Abstract
Numerous studies have focused on the beneficial effects of probiotics in animals. Even so, additional information should be obtained about the mechanisms by which a useful probiotic strain successfully exerts such beneficial effects. In this study, we evaluated the effect of the dietary supplementation of both live and disrupted Lactobacillus johnsonii (LJ) strain BS15 in broilers at different ages. Specifically, growth performance, lipid metabolism, gut microbiota, intestinal development, and digestive ability of the broilers were assessed. A total of 180 1-day-old Cobb 500 chicks were randomly distributed into three groups. These chicks were fed diets supplemented with 1 × 106 colony-forming units (cfu) LJ per gram of feed (LJ group); 1 × 106 cfu disrupted LJ per gram of feed (D-LJ group); and de Man, Rogosa, and Sharpe liquid medium (control group), respectively, throughout a 42-day experimental period. The results demonstrated that LJ supplementation of feed had a positive effect on the average daily gain and starter feed conversion ratio. In addition, LJ supplementation of feed decreased serum triglyceride and low-density lipid cholesterol levels, as well as abdominal fat deposition. LJ also reduced the mRNA levels of lipoprotein lipase in adipose tissue and stearoyl-CoA desaturase-1 in the liver. LJ diminished the mRNA quantities of the sterol regulatory element binding protein-1c and fatty acid synthase, as well as increased the level of serum high-density lipid cholesterol. LJ increased the mRNA quantities of peroxisome proliferator-activated receptor α, acyl-CoA oxidase in the liver, and carnitine palmitoyltransferase-1. LJ also improved the intestinal development and digestive ability mainly by increasing the villus height/crypt depth ratio in the ileum. The probiotic increased the levels of epidermal growth factor and insulin-like growth factor-1, as well as the activities of trypsin and lipase in the jejunum and ileum. LJ exerted beneficial effects on the intestinal flora. Specifically, LJ markedly enhanced the population of Bacteroidetes and Lactobacillus spp. Moreover, the probiotic reduced the population of Enterobacteriaceae and the Firmicutes/Bacteroidetes ratio. Slight changes caused by disrupted LJ were detected. These findings indicated that live LJ supplementation may promote growth performance and lower fat deposition in broilers.
Highlights
Given the ban on in-feed antibiotic growth promoter usage in Europe and the global trend to reduce the utilization of antibiotics as growth promoters in livestock diets, determining alternatives to the utilization of antibiotic growth promoters has attracted increasing attention (Van et al, 2009)
The average daily feed intake (ADFI) of the starter phase, the feed conversion ratio (FCR) of the finisher phase, and the overall FCR were not improved by L. johnsonii BS15 (LJ) addition (P > 0.05)
No significant difference was observed between the growth performance of the control and D-LJ groups (P > 0.05)
Summary
Given the ban on in-feed antibiotic growth promoter usage in Europe and the global trend to reduce the utilization of antibiotics as growth promoters in livestock diets, determining alternatives to the utilization of antibiotic growth promoters has attracted increasing attention (Van et al, 2009). Probiotics, live cultures of bacteria provided to benefit the host are one of the alternative treatment strategies that can be used (Upadhaya et al, 2016). As extensively used probiotics in the poultry industry, Lactobacillus strains can promote growth performance (Nakphaichit et al, 2011; Shen et al, 2014), improve meat quality (Keokamnerd et al, 2007; Lv et al, 2012), enhance immune response (Huang et al, 2004; Stringfellow et al, 2011), and prevent some avian diseases (Pascual et al, 1999; Yamazaki et al, 2012; Youn et al, 2012). It has proved difficult to demonstrate the mechanism whereby probiotics affect the gastrointestinal tract because probiotic strains exert their beneficial effects via different mechanisms in which other microbiota may be involved as well (Rubio et al, 2014; Serban, 2014; Patten and Laws, 2015). It is important to find out whether or not live microorganisms are needed to induce the benefits
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