Nutritional value of wheat for growing pigs: chemical composition and digestible energy content

Nutritional value of cereal grains varies greatly, and is currently estimated foremost by measuring density, whereas prediction based on chemical composition might be more useful. Thus, 16 samples of wheat were evaluated for density, chemical composition, and digestibility in growing pigs. The chemical evaluation included analyses for crude protein (CP), amino acids, neutral detergent fibre (NDF), acid detergent fibre (ADF), starch, and monomer sugars in non-starch polysaccharides (NSP). Digestible energy (DE) content was determined with growing pigs (barrows; 40.8 kg +/- 5.3). Density ranged from 57.8 to 77.6 kg hL(-1), CP concentration ranged From 13.0 to 18.1 %, NDF concentration ranged from 12.9 to 25.0%, NSP concentration ranged from 10.5 to 16.6%, xylose concentration ranged from 4.3 to 6.5%, and DE content ranged from 3701 to 4050 kcal kg(-1). Results of chemical analyses were expressed on a dry matter basis. Of the characteristics, xylose had the highest correlation with DE (r = -0.78; P < 0.001), and thus was the best single indicator for DE content (R-2 = 0.61; P < 0.001), followed by total NSP (R-2 = 0.54), and CP (R-2 = 0.49). Density did not predict DE content as well (R-2 = 0.43). Using two chemical characteristics, CP and NDF together resulted in the best prediction of DE content (R-2 = 0.75; P < 0.001). The results indicate that prediction of nutritional value is more accurate based on chemical characteristics than based on density.