Dietary acidifiers as an alternative to antibiotics for promoting pig growth performance: A systematic review and meta-analysis

The over-use of antibiotic growth promoters (AGPs) in livestock husbandry may have contributed on creating environmental and human health hazards. A number of acidifiers as alternative to AGPs, has been added into diets to prevent the post-weaning syndrome in pigs. However, the effect of feed acidifiers on growth performance of pigs is not consistently positive, especially in comparison with the AGPs. A systematic review and a meta-analysis were therefore conducted to determine the acidifiers those are most consistent on improving growth performance when supplemented to pig diets. Data bases (Web of Science) were searched from 1990 to 2019, unrestricted by language. Fifty-two articles were selected to assess the effects of acidifiers on average daily gain (ADG), average daily feed intake (ADFI) and feed efficiency (G:F), through the side-by-side comparisons with control diets or antibiotic supplemented diets. These acidifiers investigated in the present study were classified into four categories: organic acids, inorganic acids, salts of acids and blends of acids. Results indicated that supplementation of diets with acidifiers had positive effects on growth performance (+6.7 and +5.0% for ADG and G:F, respectively; P < 0.01) in comparison with control diets, and the most consistent improvement was observed in nursery-growing pigs (< 60 kg). In comparison with antibiotic supplementation, the acidifier-supplemented diets had the similar G:F, but lower ADG and ADFI. Furthermore, blends of acids are superior to individual organic acids or salts of acids on improving growth performance in pigs. In conclusion, addition of a range of acidifiers could provide a significant improvement in pig growth, although acidifiers were less effective than antibiotics in the most cases. ● Dietary acidifiers improve growth of pigs in comparison with pigs fed control diets. ● Pigs fed acidifiers had similar G:F as those fed AGP, but a lower ADFI and ADG. ● Blends of acids are superior to individual acids in improving growth of pigs. ● Factors related to effective dose and growth stage of pigs affect efficacy of acids.