Abstract
Five experiments were conducted to investigate the effects of different organic acid blends
(OABs) on productive performance, dressing parameters, cost-effectiveness, gut pH, intestinal
histomorphology, serum biochemical parameters, tibia ash content and fecal microbial loads in
commercial broiler chickens. The major objective of the study was to assess the suitability of
different OABs as alternatives to antibiotic growth promoters in the diet of broilers. A total of
1008 Cobb-500 one-day-old straight run broiler chicks were allotted to two separate feeding
trials to achieve the objectives of the study. Growth performance, meat yield characteristics and
cost-effectiveness of the experimental birds were studied in the first two experiments, while
samples were collected from these feeding trials for investigating gut pH, histomorphological
structure of different segments of intestine, serum chemistry, tibia ash and microbial loads in
the feces for the remain experiments 2, 3 and 5. Antibiotic Growth Promoters (AGP: Flavomycin
& Renamycin) and five OABs (OAB-1, OAB-2, OAB-3, OAB-4 & OAB-5) of different
composition were examined for their effectiveness as alternatives to antibiotics. Investigations
for productive performance, meat yield characteristics and gut pH were performed at
experimental farms while those of intestinal histomorphology, serum biochemical parameters,
tibia ash content and fecal microbial loads of were done in different laboratories. The results of
two feeding trials revealed that broiler chickens received OABs alone or in combination with
AGP showed significantly higher live weight gain and improved feed conversion than the birds
of control groups. Dressing parameters among different dietary treatments of birds were not
significantly affected. Except minor exceptions, feeding OABs incorporated diets to birds
showed superior performance than that of AGPs. Supplementation of OABs irrespective of type
when fed with or without AGP in the feed of broiler reduced gut pH value significantly (P<.01)
of duodenum, jejunum and ileum in comparison with control group. OABs alone and OABs
with AGP supplemented broilers had significantly higher (P<0.01) villus height in the jejunum
and ileum in comparison with the control & AGP alone groups. Villus width showed significant
(P<0.01) variations in duodenum and ileum among the treatments. Lowest cholesterol content
was observed in OAB-1 fed bird, highest cholesterol value was found in OAB-1+AGP and OAB2+AGP dietary groups. Triglycerides was found to be significantly (P<0.01) reduced in OAB2+AGP fed groups of birds but it was highest in OAB-1+AGP fed birds. HDL value of OAB-1 &
OAB-2 were significantly (P<0.001) increased than control & AGP groups but lower than OAВ1+AGP & OAB-2+AGP dietary groups. Feeding OAB-1 caused a significant increase in serum
albumin than the control groups of birds (P<0.01). No significant difference was observed in
serum total protein (TP) and globulin (Glu) concentrations. Total E. coli count (TEC) in the birds
receiving diets containing OAB-1 and OAB-2 with or without AGP was significantly (P<0.001)
lower than the control. A significantly higher total viable count (TVC) was found in control
groups than OAB - 2 and OAB -2 + AGP dietary groups respectively (P<0.01). Gram staining
from EMB agar for total bacterial count showed mainly Escherichia coli. Gram staining from
plate count agar for TVC showed Escherichia coli, Staphylococcus spp. and Bacillus spp. No
bacterium was detected in Salmonella shigella agar. Results of economic analyses also confirmed
the benefits of inclusion of commercial OABs in the diets of broiler chickens. Based on the
results, it may be concluded that the OABs considered in this study may safely be used as
alternatives to AGPs for profitable commercial broiler production.