Nutritional Value of Potato for Livestock
Based on percent dry matter, potatoes, when compared to other feeds, have as much crude protein as corn, slightly more than corn silage and about 60 percent that of alfalfa (Table 2). Potatoes are low in calcium, requiring that calcium be supplemented if potatoes comprise a significant portion of livestock rations. The phosphorus content of potatoes is about the same as corn, corn silage and alfalfa. Potassium on a dry weight basis is as high as alfalfa, double that of corn silage and over five times that of corn. In general, potatoes are considered somewhat similar to corn in feeding considerations.
Nutritional value of feeds depends greatly on their energy level, which is often measured as total digestible nutrients (TDN) on a percent dry matter basis. By this comparison, potatoes provide slightly less than shelled corn and more than corn silage and alfalfa (Table 2). Because of the high moisture content, potatoes have 20 percent to 25 percent of the TDN of shelled corn on an as-fed basis.
Dry matter energy equivalents may be used to compare feeds for specific livestock. They are calculated by multiplying the percent dry matter (DM) by the percent of total digestible nutrients (TDN). Dividing this equivalent for potatoes by that of a feed, you can estimate how many pounds of feed will equal the energy value (TDN) of 100 pounds of raw potatoes. Using this calculation for cattle, 100 pounds of raw potatoes equals 21 pounds of corn, 67 pounds of corn silage and 31 pounds of alfalfa. For sheep, 100 pounds of raw potatoes equals 21 pounds of corn. For swine, 100 pounds of raw potatoes before cooking equals 23 pounds of corn.
Another method to evaluate a comparison based on energy is to compare TDN on a dry weight basis (percent TDN of one feed ingredient/percent TDN of another). Using this method for cattle, potatoes have 91 percent of the value of corn (percent TDN potato divided by percent TDN corn) on a dry weight basis. For sheep and swine, potatoes have 89 percent and 97 percent of the value of corn, respectively.
The dry matter content of corn is about 4.25 times that of potatoes on a per unit weight basis. It takes 400-450 pounds of potatoes to equal 100 pounds of corn on an energy basis.
Reference:
- Rust, S.R., D.B. Buskirk and H.D. Ritchie. 1997. Feeding whole potatoes to beef cattle. Michigan State University, Animal Science Mineo No. 365.
Using Potato as Livestock Feed