Standardized ileal amino acid digestibility in eight genotypes of rye fed to growing pigs
A study was conducted to determine in growing pigs the standardized ileal digestibility (SID) of CP and AA in 8 currently available genotypes of rye. The rye genotypes were grown under the same standardized field conditions at the University of Hohenheim, Germany. The experiment was conducted with 8 barrows with an initial BW of 24 ± 2 kg, and fitted with a simple T-cannula at the distal ileum. The pigs were randomly allotted to an 8 × 8 Latin square design. Diets were based on 1 of the 8 rye genotypes each, with rye as the sole source of CP and AA. An N-free diet was fed to determine basal ileal endogenous losses of CP and AA in an additional period at the conclusion of the experiment. Diets were supplemented with titanium dioxide as digestible marker and fed at a daily intake level of 40 g/kg of pigs’ average BW corresponding to about 3 times the pigs’ energy requirement for maintenance (106 kcal of ME/kg of BW0.75). Each experimental period consisted of 4 d for adaptation to the diets and 2 d for ileal digesta collection. Ileal digesta samples were collected consecutively for a total of 24 h. Data were analyzed by the Mixed Procedure of SAS with genotype and pig as fixed effects, and pigs and periods as random effects. The CP and non-starch polysaccharides (NSP) concentrations (as-fed) in the 8 rye genotypes ranged from 9.5 to 11.2%, and 10.7 to 12.9%, respectively. The greatest concentrations of NDF, ADF and ADL were 15.1, 3.0 and 0.9% (as-fed) in the 8 rye genotypes. Among the 8 rye genotypes, SID of CP, Lys, Met, Thr and Trp ranged from 70 to 74, 60 to 65, 74 to 78, 62 to 66 and 63 to 67%, respectively. The SID of CP and AA did not differ between the 8 rye genotypes, except for SID of Cys (P= 0.044). The SID of CP and AA were not affected by NSP and NDF content. Overall, SID of CP, Lys, Met, Thr, and Trp in rye derived from the present study were up to 13, 14, 7, 12, and 13%-units lower than the values reported in current feed tables. Using these SID values will aid for accurate AA balancing when these new rye genotypes are used in pig diet formulations.
Keywords: amino acid digestibility, growing pigs, rye