Abstract

Background:
Selenium (Se) and zinc (Zn) are essential trace minerals involved in antioxidant defense, immune function, rumen metabolism, and mineral transfer into milk. However, the additional benefit of organic Se and Zn enrichment within a feed supplement for early-lactation dairy cattle, particularly within the specific constraints of smallholder tropical production systems, remains inadequately characterized.

Aim:
This study evaluated the effects of a feed supplement enriched with organic Se and Zn on nutrient utilization efficiency, milk production, mineral partitioning in serum and milk, antioxidant status, and broader biochemical and hematological profiles of cows.

Methods:
Twenty-four Friesian Holstein crossbred cows (12.82±2.08 kg/day milk yield; 452.09±35.45 kg body weight; 37.65±15.41 days in milk) were allocated to three treatments: control (CON), feed supplement (FS; 1 kg/head/day), and feed supplement enriched with organic Se and Zn (FS-SZ; 0.45 mg Se/kg dry matter [DM] and 60 mg Zn/kg DM) for 49 days under tropical smallholder conditions.

Results:
Compared with CON, FS and FS-SZ increased DM, organic matter, and crude protein (CP) intake (P0.05). Compared with FS, FS-SZ improved CP digestibility (P

Key words: Blood biochemical profiles; Dietary supplementation; Hematological indices; Lactation performance; Organic selenium and zinc.