Phytogenic and Nutritional Strategies to Improve Milk Production and Microbiological Quality in Lactating Donkeys

Donkey milk is highly regarded for its nutritional, immunological and hypoallergenic properties. In this context, the global demand is increasing, and the challenges of low production and milk hygiene need to be addressed. This study evaluated the effects of dietary and phytogenic supplementation on milk yield, nutrient digestibility, and milk quality in lactating jennies (Equus asinus). All donkeys had unrestricted access to natural pasture during the study. In addition to grazing, animals were divided into three groups (n = 10 per group) that differed only in the type of supplemental feed. The control group (CG) received pasture grass with a corn-based supplement; Group 1 (G1) received the same basal feed enriched with sunflower meal and a phytogenic blend of medicinal plants; and Group 2 (G2) received the same compound feed as G1 but without the phytogenic additives. Over an eight-week period, milk production, apparent digestibility coefficients (dry matter, protein, fibre, and ether extract), and microbiological quality were assessed. G1 demonstrated the highest milk yield (p < 0.001), improved nutrient digestibility (e.g., crude protein digestibility: 57.89 ± 4.21%), and a significant reduction in total viable counts (TVC) from 2.848 ± 0.265 to 1.898 ± 0.404 log10 CFU/mL (p < 0.001), compared to CG and G2. The latter maintained relatively stable TVC values (2.930 ± 0.260 → 2.838 ± 0.196; p = 0.356641), accompanied by reduced interindividual variability, whereas CG exhibited a slight increase (2.922 ± 0.253 → 2.949 ± 0.323; p = 0.792259) and greater variability, suggesting a negative trend. Crude protein digestibility was 55.86 ± 6.66% in G2 and 45.26 ± 9.85% in CG, further supporting the superior nutrient utilization efficiency observed in G1. The phytogenic supplement stabilized milk chemical composition, suggesting potential galactagogues, immunomodulatory, and antimicrobial effects. These findings support the use of functional feed additives as a promising strategy to enhance productive performance and milk hygiene in sustainable donkey farming systems.