Melittin and its potential in the destruction and inhibition of the biofilm formation by Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa isolated from bovine milk.

Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa stand out in veterinary and human medicine for their role in opportunistic infections and their pathogenic mechanisms, including the biofilms formation. It was investigated the antibacterial activity of melittin and antibiofilm of such bacteria. Twelve strains of these microorganisms isolated from bovine milk were used, as well as the strains S. aureus ATCC 12600, E. coli ATCC 8739 and Pseudomonas aeruginosa ATCC 15442. The minimum inhibitory concentrations (MIC) and minimum bactericidal concentration (MBC) were determined by broth microdilution technique. The biofilms were formed in 96-well plates and melittin on these colonies was added at different concentrations and times. Bacteria previously exposed to melittin were evaluated for inhibition of biofilm production. The MIC and MBC were respectively in µg/mL: S. aureus (6-7 and 32-64), E. coli (40-42.5 and 64-128) and P. aeruginosa (65-70 and 64-128). S. aureus biofilms were more sensitive to the action of melittin, since upon exposure to a concentration 10 times lower than the MIC for 4 h, was completely destroyed. In Gram negative bacteria, the pre-formed biofilm was destroyed only when exposed for 4 h under the MIC. With respect to inhibition of biofilm production, S. aureus was the most sensitive again because produced only 37.2% of the biofilm formed by the control (without previous exposure to melittin), when exposed to the MIC, and at a concentration hundred times smaller than MIC, this microorganism produced 75.2% of the biofilm. E. coli was the most resistant bacteria and produced 56.3% of the biofilm, even if previously exposed to melittin MIC. Melittin presents desirable effects in combating microorganisms studied both at your disposal, biofilm destruction and inhibition of the formation, and maybe used in future studies of new strategies to combat infections caused by these pathogens.

Rumen-protected methionine modulates body temperature and reduces the incidence of heat stress temperatures during the hottest hours of the day of grazing heat-stressed Bos indicus beef cows.

This study evaluated the effects of supplementation of rumen-protected methionine (RPM) on body thermoregulation and conception rate of Nelore cows exposed to high temperature-humidity index (THI). On -31 days before the artificial insemination protocol, 562 lactating, multiparous cows were assigned to receive (MG) or not (CG) RPM supplementation (3 g/cow mixed into 100 g of mineral supplement). Both groups remained in tropical pastures and received supplementation for 77 days. A subset of cows (n = 142) remained with an intravaginal thermometer collecting intravaginal temperature (IT). The respective minimum, average, and maximum environmental THI were 72.8, 78.0, and 83.3. Effects of treatment × hour of the day were detected (P < 0.0001) for IT. From 1330 to 1730 h and 1830 to 1900 h, IT was higher (P < 0.05) for CG versus MG cows when exposed to moderate and high THI. The supplementation with RPM did not affect conception rate (CG = 64.4% vs. MG = 58.2%; P > 0.05). In conclusion, 3 g of RPM supplementation lowered internal body temperature and possibly altered critical THI threshold in Nelore cows with no impact on reproduction.

Feed intake, milk production and metabolism of Holstein, Gyr and Girolando-F1 heifers with high body condition score during the transition period.

The transition period in taurine dairy cows is widely reported in the literature. However, little is known about the metabolism of zebu animals and their crossbreeding with taurine breeds during this phase. Considering the importance of these breeds in tropical and subtropical regions, this study aimed to evaluate the feed intake, milk production and hepatic metabolism in Holstein, Gyr and Girolando-F1 (½ Holstein × ½ Gyr) heifers presenting high body condition score (BCS) during the transition period (prepartum weeks -2 and -1 and postpartum weeks +1 and + 3). Twelve heifers of each genetic group were used, totaling 36 animals. Variables considered were blood metabolites related to liver function, dry matter intake (DMI), body condition score (BCS), body weight (BW), milk yield (MY), and fat and protein concentrations in milk. Gyr heifers had the lowest concentrations of paraoxonase in weeks -2 (43.13 U/mL), -1 (62.10 U/mL) and + 3 (77.89 U/mL), albumin in week -1 (3.07 g/dL), and the highest concentration of non-esterified fatty acids (NEFA) in weeks -2 (1.35 mmol/L) and -1 (1.19 mmol/L). ß-hydroxybutyrate (BHB) and NEFA values were negatively correlated with prepartum DMI (-0.82 and -0.57, respectively), while paraoxonase was positively correlated to DMI (0.54). Gyr cows were more susceptible to inflammation despite having intermediate BCS and lower milk yield. Girolando-F1 animals showed the highest BCS among groups, although their hepatic metabolism had better results than Gyr cows. Holstein animals had lower lipomobilization and higher DMI and MY between breeds. These results suggest that the metabolism of zebu and crossbred cows does not react equally to the metabolism of Holstein cows concerning stress factors such as transition period and obesity. Therefore, the present study addresses an emerging theme that highlights the need for differentiated management during the transition period between the different breeds studied in order to ensure the maximum health and welfare of these animals.

Multifaceted role of one-carbon metabolism on immunometabolic control and growth during pregnancy, lactation and the neonatal period in dairy cattle.

Dairy cattle undergo dramatic metabolic, endocrine, physiologic and immune changes during the peripartal period largely due to combined increases in energy requirements for fetal growth and development, milk production, and decreased dry matter intake. The negative nutrient balance that develops results in body fat mobilization, subsequently leading to triacylglycerol (TAG) accumulation in the liver along with reductions in liver function, immune dysfunction and a state of inflammation and oxidative stress. Mobilization of muscle and gluconeogenesis are also enhanced, while intake of vitamins and minerals is decreased, contributing to metabolic and immune dysfunction and oxidative stress. Enhancing post-ruminal supply of methyl donors is one approach that may improve immunometabolism and production synergistically in peripartal cows. At the cellular level, methyl donors (e.g. methionine, choline, betaine and folic acid) interact through one-carbon metabolism to modulate metabolism, immune responses and epigenetic events. By modulating those pathways, methyl donors may help increase the export of very low-density lipoproteins to reduce liver TAG and contribute to antioxidant synthesis to alleviate oxidative stress. Thus, altering one-carbon metabolism through methyl donor supplementation is a viable option to modulate immunometabolism during the peripartal period. This review explores available data on the regulation of one-carbon metabolism pathways in dairy cows in the context of enzyme regulation, cellular sensors and signaling mechanisms that might respond to increased dietary supply of specific methyl donors. Effects of methyl donors beyond the one-carbon metabolism pathways, including production performance, immune cell function, mechanistic target or rapamycin signaling, and fatty acid oxidation will also be highlighted. Furthermore, the effects of body condition and feeding system (total mixed ration vs. pasture) on one-carbon metabolism pathways are explored. Potential effects of methyl donor supply during the pepartum period on dairy calf growth and development also are discussed. Lastly, practical nutritional recommendations related to methyl donor metabolism during the peripartal period are presented. Nutritional management during the peripartal period is a fertile area of research, hence, underscoring the importance for developing a systems understanding of the potential immunometabolic role that dietary methyl donors play during this period to promote health and performance.

Rumen-protected methionine in cattle: influences on reproduction, immune response, and productive performance / Metionina protegida da degradação ruminal em bovinos: influências na reprodução, resposta imune e desempenho produtivo

Nowadays, information and knowledge generated about the main ingredients used in cattle diets have enabled greater assertiveness in their formulation. Among the ingredients, amino acids stand out as a promising tool, capable of reducing total crude protein (CP) levels and adjusting optimal metabolizable protein concentrations in diets. Nutritional programs allow diets due to amino acid requirements, providing the opportunity to increase the efficiency of the use of dietary nitrogen, increasing the scarce protein concentrates, maintaining or even boosting performance. This review aimed to present the influences of methionine, in its formulation protected from ruminal degradation, according to reproductive parameters, immune response, and productive performance in cattle. Reproduction-related benefits are linked to the early days of embryonic implantation in the uterine environment, which initially secretes through the histotroph produced by endometrial glands, the nutrients needed to develop the conceptus until implantation, and vascular communication with the mother. Given the immune response, the main results are related to the benefits of innate immunity, with marked increase in phagocytic capacity of neutrophils and monocytes, as well as an important antioxidant effect mediated by methionine products, such as glutathione. When evaluating the influences on productivity, the most evident correlation is the increase in protein in the milk of cows supplemented with methionine. Over the past decade, studies investigating the potential benefits of this strategic supplementation in beef cattle were intensified, expanding the opportunities for the development of new experimental projects.(AU)

Atualmente, as informações e o conhecimento gerado sobre os principais ingredientes utilizados em dietas para bovinos possibilitaram maior assertividade em suas formulações. Dentre esses ingredientes, os aminoácidos se destacam como uma ferramenta promissora, capaz de levar à redução nos níveis totais de proteína bruta e ajustar as concentrações ideais de proteína metabolizável nas dietas. Programas nutricionais permitem formular dietas por exigências de aminoácidos, oportunizando o aumento na eficiência de utilização do nitrogênio dietético, reduzindo dispêndios com concentrados ricos em proteína, com a manutenção, ou ainda, incremento de desempenho. Esta revisão buscou apresentar as influências da metionina, em sua formulação protegida da degradação ruminal, frente a parâmetros reprodutivos, resposta imune e desempenho produtivo em bovinos. Os benefícios relacionados à reprodução se mostram ligados aos primeiros dias de implantação embrionária no ambiente uterino, que inicialmente secreta, através do histotrofo produzido por glândulas endometriais, os nutrientes necessários para o desenvolvimento do concepto até a implantação e comunicação vascular com a mãe. Dada a resposta imune, os principais resultados estão relacionados aos benefícios da imunidade inata, com aumento acentuado da capacidade fagocitária de neutrófilos e monócitos, assim como um importante efeito antioxidante mediado por produtos originários da metionina, como a glutationa. Por fim, quando avaliadas as influências em produtividade, a correlação mais evidente é o incremento em proteína no leite de vacas suplementadas com metionina. Na última década, os estudos que investigam os potenciais benefícios dessa suplementação estratégica em bovinos de corte foram intensificados, abrindo um caminho de oportunidades para o desenvolvimento de novos projetos experimentais.(AU)