Early view

Radena Nenova, Stanimir ENCHEV

Abstract

The present study aimed to evaluate the effects of the phytogenic feed additives Stevia rebaudiana Bertoni and Hippophae rhamnoides L. on the serum biochemical profile and physicochemical characteristics of milk in dairy cows. Thirty clinically healthy black-and-white dairy cows were randomly allocated into three experimental groups (n = 10): a control group (C), a Stevia rebaudiana group (SR) receiving 100 g/day of dried stevia leaves, and a Hippophae rhamnoides group (HR) receiving 100 g/day of dried sea buckthorn leaves. The experimental period lasted 30 days. Serum concentrations of alanine aminotransferase (ALT), aspartate aminotransferase (AST), urea, glucose, total cholesterol, high-density lipoprotein (HDL) cholesterol, low-density lipoprotein (LDL) cholesterol, and triglycerides were determined at the beginning and the end of the experimental period. In addition, the principal physicochemical characteristics of milk were analyzed. The results demonstrated that supplementation with either phytogenic additive had no statistically significant effect on the physicochemical composition of milk (P > 0.05). Milk fat, protein, lactose, total solids, solids-not-fat, density, pH, titratable acidity, and ash content remained within the normal physiological ranges throughout the study. Likewise, no significant changes were observed in serum AST activity, urea concentration, or glucose levels, indicating preserved hepatic function and normal protein and energy metabolism. Although ALT activity increased significantly in both experimental groups, the recorded values remained within physiological reference limits and were not associated with evidence of hepatocellular damage. In contrast, both phytogenic supplements significantly improved the serum lipid profile by reducing total cholesterol, LDL cholesterol, and triglyceride concentrations while increasing HDL cholesterol levels (P < 0.05–0.01). These findings indicate that Stevia rebaudiana Bertoni and Hippophae rhamnoides L. are promising natural phytogenic feed additives for dairy cattle, capable of improving lipid metabolism without adversely affecting the biochemical status of the animals or the physicochemical quality of milk. Their use may therefore contribute to sustainable dairy production systems and support the gradual replacement of synthetic feed additives with natural bioactive alternatives.

Keywords

Stevia rebaudiana, Hippophae rhamnoides, phytogenic additives, dairy cows, serum biochemistry

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