Maternal Dietary Yeast Hydrolysate Alters Milk Composition and Influences Metabolic Status and Gut Microbiota in Dezhou Donkey Foals

Yeast hydrolysate (YH) has attracted increasing interest as a functional feed additive because of its potential benefits for maternal nutrition and offspring development. However, its effects on milk composition and the physiological responses of donkey foals remain poorly understood. This study evaluated the effects of dietary YH supplementation in lactating Dezhou jennies on milk composition, as well as growth performance, serum biochemical parameters, and fecal microbiota in their foals. Sixteen healthy jennies and their foals were randomly assigned to a control group (OCON) or a YH-supplemented group (OYE; 0.5 g/kg diet) for 60 days. Maternal dietary YH supplementation significantly increased milk fat and milk protein contents. Foals in the OYE group showed a tendency toward greater back skin thickness, although the difference was not statistically significant, while body weight and neck skin thickness were unaffected. Serum biochemical analysis showed increased HDL-C and total cholesterol concentrations together with decreased triglyceride and LDL-C concentrations in the OYE group. In addition, serum ALT activity was significantly decreased, whereas AST levels were significantly increased. Fecal microbiota analysis indicated that YH supplementation did not significantly affect overall microbial diversity but altered the relative abundance of several bacterial taxa, including Prevotella, Alistipes, and Olsenella. Overall, maternal dietary YH supplementation was associated with changes in milk composition, selected serum biochemical parameters, and the relative abundance of specific fecal bacterial taxa in donkey foals. However, no significant improvement in offspring growth performance was observed, and the underlying mechanisms require further investigation.