Variability in wheat middlings
Are there differences in digestibility, composition among sources?
By Charmaine D. Espinosa and Hans H. Stein
Among cereal co-products, wheat middlings is one of the most commonly used ingredients in pig diets. However, variation in nutrient composition may be observed in wheat middlings, and these variations may be attributed to the milling process and to the amount of bran and germ present in wheat middlings.
Data have been published for the composition of wheat middlings from flour mills in the United States, and data for digestible energy (DE) and metabolizable energy (ME), and standardized ileal digestibility (SID) of amino acids (AA) have been reported as well. However, it is not known if data obtained for wheat middlings from the U.S. also are representative for wheat middlings in Europe.
Therefore, two experiments were conducted to test the hypothesis that there are no differences in composition, concentrations of DE and ME, and SID of crude protein and AA between wheat middlings sourced from flour mills in Europe and in the United States. For both experiments, 10 sources of wheat middlings were used (Table 1). Five sources were procured from Europe (i.e., Germany, Spain, France, Hungary and Italy) and the other five sources were procured from the United States (i.e., sources 01, 02, 03, 04 and 05).
Amino acid, energy digestibility resultsSources from Germany and Hungary had the least SID value for crude protein (Table 2). This consequently resulted in a tendency for a reduced (P < 0.10) SID of crude protein of wheat middlings sourced from Europe compared with U.S. sources. Overall, wheat middlings from Germany and Hungary had reduced (P < 0.05) SID of AA compared with other sources. As a consequence, the SID of His, Leu, Lys, Asp, Cys, Glu and Ser of wheat middlings sourced from Europe were less (P < 0.05) compared with the SID of the same AA in wheat middlings from the United States.
Due to reduced AID and SID of crude protein and AA in wheat middlings from Germany and Hungary, increased variability for crude protein and AA digestibility values was observed in five sources of wheat middlings from Europe (i.e., mean SD for SID of crude protein and AA = 5.7). In contrast, crude protein and AA digestibility values in five sources of wheat middlings sourced from the U.S. had less variability (i.e., mean SD for SID of crude protein and AA = 2.2).
The variability of starch in wheat middlings from Europe was greater compared with sources from the U.S. Wheat middlings sourced from Germany and Hungary had the greatest concentration of total dietary fiber, whereas U.S. source 01 had the least concentration of total dietary fiber.
The apparent total tract digestibility of gross energy and dry matter in wheat middlings sourced from Europe was less (P < 0.05) compared with wheat middlings sourced from the U.S. (Table 3). Wheat middlings from Hungary had the least (P < 0.01) concentration of DE, whereas wheat middlings from Spain and U.S. source 1 had the greatest (P < 0.01) concentration of DE. Wheat middlings sourced from Europe had reduced (P < 0.05) concentrations of DE and ME compared with wheat middlings sourced from U.S.
ConclusionThe apparent total tract digestibility of gross energy and SID of most AA in wheat middlings from Hungary were less than in other sources. As a consequence, energy concentrations and AA digestibility values for wheat middling sourced from Europe were less than in wheat middlings sourced from the U.S., which is likely due to increased concentration of dietary fiber in wheat middlings from Europe. Increased variability in energy and AA digestibility values was also observed in the five wheat middlings from Europe, which is possibly a result of differences among flour mills in the production process among European countries.
Espinosa is post doctoral research fellow and Stein is a professor, both in the Department of Animal Sciences, University of Illinois, Urbana.
