Álvaro García
Branched-chain fatty acids (BCFAs) encompass various compounds, with some of the most common ones including isovaleric acid (3-methylbutanoic acid), isobutyric acid (2-methylpropanoic acid), isocaproic acid (4-methylpentanoic acid), and 2-methylbutyric acid. They play crucial roles in human skin integrity and function, present notably in amniotic fluid and vernix caseosa, influencing the delicate ecosystem of fetal development. Amniotic fluid, a protective pale-yellowish liquid, cushions and safeguards the fetus in the amniotic sac, promoting fetal growth while contributing to the healthy development of the gastrointestinal tract. Meanwhile, vernix caseosa, a creamy substance covering fetal skin, acts as a natural moisturizer, shielding against potential dehydration from amniotic fluid. Both sources contain BCFAs that contribute to fetal health, supporting skin integrity and potentially impacting the balance of gastrointestinal flora in newborns.
Research and Significance of BCFAs
Research into branched-chain fatty acids (BCFA) increased from the late 20th century, with a notable surge in the early 21st century, shedding light on their unique structural features and diverse physiological roles. These compounds, primarily saturated with sporadic monounsaturated forms, are abundant in human nutrition, notably in dairy and meat products, intricately involved in gut microbiota. Recent studies extend their significance beyond dietary roles, uncovering involvement in metabolic pathways, membrane dynamics, and immune modulation. This evolving understanding drives ongoing research, exploring BCFA complexities from their dietary origins to multifaceted biological functions.
B.subtilis and B. licheniformis synthesize BCFAs through its biochemical pathways, incorporating them into its lipid composition. These fatty acids contribute to the membrane’s fluidity, affecting the overall physiology and functionality of the bacterium. The presence of BCFAs influences the membrane’s properties, such as permeability and stability, which are crucial for bacterial survival, growth, and interaction with its environment.
Recent research in Bacillus probiotics
A recent study (Romo-Barrera et al. 2021) investigated how two Bacillus species, B. licheniformis and B. subtilis, engage with macrophages, essential immune cells that defend against harmful microbes. Using mouse cell line macrophages, the researchers observed that these cells were susceptible to infection by both Bacillus species. However, intriguingly, as the infection progressed, the macrophages efficiently eliminated these bacteria. Microscopic analysis revealed the formation of special defense structures called microbe-trapping extracellular traps (METs) within hours of infection. These traps were identified by the presence of specific proteins like myeloperoxidase and citrullinated histone. The researchers also gathered quantitative data showing the release of extracellular DNA, a process that began within the first hour of infection. More interesting was that when B. licheniformis induced METs, it significantly reduced the growth of Staphylococcus aureus, a harmful bacterium. This suggests that the activation of METs triggered by Bacillus bacteria could play a role in controlling both probiotic and harmful bacteria. The induction of these defense mechanisms, like METs, could be an innovative explanation for the positive effects observed with Bacillus probiotics. This discovery shed light on a potential new way these probiotics could be benefiting health by helping the immune system combat harmful pathogens.
Bacillus subtilis and Bacillus licheniformis, utilized as probiotics in commercial dairy herds, boast cell walls rich in BCFA. Incorporating these bacteria into dairy cow diets correlates with increased milk production and constituents like fat, protein, and lactose. Additionally, these supplements enhance fiber digestibility and reduce enteric methane emissions in ruminants. While they amplify milk yield and protein concentrations in dairy ewes, investigations into their impact on milk fatty acid composition remain unexplored.
Two early experiments (Sun et al. 2012), demonstrated that B. subtilis positively influenced milk production and components, reduced SCC, and fostered the growth of beneficial ruminal bacteria.
In the first experiment, the researchers assigned Holstein dairy cows to three groups: Control (fed total mixed ration, TMR), BS-LOW (TMR plus 0.5 × 10^11 cfu of B. subtilis /cow per day), and BS-HIGH (TMR plus 1.0 × 10^11 cfu of B. subtilis /cow per day). Over 70 days, they tracked milk production and composition daily in individual cows. Results revealed a linear increase in milk production (25.2 and 26.4 kg/day vs. 23.0 kg/day), fat-corrected milk, energy-corrected milk, milk fat, protein, and lactose yield with the supplementation of 0.5 × 10^11 and 1.0 × 10^11 colony forming units (cfu) of B. subtilis. Additionally, somatic cell counts (SCC) decreased by 3.4% to 5.5% in BS-LOW and BS-HIGH treatments compared to Control.
Urakawa et al. (2022) examined the impact of feeding dairy cows with the Bacillus subtilis (BS) C‐3102 strain on mastitis. Their findings highlighted that BS intake decreased mastitis occurrences, lessened medication days, reduced discarded milk, and maintained consistently lower milk SCC levels. Moreover, BS was associated with lower cortisol and Thiobarbituric Acid Reactive Substances levels, while boosting immune cell proportions in blood. Thiobarbituric Acid Reactive Substances (TBARS) serve as a test measuring lipid peroxidation level, indicating oxidative stress or damage due to free radicals in biological systems. Notably, BS feeding appeared to decrease granulocyte sensitivity to a milk chemoattractant, hinting at its potential for mastitis prevention in dairy cows.
Cappellozza et al. (2023: in print) looked at the impact of a Bacillus-based direct-fed microbial (DFM) on various aspects of lactating dairy cow performance, digestion, rumen activity, and metabolic responses. Lactating dairy cows of different breeds were divided into two groups: one receiving the basal partial mixed ration (PMR) without (Control) Direct Fed Microbials (DFM), and the other with an additional 3 g/head per day of a DFM containing B. licheniformis and B. subtilis. While both groups consumed the same pellet without DFM, the DFM was integrated into a protein pellet. Milk yield and composition were tracked daily and bi-weekly, respectively. The analysis showed no significant differences in final body weight or daily dry matter intake between the groups. However, cows fed the DFM exhibited higher milk yield, improved milk production efficiency, and increased lactose and total solids yield. There were also trends suggesting enhanced efficiency in energy-corrected milk production and higher milk protein yield. While nutrient digestibility and total volatile fatty acids remained consistent between groups, the DFM-fed cows showed a higher proportion of acetate and propionate in rumen fermentation. Additionally, cows receiving DFM displayed higher mean plasma insulin-like growth factor 1 (IGF-I) levels, suggesting a potential impact on metabolic responses. Overall, the inclusion of the Bacillus-based DFM positively influenced dairy cow productivity, influenced rumen fermentation, and modulated serum IGF-I levels.
The recent research into the interactions between Bacillus species and immune cells has uncovered an intriguing facet of probiotics. The study’s findings regarding macrophage response and the formation of METs in the face of Bacillus infection provide new insights into the mechanisms by which probiotics potentially enhance the immune systems. These defense mechanisms, particularly the METs, stand as a potential game-changer in understanding the beneficial effects of Bacillus probiotics in combatting harmful pathogens.
Applications in dairy cattle feeding.
Looking deeper into the practical applications of Bacillus-based direct-fed microbial (DFM) supplements in dairy cow diets, multiple studies have consistently highlighted their positive influence on milk production, composition, and rumen ecosystem. Notably, the experiments with B. subtilis supplementation elucidated significant improvements in milk yield, fat-corrected milk, and alterations in rumen microbial populations, indicating enhanced nutrient utilization and potential digestive efficiency.
Moreover, the recent study by Cappellozza et al. reinforces these observations, demonstrating the impact of a Bacillus-based DFM on lactating dairy cow performance, digestion, and rumen activity. The findings emphasize the positive effects on milk yield, production efficiency, and compositional changes, shedding light on potential pathways for enhancing milk quality and metabolic responses in dairy herds.
The extensive exploration into the roles of branched-chain fatty acids (BCFAs) and Bacillus probiotics shows their significance in both human development and animal health. From influencing fetal development by supporting skin integrity to their significant roles in the immune system’s response through microbe-trapping extracellular traps, these compounds and bacterial species show several biological impacts.
The profound effects of Bacillus-based direct-fed microbial (DFM) supplements on milk yield, composition, and rumen ecosystem underscore their potential as key additives. The consistent positive outcomes observed across various studies not only highlight their efficacy in enhancing productivity but also hint at broader implications for improving milk quality and metabolic responses in livestock.
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