Correlation between physical measurements and dietary energy values of wheat for poultry and pigs

A number of wheat samples were obtained for evaluation: for young poultry, 50 wheats (10 varieties each grown at five sites) with bushel weights/thousand grain weights ranging from 69.5 to 80.0 kg/hl and 34.6 to 59.3 g, respectively; for pigs (8 different varieties each grown at 2 sites) with bushel weights/thousand grain weights ranging from 71.0 to 81.5 kg/hl and 40.9 to 56.7 g, respectively. Apparent metabolisable energy (AME) and coefficient of metabolisability of gross energy (CAME) were determined with young broilers; Digestible energy (DE) and coefficient of total tract apparent digestibility (CTTAD) of gross energy were determined with growing finishing pigs. Wheat was added at a rate of 750 and 900 g/kg diet for poultry and pigs, respectively, in a series of metabolism trials. AME values ranged from 8.49 to 12.45 MJ/kg DM and CAME from 0.491 to 0.702. DE values ranged from 14.55 to 16.07 MJ/kg DM and CTTAD from 0.848 to 0.890. There were significant differences between variety and site (together with interaction terms) in both, the physical and biological measurements, but not in a structured fashion. There were no significant relationships between the two physical measurements and any dietary energy value (either in terms of concentration or coefficient), confirming previous work. The two lowest bushel weight wheats had among the highest AME values for poultry, confirming that evaluation of the variability in nutritional value of wheat for poultry should only proceed against a background of detailed knowledge of genotype. Comparisons on the basis of variety name alone appear inappropriate as individual varieties do not seem to respond in a uniform fashion.