Park W. Waldroup Dr. Waldroup, this discussion has been in the industry for decades, and you have actively participated with a lot of data over the years. So, I think that a little bit of history and actual data may help to illustrate, or better, illustrate again what you have done in reference to formulating to the least cost per balance calorie. At the 1995 Maryland Nutrition Conference (yes, 1995!) Waldroup et al. presented "Growing the large male broiler for further processing - dietary energy considerations".
It was the report of two trials that were conducted with male Ross (presumably 308) broilers which were randomly assigned to litter-floor pens with 50 birds per pen (4.65 sq-m or about 1 bird per sq-ft). Diets were formulated for starter (0 to 21 days), grower (21 to 42 days), and finisher (42 to 63 days) periods. All diets were formulated to meet the nutrient requirements for male broilers suggested by Thomas et al. [1992. Proceedings Maryland Nutrition Conference, University of Maryland, pages 45-53] with minimum amino acid requirements at 105% of the suggested levels. All diets contained 5% poultry by-product meal as a source of animal protein and were fortified with complete vitamin and trace mineral premixes, salinomycin (66 mg/kg) and bacitracin methylene disalicylate (55 mg/kg).
Ten diets were formulated within each period. These diets were obtained by increasing the amount of poultry oil from 0 to 9% in increments of 1% and formulating for optimum nutrient density (energy and associated nutrients). Starter diets ranged from 2985 ME kcal/kg (1357 kcal/lb) to 3333 ME kcal/kg (1515 kcal/lb); grower diets 3027 (1376) to 3379 (1536); and finisher diets ranged from 3078 (1399) to 3436 (1562). Calorie:protein ratios remained relatively constant across all diets within each age period. All diets were pelleted; starter diets were fed as crumbles. Body weights and feed intake were determined at 21, 42, 49, 56, and 63 days of age. At 63 days of age, sample birds were processed in a pilot plant to determine the influence of dietary treatments on processing characteristics and breast meal yields.
At the time of this publication, I was formulating for some of the poultry operations of the Continental Grain Company among them one in Puerto Rico. And by coincidence, I was very intrigued about the subject of this discussion: what was, based on bird performance, the lowest cost formulation? Since the paper by Waldroup et al. (1995) coincided very well with what I was trying to understand I decided to first, contact Dr. Waldroup to get the details of their protocol which was immediately kindly provided by fax, and second, I just replicated the paper's formulation in CGC's least-cost formulation program using the prices at that time in Puerto Rico for the ingredients used by Waldroup which of course were corn-soy, poultry by-product meal etc., quite closed to our formulation reality at the time.
The results and discussion presented by Waldroup et al. (1995) were targeted at live and further processed performance at 63 days of age while my specific objective was to estimate, using their data, the lowest formulation cost at 49 days which was my market. In other words, I wanted to estimate the range of metabolizable energy for the lowest cost of live performance at 49 days of age. As indicated above, overall 10 feeding programs were evaluated for which the Mean Diet Energy (MDE, kcal/kg) were calculated and performance data were reported at 21, 42, 49, 56 and 63 days of age. My final report contained nine tables, however, here for the purpose of this discussion two tables are sufficient.
Table 1 taken directly from Waldroup et al. (1995) shows that with all feeding programs the highest MDE resulted in the lowest feed conversion ratio (only a slight numerical exception at 42 days). However, at 49 days of age the lowest cost of feed per kg of gain (Table 2) was feeding program 2 with a MDE of 3069 kcal/kg and FCR 1.934 instead of feeding program 10 with a FCR of 1.826 for a MDE of 3383. The former is the optimal lower cost of ME for this dataset at 49 days of age. Table 2 also shows that there are relatively minimum differences around programs 1 to 4, which were low ME with low levels of added poultry oil. However, at much higher levels of added poultry oil (therefore higher MDE) the cost difference is economically significant. Program 2 versus Program 10 at 49 days of age for 1 million kg of broiler meat is $12,832. Just as you said, a calorie from fat is much more expensive than a calorie from corn. Nelson Ruiz Nutrition, LLC, Suwanee, GA USA.