Abstract
Antibiotics in feed select for resistant strains and is thus a threat to human health. In this study, the effect of a multi-strain probiotic and antibiotics on the growth and health of broilers was studied. Equal numbers of broilers received on a daily basis either a multi-strain probiotic or a combination of sulphadiazine, colistin and trimethoprim, whereas the control group received standard feed. The villi of immature broilers (19 days old) administered antibiotics had a larger surface area and their lymphocyte and basophil counts were higher compared to broilers from the probiotic and control groups. The cecal microbiomes of mature broilers (29 days old) that received probiotics had higher levels of Enterobacteriaceae, but lower numbers of Clostridiales, Brucellaceae, Synergistaceae, Erysipelotrichaceae and Coriobacteriaceae compared to the antibiotic-treated group. A decline in the bioluminescence of Listeria monocytogenes observed for broilers on probiotics suggested that the probiotic may be used to control bacterial infections. No significant differences in total red blood cell, haemoglobin and haematocrit content, and mean values for corpuscular volume, corpuscular haemoglobin and corpuscular haemoglobin numbers were recorded amongst broilers from the different treatment groups. This study provides valuable information on the health and performance of broilers when administered probiotics and antibiotics as additives.
Highlights
Poultry reared on a large scale in intensive production systems are more prone to develop microbial infections[1]
In this study we evaluated the effect of antibiotics and a multi-strain probiotic (L. crispatus, L. salivarius, L. gallinarum, L. johnsonii, E. faecalis and B. amyloliquefaciens) on the performance of healthy broilers
The average feed conversion ratios (FCRs) of broilers in the probiotic and antibiotic treatment groups were not significantly different from that recorded for broilers in the untreated group on days 7, 14, 21 and 28 (Supplementary Table S1), suggesting that neither the multi-strain probiotic, nor the antibiotics had an effect on growth performance
Summary
Poultry reared on a large scale in intensive production systems are more prone to develop microbial infections[1]. It is not surprising that broilers reared intensively are more susceptible to microbial infections[6] Those that do survive the first two weeks have a good chance to develop a stable consortium of intestinal microbiota during the following two weeks[7]. Numerous beneficial effects of probiotics administered to broilers have been reported, e.g. improvement in growth performance[8,9], increased digestion of nutrients[10], modulation of intestinal microflora[11], inhibition of pathogens[12,13], competitive exclusion of pathogens and antagonism[14], and modulation of gut mucosal immunity[15]. Understanding what physiological changes these feed additives induce in healthy broilers is important to assess their safety with long term use
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