Preliminary study: From biofortified maize to cow milk enriched with selenium: An on-farm strategy using selenium-enriched silage

Selenium (Se) supplementation is a common practice in dairy nutrition. However, the use of biofortified feedstuffs remains a not fully realized strategy to enhance the Se content of animal derived products. This study explored an on-farm biofortification approach by incorporating Se-enriched maize silage into the total mixed ration (TMR) of dairy cows. Sixty Holstein cows were divided into a control group (CON), receiving a conventional diet with selenite supplementation (0.6 mg/kg Se in TMR), and an experimental group (EXP), in which conventional silage was replaced with high-Se silage (0.9 mg/kg Se in TMR). The trial lasted 22 weeks, including one week of adaptation and four weeks after supplementation, when Se concentrations in milk, Se transfer efficiency, and key milk components critical for the production of Se-enriched dairy products were assessed. The higher Se concentration in the TMR had no adverse effects on milk composition or antioxidant status. Milk Se concentration in the EXP group increased rapidly, reaching 68 µg/l within two weeks, significantly higher (P < 0.005) than in the CON group (27 µg/l). Se transfer efficiency to milk was also higher in the EXP group (13.9%) compared to the CON group (8.8%). The diverse Se species in biofortified silage, confirmed through the speciation analysis, may have contributed to these outcomes. However, the gradual decline in milk Se after the initial peak warrants further investigation into physiological factors or changes in silage Se speciation during storage.