DL-Methionine : an immunopotentiator in Mycoplasma gallisepticum challenged broilers treated with Pulmotil AC® -

Abstract

The thesis experiment was performed to determine the effect of 20percent dietary DL-Methionine (Met) in excess of modern breeder requirement level compared to Tilmicosin (Pulmotil AC®); on the immune response and growth performance of male Ross 308 broilers challenged with Mycoplasma gallisepticum (MG). The experiment is divided into 3 part studies. Study A constituted a preliminary trial for evaluating three separate MG field isolates on inducing clinical signs and symptoms of challenged Ross 308 broilers. Study B aimed at molecularly identifying the strain of each evaluated field isolate adopted in Study A via MG pvpA gene based conventional PCR amplification and sequencing. Study C comprised a 2x2x2 factorial arrangement of treatments with interactions in a complete randomized design. The main factors were Mycoplasma gallisepticum a) challenged vs. b) unchallenged; Methionine: a) adequate vs. b) excess, and Antibiotic a) Pulmotil AC® treated vs. b) Non-treated. A total of 1200-day old male Ross 308 broilers were randomly divided into 8 treatments with 3 replicates (pen) of 50 birds each. Starter, grower and finisher diets were formulated to meet 100 and 120percent of Met requirements in the adequate and excess Met groups, respectively. Feed and water were offered ad libitium for a period of 35 days. Results of Study A and B revealed that all MG isolates were of the F-strain and MG2 isolate resulted in higher frequency of disease signs in comparison to the other groups; this strain was retained in challenging birds in Study C. Results of Study C demonstrated that 20percent excess Methionine significantly increased average body weight (BW) at 10 days of age; with no significant differences in BW and feed conversion ratio (FCR) at 17 and 35 days of age. Pulmotil AC® significantly reduced BW at 10 days of age; however, it did not affect BW and FCR at 17 and 35 days of age. In MG-challenged birds, the 20percent excess Met treatment significantly increased IgG titers (3170) in comparison to adequate Met level (1843) alon