Standardized ileal crude protein and amino acid digestibility of eight wheat genotypes fed to growing pigs
The objective of this study was to determine in growing pigs the standardized ileal digestibility (SID) of CP and AA of 8 currently available wheat genotypes grown in Southern Germany under standardized field test conditions. The assay diets were formulated to contain 1 of the 8 wheat genotypes each, with wheat as the sole dietary source of CP and AA. All diets were supplemented with 0.7% titanium oxide as an indigestible marker. Nine ileal cannulated barrows (32 ± 2 kg BW) were fed 8 diets in 8 periods of 6 d each at a daily intake level of 40 g/kg of their average BW, corresponding to about 3 times the animals’ energy requirement for maintenance (106 kcal of ME/kg of BW0.75). The SID of the 8 wheat genotypes was calculated using literature data for correction of basal ileal endogenous losses of CP and AA. Data were analyzed using the MIXED procedure of SAS with genotype and pig as fixed effects, and periods and pigs as random effects. Effects of chemical composition of the wheat genotypes on SID of CP and AA in the wheat genotypes were analyzed by linear regression analyses. Among proximate nutrients, only small differences in DM, crude ash, and ether extract content were observed between the 8 different wheat genotypes. On as-fed basis, concentrations of CP and starch ranged from 10.9 to 13.3 and 61.5 to 64.4% in the 8 wheat genotypes, respectively. The greatest concentrations of NDF and ADF were 11.6 and 3.3% (as-fed), respectively, whereas ADL concentration did not exceed 0.7% (as-fed) in the 8 wheat genotypes. Among the 8 wheat genotypes, SID of CP, Lys, Met, Thr, and Trp ranged from 83 to 87% (P = 0.010), 69 to 74 (P = 0.037), 84 to 88 (P = 0.010), 78 to 82 (P = 0.053), and 80 to 85% (P= 0.005), respectively. Fiber fractions and CP contents in the 8 wheat genotypes had minor effects on SID of CP, Lys, Met, Thr, and Trp. Moreover, SID of CP, Lys, Met, Thr, and Trp of this study were up to 5, 15, 6, 8, and 8% lower when compared with current feed tables. Due to the observed variations in SID of CP and AA between wheat genotypes in the present study, differences in SID between different batches of wheat should be taken into account for pig diet formulations.
Keywords: digestibility, pig, wheat