A common method to evaluate feed alternatives is the “cost per unit of nutrient” method.  This method is most useful in situations where only one major nutrient (usually energy or protein) is determined to be deficient.  Table 1 includes cost per ton and cost per unit of protein and energy for several feeds.  Costs for these feeds were estimated based on prices during early November, 1999 with the assumption that they would be delivered to the central Oklahoma area.  Certainly, costs will vary from the values in the table, depending on source, transportation costs and other factors.  Consequently, the data presented should be considered a demonstration of the “evaluation” technique, and not an absolute evaluation of feed stuffs for all producers. 
 

Higher protein feeds are usually cheaper sources of protein and high-energy feeds that are low in protein are cheaper sources of energy.  Cost per unit of nutrient can not be used exclusively in evaluating various feeds.  In the current example, the model cowherd requires supplemental protein and energy.  If the cows were in excellent condition (condition score of 6 or greater), 2 lb. of the 38% cube or 2 lb. of cottonseed meal could be fed to meet the protein requirement.  The net effect would be to maximize forage intake and digestion, with the understanding that the cows would lose some weight and condition, due to a slight deficiency in energy intake.  For cows in moderate body condition, both energy and protein requirement must be met in order to maintain weight and body condition prior to calving.  Table 2 demonstrates various supplementation programs and costs that would meet or exceed both protein and energy supplementation needs. 

Notice that protein must be overfed with the 38% cubes in order to meet the energy need.  Conversely, energy must be overfed in the case of soybean hulls and wheat middlings in order to meet the protein need.  In fact, forage intake would be substantially reduced by feeding this much concentrate (greater than 4 lb. per head).  Therefore, the protein and energy contribution from the forage would need to be reduced.  Because of the low quality forage diet, these cows require considerable supplemental protein and energy.  Consequently, feeds that are moderate in protein (around 25% CP) and high in energy are the most economical supplements in this scenario.  Obviously, for cows receiving bermuda hay or sorghum sudan hay, low protein, high energy feeds would be more economical. 

 Another rule of thumb to consider is to keep total grain intake below 2 to 3 lb. per head per day (.2% of body weight).  Greater amounts cause reduced forage digestibility and intake.  However, supplements that combine grain and high fiber feeds, such as soybean hulls and wheat middlings can be fed up to 4 - 5 lb. (.4 % of body weight) without having much effect on forage utilization.  Recent research suggests that the negative effects of feeding greater amounts of concentrates can be somewhat offset by slightly overfeeding natural protein sources.  It is thought that the microbial population’s requirement for protein is highly associated with the amount of fermentable feed provided.  Obviously, feedgrains and the byproduct feeds listed in table 1 are highly fermentable. 

In summary, reducing feed costs, while maintaining performance is a must for cow/calf producers.  By using a systematic approach to evaluating beef cow nutritional requirements, forage nutrient contribution and alternative supplemental sources, an optimal winter nutrition program can be designed.  The lowest cost alternative will not always be the best program, due to the relative value of convenience, labor availability and feeding system.  The most effective way to evaluate alternatives is to first determine the cost of the total supplementation program, then compare differences in cost with other factors.