What's in That Feed Pile? Why Test Feed and Balance Rations?
You have all your feed put up, know how much you have got and now want to determine how to best use it to feed your animals. To do so, feed testing and ration balancing can be an effective tool to better manage your feed supply and often substantially contribute to reducing your cost of production.
Sampling
To start with, you will sample your major feed inventory. If half of your hay was put up without rain and the other half with rain then you would take two separate samples. Sampling of feed is done randomly by probing a minimum of 10 bales representative of the feed available. Contact Manitoba Agriculture or Central Testing Lab to discuss feed testing options.
The Feed Test
Necessities for determining forage quality are:
Dry matter (DM), crude protein (CP), acid detergent fiber (ADF), neutral detergent fiber (NDF), calcium (Ca) and phosphorus (P).
CP is both true protein and nonprotein nitrogen. It is determined by measuring total nitrogen and multiplying this number by 6.25. Protein levels decline as forage becomes more mature.
ADF is the percentage cellulose, pectin and lignin, the former two are highly indigestible and the latter is slowly digestible.
NDF is ADF and hemicellulose, which is partially digestible.
TDN is the energy content. It can be estimated from the ADF content: TDN% = 88.9-(0.779*ADF%). As the quality of feed declines, ADF and NDF content rise and TDN falls.
Further factors besides plant maturity that influence feed quality are plant species, leafiness, harvest efficacy, storage method and environment (rain etc.). Below is an example of feed test value results
% Feed Value -DM | ||||
Feed type |
CP |
TDN |
Ca |
P |
Hay | ||||
Alfalfa Grass |
16.20 |
62.56 |
1.48 |
0.20 |
Grass |
12.73 |
58.69 |
0.75 |
0.32 |
Straw | ||||
Barley |
4.53 |
48.11 |
0.39 |
0.12 |
Wheat |
3.36 |
46.91 |
0.32 |
0.14 |
Greenfeed | ||||
Barley |
11.03 |
59.22 |
0.48 |
0.16 |
Oats |
13.42 |
61.79 |
0.50 |
0.26 |
Barley Silage |
10.76 |
62.80 |
0.43 |
0.22 |
Feed Test Interpretation
Two columns are listed on the feed test: as fed and dry matter (DM) basis. The only value of concern on the ‘as fed’ column is moisture; the rest of the evaluation is done on a dry matter basis.
Using the information from your feed test and guidelines for nutrient requirements of beef cattle, different feeds can be combined to meet the needs of your cowherd or feeder cattle.
The Beef Cattle Research Council (BCRC) developed a Tool for Evaluating Feed Test Results. This calculator can help you determine if individual feeds meet the basic nutritional needs of your livestock.
The Feedplan Calculator can help you calculate and determine lowest cost feed supplements based on CP, TDN and Dry Matter.
Common Questions on Feed Testing
My feed test contains analysis and information for Digestible Energy (DE), Net energy for maintenance and gain (NEm; NEg). What do they mean?
All these are different ways to express the energy content of feed – for basic nutrition formulation TDN is sufficient for formulating for energy requirements of cattle.
Are there toxic/deficient levels for Calcium, Phosphorus, Magnesium and Potassium? Are the ratios of any of these macrominerals significant?
The Calcium and Phosphorus ratio should be a minimum of 2:1. Dietary concentrations of Calcium have to exceed 4.4% before having negative effects. Phosphorus does not ever reach its upper limit to cause toxic effects in feed. Potassium should not exceed 3%; however, if it does, ratios of Potassium, Magnesium and Calcium will have to be adjusted. Magnesium concentration in feed is rarely a problem in beef cattle diets, as it does not usually exceed 1.2%.
Can I formulate my own rations and what steps do I need to take to get going?
There are several software programs available to formulate beef cattle rations, one of the most commonly used being Cowbytes.