Effects of fermented feed supplementation on pig growth performance: A meta-analysis

Abstract

Fermented feed (FF) is recommended due to its high nutritional value and digestibility, but the effects on pig growth performance are inconsistent. This meta-analysis was conducted to quantify the effects of FF on pig growth performance. We systematically searched in PubMed and Web of Science for studies (published between January 1st, 2000 and December 20th, 2018) comparing the effects of FF supplementation with basal diet on pig growth performance. The main outcomes were average daily gain (ADG), average daily feed intake (ADFI), and gain: feed ratio (G/F). Random-effects model was used to compute the weighted mean difference (WMD) and 95% confidence interval (95% CI). The robustness of the pooled estimates was determined using sensitivity and subgroup analyses. Fermented materials included in the subgroup analysis were classified as ingredients (protein and energy sources) and additives (plant materials added at low levels). Of 1371 identified articles, 25 were eligible and were included in the meta-analysis (n = 2391 pigs). Compared with the basal diet, FF supplementation improved ADG and G/F of weaned piglets (ADG: WMD = 20.869 g/day, 95% CI: 15.007–26.731, P < 0.001; G/F: WMD = 0.023, 95% CI: 0.013 to 0.032, P < 0.001), growing pigs (ADG: WMD = 23.938 g/day, 95% CI: 15.342–32.533, P < 0.001; G/F: WMD = 0.014, 95% CI: 0.006 to 0.022, P = 0.001), and finishing pigs (ADG: WMD = 40.151 g/day, 95% CI: 6.118–74.183, P = 0.021; G/F: WMD = 0.022, 95% CI: 0.005 to 0.038, P = 0.009), but had no effect on ADFI (P > 0.05). The subgroup analyses revealed that fermented feed ingredients could boost the growth performance of weaned piglets and growing pigs. The fermented feed additives promoted growth at all stages. FF supplementation can enhance pig growth performance of which the enhancement in feed efficiency is due to the improvement in nutritional value and availability rather than feed intake.