Evaluating the potential of fermented concentrate feeds on lamb growth performance: A meta-analysis

Fermented feeds (FFs) are known for high nutritional value and digestibility, but their impact on sheep growth performance remains inconsistent between studies. This meta-analysis systematically evaluates the effect of FFs on sheep growth. A comprehensive search was conducted using Google Scholar, ScienceDirect, and PubMed databases to identify relevant studies published between January 1990 and June 2024. Eleven studies comprising a total of 366 lambs met the established criteria. Growth parameters, including average daily gain (ADG), average daily feed intake (ADFI), and feed conversion ratio (FCR) were extracted and analysed using a random-effects model. Sensitivity and subgroup analyses were conducted to assess the stability of the results. FF supplementation as an energy source significantly improved ADG by 2.86 g/day (95% CI: 0.24–5.48, P = 0.032) but did not affect ADFI (P > 0.05). When used as a protein source, FF elevated ADFI (95% CI: 0.93–21.95, P = 0.032). Marked improvements in FCR were observed with both energy (standardised mean difference (SMD) = −3.95; P < 0.001) and proteinbased FF (SMD= −5.02; P < 0.001). Microbial inoculants (Lactobacillus/Bacillus and Saccharomyces cerevisiae) positively affected ADG and FCR, although with significant heterogeneity (I2 > 75%), likely due to variations in substrates, strains, or feeding protocols. FFs used as either an energy or protein source can significantly improve lamb growth performance, particularly in terms of FCR and ADG, with microbial agents playing an important role.