Concentrations of digestible and metabolizable energy are greater in pistachio blanks than in wheat middlings, but some amino acids in pistachio blanks have reduced digestibility compared with soybean meal when fed to growing pigs.

Pistachio blanks are a mixture of pistachio byproducts that consist of undersized or unripe seeds and hard shells that may potentially be used as a high-fiber feed ingredient in diets for pigs, but there is limited information about the nutritional value of pistachio blanks when fed to pigs. Therefore, two experiments were conducted to determine the chemical composition and energy and amino acid (AA) digestibility of pistachio blanks fed to growing pigs. In experiment 1, the objective was to test the null hypothesis that apparent total tract digestibility (ATTD) of gross energy and digestible energy (DE), and metabolizable energy (ME) in pistachio blanks are not different from values obtained in wheat middlings when fed to growing pigs. Twenty-four growing pigs with an initial body weight of 23.01 ± 0.90 kg were individually housed in metabolism crates. A basal diet contained corn and soybean meal as the sole sources of energy, and two diets contained corn, SBM, and 30% pistachio blanks, or corn, SBM, and 30% wheat middlings. Twenty-four pigs were allotted to the three diets with eight replicate pigs per diet. Feces and urine samples were quantitatively collected for 4 d after seven days of adaptation. Results indicated that the ATTD of dry matter and gross energy and DE and ME were greater (P < 0.05) in pistachio blanks than in wheat middlings. In experiment 2, nine growing barrows (initial body weight: 22.67 ± 0.93 kg) were equipped with a T-cannula in the distal ileum and allotted to a triplicated 3 × 3 Latin square design with three diets and three 7-d periods, for nine replicate pigs per treatment. Two diets contained pistachio blanks or soybean meal as the sole source of AA and a nitrogen-free diet was also formulated. The apparent ileal digestibility of dry matter, crude protein, indispensable AA, and dispensable AA was greater (P < 0.05) in soybean meal than in pistachio blanks. The standardized ileal digestibility (SID) of Ile, Leu, Phe, Val, Ala, Asp, Gly, Pro, and Ser was not different between pistachio blanks and soybean meal, but the SID of Arg, His, Lys, and Met was greater (P < 0.05) in soybean meal than in the pistachio blanks. In contrast, the SID of Thr and Trp was greater in pistachio blanks than in in soybean meal. In conclusion, pistachio blanks contain more DE and ME than wheat middlings, but the SID of some, but not all, indispensable AA is less than in soybean meal.