ABSTRACT
In mammals, lactation is the most energetically demanding period of a female's reproductive life. In the wild, investment in reproduction is associated with a decrease in survival in both large and small mammals. Energy intake typically increases by 66-188% but in some animals such as laboratory mice, intake can increase by up to 400 per cent. As a consequence, daily energy expenditure and basal metabolic rate can be increased in lactating females when compared with non-reproductives. This has led to the suggestion that oxidative stress may be elevated during lactation, unless antioxidant defences are sufficiently upregulated. The study was designed to evaluate the effect of fermented Soya bean and Vitamin C supplement in stimulating milk production in lactating albino rats. Thirty five (35) adult female rats were used for this study. At parturition, the animals were randomly divided into five groups of five (5) rats each. Except group four (4) that was subdivided into three (3) sub groups of five animals each (n=5). Treatment was carried out as follows: Group I: (Normal control) was given normal feed and distilled water, oraly (1 ml/kg), Group II: metoclopramide (5 mg/kg), Group III: 100 mg/kg of Vitamin C. The three (3) sub groups under group four (4) received 10%, 20% and 40% soya bean, respectively, Group V: was co-administered with 20% soya bean supplement and Vitamin C (100 mg/kg). Treatment was done for the period of ten (10) days at 06:00h daily. Milk yield was assessed daily at 18 h and 23 h after gavage for the period of ten (10) days. At the end of experiment, animals were euthanized using chloroform inhalation in a closed chamber and sacrificed afterwards. Blood samples were collected and the serum separated for determination of physiological parameters: prolactin, growth hormone, oxytocin, thyroxine (T3 and T4), insulin, progesterone oestrogen and biochemical parameters: SOD, catalase, GPx, MDA, ALP, ALT, AST, sodium, potassium, chloride, bicarbonate, calcium and magnesium. Mammary gland tissues excised were used for histological assessments. The result of this study showed no significant increase in milk yield 18 hours after gavage compared to the control. The result of 23 hours after gavage showed a significant increase in milk yield in SB 20% (2.36 � 0.49), SB 40% (1.98 � 0.42) and SB 20% + VIT C (1.90 � 0.46) (P< 0.05) compared to the control (0.8 � 0.26), with the highest milk yield in the SB 20% treated group. Although the level of milk yield in the METCL (1.16 � 0.29 vs 0.8 � 0.26), VIT C (1.24 � 0.46 vs 0.8 � 0.26) and SB 10% (1.70 � 0.44 vs 0.8 � 0.26) increased, it was however not statistically significant. The result for serum prolactin concentration (ng/ml) showed a significant increase in the group treated with SB 20% + VIT C (63.70 � 2.27) when compared to the control (43.98 � 5.57). The result of serum level of Growth hormone showed significant Increase in the groups treated with VIT C, SB 10%, SB 20% and SB 20% + VIT C. (P< 0.05) compared to the control. There was no statistically significant difference in serum oxytocin levels in all the treated groups, despite the relative increase in some of the treated groups when compared to the control (P> 0.05). The results of soya bean supplemention, metoclopramide and Vitamin C showed no significant difference (P> 0.05) on serum triiodothyronine (T3) viii concentration compared to the control. There was however, significant increase in SB 40% (100.80 � 9.95) in serum thyroxine (T4) compared to the control (68.00 � 3.91) (P< 0.05). There was no significant difference (P> 0.05) in serum insulin level between treatment and control groups. However, serum progesterone level was significantly high in the groups treated with METCL (26.18 � 1.87), VIT C (25.78 � 1.53), SB 10% (26.52� 2.47) and SB 20% (28.70 � 1.29) when compared to the control (16.66 � 1.99) (P< 0.05). A significant difference in serum estrogen level was recorded in the groups treated with VIT C (669.60 � 54.04), SB 10% (705.00 � 27.53), and SB 20% + VIT C (725.40 � 29.62) compared to the control (632.60 � 42.96) (P< 0.05). The result on serum ALP level showed a significant increase in all the supplement treated groups; SB 10% (110.80 � 1.63), SB 20% (127.60 � 9.60), SB 40% (122.80 � 2.60) and SB 20% + VIT C (129.40 � 4.90) compared to the controls (86.60 � 3.73) (P< 0.05). The co-administration of the soya bean supplement and Vitamin C showed a significant increase in serum ALP, ALT and AST levels suggesting a tendency of such combination to be more detrimental to the hepatocytes. Although there was an increase in serum MDA concentrations in all the treated groups compared to the control, lipid peroxidation was however significantly higher (P< 0.05) in the metoclopramide group relative to the soya bean supplemented groups. This study has shown that supplementation with soya bean induces a mild antioxidant effect by increasing serum level of superoxide dismutase. There was however a significant decrease in serum SOD in the 10% SB group compared to the control. There was a significant difference in serum catalase activity in the group treated with METCL (46.20� 1.53), SB 10% (44.00 � 1.14) and SB 20% (45.20 � 1.28) compared to the control (52.00 � 0.71) (P< 0.05). Serum level of glutathione peroxidase GPx showed a significant difference in the group treated with VIT C, SB 10%and SB 20% compared to the control (P< 0.05). Soya bean supplementation showed no significant effect on serum electrolytes concentrations. There was a significant decrease in RBC count in the groups treated with SB 40% and SB 20% + VIT C, compared to the control (P< 0.05). Soya bean supplementation at SB 40% and SB 20% + VIT C boosted the immunity of the animal significantly by increasing WBC compared to the control. Although there was no significant difference in PCV and Hb concentration, there was however a significant decrease in platelet count in all the soya bean supplemented groups compared to the control (P< 0.05). All the treated groups showed an improvement in alveoli distention in the histology of the mammary gland, enhancing its lactogenic properties. In conclusion, soya bean supplement increased milk yield, especially at 20% supplementation compared to metoclopramide treated rats. However, supplementation with soya bean to improve milk yield should be done with caution due to the hepatoxicity in treated rats..