Nutritive value of wheat and wheat by-products in pig nutrition: A review

Wheat is an important energy component in diets for pigs which is mainly attributed to its high starch content. The crude protein (CP) content is rather low compared to protein supplements, but due to its high dietary inclusion level wheat provides significant amounts of indispensable amino acids (AA) in diets for pigs. Currently available feed tables on the chemical composition and nutritional value of wheat have in common that they hardly take into account the impact of recent advances in plant breeding including introduction of new cultivars and by-products on the nutritive value of wheat and its by-products. These by-products such as wheat bran, wheat middlings and wheat distillers dried grains with solubles have gained increasing attention in pig nutrition. In particular, processing of wheat for biofuel production resulted in the production of different by-products characterized by relatively high CP and ether extract contents. Moreover, wheat contains various proportions of non-starch polysaccharides (NSP) including arabinoxylans, β-glucans and pectins, which are enriched during processing of wheat to produce flour for human consumption. These components can be used as dietetic components, but they also may interfere with nutrient digestibility. The use of feed enzymes in diets based on wheat and wheat by-products may alleviate the negative effects of NSP on nutrient and energy digestibility, thereby improving the feeding value of these feed ingredients. Accordingly, other processing procedures, such as grinding, extruding, pelleting, micronizing, fermenting and ensiling can improve the nutrient and energy digestibility of wheat in diets for pigs. The object of the present review is to revise the information on the nutritive value of wheat and its by-products in pig nutrition. This revision comprises updated data on the content of AA, energy and carbohydrates in wheat and several wheat by-products including information on standardized ileal protein and AA digestibility.