Sunflower meal, which is the co-product derived from sunflower seeds after oil extraction, has a high concentration of digestible amino acids (AA) and fiber. The nutritive value and quality of sunflower meal is partially dependent on the degree of dehulling, the variety of the sunflower, and the oil extraction process. Sunflower seeds are initially de-hulled and then partially de-oiled using a mechanial prepress procedure. A second de-oiling procedure is performed using a solvent extraction procedure or by usign a second mechanical expelling procedure. The prepress-solvent extraction procedure results in production of sunflower oil and sunflower meal that contains 1 to 3% oil, whereas the double-press procedure results in production of sunflower oil and a sunflower product that contains 5 to 10% residual oil and commonly is referred to as sunflower expellers. Some of the hulls may be added back to the sunflower meal or the sunflower expellers resulting in differences in concentrations of total dietary fiber among sources.

The apparent ileal digestibility and the standardized ileal digestibility (SID) of crude protein (CP) and AA in individual sources of partially de-hulled sunflower meal fed to pigs have been reported. However, there are no comparative values for the SID of AA in sunflower meal produced in different parts of the world, and it is not known if the SID of AA in sunflower meal are different from those in sunflower expellers. Therefore, the objective of the current study was to test the hypothesis that there is no difference in the SID of CP and AA in different sources of sunflower meal and sunflower expellers obtained from different countries.

Experimental design

Six sources of sunflower meal from Ukraine (2 sources), Hungary, Italy, and the U.S. (2 sources) and one source of sunflower expellers from the U.S. were included in the experiment (Table 1). Each source of sunflower meal or sunflower expellers was included in one diet as the sole source of AA. An N-free diet that was used to calculate basal endogenous losses of AA and CP was also formulated. Thus, a total of 8 diets were used.

Eight growing pigs with an average initial body weight of 25.20 ± 3.20 kg were used. Pigs were equipped with a T-cannula in the distal ileum and allotted to one of the 8 diets using an 8 × 8 Latin square design with 8 diets and 8 periods. The initial 5 d of each period was considered an adaptation period to the diets and ileal digesta were collected for 9 h on d 6 and 7. The statistical model included sunflower meal source as fixed effect and period and animal as random effects. A second analysis was performed to compare results for sunflower expellers with the results for sunflower meal using a contrast statement and this model also included diet as fixed affect and period and animal as random effects. Results were considered significant at P ≤ 0.05 and considered a trend at P ≤ 0.10. The pig was the experimental unit for all analyses.

Results

Concentrations of total dietary fiber varied greatly among the 6 sources of sunflower meal and there was an inverse relationship between concentration of total dietary fiber and CP. This observation is a result of different quantities of sunflower hulls being added back to the sunflower meal after oil extraction and the more hulls that are added, the greater is the concentration of dietary fiber and the lower is the concentration of CP and AA. The sunflower expellers that was used contained more fat than the 6 sources of sunflower meal, which was expected due to the lower efficiency of oil extraction in the mechanical press compared with solvent extraction of oil. However, the sunflower expellers was also high in total dietary fiber and low in CP indicating that a substantial amount of hulls was added back to the sunflower expellers.

The SID of CP was greater (P < 0.05) in sunflower meal sources 1, 5, and 6 compared with sunflower meal sources 3 and 4, but there was no difference in the SID of CP among sunflower meal sources 1, 2, 5, and 6 (Table 2). Values for the SID of most AA in sunflower meal sources 2 and 6 were greater (P < 0.05) than in source 4, but there was no difference in the SID of most AA among sunflower meal sources 1, 2, 5, and 6. The SID of CP and all AA except Cys did not differ between sunflower meal sources 3 and 4. Values for the SID of Lys, Met, and Trp were not different among the 6 sources of sunflower meal. The SID of CP and all AA except Trp were greater (P < 0.05) in sunflower expellers compared with sunflower meal, which is likely a result of the increased oil concentration in sunflower expellers because oil slows down gastric emptying, and therefore, results in more time for enzymes to digest feed protein and more time for absorption of AA.

Based on the results from the study it is concluded that different sources of sunflower meal vary in nutrient composition, primarily fiber and AA, which is likely the result of different inclusion rates of hulls in the meals. However, although some variation in SID of AA was observed, the 6 sources of sunflower meal used in this experiment were not different in SID of Lys, Met, and Trp. It is also concluded that the SID of AA in sunflower expellers is greater than in sunflower meal.

Key points

• Concentrations of fiber and AA in the 6 sources of sunflower meal were more variable compared with other nutrients, which is a result of different inclusion levels of hulls in the final product.
• Sun flower expellers contain more fat than sunflower meal.
• The SID of CP and some AA varied among the 6 sources of sunflower meal, but the SID of Lys, Met, and Trp was not different among sunflower meal produced in Ukraine, Hungary, Italy, or the U.S.
• The SID of CP and AA was greater in sunflower expellers than in sunflower meal.

Table 1. Analyzed nutrient composition of 6 sources of sunflower meal and in one source of sun flower expellers, as-fed basis

¹AEE = acid hydrolyzed ether extract

Table 2. SID of CP and AA in 6 sources of sunflower meal (SFM) and 1 source of sunflower expellers (SFE) ^{1, 2}

^a-cWithin a row, means without a common superscript differ (P < 0.05).

¹Each least squares mean is the mean of 8 observations with the exception that the SID of CP in source 4 is the mean of 7 observations.

²Values for SID were calculated by correcting the values for apparent ileal digestibility for basal ileal endogenous losses. Basal ileal endogenous losses were determined (g/kg of dry matter intake) as CP, 27.25; Arg, 1.36; His, 0.25; Ile, 0.40; Leu, 0.63; Lys, 0.52; Met, 0.10; Phe, 0.37; Thr, 0.61; Trp, 0.13; Val, 0.63; Ala, 1.05; Asp, 0.97; Cys, 0.20; Glu, 1.16; Gly, 2.93; Ser, 0.63; and Tyr, 0.33.