Meta-analysis of the benefits of dietary Saccharomyces cerevisiae intervention on milk yield and component characteristics in lactating small ruminants

Milk yield and components in small ruminants fed Saccharomyces cerevisiae (SC) have been investigated, but results were not consistent among investigators. Hence, this trial aimed to explore the efficacy of SC supplementation in improving milk yield and components (i.e., milk proteins, fat, lactose, total solids and ash) in small ruminants. A search performed in Scopus, PubMed and Google Scholar databases yield 1,826 studies, of which 26 met the inclusion criteria. Random-effects model was used to aggregate milk production variables. Meta-regression analysis examined the effect of the following moderators: SC type, ruminant type (sheep or goat), diet type, breed, duration of supplementation and supplementation levels on outcome measures. Subgroup analysis explored the influence of the following moderators: SC type and ruminant type on outcomes measures. SC had positive moderate effect on milk yield (standardised mean difference [SMD] = 0.72; p < 0.001; heterogeneity [I (2)] = 73%) and small effect on milk proteins (SMD = 0.46; p = 0.004; I (2) = 83%), milk lactose (SMD = 0.17; p = 0.007; I (2) = 0%) and fat (SMD = 0.28; p = 0.016; I (2) = 70%). Subgroup analysis revealed that SC improved milk yield, lactose and proteins in lactating sheep and milk yield and fat in lactating goats. Our results show that moderators influenced the results of the meta-analysis and explained most of the sources of heterogeneity. In conclusion, SC should be included in small ruminant diets as it had small-to-moderate effects on milk yield and aspects of milk components.