Thesis Abstract

Abstract
In the humid tropics, laying hens often face challenges related to heat stress, which can impact their performance and overall health. This study aimed to investigate the effects of dietary supplementation of vitamin C and vitamin E on the performance of laying hens under humid tropical conditions. A total of 200 laying hens were randomly assigned to four dietary treatment groups control (basal diet), vitamin C supplementation (500 mg/kg), vitamin E supplementation (250 mg/kg), and a combination of vitamin C (500 mg/kg) and vitamin E (250 mg/kg). The trial lasted for 16 weeks, during which various parameters related to hen performance, egg quality, and antioxidant status were measured. Results indicated that dietary supplementation of both vitamin C and vitamin E, either alone or in combination, had positive effects on the performance of laying hens in the humid tropics. Hens receiving the combined supplementation of vitamin C and E showed the best performance in terms of egg production, feed conversion ratio, and egg quality. Additionally, hens in the vitamin C and E supplemented groups exhibited improved antioxidant status, as indicated by higher levels of plasma vitamin C and E, as well as lower levels of malondialdehyde, a marker of oxidative stress. Furthermore, the supplementation of vitamin C and vitamin E positively influenced egg quality parameters, including egg weight, shell thickness, and yolk color. Hens receiving vitamin C and E supplementation laid eggs with higher shell thickness and yolk color intensity compared to the control group. These findings suggest that dietary supplementation of vitamin C and E can enhance the overall performance and egg quality of laying hens in humid tropical environments. In conclusion, the results of this study demonstrate that dietary supplementation of vitamin C and E can be beneficial for improving the performance and health of laying hens in the humid tropics. The combined supplementation of both vitamins showed synergistic effects on hen performance, egg quality, and antioxidant status. Therefore, incorporating vitamin C and E supplementation in the diets of laying hens in humid tropical regions may be a valuable strategy to enhance productivity and welfare in poultry production systems.

Thesis Overview

This study which lasted for 52 weeks investigated the effects of dietary Vitamin C (Lascorbicacid) and Vitamin E (dl- alpha tocopheryl acetate) on the performance of layinghens in the humid tropics. A total of 240 twenty-four week old Golden Neslink pullets wererandomly selected from a flock of 550 birds and randomly divided into sixteen treatments of15 pullets. The birds were initially vent examined to ensure that they were at point of laybefore commencing the study. Each pullet was randomly assigned to a previously cleanedand 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 combinedwith four dietary levels of Vitamin E: 0, 125, 250 and 375mg Kg-1 basal diet in a 4 x 4factorial arrangement in a Completely Randomized Design. All management principles wereobserved. Dead birds were promptly removed for autopsy when the need arose. At the end ofthe study, three birds were selected per treatment for haematological investigation. Bloodsamples were collected from the wing vein of the birds using a 3ml syringe and a 23-gaugeneedle and placed in micro tubes with Ethlene diamine tetra acetic acid (EDTA) as anticoagulantfor determining the haematological values. The samples were cooled to 4 oC, usingicepacks and transferred to the laboratory within 12h of blood collection. The economicimplication of the study was then calculated. Data obtained were subjected to analysis ofvariance (ANOVA) using SPSS. The mean minimum and maximum indoor temperaturesrecorded during the study ranged between 18.3-25.0 oC and 27. 15-34 oC respectively whilethe RH values lay between 53.0 and 88.9%. These were well outside the zone of thermoneutrality for laying hens. Results obtained indicated that, there were highly statisticaldifferences (P < 0.01) between Vitamin 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 vitaminE Kg-1 basal diet) was superior to all the other treatments and had the highest values forHDP (85.45±1.15), FI (113.15±0.56), HUS (96.27±0.47), and EWT (69.11±1.52). Thesevalues were however, statistically similar (P > 0.05) to T8 (600mg Vitamin C + 125 mgVitamin 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 betweenVitamin C and E is different from the sum of the two vitamins applied separately. Loss inbody weight, incidence of cracked eggs and mortality were statistically higher (P < 0.01) inT1 (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) weresuperior 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 thehighest 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 netincome/dozen egg of N1, 627.11±28.68 while the least net income (N560.50±32.12) wasgenerated from T1. This work therefore upholds that vitamins C and E act in synergy, andthat the combined effects of the two antioxidants are additive, immunomodulatory, antiparasitic

and economical.