Growth response of broilers fed with organic acids supplement, antibiotics, probiotics and prebiotic under heat stress conditions

A total of 160 Ross 308 male broilers were used in a randomized complete design, with five treatments and four replicates for each treatment (eight chicksper pen),from 7 to 42 days of age. Feed  intake (FI), body weight (BW), weight gain (WG) and feed conversion ratio (FCR) were measured during the experiment and  carcass yield, relative weight of internal organs were measured at the end of the experiment. A corn-soybean-based diet was used as the basal diet (control, treatment 1). The basal diet was supplemented with an antibiotic growth promoter (Oxytetracycline, 150 g/ton, treatment 2), commercial organic acid (Orgacid, 0.3%, treatment 3), probiotic (Protoxin, 150 g/ton, treatment 4) and prebiotic (Mannanoligosaccharides, 2 kg/ton, treatment 5). Chickens fed with diets containing organic acids had the lowest FI, as well as the best FCR as comparedto other treatments. Numerically, chickens fed with diets containing probiotics had the highest WG during the period of 22 to 42 daysof age, but inclusion of antibiotics caused a non-significant increase in WG. On age 42d, chicks fed with basal diet had the highest BW. However, the lowest BW was relevant to the diet containing organic acids. The relative weight of heart and wing showed significant (P<0.05) increase in the treatment containing prebiotic.Higher levels of the additives are suggested to be utilised for improving performance of the broilers reared under heat stress.