The effects of heat-killed Lactobacillus plantarum L-137 supplementation on growth performance, intestinal morphology, and immune-related gene expression in broiler chickens

Abstract

The present study was conducted to investigate the effects of heat-killed Lactobacillus plantarum L-137 (HK L-137) supplementation on the growth performance, intestinal morphology, and immune-related gene expression in broiler chickens. A total of 600 5-day-old male Ross 308 broilers were randomly separated in a completely randomized design with to 2 dietary treatments, each with 6 replicates of 50 birds. The basal diets were formulated and prepared using HK L-137 at a level of 0 or 10 mg/kg. Chickens were fed basal diets with or without HK L-137 from 5 to 42 days of age. In addition to performance parameters, 5 birds with a live weight close to the group average were selected from each group and euthanized to collect their spleens for gene expression analysis (at 5, 10, 22, and 42 days old) as well as the whole small intestine for morphological analysis (at 22 and 42 days old). Thirty chickens with uniform weight from each group were slaughtered at the last trial day to measure carcass characteristics. Results showed that HK L-137 supplementation from the 5th to the 22nd day could enhance the body weight (BW), and average daily gain (ADG) in broilers (P < 0.05), and showed a lower value (P < 0.05) of average daily feed intake (ADFI). HK L-137 fed birds showed a significant improvement (P < 0.05) in BW, weight gain, and feed conversion ratio (FCR) at 42 days old, but there were no significant differences on feed intake, survival rate, carcass characteristic, and visceral organs. The intestinal morphometric examination of the broilers at 22 days-old showed that villus height (VH), villus area (VA), and the ratio of VH and crypt depth (CD; VH/CD ratio) trended to be higher in the HK L-137 group. The duodenal VH and jejunal VH/CD ratio significantly increased (P < 0.05) in birds fed HK L-137. This might indicate that the birds fed dietary HK L-137 might have increased growth rate due to the increased VH and VH/CD ratio, resulting in raising the absorptive surface area for available nutrients. However, chickens at 42 days old presented that the intestinal VH, VA, CD, and VH/CD ratio did not differ between dietary groups (P > 0.05). The gene expression levels of IL-12β, IFN-β, and IFN-γ in HK L-137 group were significantly higher than those of the control (P < 0.05, P < 0.01, P < 0.05, respectively) at 22 days of age. These results suggest that HK L-137 has some properties to stimulate the growth performance and immune response in young broiler chickens, and thus that it may be a potential alternative replacement for antibiotic growth promoters (AGPs) in the broiler chicken industry.