A study was carried out to evaluate the effect of dietary probiotic supplementation and stocking density on the performance, relative carcass yield, gut microflora, and stress markers of broilers. One-day-old Ross 308 male broiler chickens (n = 480) were allocated to 4 experimental groups for 42 d. Each treatment had 8 replicates of 15 chicks each. Two groups were subjected to a high stocking density (HSD) of 20 birds/m² and the other 2 groups were kept at low stocking density (LSD) of 10 birds/m². A basal diet supplemented with probiotic 1 and 0.5 g/kg of diet (in starter and finisher diets, respectively) was fed to 2 treatments, one with HSD and the other with LSD, thereby making a 2 × 2 factorial arrangement. There was no interaction between stocking density (LSD and HSD) and dietary probiotic (supplemented and unsupplemented) for all the variables. Feed intake and weight gain were significantly low and feed conversion ratio was poor in broilers at HSD. Dietary probiotic significantly enhanced the feed intake and weight gain in starter phase only. Dietary probiotic supplementation had no effect (P > 0.05) on total aerobs, Salmonella sp., and Lactobacilli populations in the intestines of broilers. However, HSD reduced the Lactobacilli population only (P < 0.05). Relative breast yields were significantly higher in broilers reared at LSD than HSD. Thigh meat yield was higher in broilers in HSD group compared to LSD. Dietary probiotic did not affect the relative carcass yield and weight of lymphoid organs. Serum malondialdehyde, corticosterone, nitric oxide, and plasma heterophil:lymphocyte ratio were not affected either by stocking density or dietary probiotic supplementation. In conclusion, HSD negatively affected the performance and intestinal Lactobacilli population of broilers only, whereas probiotic supplementation enhanced the performance of broilers during the starter phase only. Total aerobes, Salmonella, Lactobacilli carcass yield, and stress indicators of broilers were not affected by the dietary supplementation of probiotic under the conditions of the present study.

The present study was conducted to investigate the influence of different levels of dietary phytogenic feed additive (PFA) on growth performance, caecal microbiota, and intestinal morphology of broilers. A total of 480 Ross-308 one-day-old male broilers chicks (body weight 43+3 g) were randomly assigned to 32 replicate pens of four experimental groups, each experimental group consisting of 8 replicates (each replicate pen consisting of 15 chicks). A basal diet was formulated based on corn and soybean meal that was fed to the control group. Other dietary treatments received a commercial PFA at 100 mg/kg (PFA100), 125 mg/kg (PFA125), and 150 mg/kg (PFA150). Body weight gain, feed intake, and feed conversion rate of broilers were recorded on 1-21, 22-42, and 1-42 days of age. One bird was slaughtered on the 21 st and 42 nd days and caecal contents were aseptically collected. Jejunal tissue samples were also collected on the same days. Total aerobic bacteria, coliforms, Escherichia coli, and lactobacilli were counted in the caecal contents. Villus height, villus diameter, crypt depth, muscular thickness, and goblet cell number per villus were recorded. There was no difference among the dietary treatments for growth performance and caecal microbe populations at any phase. However, the dietary PFA supplementation increased the villus height, villus width, muscularis thickness, and reduced the crypt depth and goblet cell number per villus in broilers compared to those fed control diets. In conclusion, this study suggests that dietary supplementation of a PFA consisting of blend of different spices and essential oils did not improve growth performance and caecal microbial populations despite a positive improvement in the jejunal morphometry of broilers.

ABSTRACT:A trial was conducted to investigate the effects of a dietary organic acid blend for a period of 35 days on the growth performance, intestinal histomorphology and microflora of male broiler chicks with delayed access to feed. One hundred and ninety two one day old broiler chicks (ROSS 308) were randomly distributed into 4 groups housed in four replicate pens with 12 birds in each. A 2 × 2 factorial design was implemented. Four experimental groups were formed by two levels of dietary organic acid blend supplementation (Control and Fysal Dry ® ) and two periods of delayed feed access (0 and 36 h). At 36 h after hatching body weight and body weight change of chicks were significantly (P < 0.001) lower than groups fed immediately after hatching. Delayed feed access had an adverse impact (P < 0.001) on the body weight and feed consumption of broiler chickens on days 14 and 28. Between the days 28 and 35 of the feeding period, these differences disappeared. The relative weight of gizzard (P < 0.05), pancreas (P < 0.01) on day 6 and intestine (P < 0.05) on day 10, and gizzard (P < 0.01) on day 10 were reduced in birds subjected to delayed feed access. Dietary organic acid blend inclusion increased villus length (P < 0.001), whereas delayed feed access decreased villus length (P < 0.05) and increased the incidence of epithelial degeneration and basal membrane separation of the propria mucosa of villus in the jejenum. A significant decrease in Enterobacteriaceae count (P < 0.01) was noted in organic acid blend supplemented groups on day 25. Pectoral muscle malondialdehyde levels were decreased (P < 0.01) with dietary organic acid blend supplementation at day 10. Delayed feed access significantly increased (P < 0.05) the heterophil:lymphocyte ratio at day 6. Overall, dietary organic acid blend supplementation helped broiler chicks to develop a healthier intestinal microflora and this may, in turn, inhibit the delayed feed access-induced increase in malondialdehyde in the early growing period. However, the inclusion of organic acid blend to broiler diets may not be a protective management practice in preventing delayed feed access-related growth depression of broiler chickens.

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