The Effect of increasing dietary threonine to lysine ratio on carcass characteristics, mucin gene expression and morphological analysis of ileum of male broiler chickens challenged with Salmonella

摘要

The aim of this study was to assess threonine/lysine ideal ratio for optimum carcass characteristics, mucin gene expression and intestinal barrier function of broiler chickens. Additional threonine (equal or 25% more than breed's threonine/lysine ratio requirement) w as added to a threonine deficient diet as control, fed to 288 one - day - old male Ross 308 broiler chicks (three treatments and eight replications per treatment). Amino acids and other ingredients were analyzed by NIR and analyses data were used to formulate the starter, grower and finisher rations based on breed's nutritional catalog. On day 32 of age, all chickens of four replications of each treatment were infected orally with equal numbers of Salmonella Paratyphi A (5×10 4 cfu/bird), individually. To confir m success of challenge, cloacae swab samples on day 39 and spleen samples on day 42 were cultured on XLD agar for isolation of Salmonella Paratyphi A. One chicken per replicate on day 42 was sacrificed for carcass characteristics analysis and ileal samples caught for morphological analysis and quantifying mucin 2 gene expression by relative quantification. Salmonella cultures of samples showed success of challenge. Increase in Thr/Lys ratio resulted in an increase of villus height, crypt depth, villus heigh t/villus width ratio and goblet cell density in challenged and unchallenged group. Also, it was increased the mucin 2 gene expression in unchallenged group. It had no significant effect on carcass yiel d and weight percentage of breast and legs in each chal lenged or unchallenged group. These findings indicated that increase in Thr/Lys ratio in diet had beneficial effect on mucosal health, but was not sufficient to overcome Salmonella Paratyphi A infection.