EFFECTS OF DIETARY VITAMIN C AND VITAMIN E ON THE PERFORMANCE OF LAYING HENS IN THE HUMID TROPICS
This study which lasted for 52 weeks investigated the effects of dietary Vitamin C (L-ascorbic acid) and Vitamin E (dl- alpha tocopheryl acetate) on the performance of laying hens in the humid tropics. A total of 240 twenty-four week old Golden Neslink pullets were randomly selected from a flock of 550 birds and randomly divided into sixteen treatments of 15 pullets. The birds were initially vent examined to ensure that they were at point of lay before commencing the study. Each pullet was randomly assigned to a previously cleaned and disinfected cage measuring 49 x 35 x 42cm at a stocking density of one bird per cage. Four dietary levels of Vitamin C: 0, 200, 400, and 600mg Kg-1 basal diet were combined with four dietary levels of Vitamin E: 0, 125, 250 and 375mg Kg-1 basal diet in a 4 x 4 factorial arrangement in a Completely Randomized Design. All management principles were observed. Dead birds were promptly removed for autopsy when the need arose. At the end of the study, three birds were selected per treatment for haematological investigation. Blood samples were collected from the wing vein of the birds using a 3ml syringe and a 23-gauge needle and placed in micro tubes with Ethlene diamine tetra acetic acid (EDTA) as anti-coagulant for determining the haematological values. The samples were cooled to 4 oC, using icepacks and transferred to the laboratory within 12h of blood collection. The economic implication of the study was then calculated. Data obtained were subjected to analysis of variance (ANOVA) using SPSS. The mean minimum and maximum indoor temperatures recorded during the study ranged between 18.3-25.0 oC and 27. 15-34 oC respectively while the RH values lay between 53.0 and 88.9%. These were well outside the zone of thermo neutrality for laying hens. Results obtained indicated that, there were highly statistical differences (P < 0.01) between Vitramin C and Vitamin E treated birds for hen day production (HDP), feed intake (FI), feed conversion ratio (FCR), Haugh unit score (HUS), , egg weight (EWT) and incidence of cracked eggs. The treatment, T7 (400mg vitamin C + 125 mg vitamin E Kg-1 basal diet) was superior to all the other treatments and had the highest values for HDP (85.45±1.15), FI (113.15±0.56), HUS (96.27±0.47), and EWT (69.11±1.52). These values were however, statistically similar (P > 0.05) to T8 (600mg Vitamin C + 125 mg Vitamin E Kg-1 basal diet). The lowest values for HDP (42.33±1.43), FI (65.42±0.61), HUS (75.50±2.10) and EWT (54.50±1.15) were observed in T1 (Controls). The synergism between Vitamin C and E is different from the sum of the two vitamins applied separately. Loss in body weight, incidence of cracked eggs and mortality were statistically higher (P < 0.01) in T1 (controls) than vitamin treated birds which showed no significant (P > 0.05) differences. With Vitamin C supplementation, birds on T3 (400 mg Vitamin C kg-1 basal diet) were superior to T2 (200 mg Vitamin C kg-1 basal diet) and T4 (600 mg Vitamin C kg-1 basal diet). Similarly, for Vitamin E supplementation, birds on T9 (250 mg Vitamin E kg-1 basal diet) were statistically different (P < 0.01) from T5 (125 mg Vitamin E kg-1 basal diet) and T13 (375 mg Vitamin E kg-1 basal diet). For haematological values investigated T7 recorded the highest values for RBC (4.11±0.15×106), Hb (8.80±0.31g/dl), and WBC (18300±519.62/mm3) and these were statistically similar (P > 0.05) to T8 but highly statistically different (P < 0.01) from the rest of the treatments. There was highly significant interaction (P < 0.01) in the net income/dozen of eggs that accrued from the study. T7 had the highest net income/dozen egg of N1, 627.11±28.68 while the least net income (N560.50±32.12) was generated from T1. This work therefore upholds that vitamins C and E act in synergy, and that the combined effects of the two antioxidants are additive, immunomodulatory, anti-parasitic and economical.