Determination and prediction of digestible energy, metabolizable energy, and standardized ileal digestibility of amino acids in barley for growing pig

Two experiments were performed to determine the digestible energy (DE), metabolizable energy (ME) and standardized ileal digestibility coefficients (SIDC) of amino acids (AA) in barley for pigs, and to develop prediction equations for the DE, ME and SIDC of AA based on its chemical composition. In Exp. 1, twenty-two castrated male pigs (29.5 +/- 1.3 kg) were allotted to a replicated 11 x 3 incomplete Latin square design, including 11 diets and 3 consecutive periods. A corn-soybean meal basal diet and 10 test diets containing 400 g/kg of each barley at the expense of corn and soybean meal were prepared, and all diets had a constant ratio of corn to soybean meal. Each period includes 7 d of adaption and 5 d of total feces and urine collection. The DE and ME contents were measured by the total collection method. In Exp. 2, twenty-two ileal-cannu-lated pigs (30.5 +/- 2.1 kg) were used in a duplicated 11 x 3 incomplete Latin square design with 11 diets and three 7-day periods. Titanium dioxide (3 g/kg) was added to all diets as indicator and ieal digesta were collected on d 6 and 7 of each period. Barley was the sole nitrogen source in 10 barley diets and a nitrogen-free diet was used for the endogenous nitrogen losses. The results showed great variations in ether extract (EE), calcium (Ca), ash, acid detergent fiber (ADF) and crude fiber (CF) among samples of barley. On an air-dry basis, the DE and ME in barley for pigs were 12.26 (11.29-13.58) MJ/kg and 11.87 (10.95-13.15) MJ/kg, respectively. The optimal prediction equations for DE and ME were: DE (MJ/kg) =-23.594 + 0.358 crude protein (CP) + 0.043 EE (R2 =0.95) and ME (MJ/kg) = 0.338 + DE -0.014 ADF (R2 =0.99), respectively. The SIDC of lysine (Lys), methionine (Met), threonine (Thr), and tryptophan (Trp) in barley were 0.767 (0.731-0.809) g/kg, 0.825 (0.803-0.872) g/kg, 0.809 (0.793-0.822) g/kg, and 0.794 (0.760-0.858) g/kg, respectively. The best-fit prediction equations for SIDC of Lys, Met, Thr and Trp in barley fed to pigs were: SIDC Lys = 0.721 + 0.002 EE (R2 =0.79), SIDC Met = 1.045-0.00041 total starch (R2 =0.69), SIDC Thr = 0.739 + 0.001 ADF (R2 =0.69) and SIDC Trp = 1.468-0.006 CP -0.001 neutral detergent fiber (R2 =0.99), respectively. The study confirms the large variations in chemical composition of different sources of barley, which contributes to the differences of DE, ME and SIDC of AA in barley fed to pigs and the fiber fraction can be used as key predictors.

Automated summary

Two experiments were conducted to determine the DE, ME, and SIDC of amino acids in barley for pigs and develop prediction equations based on its chemical composition. The results showed that barley had variations in its chemical composition, which influenced its DE, ME, and SIDC. Fiber fraction was found to be a key predictor for the energy and amino acid digestibility.