Source: Manitoba Agriculture, Food and Rural Initiatives
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.
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 a minimum of 10 bales of representative of the feed available. Feed testing probes and information on getting feed samples sent out is available through Manitoba Agriculture 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; 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 an example of feed test value results
|% Feed Value -DM|
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 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.
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.