INFLUENCE OF NUTRIENT SUPPLEMENTATION ON THE PERFORMANCE AND IMMUNOLOGICAL RESPONSES OF BROILER CHICKENS TO NEWCASTLE DISEASE VACCINATIONS

Abstract

Four inter-related experiments were conducted to determine the effects of supplementation at varying concentration levels of amino acids (methionine and lysine) and vitamins (Vitamins C and E) in diets of broiler chickens on growth performance and immune responses to Newcastle disease vaccinations. In each of the experiment, a total of one hundred and fifty birds were used. They were distributed into four treatments A, B, C and D with three replicates per treatment, each replicate having 10 birds. There were four experimental diets A, B, C and D at both starter and finisher phases of the experiments. The birds were vaccinated with Newcastle disease vaccines following a stipulated vaccination regime. During the course of the experiments, variable measurements were taken which include weekly feed intake, weight gain and final body weight to evaluate the performance characteristics of experimental birds. Blood and serum samples were also collected for haematological analysis and immunological response to the Newcastle disease vaccinations. After slaughtering of experimental birds data on carcass and organ weights were taken and histopathological analysis of major organs (liver, heart and spleen) was done. In the 1st experiment diets used include: Diet A, the negative control diet which had 25% methionine less than the National Research Council (NRC) requirement, diet B contained the NRC requirement level of 0.5% methionine, while diets C and D contained 0.625 and 0.75% which are 25 and 50% above NRC requirement of methionine supplementary levels respectively. Experimental birds fed on diets C and D by the 3rd week into the trial exhibited leg weakness, thereafter complete paralysis in 40% of the birds. Mortality was recorded in 70% of the paralysed birds. The final weight, weight gain, feed intake and feed conversion ratio were significantly (p<0.05) different among treatments. Birds fed diet B had the highest final weight (1.62kg) and feed intake (2.57kg). Immunological response to Newcastle disease vaccinations was significantly different among treatments with birds on diet B having the highest antibody titre values (log27 and log29) and those on diet D having the least (log25 and log27). In the 2nd experiment, the diets used include- diet A with 25% methionine less than NRC requirement; diet B contained 0.5% methionine (NRC requirement); while diets C and D were supplemented with 10% and 15% increment above NRC requirements of methionine. Significant (P < 0.05) differences were observed for the performance characteristics. The final weight of birds both at the starter and finisher phases in treatment B (658.63g, 2560g) was the highest and was not significantly different (P>0.05) from treatment C (642.58g, 2430g) but was significantly different from those on the other diets. The immunological responses revealed that after administration of NDVi/o, the chickens on diet C had the highest mean titre value (log2 8) while those on diet A had the lowest titre value (log2 6). After NDV LaSota and infection birds on diet B recorded titre values higher than that seen in other groups. In the 3rd experiment lysine was supplemented in diets of broiler chickens at different concentration levels. Diet A had no lysine supplementation; diet B contained 1.12% of lysine, which is the NRC requirement; diet C contained 1.13% of lysine; and diet D contained 1.14% of lysine. Performance characteristics of experimental chickens were significantly influenced by the different diets (P < 0.05). Birds on diet C had the highest final weight, feed intake and the best FCR during the experimental period. The immunological response of experimental chickens showed that birds on diet C had the highest mean antibody titre value (log28, log29 and log211), after administration of ND vaccines and the challenge phase while chickens fed diet A (log26, log27, log28) had the least immune response. In the fourth experiment, birds were divided into 2 groups. In the first group birds were fed diets supplemented with vitamin E. The 4 dietary treatments had diet A serving as the control group with no vitamin E supplement; diet B was supplemented with 100mg of vitamin E per kg of feed; diet C with 200mg/kg; and diet D with 300mg/kg. The second group was fed diets supplemented with vitamin C with the same supplementary rates as in the first group. The performance characteristics of birds fed vitamin C supplemented diets were significantly different among treatments. Birds fed 100mg/kg of vitamin C had the highest final weight (2230g) and feed intake (5.08kg). Immune response to ND vaccination was also seen to be highest in this group of birds. The performance characteristics of birds fed vitamin E supplemented diets were also significantly influenced by the varying diets. Birds fed 300mg/kg of vitamin E diets had the highest final weight (2350g) and feed intake (4.18kg). However, immune response to ND vaccinations was highest in birds fed 100mg/kg of vitamin E. In conclusion it was observed that methionine supplementation at high inclusion levels were detrimental to the immune response to ND vaccinations and growth performance of broiler chickens but inclusion at the NRC requirement level or at 10% increment above it may be adopted for optimal productive performance. Finally, lysine supplementation at 10% increment above NRC requirements and 100mg/kg of both vitamins C and E supplementation in broiler diets would be beneficial to growth performance and immunological response to ND vaccinations. This study has inadvertently established the maximum supplementary rates of nutrients (methionine, lysine, vitamins E and C) in diets of broiler chickens that are beneficial to optimal productivity and enhanced immune status