Effects of a blend of deactivated yeast, carob’s condensed tannins and bentonite on lactating dairy cows performance and in vitro fermentation testing long and short term effects

Sustainable livestock farming is crucial for mitigating agriculture’s environmental impact. This study evaluated in vivo effects of a feed additive, SOP® STAR COW, based on inactivated yeast, carob condensed tannins and bentonite, on lactating dairy cows, focusing on milk yield and quality, and immune and metabolic profiles. Twelve mid-late lactating dairy cows divided into two groups (control group [CTR] and treated group [STAR]) were fed the same diet for 6 weeks, with the STAR group receiving an additional 8 g/d of the additive. Milk yield and composition, blood metabolic profile, rumination, feed digestibility and rumen parameters were monitored. Results showed no significant effects on rumen parameters, digestibility or milk yield. However, STAR cows exhibited higher milk fat content under heat stress conditions (p < 0.05) and a tendency towards increased rumination (p < 0.10). Most blood metabolites were unaffected, although albumin and calcium concentrations were higher in STAR (p < 0.05). In addition, a 24 h in vitro fermentation was performed using rumen fluid from STAR and CTR cows as inocula to evaluate the effects of a prolonged administration of the additive in vivo (long-term effect) and of the addition of the additive at the start of the fermentation (short-term effect). Long term in vivo adaptation reduced total gas but not methane, increased acetate and isobutyrate proportions, and improved the efficiency of microbial protein synthesis. Overall, the results suggest that the additive may improve milk quality under heat stress conditions and animal welfare, and that its long and short term effects can be distinguished in vitro.