TITLE:
Reducing Protein Content with and without Yeast Probiotic Actisaf Sc 47 Supplementation in the Diet of Dairy Cow: Effects on Milk Performance, Milk Fatty Acid Composition, Digestibility, Feed, and Economic Efficiency
AUTHORS:
Nizar Salah, Brigitte Gestes, Pauline Ly, Axel Blancou, Kheira Hadjeba, Julie Duclos, Julie Schulthess, Eric Pinloche
KEYWORDS:
Yeast Probiotic, Actisaf Sc 47, Dietary Crude Protein, Milk Performance, Fatty Acids, Economics
JOURNAL NAME:
Agricultural Sciences,
Vol.17 No.7,
July
21,
2026
ABSTRACT: The objective of the present study was to evaluate the effect of reducing CP levels in the diet of dairy cows alone or in combination with a yeast probiotic on milk quantity and quality, milk fatty acid profile, feed and economic efficiency. In total, six cows were included in a 3 × 3 Latin square design with 3 experimental periods of 28 days long (23 days for adaptation and 5 days for data collection). Cows were randomly assigned to one of the three diets according to protein level and supplementation: control diet with 16.5 CP%DM (CTR), a diet with 14.5 CP%DM without Actisaf Sc 47 supplementation (LCP), and a diet with 14.5 CP%DM with Actisaf Sc 47 supplementation at 5 g/cow/day (LCPActisaf). Regarding total milk yield (TMY), a tendency for lower TMY was observed in LCP group compared with the CTR group (P = 0.1). No difference was observed between CTR and LCPActisaf groups (P = 0.90). The use of Actisaf Sc 47 mitigated the TMY reduction observed in LCP group. Milk fat (MF) and energy-corrected milk (ECM) were unaffected by treatments. Milk protein (MP, kg/d) resulted higher and tended to be higher in LCPActisaf compared to CTR (P = 0.03) and LCP (P = 0.06) but similar between CTR and LCP (P = 0.4). Compared with the CTR group, milk urea nitrogen (MUN) was reduced by both LCP and LCPActisaf (−31.8% and −23.8%, respectively, P = 0.04). No difference was observed between LCP and LCPActisaf (P = 0.49). Reducing protein alone or in combination with Actisaf Sc 47 did not impact feed efficiency (FE) when compared to CTR (P = 0.15 and P = 0.39, respectively) but reducing protein in combination with Actisaf Sc 47 increased FE compared to reducing protein alone (P = 0.02). No differences in milk fatty acid (FA) profile were observed with the exception of a tendency for a greater concentration of linoleic acid in LCPActisaf group compared with the CTR group (P = 0.09) and LCP group (P = 0.08). Linoleic acid concentration was similar between CTR and LCP groups (P = 0.93). De novo fatty acid concentration resulted higher (P = 0.13) in LCPActisaf (28.90%) compared to CTR (27.75%) and LCP (27.9%). Health indexes explained by Atherogenic index, Thrombogenic index and omega 6/omega 3 were similar between the three treatments. From economic perspective, compared with the CTR and LCP, net revenue/kg of milk was increased and tended to increase with LCPActisaf (P = 0.05 and P = 0.1, respectively). No difference was observed between CTR and LCP groups (P = 0.77). The use of Actisaf Sc 47 increased economic efficiency (EE) by 10% and 8.24% compared with the CTR and LCP groups, respectively. Supplementing reduced-protein diets with Actisaf Sc 47 maintained milk yield, enhanced milk protein output, improved feed efficiency, and increased economic returns, supporting its use as a strategy to optimize dairy production under lower dietary protein conditions.