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The effects of organic acid, probiotic and a combination of the two on performance and gut morphology in broiler chickens were investigated. Two hundred and forty one-day-old Arbor Acre broiler chicks were randomly assigned to five dietary treatments with six replicates, each with eight birds. The treatments were basal diet (negative control, NC), basal diet + antibiotic (positive control (PC)), NC + 0.4% organic acid (OA), NC + 0.3% probiotic (PB) and NC + 0.4% OA and 0.3% PB. Reduced body weight gain (BWG) was recorded for birds on the NC diet at the starter phase and over the total period. The addition of OA significantly increased BWG compared to values obtained in birds on the NC and other diets. Diet had no effect on BWG at the grower phase or on feed intake, dry matter intake and feed conversion ratio in any growth phase. Gain : feed ratio was lowered in the NC diet, but improved significantly by OA and PB in the starter phase. Organic acid supplementation reduced the weight of the bursa of Fabricius. The weight of pancreas, height of villi and crypt depth were reduced in birds on the NC diet compared with those on OA, PB and a combination of these. Diet had no effects on the weights of the lungs, heart, spleen, kidneys, liver, villus width, villus height : crypt depth ratio, lactic acid bacteria, coliform bacteria and total bacterial count in any gut section. In conclusion, supplementation of broiler diets with OA and PB could improve their growth and gut morphology better than antibiotics would, with a greater positive effect in the starter phase. ______________________________________________________________________________________

This study investigated the amount of energy available to growing pigs from fermentation of dietary fiber in the hindgut. Eighteen growing barrows, fitted with a simple T-shaped cannula at the terminal ileum, were allocated to 3 experimental diets in a completely randomized design. The 3 diets were a standard-fiber diet (SFD), which contained 75.1 g NDF/kg diet; a medium-fiber diet (MFD) of 105.7 g NDF/kg diet; and a high-fiber diet (HFD), which contained 146.9 g NDF/kg diet. Each diet had 6 replicate pigs. After a 5-d period of adjustment of the pigs to the cage environment, feces were collected on d 6 and 7 and ileal digesta on d 8 and 9 and subsequently freeze-dried. Fecal slurry from a pig was used to inoculate the ileal digesta from the same pig. The amount of energy available was calculated from the amount of short-chain fatty acids (SCFA) produced from a 48-h in vitro fermentation of the ileal digesta. Increasing NDF enhanced ( < 0.01) the ileal DM flow and DM in feces. The energy available in the foregut was reduced ( < 0.05) from 3,360 to 2,974 kcal/kg feed DM and increased ( < 0.01) from 619 to 1,009 kcal/kg feed DM produced in the hindgut with increasing dietary NDF. The amount of SCFA increased ( < 0.01) with higher dietary NDF. Acetic acid was highest ( < 0.01) in the HFD whereas propionic and valeric acids were highest ( < 0.05) in the SFD. The amount of butyric acid was not affected by diet. The amount of energy contributed from SCFA fermentation to total tract digestible energy increased ( < 0.01) from 10.7 to 24.2% as dietary NDF level increased from 75 to 147 g/kg feed. The results of the study showed that increasing level of dietary NDF resulted in reduced energy digestibility in the foregut of growing pigs with a corresponding increase in the amount of energy from microbial fermentation in the hindgut.