Should I purchase feed for my livestock based on protein content or energy content?
Depending on the type of animal you are feeding will help you decide if energy or protein are more important. Generally, maintenance rations for mature cows require low protein levels and moderate energy levels. Whereas, growing or feeder calves, will require higher levels of protein and energy.

How do you determine the cost of energy in a feed product?
In an extremely simplified way, using TDN (total digestible nutrients) as the energy estimate, you can first determine the price per kilogram of product and then divide by the %TDN. This will result in the price per kg of TDN. If I am concerned with feeding mature cows my energy sources may be forages whereas in a calf feeding program energy sources should be grains. Ex. Alfalfa grass hay with 60% TDN if priced at \$85/tonne will have a value of 14 cents per kg of TDN. If you compared that hay to another possible feed, ex. barley greenfeed with 56% TDN priced at \$65/tonne, the value of TDN for the greenfeed would be 65/1000 = 0.065/56%=0.12. The cost of TDN in the greenfeed is 12 cents per kg which is a cheaper buy than the alfalfa mixed hay for your cow herd.

For your feeder calves, barley compared to grain screening pellets is likely a more obvious comparison for their energy source. Be aware that pellets may have added minerals or vitamins that will have to be taken into account before determining the final value of the feed. Barley priced at \$125/tonne with 83% TDN has a value of 125/1000=0.125/.83=0.15. Barley energy is costing you 15 cents per kg of TDN. Grain screening pellets priced at \$95/tonne with 72% TDN would be valued at 13 cents per kg TDN making the pellets at these prices the more economical energy source.

How do I compare the different protein levels?
Protein cost comparisons can be done in the same way. For calves, an example may involve comparing a 32% protein beef supplement worth \$325/tonne to 34% protein canola meal priced at \$225/tonne. However, with this comparison remember the supplement likely has added value in added minerals and vitamins that will have to be taken into account before making your final purchase decision. The 32% beef supplement would have a protein value of 325/1000=0.325/32%= \$1.02/kg protein. The canola meal would have a value of 225/1000=0.225/34%= \$0.66/kg protein.

Don't ignore putting a value to the minerals and vitamins that may be added in some prepared feeds.
It is important to note that some products will contain added macro and trace minerals and vitamins and these need to be taken into account before your final purchasing decision is made. Supplemental mineral and vitamins comes at a cost and must be added to the protein or energy source to arrive at a true feed cost. While some products may provide more protein and energy at less cost, it is false economy and bad management to purchase the most economical source of protein and energy unless care is taken to adequately supplement both minerals and vitamins in the total diet. Once cost comparisons between products are made the rations must be balanced to meet the needs of the animals. This process of valuing the energy and protein components of the feeds will help you to eliminate excessively costly feeds and narrow your choices to the more economical ones for your specific situation.

Drought Options: Ration Options for Beef Cows