Today, one of the major challenges of dairy farmers is to reduce their environmental footprint to establish more effective, efficient, and sustainable production systems. Feed additives such as yeast probiotics could potentially allow them to achieve these objectives through the improvement of milk production, feed efficiency, and ration valorization, hence mitigating the environmental impacts of milk production. In this study, the life cycle assessment (LCA) principle was performed to estimate the environmental impact of the production and supplementation of a commercial yeast probiotic (Actisaf Sc 47) in three trials performed in three different countries that are representative for around 50% of the milk production in Europe: France (French trial), United Kingdom (UK trial), and Germany (German trial). For each trial, two groups of animals were compared: control, without Actisaf Sc 47 supplementation, used as baseline; and experimental, with Actisaf Sc 47 supplementation at 5 or 10 g/cow/day. Different impact categories were analyzed for each group to calculate the impact of producing 1 kg of fat- and protein-corrected milk. An initial analysis was done only during the period of Actisaf Sc 47 supplementation and showed than the supplementation with Actisaf Sc 47 reduced, on average by 5%, the carbon footprint during the three trials. A second analysis was done via the extrapolation of all the data of each trial to an annual farm level, including the lactation period (305 days), dry period (60 days), and the period with and without Actisaf Sc 47 supplementation. Reported at a farm annual scale, the average reduction allowed by Actisaf Sc 47 supplementation was 2.9, 2.05, 2.47, 1.67, 2.28, 2.18, 2.14, and 2.28% of the carbon footprint, land use, water use, resource use, acidification, freshwater eutrophication, marine eutrophication, and terrestrial eutrophication, respectively. On average, the production of 1 kg of fat- and protein-corrected milk by using Actisaf Sc 47 was shown to improve environmental impacts compared to control. Regarding Actisaf Sc 47 production, the LCA showed that the production of 1 kg of Actisaf Sc 47 emitted 2.1 kg CO₂ eq with a negligible contribution to total the carbon footprint of milk ranging from 0.005 to 0.016%. The use of Actisaf Sc 47 in dairy cows could then result in different positive outcomes: improving performance and efficiency while reducing the global carbon footprint.

The administration of yeast products as feed additives has been proven to beneficially affect animal productivity through energy, oxidative, and immune status improvement. This study evaluated a combination of Saccharomyces cerevisiae live yeast (LY) with yeast postbiotics (rich in mannan-oligosaccharides (MOS) and beta-glucans) and selenium (Se)-enriched yeast on ewes’ milk performance and milk quality, energy and oxidative status, and gene expression related to their immune system during the peripartum period. Ewes were fed a basal diet (BD; F:C = 58:42 prepartum and 41:59 postpartum) including inorganic Se (CON; n = 27), the BD supplemented with a LY product, and inorganic Se (AC; n = 29), as well as the combination of the LY, a product of yeast fraction rich in MOS and beta-glucans, and organic-Se-enriched yeast (ACMAN; n = 26) from 6 weeks prepartum to 6 weeks postpartum. The β-hydroxybutyric acid concentration in the blood of AC and ACMAN ewes was lower (compared to the CON) in both pre- and postpartum periods (p < 0.010). Postpartum, milk yield was increased in the AC and ACMAN Lacaune ewes (p = 0.001). In addition, the activity of superoxide dismutase (p = 0.037) and total antioxidant capacity (p = 0.034) measured via the 2,2-Azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) method was increased in the blood plasma of the ACMAN postpartum. Higher ABTS values were also found (p = 0.021), while protein carbonyls were reduced (p = 0.023) in the milk of the treated groups. The relative transcript levels of CCL5 and IL6 were downregulated in the monocytes (p = 0.007 and p = 0.026 respectively), and those of NFKB were downregulated in the neutrophils of the ACMAN-fed ewes postpartum (p = 0.020). The dietary supplementation of ewes with yeast postbiotics rich in MOS and beta-glucans, and organic Se, improved energy status, milk yield and some milk constituents, and oxidative status, with simultaneous suppression of mRNA levels of proinflammatory genes during the peripartum period.

Increasing animal protein, especially from beef, is necessary to satisfy the requirements of the growing global population. However, this is becoming increasingly challenging due to stakeholders prioritizing sustainable systems with low environmental impacts. To answer these challenges, the use of feed additives such as yeast probiotics seems to be an effective route for improvements in feed efficiency and growth performance. The current study was performed to quantify the environmental impacts of the production and use of a yeast probiotic (Actisaf^® Sc 47) through an LCA method in four trials performed during the fattening period: France (French trial), Spain (Spanish trial), and Italy (Italian trials A and B). During each trial, two groups of animals with the same characteristics were compared during the fattening period: the control group without Actisaf^® Sc 47 supplementation used as a baseline, and the experimental group with Actisaf^® Sc 47 supplementation. The calves started the trial at the ages of 224, 92, and 186 days during the French, Spanish, and Italian trials A and B, respectively. Of the sixteen impact category indicators, nine were analyzed. In Italian trials A and B, the Spanish trial, and the French trial, the use of Actisaf^® Sc 47 reduced CC by 4.8, 3.8, 6.6, and 5.4%; FE by 4.8, 3.9, 8.2, and 6.3%; ME by 4.9, 4.0, 6, and 6.4%; and TE by 5.3, 4.1, and 6.2%, respectively. Moreover, during the same trials, Actisaf^® Sc 47 reduced AC by 6.0, 4.1, 6.3, and 7.1%; LU by 4.7, 3.9, 5.8, and 6.1%; WU by 4.5, 3.4, 5.2, and 5.9%; RU (fossils) by 4.8, 3.7, 7.3, and 4.8%; and PM by 5.2, 4.1, 6.3, and 7.1%, respectively. The use of Actisaf^® Sc 47 has beneficial effects on the environment. Regarding Actisaf^® Sc 47 production, the results showed that the production of 1 kg of Actisaf^® Sc 47 emitted 2.1 kg of CO₂ eq, 60% of which came from the fermentation process and 39% from drying. The results demonstrate the interest in using Actisaf^® Sc during the fattening period for its multiple positive outcomes: improving performance and efficiency, while reducing the global carbon footprint.