Carry over effects of dietary methionine on the immune system in chickens.

Abstract

31A Carry_over effects of dietary methionine on the immune system in chickens Kaidong Deng, C.W. Wong and J.V. Nolan Animal Science, University of New England, Ar midale NSW 2351 kdeng3@metz.une.edu.au Methionine is often the first limiting amino acid in typical chicken diets and a supplement is essential for growth. Additions to the diet may enhance or depress immune responses depending on factors that include the amount of the supplement and its interactions with other amino acids and nutrients (Bhargava et al. 1970; Tsiagbe et al. 1987; Konashi et al. 2000). Day_old ISA_ Brown cockerels (n=180) were allocated to 3 treatment groups, each with 6 replicates of 10 birds, to examine possible carry_over of effects on the immune system of a short_term methionine supplement. For 4 weeks they were given (i) a peanut meal_based diet containing 0.20% methionine (LM); (ii) LM + 0.20% methionine (MM); or (iii) LM + 0.40% methionine (HM), and then for 8 weeks a commercial pullet grower diet. Two birds per replicate were randomly selected and immunised with 12.5% sheep red blood cells (SRBC) one week before bleeding and slaughter at Weeks 4, 8 and 12. Body_weight (BW), lymphoid organ weights, serum levels of primary antibody to SRBC, and 24 h cutaneous response of foot webs to a T_cell mitogen phytohaemagglutimin (PHA)_M, were measured. Methionine promoted growth (P<0.05) in birds in a dose_dependent manner, indicating an inadequacy in the LM and MM diets, and LM vs HM showed a clear effect on the immune system. LM resulted in a lower (P<0.05) weight of the T_cell producing thymus during the supplementation, but this was not carried over into later life and T cell function was not altered. The higher relative thymic weight (P<0.05) in LM birds at Week 12 suggests that their diet might have retarded the normal atrophy with age of the thymus. The bursa of Fabricius is an important site for antibody_forming B cells in newborn birds, and relative weight was significantly lower with LM ( P<0.05) during the supplementation period than with the other treatments. This effect continued for up to 4 weeks; the difference ( P <0.05) between LM and HM at Week 8 had disappeared by Week 12, probably because of a gradual involution of the bursa within the first 2 weeks of life. The function of B cells might be altered by diet, as shown by the difference (P<0.05) in serum antibody against SRBC between LM and HM birds during the supplementation; the effect was carried over to Week 12. This effect might not be associated with any effect of the diets on the involuting bursa but rather on other lymphoid tissues. Our findings indicatethat the immuno_ modulatory effects of dietary methionine in early life of chickens can persist into a later stage of life. Bhargava, K.K., Hanson, R.P. and Sunde, M.L. (1970). Effects of methionine and valine on antibody production in chicks infected with Newcastle disease virus. Journal of Nutrition 100, 241_248. Konashi, S., Takahashi, K. and Akiba, Y. (2000). Effects of dietary essential amino acid deficiencies on immunological variables in broiler chickens. British Journal of Nutrition 83, 449_456. Tsiagbe, V.K., Cook, M.E., Harper, A.E. and Sunde, M.L. (1987). Enhanced immune responses in broiler chicks fed methionine_supplemented diets. Poultry Science 66, 1147_1154. Table 1 Body_weight (BW), relative lymphoid organ weights (% BW), primar y antibody to SRBC and foot web responses to PHA_M in chickens at 4, 8 and 12 weeks of age given a LM, MM or HM diet. Week 4 LM BW (g) Relative thymus wt. (%) Relative spleen wt. (%) Relative bursa wt. (%) Anti_SRBC titre (log titres) 218a 0.25a 0.13 0.32 a Week 8 HM 353 b b Week 12 HM 934 b MM 350 b ab LM 661 a MM 916 b LM 1376 a a MM 1657 b b HM 1693 b b 0.32 0.34 0.37 0.18 0.34 5.33 a a 0.33 0.18 0.39 4.75 ab ab 0.35 0.17 0.42 4.17 b b 0.45 0.34 0.17 0.28 0.32 0.15 0.49 2.80 b ab 0.14 0.40 1.67 c b 0.17 0.30 5.42 a 0.16 0.24 ab b 3.25a 5.08 3.42 Foot web PHA_M response (mm) 0.22 a, b, c 0.20 0.30 0.30 0.20 0.32 0.48 0.51 0.57 Means bearing different superscripts in the same row within the same age differ (P<0.05) Recent Advances in Animal Nutrition in Australia, Volume 13 (2001)