Pistachio blanks are co-products from pistachio production and consist of unmarketable pistachio components including the hard outer shells, undersized or unripe kernels, hull fragments, and occasionally woody debris from pruning or sorting operations. As global pistachio production of pistachios increases increased quantities of pistachio byproducts are generated and interest in utilizing some of the co-products in livestock feeding has increased. Data from previous research indicated that pistachio shell powder can be utilized in diets for sows, but because pistachio shell powder and pistachio blanks are very high in fiber, the metabolizable energy in these ingredients fed to weanling pigs is expected to be less than in sows. However, weanling pigs may benefit from the insoluble dietary fiber in pistachio co-products to improve intestinal health, but there are no data to demonstrate effects of including pistachio blanks in diets for weanling pigs. Therefore, an experiment was conducted to test the null-hypothesis that pistachio blanks may be included in diets for weanling pigs without compromising pig growth performance. 

Experimental procedures

Pistachio blanks were procured from the Wonderful Company (Los Angeles, CA, USA) and soybean meal was procured from Solae LLC (Gibson City, IL, USA). Locally produced corn was also used. A two-phase feeding program was used with days 1 to 21 being phase 1 and phase 2 to 42 being phase 2. In both phase 1 and phase 2, a control diet based on corn and SBM was formulated, and three additional diets were formulated based on corn and 5% pistachio blanks, corn and 7.5% pistachio blanks, or corn and 10% pistachio blanks. All diets were formulated to meet current nutrient requirements for weanling pigs (NRC, 2012). Pistachio blanks were included in the diets at the expense of corn and enzyme treated soybean meal.

A total of 160 newly weaned pigs with an initial body weight of 5.73 ± 0.33 kg were used in a randomized complete block design with 10 blocks of 16 pigs per block. Pigs were housed in fully slatted pens (1.2 × 1.4 m) in an environmentally controlled barn. A 4-hole feeder and a nipple drinker were installed in each pen. Temperature, humidity, lighting, feeder and water space were identical for all pens. The barn temperatures were 30^oC in week 1 post-weaning, 28 ^oC in week 2, 26 ^oC in week 3, 24 ^oC in week 4, and 22 ^oC in weeks 5 and 6 post-weaning.

Individual pig weights were recorded at the beginning of the experiment, on day 21, and at the end of the 42-day experiment. Daily feed allotments were recorded and the weight of feed left in the feeders was measured on day 21 and on the last day of the experiment to calculate feed consumption. Data were summarized to calculate average daily gain, average daily feed intake and average gain to feed ratio.

Results and discussion

All pigs remained healthy throughout the experiment and readily consumed their assigned diets. Overall average daily gain, average daily feed intake and gain to feed ratio were not impacted by dietary treatments. There were also no differences among treatment groups during each of the 2 phases. These results are somewhat surprising because the concentration of metabolizable energy in pistachio blanks is less than in corn and it was, therefore, expected that gain to feed would be reduced as pistachio blanks in the diets increased. It is however possible that the high concentration of insoluble dietary fiber in pistachio blanks positively impacted intestinal health, which therefore counteracted the reduced energy in pistachio blanks. However, because intestinal health was not measured in this research, we cannot confirm this hypothesis. Nevertheless, based on the growth performance results, it appears that up to 10% pistachio blanks may be included in diets for weanling pigs without compromising pig growth performance. Future research is needed to determine if pistachio blanks positively impact intestinal health of pigs.

Appreciation

Funding for this research from the Wonderful company (Los Angeles, CA) is greatly appreciated.

Table 1. Analyzed nutrient composition of feed ingredients, as-is basis

Table 2. Ingredient and nutrient compositions of diets

¹Provided the following quantities of vitamins and micro-minerals per kilogram of complete diet: Vitamin A as retinyl acetate, 11,136 IU; vitamin D₃ as cholecalciferol, 2,208 IU; vitamin E as _DL-alpha tocopheryl acetate, 66 IU; vitamin K as menadione dimethylprimidinol bisulfite, 1.42 mg; thiamin as thiamine mononitrate, 0.24 mg; riboflavin, 6.59 mg; pyridoxine as pyridoxine hydrochloride,0.24 mg; vitamin B₁₂, 0.03 mg; _D-pantothenic acid as _D-calcium pantothenate, 23.5 mg; niacin, 44.1 mg; folic acid, 1.59 mg; biotin, 0.44 mg; Cu, 20 mg as copper chloride; Fe, 126 mg as ferrous sulfate; I, 1.26 mg as ethylenediamine dihydride; Mn, 60.2 mg as manganese hydroxychloride; Se, 0.3 mg as sodium selenite and selenium yeast; and Zn, 125.1 mg as zinc hydroxychloride.

Table 3. Growth performance of weanling pigs fed experimental diets