Data for the composition of wheat middlings from flour mills in the U.S. and for the standardized ileal digestibility (SID) of crude protein (CP) and amino acids (AA) have been published for wheat middlings from the U.S. However, it is not known if the data obtained from wheat middlings from the U.S. also are representative for wheat middlings in Europe. Therefore, an experiment was conducted to test the hypothesis that there are no differences in composition and SID of CP and AA between wheat middlings sourced from flour mills in Europe and in the U.S.

Experimental design

Ten sources of wheat middlings were used in the experiment (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 U.S. (i.e., sources 01, 02, 03, 04, and 05). Ten diets contained one source of wheat middlings as the only source of crude protein and AA. The last diet was a nitrogen-free diet that was used to determine the endogenous loss of AA from the pigs. Each experimental period lasted 7 d. The initial 5 d of each period was considered an adaptation period. Ileal digesta were collected on d 6 and 7 for 9 h using standard procedures. Diets and ileal digesta samples were analyzed for AA and Cr to calculate the apparent ileal digestibility (AID) of CP and AA in wheat middlings sources. The AID values were then corrected using the basal endogenous losses of CP and AA to calculate the SID values.

Results

All European sources contained approximately 15% CP except for the wheat middlings from Italy which contained 17.4% CP (Table 1). Wheat middlings sourced from the U.S. also contained approximately 15 to 16% CP except for source 05 which contained 13.8% CP. Differences (P < 0.01) in SID of CP were observed with sources from Germany and Hungary having the least SID value for CP (Table 2). This consequently resulted in a tendency for a reduced (P < 0.10) SID of CP 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 that of wheat middlings from the U.S. Due to reduced AID and SID of CP and AA in wheat middlings from Germany and Hungary, increased variability on CP and AA digestibility values was observed in five sources of wheat middlings from Europe (i.e., mean SD for SID of CP and AA = 5.7). In contrast, CP 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 CP and AA = 2.2).

Key points

• The SID of CP and most AA in wheat middlings from Germany and Hungary were less than in other sources.
• Amino acid digestibility values for wheat middlings sourced from Europe were less than in wheat middlings sourced from the U.S.
• Increased variability on CP and AA digestibility values was observed in five sources of wheat middlings from Europe, which is possibly a result of differences among flour mills in the production process within European countries.

Table 1. Analyzed composition of the ten sources of wheat middlings (as fed basis)

¹G = Germany; S = Spain; F = France; H = Hungary; I = Italy.

Table 2. Standardized ileal digestibility (SID) of crude protein (CP) and amino acids (AA) in ten sources of wheat middlings^1,2

¹Data are least squares means of 7 to 8 observations per treatment.

²Values for SID were calculated by correcting the values for AID for basal ileal endogenous losses. Basal ileal endogenous losses were determined (g/kg of dry matter intake) as CP, 16.94; Arg, 0.64; His, 0.17; Ile, 0.30; Leu, 0.47; Lys, 0.55; Met, 0.07; Phe, 0.27; Thr, 0.49; Trp, 0.08; Val, 0.39; Ala, 0.65; Asp, 0.72; Cys, 0.17; Glu, 0.90; Gly, 1.59; Ser, 0.48; and Tyr, 0.24.

³G = Germany; S = Spain; F = France; H = Hungary; I = Italy.

⁴Comparison of the ten sources of wheat middlings.

^a-dMeans within a row lacking a common superscript differ (P < 0.05).

^x-zMeans within a row lacking a common superscript tended to differ (P < 0.10).