing software offers many features; however, it has some disadvantages or offers features that are not needed in many cow-calf operations. Some disadvantages of these programs include the fact that they can be frustrating to use for the first time and occasional user, and that they may have too high of a price tag for the average producer. In general, it takes some time to learn how to properly get through the programs, to have enough nutritional wisdom to know if the results are reasonable, and then to have enough use to stay familiar with the program.

Another dilemma with the more complex software is that in farm and ranch cattle operation the amount and nutrient composition of the major ingredient in the ration, the grazed forage, is often unknown. Therefore, we may be using a tool that is highly specific. However, we do not have the precision and/or accuracy on the grazed forage actually consumed to take advantage of the precision offered.

Ration Analysis or Building by Trial and Error: Some software is designed to either analyze the ration that is currently fed, by simply inputting the amount of each ingredient and their composition and allowing the computer to do the mathematical calculation. Many of these software packages offer estimates of the cattle’s requirement so the nutrients offered by the ration can be compared to the given animal requirements. Deficiencies and excesses are then calculated. Most of this software is in computer spreadsheet format so the amount of the ingredient or the nutrient content can be changed, allowing the producer to instantly see the effect on the overall ration nutrient level as well as cost. These software packages are usually easy to use and can be utilized with minimal or no training and can be used appropriately with less basic nutritional knowledge.

Hand Calculating Ration: It is easy to hand calculate a good balanced economical ration in most cattle operations with some nutritional knowledge and common sense. This can be done with a simple notebook, pencil and calculator, or with very little effort, can be put on the home computer worksheet. The worksheet offers more efficiency in considering alternatives.

The following example will present the concept. One may alter rows or columns to fit the desired complexity. To establish the cattle requirements, a producer must choose how many ingredients they want to consider, their nutrient composition, nutrients that are of significant concern in the overall ration, and the class of cattle and level and stage of production to establish the cattle requirements. Currently, the most recent nutrient requirement (NRC ’96) does not publish tables of all stages of growth, or in the case of cows, all stages of production for CP and TDN. These numbers are included in the software and are dependent of the user inputs such as cow weight, stage of pregnancy or lactation, plus other factors. Therefore, this chapter utilizes the ’84 nutrient requirement tables with slight revisions. The revised numbers reflect requirements in the ’96 NRC publication. Although there may be some special situations where the newer procedures would be beneficial, perhaps 90-95% of the rations calculated utilizing the revised ’84 requirements will be sufficient.

The following format will be utilized:

First, look up the requirements for a dry pregnant 1200 pound beef cow in late pregnancy (Tables 1, 2 and 3).

From the previous 3 tables input the intake and nutrient requirements as follows:

We will choose to consider the following at the indicated price.

We estimate the 1,200 pound cow will eat about 2.00% of body weight in ration dry matter, so initially we decide to feed the following:

After feeds are inserted into the form, simply do the math by multiplying the amount of dry fed per day by the percentage of the desired nutrient . For example, 20 lb of grass hay with a 90% DM is to be fed.

20 lb X 90% = 18.0 lb of DM from the hay

18.0 lb dry matter X 6.5% (%CP) = 1.17 lb of CP coming from the grass hay.

The nutrients are then totaled and compared with the requirements as follows. Some question if the correction for DM in the feeds is needed for most dry hays, and perhaps it is not as important; however, when silages or haylages are fed it is extremely important.

As can be noted, the feeds we selected essentially meet the requirements of the 1200 lb cow. Let’s assume we want to compare an alternative ration of grass hay, alfalfa hay and corn. The following example can be calculated:

As can be observed, this ration has slightly more protein and energy at a lower cost.

One method to determine which is the best buy for a nutrient is to calculate the cost or value of any given nutrient as outlined in the following paragraph.

Many methods can be used to compare supplement value. Price per ton of a feed is only a starting place. A simple calculation using the following formula can be used to compare relative cost of supplements when buying supplements for a specific nutrient.

For example:

Alfalfa hay cost $60/ton ($0.03/lb.) and is 18 percent crude protein:

Non-protein nitrogen (NPN) products, such as urea and biuret in protein supplement, usually are not well utilized when cows are fed low to medium quality forages. For supplements that contain NPN, increase the cost of protein 30 to 50 percent.

For example, if the cost of the nutrient is $.30/lb. of protein and the supplement contained NPN, then the cost of the nutrient increases to $.40/lb. to $.45/lb. of protein.

Calculating the cost of feeds using this formula does not consider convenience or labor of feeding. Each producer attaches a different price to convenience and labor. One feed may be more expensive per unit of nutrient compared to another, and a producer might consider that feed because it fits that producer’s feeding program and labor restrictions.

The following are some general guidelines for balancing beef cow rations for energy and protein.

1. Winter range, crop residues, and low quality harvested roughages will usually provide adequate energy for bred females if the feed is properly supplemented with protein. Yearling heifers fed low quality feeds such as straw, mature cereal grain hays, or sudan-grass hay may be an exception. Grain, in addition to protein, may be needed for heifers fed low quality feedstuffs. Higher quality forages should provide adequate energy and protein for the cow or heifer prior to calving.
    
2. Supplementing low quality forages with a natural plant protein will improve the cow’s energy nutrition more than feeding small amounts of high energy, low protein grains. Supplemental protein increases the digestibility and intake of low quality forages and increases energy intake. However, a low level of supplementation will not compensate for a lack of feed.
    
3. Feeding small amounts of grain or molasses (without natural protein supplementation) usually lowers energy intake of cows eating low quality forages because feeds high in starch and sugars tend to decrease forage digestibility and intake. Grain should be considered primarily as a forage substitute to spare the forage supply.
    
4. Feeding small amounts of grain to cows eating high quality protein hays, such as alfalfa or low quality forages with adequate protein supplementation, improves the animal’s energy status. When there are severe roughage shortages, grain can be fed to meet nutrient requirments as long as 3 to 5 pounds of roughage is fed daily. It appears that the response to grain supplements is better with high quality forages than with low quality forages.
    
5. Spring calving cows that graze dormant pasture after calving and before new grass growth is adequate will not consume enough energy to meet their nutritional needs. Inadequate nutrition shortly before and after calving can reduce fertility and increase the interval from calving to first heat.
    
6. If grass is in short supply, weaning the calves early can be more profitable than feeding cows for greater milk production. Calf removal reduces lactational stress and helps initiate estrous cycles in cows that are not cycling.
    
7. Consider feeding grain by-products when energy is not adequate. Feeds like corn gluten feed, distillers grains (wet or dry), soyhulls, wheat middlings, and beet pulp may be economical in beef cow feeding programs. These by-product feeds have the advantage of providing energy primarily through highly digestible fiber rather than starch, which is the source of energy from grain.
   
   Research shows that when grain is added to a forage ration, the digestibility of the forage decreases due to the starch from the grain. Research also indicates that when by-product feeds are added to a forage ration at a level of .5% of body weight or less (dry matter basis), there are no adverse effects on forage digestibility and there may be an improvement in forage digestibility. Therefore, grain by-products appear to be an alternative to grain in beef cow rations that require extra energy. Grain by-products may be included in rations for replacement heifers, first-calf-heifers after calving, or mature cows that have high milk potential.

1. Protein requirements should be met to provide adequate rumen nitrogen to maximize forage digestion.
    
2. Protein can increase the digestibility and intake of low quality forages that are the primary energy sources in the ration.
    
3. Cows have an internal system to recycle nitrogen as urea back into the rumen. This can then be combined with the energy source in the rumen to make microbial protein.
    
4. It is essential that the rumen degradable protein needs are met to ensure maximum forage digestion. NPN (urea) may be included in beef cow rations to meet the rumen degradable protein needs.
    
5. NPN (urea) and a portion of the natural (i.e., plant and animal proteins) protein is degraded in the rumen of cattle. If urea or proteins extensively degraded in the rumen are used as a protein source for the rumen microbes to make their own protein, a rumen bypass (proteins that escape microbial degradation in the rumen; e.g. feather meal, fish meal, meat and bone meal) protein should also be included in the supplement.
    
6. Natural plant protein supplements, including SBM, CSM, and legumes appear to be as effective when fed two or three times a week as when fed daily. When greater amounts are fed less frequently, timid cows may be more likely to eat their fair share.
    
7. Protein supplements should be evaluated and purchased by nutrient cost and feeding cost. Protein sources, such as alfalfa hay, can be an inexpensive or cost effective supplement.

Ivan G. Rush, Beef Specialist
University of Nebraska
Panhandle Research and Extension Center