Chemical composition and standardized ileal amino acid digestibility of eight genotypes of rye fed to growing pigs.

A study with growing pigs was conducted to determine the chemical composition, physical characteristics, and standardized ileal digestibility (SID) of CP and AA of 8 rye genotypes that have recently been added to the German Descriptive Variety List. Eight barrows with an initial BW of 24 ± 2 kg were fitted with T-cannulas at the distal ileum and allotted to an 8 × 8 Latin square design with 8 periods of 6 d each and 8 pigs receiving 8 different diets. The N-free method was used to determine the basal ileal endogenous CP and AA losses. The 8 assay diets contained 1 of 8 rye genotypes (Guttino, Palazzo, Visello, Bellami, Dukato, Conduct, Helltop, and Dankowski Diament) as the sole source of CP and AA. The rye genotypes were grown under identical environmental conditions on the same site. Among the 8 rye genotypes, contents of CP ranged from 9.5 to 11.2% (as-fed basis) and contents of total nonstarch polysaccharides (NSP) ranged from 10.7 to 12.9% (as-fed basis). Arabinoxylan (AX) constituted the major NSP fraction, with values ranging from 6.5 to 7.6% (as-fed basis). Among the 8 rye genotypes, starch contents ranged from 55.7 to 57.5% (as-fed basis). The SID of CP in the 8 rye genotypes ranged from 70 to 74%. The SID of Cys in genotypes Visello, Bellami, Dukato, and Dankowski Diament was lower ( < 0.05) when compared with Palazzo, Conduct, and Helltop. For all other AA, SID in the 8 rye genotypes did not differ. The standardized ileal digestible content (cSID) of CP was greatest ( < 0.001) in genotype Dankowski Diament (8.1%, as-fed basis) and lowest ( < 0.001) in genotype Guttino (6.9%, as-fed basis). Genotype Guttino had the lowest ( < 0.05) cSID of AA among all rye genotypes, except for Trp, Gly, and Pro. For Thr, Ala, and Gly, there were no differences in cSID among the 8 rye genotypes. For CP and most AA, cSID decreased as contents of total and insoluble β-glucan ( < 0.05), total AX, and soluble NSP increased ( < 0.05). The results of the present study provide a comprehensive database on chemical composition, physical characteristics, and SID of CP and AA of 8 rye genotypes grown under same conditions. However, as present SID values of these recently introduced genotypes are lower compared to values in feed tables, adjustments are possibly required to minimize the risk of overestimating the actual protein value of rye for pigs.