Dietary red palm oil inclusion on growth performance, haematology, serum biochemistry, lipid profile, and oxidative stress markers of Wistar rats

Abstract

Red palm oil (RPO), rich in carotenoids, tocopherols and tocotrienols, has been associated with antioxidant, lipid-modulating and haematopoietic effects. However, its effects on growth performance, haematology, serum biochemistry, lipid metabolism and oxidative status remain debated. This study evaluated graded dietary RPO inclusion in Wistar rats over 42 days. Forty-eight 60-day-old rats (initial body weight 149 ± 1.0 g; 50:50 males and females) were individually housed and randomly assigned to four treatments (n = 12): basal diet containing 0 (control), 200, 300, or 400 mg RPO kg diet^-1. RPO was manually incorporated into the diet and was not chemically characterised. Growth performance was monitored daily and weekly. At the end of the trial, blood samples from eight rats per treatment were analysed for haematological, serum biochemical, lipid and oxidative stress indices. Growth data were analysed using a 2×4 factorial arrangement (gender×diet), while treatment effects were assessed by analysis of variance and Student–Newman–Keuls mean separation (p < 0.05). Dietary RPO significantly influenced weight gain and daily weight gain in males compared to females (p < 0.05). Treatment × gender interactions were observed for daily weight gain, weight gain, and feed conversion ratio, whereas feed intake and feed efficiency were unaffected. Red blood cell counts were higher in the control and 200 and 400 mg kg^-1 groups than in the 300 mg kg^-1 group. White blood cell counts declined progressively across RPO-supplemented groups. Haemoglobin concentrations were higher at 200 and 400 mg kg^-1 than in the control and 300 mg kg^-1 groups. Mean corpuscular volume and mean corpuscular haemoglobin were higher at 300 and 400 mg kg^-1, while platelet counts were lower at 200 mg kg^-1 than in the other groups. Serum urea increased with RPO inclusion, whereas creatinine was highest at 300 mg kg^-1 (p < 0.05). Total cholesterol (55.62 mg dL^-1), triglycerides (83.70 mg dL^-1), and low-density lipoprotein cholesterol (13.00 mg dL^-1) decreased significantly following RPO inclusion (p < 0.05). High-density lipoprotein cholesterol, very-low-density lipoprotein cholesterol, and total cholesterol-to-HDL ratio were unaffected (p > 0.05). Catalase (9.78: p < 0.04), glutathione peroxidase (44.26: p < 0.05), superoxide dismutase (1.51: p < 0.05), glutathione (0.36: p < 0.04), and malondialdehyde (15.31: p < 0.02) were significantly influenced by dietary treatment, with the highest mean values varying across inclusion levels. Dietary RPO at 200–400 mg kg^-1 produced non-linear, biomarker-specific and gender-dependent responses, with no inclusion level uniformly favourable. These findings indicate a modulatory rather than consistently protective effect under the conditions investigated. Larger, longer-term, gender-stratified studies using chemically characterised RPO and incorporating tissue- and pathway-level analyses are needed before optimal inclusion levels can be recommended.