BACKGROUND
This study examined whether extracts from apricot kernels (AKE; Prunus armeniaca), peach kernels (PKE; Prunus pérsica), or their 1:1 mixture could improve growth and health-related outcomes in growing rabbits during the vulnerable post-weaning period. The rationale was that these fruit kernels are rich in biologically active phytochemicals with antioxidant and antimicrobial properties, and prior literature suggests that plant secondary compounds can improve gut microbial balance, nutrient utilization, immunity, and oxidative status. The authors specifically aimed to test effects on growth performance, nutrient digestibility, nitrogen balance, cecal fermentation and microbiota, antioxidant biomarkers, and immune response.
METHODS
The experiment used 84 weaned male New Zealand White rabbits at 6 weeks of age, with an initial body weight of 736 ± 23.9 SE g. Rabbits were randomly allocated to 4 dietary treatment groups. The control group received 0.3 mL/kg BW of distilled water, the second group received 0.3 mL/kg BW of AKE, the third group received 0.3 mL/kg BW of PKE, and the fourth group received 0.3 mL/kg BW of a 1:1 mixture of AKE and PKE. Treatments were administered orally each day for 56 days (8 weeks). Rabbits were housed 3 per cage, yielding 7 cages per treatment for growth and digestibility analyses. Environmental conditions were reported as 60 to 65% relative humidity and 22 to 25 °C. The basal pelleted diet contained 17.2% crude protein, 13.1% crude fiber, and 3.45% ether extract. Growth was monitored by weekly body weight and daily feed refusal measurement; feed conversion ratio was calculated from dry matter intake and average daily gain. At 87 days of age, feed refusals, urine, and feces were collected for 5 consecutive days for digestibility and nitrogen balance. For blood and cecal endpoints, 10 animals per treatment were sampled. At 10 weeks of age, selected rabbits were immunized intramuscularly with 0.5 mL of 10% sheep red blood cells (SRBCs), and antibody titers were measured at 11, 12, and 13 weeks as log2 values. On day 92, blood was collected after 12 h of fasting to assess malondialdehyde (MDA), total antioxidant capacity (TAC), catalase, and superoxide dismutase. The same animals were then slaughtered for cecal measurements, including weight, length, pH, ammonia, short-chain fatty acids (SCFAs), and microbial counts. Statistical analysis used one-way ANOVA with Duncan testing, with significance set at p ≤ 0.05.
KEY RESULTS
Gas chromatography/mass spectrometry showed that AKE contained 15 phytochemicals and PKE contained 26 phytochemicals. Both extracts contained abundant 2(3h)-Furanone, 5-Heptyldihydro, with AKE containing almost double the concentration reported for PKE. The most prominent AKE constituents included 1,1-Dimethyl-2 Phenylethy L Butyrate and 1,3-Dioxolane, 4-Methyl-2-Phenyl-, whereas PKE had abundant Cyclohexanol and 10-Methylundecan-4-olide.
All experimental treatments improved growth performance relative to control. Specifically, AKE, PKE, and the mixture increased final body weight, total weight gain, and average daily gain and improved feed conversion ratio (all p < 0.05). PKE and the mixture showed the strongest growth response, with the highest total weight gain and average weight gain (p = 0.001), and this occurred without affecting feed intake. Exact body weight, gain, intake, and feed conversion values were not clearly reported in the provided text.
Digestibility findings favored the mixed extract. The mixture produced the highest dry matter, organic matter, crude protein, ether extract, and non-fiber carbohydrate digestibilities compared with the other treatments (p < 0.05). No differences were found among groups for fiber digestibility. The mixture also had the highest nitrogen retention and the lowest cecal ammonia concentration (p = 0.001 in the abstract; p = 0.01 for lowest cecal ammonia among treatments in the results section). Exact digestibility percentages and nitrogen balance values were not clearly reported in the provided text.
Blood biomarkers also improved with all extracts. Compared with control, all treated rabbits had lower plasma MDA concentrations (p < 0.001), higher TAC (p < 0.001), higher superoxide dismutase (p = 0.017), and higher catalase (p = 0.019). In the immune assessment, all fruit-kernel-treated groups had higher antibody titers against SRBCs than control at 11, 12, and 13 weeks of age (p < 0.05). Exact biomarker concentrations and antibody titer values were not clearly reported in the provided text.
Cecal measurements were also favorably altered. All extracts increased cecal length and both empty and full cecal weights (p < 0.05), and reduced cecal pH (p = 0.0009). All treated groups showed increased total and individual SCFAs versus control (p < 0.05), although exact acetate, propionate, butyrate, and total SCFA values were not clearly reported. Microbiologically, total bacteria, coliforms, and anaerobic counts decreased (p < 0.05), while Lactobacillus acidiophilus and L. cellobiosus counts increased (p < 0.05).
CLINICAL IMPLICATIONS
Although this was not a human clinical study, the work has practical veterinary and livestock relevance. The findings support the concept that phytochemical-rich fruit kernel extracts can act as natural growth-promoting and health-supporting feed additives during the stressful post-weaning period. The mixture of AKE and PKE appeared particularly advantageous, suggesting possible synergistic effects on digestion, nitrogen utilization, cecal ecology, antioxidant defenses, and humoral immunity. The study also raises the possibility that these extracts may help reduce ammonia-related waste burden through lower cecal ammonia. Important limitations acknowledged by the authors include the restricted number of experimental rabbits and the fact that oral administration may not be the most practical approach for commercial use. Further studies are needed to clarify mechanisms of action and determine more scalable delivery methods.