Effects of a dietary synbiotic supplement on thyroid hormones, intestinal histomorphology, and heat shock protein 70 expression in broiler chickens reared under cyclic heat stress

Authors: MOHAMMED, A. - Purdue University; Jacobs, Jacquelyn; CRAMER, T. - Texas Tech University; Cheng, Heng-Wei

Submitted to: Poultry Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/15/2019
Publication Date: 12/30/2019
Citation: Mohammed, A.A., Jacobs, J.A., Cramer, T.A., Cheng, H. 2019. Effects of a dietary synbiotic supplement on thyroid hormones, intestinal histomorphology, and heat shock protein 70 expression in broiler chickens reared under cyclic heat stress. Poultry Science. 99(1), 142-150. https://doi.org/10.3382/ps/pez571.
DOI: https://doi.org/10.3382/ps/pez571

Interpretive Summary: Dietary supplementation of probiotics has become an important management strategy in improving farm animal production. Compared to controls, synbiotic fed broiler chickens had increased concentrations of thyroid hormones and improved intestinal architecture, but reduced heat shock protein 70 expression in the liver and hypothalamus. The results indicate that the negative effects of heat stress on health of broiler chickens can be alleviated by feeding a synbiotic. These results can be used by the poultry industry to develop management guidelines for improving poultry health and welfare under high-temperature conditions.

Technical Abstract: This study examined the effects of a dietary synbiotic supplement on the expression of thyroid hormones, heat shock protein 70 (HSP70), and intestinal histomorphology in broiler chickens exposed to cyclic heat stress (HS). Three hundred and sixty 1d-old male Ross 708 broiler chicks were randomly distributed among three dietary treatments containing a synbiotic at 0 (control), 0.5 (0.5X), and 1.0 (1.0X) g/kg. Each treatment contained 8 replicates of 15 birds each housed in floor pens. Heat stimulation was established from d 15 to 42 at 32°C for 9 h daily. The results indicated that both synbiotic fed groups had lower HSP70 levels in the liver and hypothalamus (P < 0.001) compared to the control group, however, HSP70 mRNA expression was not different between treatments (P > 0.05). The levels of triiodothyronine (T3) were increased in the 0.5X synbiotic group compared to controls (P < 0.01), with no difference in the levels of thyroxine (T4) and T3/T4 ratio (P > 0.05) between treatments. In the duodenum, 1.0X group had greater villus height (P < 0.05) compared to the control group, and consequently led to a higher villus height:crypt depth ratio (P < 0.05) compared to both 0.5X and control groups. The villus height, width, and villus height:crypt depth ratio were greater in the jejunum for 1.0X synbiotic group compared to controls (P < 0.05). There were no differences between treatments on the measured intestinal parameters in the ileum (P > 0.05). The results suggest that the synbiotic may ameliorate the negative effects of HS on chicken health as indicated by the changes in the intestinal architecture and the levels of HSP70 and T3. Synbiotics could be a feasible nutritive supplement for the poultry industry to improve the health and well-being of chickens when exposed to high environmental temperatures.