Lactic acid bacteria (LAB) are usually employed as alfalfa silage inoculants to obtain high-quality feed for animal husbandry. However, the effects of these inoculants are still unclear and need to be studied extensively. Therefore, the objective of this meta-analysis was to quantitatively summarize published research studies that assess the effects of homofermentative (HoLAB) and heterofermentative lactic acid bacteria (HeLAB) on fermentation parameters, nutritive value, microbiological composition and aerobic stability of alfalfa silage. PubMed, ScienceDirect and Scopus have been screened for articles published from 1980 to 2018. The criteria for inclusion were: randomized and controlled trials using alfalfa silage and published in peer-reviewed journals. It was found that inoculation with LAB decreased silage pH, neutral detergent fibre, acid detergent fibre and ammoniacal nitrogen, while it increased dry matter and crude protein compared to control in the pooled raw mean difference random-effect model. Additionally, LAB inoculation decreased acetate, propionate, ethanol and butyrate concentrations, whereas it increased lactate. In addition, inoculants reduced the counts of yeasts and moulds. Lastly, LAB inoculation improved aerobic stability. To the best of our knowledge, this is the first meta-analysis that aims at comparing the application of HoLAB and HeLAB for alfalfa silage. In the pool estimate, positive effects attributable to the application of microbial silage inoculants were found in most of the evaluated parameters; supporting the importance of applying both types of inoculants to improve forage preservation for the livestock industry.

1. The aim of this meta-analysis was to investigate the effects of probiotics on the growth performance of broilers. PubMed, Scopus and Scholar Google databases were searched in all languages from 1980 to 2012. The studies in the meta-analysis were only selected if they were randomised and controlled experiments using broilers without apparent disease and the results were published in peer-reviewed journals. 2. A total of 48 and 46 studies were included to assess probiotic effects on body weight gain (BWG) and feed efficiency (FE), respectively. Probiotics increased BWG compared to controls (SMD = 0.661, 95% CI 0.499 to 0.822) and improved FE (SMD = − 0.281, 95% CI −0.404 to −0.157) in the pooled standardised mean difference random effect model, considering the source of heterogeneity and publication biases. However, there are evidences of publication bias and heterogeneity, so the results of this meta-analysis should be considered with caution. Applying the Duval and Tweedie’s trim-and-fill methods, the adjusted value for BWG was 0.0594 (95% CI −0.122 to 0.242), and the adjusted value for FE did not show any modifications. 3. The meta-analysis showed that application of probiotics via water resulted in greater BGW and FE than administration through the feed. The effect was not related to the use of mono-strain or multi-strain probiotics, although it may depend on the strain used. The number of broilers and the duration of the experiments had an impact on the outcomes. 4. Additional studies should be conducted with the aim to identify the covariates which can explain the differences in the estimated effect sizes.