California is a leading producer of pistachios in the United States and globally and it is estimated that annual production will reach 2.08 billion pounds in 2031. As a result, about 31.2 million pounds of shells will be produced after the nuts are processed for human consumption. Pistachio shells have been viewed as a waste product and are frequently disposed of using ecologically friendly practices. However, it is possible that pistachio shell powder can be used as a high fiber ingredient for swine. Specifically, gestating sows may benefit from the high fiber concentration in pistachio shell powder because this may increase satiety and reduce stress. However, at this time, there is no information about the nutritional value of pistachio shell powder when fed to sows. Therefore, an experiment was conducted to test the hypothesis that apparent total tract digestibility (ATTD) of gross energy (GE) and concentrations of digestible energy (DE) and metabolizable energy (ME) in pistachio shell powder are not different from those in soybean hulls when fed to gestating sows. The second hypothesis was that the ATTD of GE and DE in pistachio shell powder are not different from those in soybean hulls when fed to lactating sows.

Experimental design

Exp. 1. Gestating sows- Twenty-four gestating sows (parity: 2 to 6) that were approximately 65 days into gestation were allotted to 2 blocks of 12 sows using a randomized complete block design with three diets and four sows per treatment in each block for a total of 8 replicate sows per diet. A corn-based basal diet and two diets containing corn and 20% pistachio shell powder or corn and 20% soybean hulls were formulated. Vitamins and minerals were included in all diets to meet or exceed requirements (NRC, 2012). Daily feed allowance was 1.5 times the maintenance energy requirement for gestating sows (i.e., 100 kcal/kg BW^0.75; NRC, 2012). Sows had free access to water throughout the experiment.

Exp. 2. Lactating sows- Twenty-four multiparous sows in lactation were used in a randomized complete block design with 2 blocks of 12 sows, 3 diets, and 4 sows per diet in each block for a total of 8 replicate sows per treatment. The basal diet was formulated based on corn and soybean meal (SBM) and this diet met all nutrient requirement estimates for lactating sows (NRC, 2012). Two additional diets were formulated by including corn and SBM and 20% of either pistachio shell powder or soybean hulls in the diet. All diets contained corn and SBM at a ratio of 2.87:1.00 and 0.40% TiO₂ was included in all diets as an indigestible marker.

Results

Exp. 1. Gestating sows. Concentrations of DE and ME on an as-fed basis as well as on a DM basis were less (P < 0.05) in pistachio shell powder compared with corn and soybean hulls (Table 1). On a DM basis, DE and ME in soybean hulls were less (P < 0.05) than in corn. The DE:GE and the ME:GE ratios in corn were the greatest (P < 0.05), followed by soybean hulls (P < 0.05) and pistachio shell powder (P < 0.05).

Exp.2. Lactating sows. Feed intake and GE intake of sows fed the basal diet or the diet containing pistachio shell powder were greater (P < 0.05) than of sows fed the diet containing soybean hulls, but there were no differences in feed intake between sows fed the basal diet and sows fed the diet containing pistachio shell powder (Table 2). The ATTD of DM and GE and the concentration of DE in the basal diet was the greatest (P < 0.05), followed by soybean hulls (P < 0.05) and pistachio shell powder (P < 0.05). The concentration of DE in pistachio shell powder was less (P < 0.05) than in soybean hulls.

Key Points

• Pistachio shells can be fed to gestating and lactating sows without causing any problems with feed intake.
• The DE and ME for pistachio shells for gestating sows is around 2,700 and 2,600 kcal per kg DM, respectively, which is less than for corn and soybean hulls.
• The DE in pistachio shells included in a diet for lactating sows is around 1,664 kcal/kg DM.

Table 1. Concentrations of digestible energy (DE) and metabolizable energy (ME) in corn, pistachio shell powder, and soybean hulls fed to gestating sows¹ (Exp. 1)

Table 2. Apparent total tract digestibility (ATTD) of dry matter (DM) and gross energy (GE) and concentrations of digestible energy (DE) in experimental diets fed to lactating sows¹