Abstract
BackgroundAntibiotic growth promoters are widely used to improve weight gain. However, the abuse of antibiotics can have many negative effects on people. Developing alternatives to antibiotics is an urgent need in livestock production. We aimed to perform a meta-analysis and network meta-analysis (NMA) to investigate the effects of feed additives as potential antibiotic substitutes (ASs) on bacteriostasis, growth performance, intestinal morphology and immunity. Furthermore, the primary, secondary, and tertiary ASs were defined by comparing their results with the results of antibiotics.ResultsAmong 16,309 identified studies, 37 were summarized to study the bacteriostasis effects of feed additives, and 89 were included in the meta-analysis and NMA (10,228 pigs). We summarized 268 associations of 57 interventions with 32 bacteria. The order of bacteriostasis effects was as follows: antimicrobial peptides (AMPs) ≈ antibiotics>organic acids>plant extracts>oligosaccharides. We detected associations of 11 feed additives and 11 outcomes. Compared with a basal diet, plant extract, AMPs, probiotics, microelements, organic acids, bacteriophages, lysozyme, zymin, and oligosaccharides significantly improved growth performance (P < 0.05); organic acids, probiotics, microelements, lysozyme, and AMPs remarkably increased the villus height:crypt depth ratio (V/C) (P < 0.05); and plant extracts, zymin, microelements, probiotics, and organic acids notably improved immunity (P < 0.05). The optimal AMP, bacteriophage, lysozyme, microelements, oligosaccharides, organic acids, plants, plant extracts, probiotics, and zymin doses were 0.100%, 0.150%, 0.012%, 0.010%, 0.050%, 0.750%, 0.20%, 0.040%, 0.180%, and 0.100%, respectively. Compared with antibiotics, all investigated feed additives exhibited no significant difference in effects on growth performance, IgG, and diarrhoea index/rate (P > 0.05); AMPs and microelements significantly increased V/C (P < 0.05); and zymin significantly improved lymphocyte levels (P < 0.05). Furthermore, linear weighting sum models were used to comprehensively estimate the overall impact of each feed additive on pig growth and health.ConclusionsOur findings suggest that AMPs and plant extracts can be used as primary ASs for weaned piglets and growing pigs, respectively. Bacteriophages, zymin, plants, probiotics, oligosaccharides, lysozyme, and microelements can be regarded as secondary ASs. Nucleotides and organic acids can be considered as tertiary ASs. Future studies should further assess the alternative effects of combinational feed additives.
Highlights
Antibiotic growth promoters are widely used to improve weight gain
1) How should antibiotic substitutes (ASs) be defined? 2) What are the effects of many feed additives on bacteriostasis, growth promotion, improvement of intestinal morphology and immunity? 3) What is the optimal dose for these feed additives? 4) Which additive is the most powerful AS? In this study, we performed a set of metaanalyses to investigate the effects of different feed additives regarded as ASs on growth performance, intestinal morphology and immunity in pigs
Effects of feed additives on bacteriostasis We summarized 268 associations of 57 interventions with 32 bacteria (Table S4)
Summary
Antibiotic growth promoters are widely used to improve weight gain. We aimed to perform a meta-analysis and network meta-analysis (NMA) to investigate the effects of feed additives as potential antibiotic substitutes (ASs) on bacteriostasis, growth performance, intestinal morphology and immunity. Antibiotics are widely used in commercial pig production for growth promotion and disease prevention [1]. Subtherapeutic doses of antibiotics are used as feed additives to promote growth performance, improving average daily gain (ADG) and gain:feed ratio (G/F) through alterations in intestinal morphology and digestion and the suppression of harmful bacteria [2]. 2) What are the effects of many feed additives on bacteriostasis, growth promotion, improvement of intestinal morphology and immunity? We performed a set of metaanalyses to investigate the effects of different feed additives regarded as ASs on growth performance, intestinal morphology and immunity in pigs. To the best of our knowledge, this study is the first to comprehensively and systematically define ASs and investigate their effects
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