Pistachio blanks may serve as a high-fiber feed for pigs, offering strong energy digestibility but mixed amino acid performance.

Pistachio blanks are byproducts made up of undersized or unripe seeds and hard shells. They may potentially serve as a high-fiber feed ingredient in pig diets, but little is known about their nutritional value when fed to pigs.
To address this gap, Yeonwoo Kim and his team at the University of Illinois at Urbana-Champaign in the US conducted two experiments to evaluate the chemical composition, energy content, and amino acid digestibility of pistachio blanks in growing pigs.
Experiment 1: Energy digestibility
The first experiment tested the null hypothesis that apparent total tract digestibility (ATTD) of gross energy and digestible energy (DE), and metabolizable energy (ME) in pistachio blanks are similar to wheat middlings.
Twenty-four growing pigs with an initial body weight of 23.01 ± 0.90 kg were individually housed in metabolism crates.
Three diets were formulated: a basal diet with corn and soybean meal, a diet with 30% pistachio blanks, and a diet with 30% wheat middlings. Eight pigs were assigned to each diet. After a seven-day adaptation period, feces and urine were collected for four days.
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.
Results indicated that pistachio blanks had greater ATTD of dry matter, gross energy, DE, and ME were greater (P < 0.05) than wheat middlings.
Experiment 2: Amino acid digestibility
The second experiment focused on amino acid digestibility. Nine growing barrows (initial body weight: 22.67 ± 0.93 kg) were fitted with a T-cannula in the distal ileum. They were 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. However, 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 soybean meal.
Conclusion
The study found that pistachio blanks provide more digestible and metabolizable energy than wheat middlings, making them a promising alternative feed ingredient.
However, their amino acid digestibility is lower than soybean meal for several indispensable amino acids, though they perform better for Thr and Trp.
These findings highlight both the potential and limitations of pistachio blanks in pig diet.
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