Effect of the Inclusion of Bacillus spp. in Growing-Finishing Pigs' Diets: A Meta-Analysis

Abstract

This meta-analysis determined the effect of Bacillus spp. on growth performance of growing−finishing pigs and then assessed causes for the heterogeneity of responses detected using meta-regression. A database of 22 articles published from 2000 to 2020 was identified, and 9 articles fitted the selection criteria and were integrated in the final database. Statistical analysis was performed to analyze the effect size for ADG, average daily feed intake (ADFI), and F:G ratio using a standardized means difference (SMD) at a 95% confidence interval. A meta-regression analysis was used to investigate the cause of heterogeneity, using the individual SMD for each study assessment as the outcome and the associated SE as the measure of variance. Dietary Bacillus spp. supplementation had no effect on ADFI (SMD: −0.052, p = 0.138) and numerically increased ADG (SMD: 0.113, p = 0.081) and reduced the F:G ratio SMD: −0.127, p < 0.001). Meta-regression outcomes suggested that the number of animals per group was an essential component promoting heterogeneity in ADG. Overall, the inclusion of Bacillus spp. (median 486 mg/d) in growing−finishing pigs can increase ADG and can decrease the F:G ratio.

Keywords: growth promoters; probiotics; sustainable animal diet.

Figure 1

PRISMA flow diagram of the systematic review from the initial search and screening to the final selection of publications included in the study.

Figure 2

Forest plot of the effect of Bacillus spp. on mean daily feed intake in growing and finishing pigs, based on standardized mean differences (Std. diff in means). The diamond at the bottom indicates the mean effect size, while the size of the squares illustrates the weight of each study in relation to the mean effect size. Smaller squares represent smaller weights. The confidence intervals (95% for the study) are represented by horizontal bars.

Figure 3

Forest plot of the effect of Bacillus spp. on average daily gain in growing–finishing pigs based on standardized mean differences (Std. diff in means). The diamond at the bottom indicates the mean effect size, the size of the squares illustrates the weight of each study in relation to the mean effect size, and horizontal bars represent confidence intervals (95% for the study).

Figure 4

Forest plot of the effect of Bacillus spp. on feed:gain ratio in growing–finishing pigs based on standardized mean differences (Std. diff in means). The size of the squares illustrates the weight of each study, smaller squares represent lower weight, and the diamond indicates the mean effect size. Horizontal bars represent confidence intervals (95% for the study).