What's in That Feed Pile? Why Test Feed and Balance Rations?

So you’ve got all your feed put up, know how much you’ve 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 lots.  For example, if you have 300 barley straw bales, 600 alfalfa grass hay bales and 50 greenfeed bales, you would sample the straw and the alfalfa hay.  If 300 bales of the hay were put up without rain and the other 300 with rain then you would take two samples for the hay.  Sampling of feed is done randomly by probing 5 to 7 bales of feed representative of the hay available. Feed testing probes and information on getting feed samples sent out is available through district Manitoba Agriculture, Food and Rural Initiatives offices.

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.  Energy content (TDN or net energy) can be calculated from the ADF content of grass and legume hay; TDN% = 88.9-(0.779*ADF%).  As the quality of feed declines, ADF and NDF content rise and TDN falls.  Further factors beside plant maturity that influence feed quality are: plant species, leafiness, harvest efficacy, storage method and environment (rain etc.).  Below is a listing of feed value averages for the South West Region of Manitoba in the past years.

% Feed Value - DMB
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

You got your sheets back and want to get a ‘glimpse’ on what it all means. 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 formulation is done on a dry matter basis.

For example, if the protein is 17.5 %, it will be excessive for growing calves, dry cows or lactating cows.  In most cases when feeding rations to cattle containing more than 75% alfalfa grass hay, protein is fed in excess.  Below is an example of the feed requirement of a 1200 lb cow with 20 lbs of peak milk production (NRC 1996) in temperatures of -5 to 15 0C.

1200 lb Mature Cow Months Since Calving
  1 3 5 7 9 11
DM Consumption (lbs) 26.8 28.4  26.5 24.2 24.0 24.1
TDN %DM  58.7  57.6  54.7 44.9 47.1 52.3
CP% DM   10.1 9.92 8.54 5.99 6.50 7.73
Ca % DM   0.29 0.29  0.24 0.15 0.15 0.25
P % DM   0.19 0.19 0.17 0.12 0.12 0.16

Using the information from your feed test and guidelines for nutrient requirements of beef cattle, different feeds can be combined to best meet the needs of your cow herd or feeder cattle.

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 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?

For starters, the Calcium and Phosphorus ratio should be 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 ones likely being Cowbytes which is available through the Alberta Agriculture and Rural Development Home Study program.  There is also help available through agriculture extension services on troubleshooting concerns.

Prepared by:

John Popp, Melinda German and Heather Hockley
Manitoba Agriculture, Food and Rural Initiatives