Effects of a synbiotic as an antibiotic alternative on behavioral exhibition, production performance, cecal microbial ecology, and jejunal histomorphology of broiler chickens under heat stress

Authors: MOHAMMED, AHMED - Purdue University; MURUGESAN, RAJ - Biomin America, Inc; HU, JIAYANG - Purdue University; Cheng, Heng-Wei

Submitted to: Applied Animal Behaviour Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/24/2022
Publication Date: 9/22/2022
Citation: Mohammed, A.A., Murugesan, R.G., Hu, J., Cheng, H. 2022. Effects of a synbiotic as an antibiotic alternative on behavioral exhibition, production performance, cecal microbial ecology, and jejunal histomorphology of broiler chickens under heat stress. Applied Animal Behaviour Science. 17(9): e0274179. https://doi.org/10.1371/journal.pone.0274179.
DOI: https://doi.org/10.1371/journal.pone.0274179

Interpretive Summary: The use of antibiotics in animal husbandry has caused growing public concerns about drug residues in meat products and the development of antibiotic-resistant bacteria. The aim of this study was to examine if synbiotics can be used as replacements for antibiotics in poultry production, especially under heat stress conditions. Day-old broiler chicks were randomly distributed among the treatments for a 42-day trial: thermoneutral control birds were fed basal diets; while heat stressed birds were fed the basal diets, the basal diets mixed with an antibiotic (0.05g/kg of feed) or a synbiotic (0.6 g/kg of feed). The feeding program was started at day 1 and heat stress was started at day 15. The results indicate that the dietary synbiotic supplement has significant performance and welfare benefits, with the potential to be used as an alternative to antibiotics for poultry meat production, especially during hot seasons. The findings provide insights for egg producers and animal scientists to develop novel management strategies for improving hen health and welfare, especially in the tropical and subtropical regions.

Technical Abstract: It has been proposed that synbiotics as well as prebiotics and probiotics can be used as alternatives to antibiotics in farm animal production. The aim of this study was to examine if synbiotics present similar efficiency to a common antibiotic used in poultry production under heat stress conditions. Three hundred and twenty day-old male Ross 708 broiler chicks were randomly distributed among 4 treatments with 8 pens per treatment of 10 birds each in two temperature controlled rooms for a 42-day trail. From day 15, control birds were continuously kept at a regular thermoneutral condition (26°C, TN) and fed a basal diet (TN-CONT); while treated birds were heat stressed (32°C for 9 h daily, HS) and continuously fed the basal diet (HS-CONT), the basal diet mixed with Bactiracin Methylene Disalicylate (0.05g/kg of feed. HS-BMD) or a synbiotic (0.6 g/kg of feed. HS-SYN). The treatment effects on bird behavioral exhibition, production performance, jejunal histomorphology, and cecal microbial ecology were examined. Behavioral observation was recorded by using instantaneous scan sampling technique. Production parameters were performed on day 14, 28, and 42. Cecal microbial populations of Escherichia coli and Lactobacilli and jejunal histomorphological parameters were measured at day 42. The results showed that TN-CONT birds exhibited more standing and sitting with less wing spreading and panting compared with HS-CONT birds (P < 0.05). TN-CONT birds also had higher body weight (BW) and body weight gain (BWG) than that of HS-CONT birds at day 42 (P < 0.05). Among HS groups, HS-SYN birds exhibited more feeding and preening but less drinking and panting behaviors compared with both HS-BMD and HS-CONT birds (P < 0.05). The HS-SYN birds also had higher BW at both day 28 and 42 compared to HS-CONT birds (P < 0.05) but not HS-BMD birds (P > 0.05). At the end of the experiment, the counts of Escherichia coli of HS-SYN birds were at the similar levels of both TN-CONT and HS-BMD birds (P > 0.05) but were lower than that of HS-CONT birds (P < 0.05); while there were no treatment effects on the populations of Lactobacilli (P > 0.05). In addition, HS-SYN birds had greater villus height compared with both HS-CONT and HS-BMD birds (P < 0.05) but not TN-CONT birds (P > 0.05). These findings suggest that the dietary SYN supplement has significant performance and welfare benefits, with the potential to be used as an alternative to antibiotics for poultry meat production, especially during hot seasons.