Effects of Schizochytrium powder products supplementation: 1. Enrichment of milk docosahexaenoic acid and rumen microbial composition in lactating dairy cows

Supplementation with docosahexaenoic acid (DHA) from microalgae is considered a promising strategy to enhance the n-3 content of bovine milk. However, DHA transfer efficiency into milk is typically low and highly variable. This study evaluated the effects of 2 Schizochytrium-derived DHA powder products on milk performance, DHA enrichment, milk fatty acid (FA) profile, and rumen microbiota composition in lactating Holstein dairy cows. Forty-five Holstein cows were randomly assigned into 3 treatments (n = 15 each), a control without any supplementation (CON), and 2 treatments receiving different Schizochytrium sp. powder products at 200 g/d (TRT1 and TRT2). The feeding trial lasted for 8 wk, with weekly milk samples collected for analysis of milk composition, DHA content, and milk FA profile. Rumen content was sampled in wk 8 for 16S rRNA gene sequencing to assess microbial structure. Both Schizochytrium treatments supported similar milk yield and composition. However, TRT1 increased milk DHA and total n-3 FA while reducing concentrations of DHA biohydrogenation products such as C22:0 and C22:2. No differences were observed in de novo synthesized FA. Although both treatment groups exhibited similar microbial α diversity and shared dominant taxa at the phylum, family, and genus levels, β-diversity analysis revealed distinct microbial community structures. Treatment 1 was associated with greater abundances of Desulfuromonadia, Acholeplasmataceae, and Bradymonadales, and TRT2 showed higher levels of Bifidobacteriaceae. In conclusion, even Schizochytrium-derived DHA supplements of similar origin can yield distinct effects on milk FA profiles and DHA enrichment efficiency.