Comparative Effect of Different Growth Promoters on Performance, Gross Measurements of Major Organs and Intestinal Histomorphometry in Broilers

A trial was conducted on day old chicks (n=160) to evaluate the effects of different growth promoters (antibiotic, prebiotic and probiotic) on broiler performance, gross measurements of major organs and intestinal histomorphometric variables including intraepithelial lymphocytes and total goblet cells count. All the chicks were randomly divided into four groups (n=40 in each group). Group 1 served as control whereas Group 2, 3 and 4 were subjected dietary treatments for 5 weeks; Group 2-basal diet supplemented with antibiotic, 0.04% zinc bacitracin (ZnB), Group 3-basal diet supplemented with prebiotic, 0.1% mannan oligosaccharides (MOS) and Group 4-basal diet supplemented with probiotic, 0.1% lactobacillus based probiotic (LBP). Body weight (BW) and feed conversion ratio (FCR) were recorded weekly. Duodenum, jejunum, ileum and caecum histology was analyzed at day 35. BW and FCR were significantly increased (P<0.05) by the dietary supplementation of MOS and LBP compared with the control and ZnB fed broilers. No significant difference was observed (P>0.05) on absolute liver, gizzard and small intestinal weight among all groups. The weight of spleen tended to be greater (P<0.05) in the LBP supplemented group compared to all dietary treatments. The large intestine weight was greater (P<0.05) for MOS fed birds compared to control. Dietary supplementations of LBP and MOS numerically increased (P>0.05) the intestinal lengths. Furthermore, dietary treatments influenced the histomorphological measurements. MOS and LBP supplements group increased (P<0.05) the villus height and villus surface area in duodenum, jejunum, ileum and ZnB fed birds had shorter villi in both duodenum and ileum. However, jejunum villus surface area remained unaffected. Duodenum villus width was greater (P<0.05) among MOS fed birds compared to control. Ileal crypt depth was decreased (P<0.05) in LBP treatment group whereas, muscularis mucosa and muscularis externa thickness were reduced in ileum in ZnB supplemented group compared with the control. In ileum, lamina propria thickness was greater (P<0.05) in MOS treatment group compared with all other dietary treatments. Goblet cells counts were significantly higher (P<0.05) in LBP fed birds in duodenum and ileum and in MOS supplemented birds in jejunum and caecum compared to all dietary treatments. Intraepithelial lymphocytes were higher (P<0.05) in both jejunum and ileum among birds fed LBP supplemented diet compared to all other treatment groups. Overall results demonstrated that MOS and LBP can be used as growth promoters as an alternative to antibiotic to enhance the broiler production performance.