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Lipopolysaccharide (LPS) has been reported to contribute to a ruminal acidosis of cattle by affecting ruminal bacteria. The goal of this study was to determine how LPS affects the growth of pure cultures of ruminal bacteria, including those that contribute to ruminal acidosis. We found that dosing LPS (200,000 EU) increased the maximum specific growth rates of four ruminal bacterial species (Streptococcus bovis JB1, Succinivibrio dextrinosolvens 24, Lactobacillus ruminis RF1, and Selenomonas ruminantium HD4). Interestingly, all the species ferment sugars and produce lactate, contributing to acidosis. Species that consume lactate or ferment fiber were not affected by LPS. We found that S. bovis JB1 failed to grow in LPS as the carbon source in the media; growth of S. bovis JB1 was increased by LPS when glucose was present. Growth of Megasphaera elsdenii T81, which consumes lactate, was not different between the detoxified (lipid A delipidated) and regular LPS. However, the maximum specific growth rate of S. bovis JB1 was greater in regular LPS than detoxified LPS. Mixed bacteria from a dual-flow continuous culture system were collected to determine changes of metabolic capabilities of bacteria by LPS, and genes associated with LPS biosynthesis were increased by LPS. In summary, LPS was not toxic to bacteria, and lipid A of LPS stimulated the growth of lactate-producing bacteria. Our results indicate that LPS not only is increased during acidosis but also may contribute to ruminal acidosis development by increasing the growth of lactic acid-producing bacteria.IMPORTANCE Gram-negative bacteria contain lipopolysaccharide (LPS) coating their thin peptidoglycan cell wall. The presence of LPS has been suggested to be associated with a metabolic disorder of cattle-ruminal acidosis-through affecting ruminal bacteria. Ruminal acidosis could reduce feed intake and milk production and increase the incidence of diarrhea, milk fat depression, liver abscesses, and laminitis. However, how LPS affects bacteria associated with ruminal acidosis has not been studied. In this study, we investigated how LPS affects the growth of ruminal bacteria by pure cultures, including those that contribute to acidosis, and the functional genes of ruminal bacteria. Thus, this work serves to further our understanding of the roles of LPS in the pathogenesis of ruminal acidosis, as well as providing information that may be useful for the prevention of ruminal acidosis and reducetion of economic losses for farmers.

The increasing costs of traditional protein sources, such as soybean meal (SBM), have prompted interest in alternative feeds for ruminants. Non-protein nitrogen (NPN) sources, like urea, offer a cost-effective alternative by enabling rumen microorganisms to convert NPN into microbial protein, which is crucial for ruminant nutrition. However, the rapid hydrolysis of urea in the rumen can result in excessive ammonia (NH3) production and potential toxicity. Slow-release urea (SRU) has been developed to mitigate these issues by gradually releasing nitrogen, thereby improving nutrient utilization and reducing NH3 toxicity risks. This review explores SRU's development, types, mechanisms, and benefits, highlighting its potential to enhance ruminal fermentation, microbial protein synthesis, and overall feed efficiency. SRU formulations include polymer-coated urea, lipid-coated urea, calcium-urea, starea, and zeolite-impregnated urea, each designed to control nitrogen release and minimize adverse effects. Studies have demonstrated that SRU can improve microbial nitrogen efficiency and reduce nitrogen losses, although results regarding feed intake, digestibility, and milk yield are mixed. These discrepancies indicate that factors such as SRU type, diet formulation, and animal breed may influence outcomes. Continued research is essential to optimize SRU applications, aiming to enhance ruminant production, economic viability, and environmental stewardship. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the sulfur hexafluoride (SF6) tracer technique for estimating methane (CH4) emissions in dual-flow continuous culture systems (DFCCS). In experiment 1 (Exp1), fermenters were filled with water, and known CH4 concentrations (0, 1.35, 2.93, or 4.43 g/d) were injected using permeation tubes with SF6 release rates (3.30 or 9.65 mg/d). Headspace gas was collected using canisters, and the SF6 technique estimated CH4 recovery. Experiment 2 (Exp2) involved a DFCCS fermentation trial with ruminal fluid from three Holstein cows, testing diets with soybean meal or its partial replacement (50%) by Chlorella or Spirulina. Headspace gas was collected at intervals post-feeding. Standard curves for SF6 and CH4 quantification were inadequate for DFCCS samples, with the CH4:SF6 ratio differing from standards, indicating the data needs further SF6 release rate evaluation. In Exp1, a high correlation (r = 0.97) was found between infused and calculated CH4, indicating good repeatability. Low and high SF6 rates performed similarly at low CH4 infusion, but high SF6 overestimated CH4 at high infusion. Exp2 showed CH4 emissions irrespective of SF6 rate and indicated reduced CH4 emissions and increased NDF degradation with algae-containing diets. Further evaluation of the SF6 tracer technique is warranted for DFCCS. [ABSTRACT FROM AUTHOR]

Nutrients derived from ruminal fermentation supply a substantial amount of metabolizable nutrients for ruminants. These include amino acids, carbohydrates, fatty acids, vitamins, and fermentation end products, such as ammonia and volatile fatty acids. Furthermore, ruminal fermentation modifies dietary nutrients in such a way that nutrients reaching the small intestine for absorption may substantially differ from those being consumed in the diet. Therefore, understanding ruminal fermentation kinetics and quantification of nutrients flowing out of the rumen is an important aspect of ruminant nutrition. Accurate quantification of these nutrients, using in vivo experiments, is laborious, costly, and invasive, requiring surgical procedures such as ruminal, abomasal, and intestinal cannulas. To decrease the time and cost of experiments as well as the use of animals, in vitro methodologies are important tools in ruminant nutrition. Therefore, the objectives of this presentation are i) describe different in vitro methodologies, ii) discuss the advantages of in vitro methodologies, iii) discuss shortcomings of in vitro methodologies, and iv) describe potential developments that may improve in vitro methodologies. Having been used for decades, in vitro methodologies such as pure, batch, and continuous cultures have been well documented to investigate a wide array of aspects of nutrition, including the effects of different dietary compositions, individual fermentation end products, and impacts on the microbiome. However, both batch and pure cultures can result in a build-up of end products that may inhibit fermentation. Continuous culture, however, allows for the removal of end products but, similar to pure and batch cultures, is applicable only to ruminal fermentation and cannot provide information regarding intestinal digestion. The dual-flow continuous culture system (DFCC), developed in the 1970s and used by various laboratories in the USA and Europe consists of fermentation vessels of approximately 1.5 L that are capable of simulating ruminal fermentation for periods longer than 10 d. It has been extensively used and evaluated by meta-analyses. When compared with other in vitro methodologies, the DFCC has longer fermentation time, larger volume, and the possibility of sampling from the liquid and the solid flows. When compared with in vivo experiments the DFCC is faster, less costly, less invasive, allows for greater range of treatments, allows for more controlled condition, and isolates ruminal function. Limitations of the DFCC include it does not predict in vivo response, it assumes equal saliva flow and concentration, no effects of intake, no ruminal absorption, less retention of protozoa, possible differences in microbiome, and limited gas emission data. Therefore, while in vitro methodologies provide useful data into the field of ruminant nutrition, some in vitro methodologies are more robust than others. Furthermore, in vivo experiments are still the ideal approach for assessing nutrient utilization and necessary to evaluate animal responses. [ABSTRACT FROM AUTHOR]

Aflatoxin B1 (AFB1) is a mycotoxin known to impair human and animal health. It is also believed to have a deleterious effect on ruminal nutrient digestibility under in vitro batch culture systems. The objective of this study was to evaluate the effects of increasing the dose of AFB1 on ruminal dry matter and nutrient digestibility, fermentation profile, and N flows using a dual-flow continuous culture system fed a diet formulated for lactating dairy cows. Eight fermenter vessels were used in a replicated 4 × 4 Latin square design with 10 d periods (7 d adaptation and 3 d sample collection). Treatments were randomly applied to fermenters on diet DM basis: (1) 0 μg of AFB1/kg of DM (Control); (2) 50 μg of AFB1/kg of DM (AF50); (3) 100 μg of AFB1/kg of DM (AF100); and (4) 150 μg of AFB1/kg of DM (AF150). Treatments did not affect nutrient digestibility, fermentation, and N flows. Aflatoxin B1 concentration in ruminal fluid increased with dose but decreased to undetectable levels after 4 h post-dosing. In conclusion, adding incremental doses of AFB1 did not affect ruminal fermentation, digestibility of nutrients, and N flows in a dual-flow continuous culture system fed diets formulated for lactating dairy cows. [ABSTRACT FROM AUTHOR]

The utilization of microencapsulated organic acids and pure botanicals (mOAPB) is widely used in the monogastric livestock industry as an alternative to antibiotics; in addition, it can have gut immunomodulatory functions. More recently, an interest in applying those compounds in the ruminant industry has increased; thus, we evaluated the effects of mOAPB on ruminal fermentation kinetics and metabolite production in an in vitro dual-flow continuous-culture system. For this study, two ruminal cannulated lactating dairy Holstein cows were used as ruminal content donors, and the inoculum was incubated in eight fermenters arranged in a 4 × 4 Latin square design. The basal diet was formulated to meet the nutritional requirements of a 680-kg Holstein dairy cow producing 45 kg/d of milk and supplemented with increasing levels of mOAPB (0; 0.12; 0.24; or 0.36% of dry matter [ DM ]), which contained 55.6% hydrogenated and refined palm oil, 25% citric acid, 16.7% sorbic acid, 1.7% thymol, and 1% vanillin. Diet had 16.1 CP, 30.9 neutral detergent fiber (NDF), and 32.0 starch, % of DM basis, and fermenters were fed 106 g/d split into two feedings. After a 7 d adaptation, samples were collected for 3 d in each period. Samples of the ruminal content from the fermenters were collected at 0, 1, 2, 4, 6, and 8 h postmorning feeding for evaluation of the ruminal fermentation kinetics. For the evaluation of the daily production of total metabolites and for the evaluation of nutrient degradability, samples from the effluent containers were collected daily at days 8 to 10. The statistical analysis was conducted using MIXED procedure of SAS and treatment, time, and its interactions were considered as fixed effects and day, Latin square, and fermenter as random effects. To depict the treatment effects, orthogonal contrasts were used (linear and quadratic). The supplementation of mOAPB had no major effects on the ruminal fermentation, metabolite production, and degradability of nutrients. The lack of statistical differences between control and supplemented fermenters indicates effective ruminal protection and minor ruminal effects of the active compounds. This could be attributed to the range of daily variation of pH, which ranged from 5.98 to 6.45. The pH can play a major role in the solubilization of lipid coat. It can be concluded that mOAPB did not affect the ruminal fermentation, metabolite production, and degradability of dietary nutrients using an in vitro rumen simulator. [ABSTRACT FROM AUTHOR]

The transition of courses from in-person to an online format due to the COVID-19 pandemic could have potentially affected overall student performance in lecture-based courses. The objective of this case study was to determine the impact of course format, as well as the effects of student sex, time of year at which the course was taken, and the institution it was taken at on student performance in an undergraduate animal science course. The course used for this study was taught at two institutions (University of Florida; UF and University of Nevada, Reno; UNR) over 7 yr (2014–2017 at UNR and 2018–2021 at UF). Student's performance (n  = 911) was evaluated using both quizzes and exams from 2014 through the spring semester 2020 and only exams were used for summer and fall semesters of 2020 and the spring and summer semesters of 2021. The final score (out of 100%) for each student was used to evaluate student's performance. In addition, students were classified as high-performing students, if they scored ≥95% and low-performing students, if they scored ≤70%. The variables evaluated were the effects of semester (spring, summer, or fall), institution (UF or UNR), sex (male or female), number of teaching assistants (TAs; 0–13), and course format (online or in-person). The course was taught in-person at UNR and in-person and online at UF. The spring semester of 2020 was taught in-person until March but was switched to online approximately 9 wk after the semester started and was considered an online semester for this analysis. As the course was only taught online at UF, the variable course format was assessed using UF records only. Data were analyzed using both linear models and logistic regressions. The probability that students were high performing was not affected by sex or institution. Interestingly, both fall semester and the online format had a positive, desirable effect on the probability that students were high performing. The probability that students were low performing was not affected by sex. However, if a student performed poorly in the class, they were more likely to have taken the course at UNR, or at UF with many TAs. Thus, student's performance was impacted by changing the course format, as well as institution, the number of TAs, and the semester in which the course was taken. [ABSTRACT FROM AUTHOR]

Climate change may have an adverse effect on feed production. Hydroponic fodders produced in controlled environments are alternative feeds that may be used for dairy cattle. The objective of this study was to evaluate in-situ dry matter ruminal degradability of hydroponic fodders and corn silage. Two rumen-canulated lactating Holstein cows were used in a complete randomized block design with four treatments and 9 times (0, 2, 4, 8, 12, 24, 48, 72, and 240 h). Treatments were corn silage (CS), hydroponic sprouts of barley, wheat, and triticale. Quadruplicate samples were placed in Dacron bags (10 x 20 cm, 50 μm porosity) and incubated in the rumen. After incubation, samples were washed and dried in an air-forced oven set at 60°C for 48 h and DM recovery was weighted. Ingredients nutrient composition were CS (32.3% NDF, 8.4% CP, and 41.6% starch, 1.3% WSC; % of DM), barley (34.3% NDF, 17.1% CP, and 4.2% starch, 32.9% WSC; % of DM), wheat (23.7% NDF, 23.3% CP, and 8.5% starch, 32.7% WSC; % of DM), triticale (20.0% NDF, 16.2% CP, and 21.7% starch, 33.2% WSC; % of DM). Model included fixed effects of treatment and random effects of cow and replicate(cow). Data were analyzed using PROC MIXED of SAS. Degradation fractions were calculated based on DM disappearance. There were treatment effects (P < 0.01) on fraction A (degradable), fraction B (potentially degradable), fraction C (undegradable), effective ruminal degradability (ERD), and rate of degradation (kd: %/h). Fraction A was greater for triticale (74.1%) compared with wheat (70.2%), CS (63.1%), and barley (55.0%). Fraction B was greater for barley (28.5%) compared with CS (23.2%), wheat (19.1%), and triticale (13.9%). Fraction C was less for wheat (10.6%) than triticale (12.0%), CS (13.7%), and barley (16.4%). The ERD was greater for wheat (90.8%) compared with triticale (89.0%), CS (88.0%), and barley (85.6%). The kd for barley (2.4%) was less than triticale (4.9%). The kd for CS (1.8%) was less than triticale (4.9%). Overall, triticale had the greatest fraction A, barley had the greatest fraction B, and wheat had the least fraction C and the greatest ERD and kd. [ABSTRACT FROM AUTHOR]

The objectives of this study were: 1) to compare the effects of live yeast (LY), yeast fermentation product (YFP), a mix of Lactobacillus acidophilus and Propionibacterium freudenreichii (MLP), and Lactobacillus plantarum included as additives in dairy cows' diets on in vitro ruminal fermentation and gas production (GP); and 2) to evaluate the effects of L. plantarum as direct-fed microbials (DFM) in dairy cows' diets on in vitro ruminal fermentation, GP, nutrient digestibility, and N metabolism. Three experiments were carried out: Exp. 1 had the objective to compare all additives regarding ruminal fermentation parameters: an Ankom GP system was used in a completely randomized design, consisting of four 48 h incubations, and eight replications per treatment. There were eight treatments: a basal diet without additive (CTRL) or with one of the following additives: LY, YFP, MLP, or L. plantarum at four levels (% of diet Dry Matter (DM)): 0.05% (L1), 0.10% (L2), 0.15% (L3), and 0.20% (L4). In Exp. 2, a batch culture was used to evaluate ruminal fermentation, and CO2 and CH4 production using the same treatments and a similar experimental design, except for having 16 replications per treatment. Based on Exp. 1 and 2 results, Exp. 3 aimed at evaluating the effects of the L. plantarum on ruminal true nutrient digestibility and N utilization in order to evaluate the use of L. plantarum as DFM. The treatments CTRL, MLP, L1, and L2 were used in a replicated 4 × 4 Latin square design using a dual-flow continuous culture system. Data were analyzed using linear and nonlinear regression; treatment means were compared through contrasts, and L treatments in Exp. 1 and 2 were tested for linear, quadratic, and cubic effects. In Exp. 1, all treatments containing additives tended to reduce OM digestibility as well as reduced total volatile fatty acids (VFA) concentration and total GP. The YFP had greater OM digestibility than LY, and MLP treatment had greater total VFA concentration compared to L. plantarum treatments. In Exp. 2, additives reduced CO2 production, and there were no major differences in CH4. In Exp. 3, all additives reduced NH3-N concentration. In conclusion, pH and lactate concentration were not affected in all three experiments regardless of additive tested, suggesting that these additives may not improve ruminal fermentation by pH modulation; and L. plantarum may improve ruminal N metabolism when used as DFM in high-producing dairy cows' diets, mainly by reducing NH3-N concentration. [ABSTRACT FROM AUTHOR]

Bovine mammary epithelial cells (MAC‐Ts) are a common cell line for the study of mammary epithelial inflammation; these cells are used to mechanistically elucidate molecular underpinnings that contribute to bovine mastitis. Bovine mastitis is the most prevalent form of disease in dairy cattle that culminates in annual losses of two billion dollars for the US dairy industry. Thus, there is an urgent need for improved therapeutic strategies. Histone deacetylase (HDAC) inhibitors are efficacious in rodent models of inflammation, yet their role in bovine mammary cells remain unclear. HDACs have traditionally been studied in the regulation of nucleosomal DNA, in which deacetylation of histones impact chromatin accessibility and gene expression. Using MAC‐T cells stimulated with tumor necrosis factor α (TNF‐α) as a model for mammary cell inflammation, we report that inhibition of HDACs1 and 2 (HDAC1/2) attenuated TNF‐α‐mediated inflammatory gene expression. Of note, we report that HDAC1/2‐mediated inflammatory gene expression was partly regulated by c‐Jun N‐terminal kinase (JNK) and extracellular signal‐regulated kinase (ERK) phosphorylation. Here, we report that HDAC1/2 inhibition attenuated JNK and ERK activation and thus inflammatory gene expression. These data suggest that HDACs1 and 2 regulate inflammatory gene expression via canonical (i.e., gene expression) and noncanonical (e.g., signaling dependent) mechanisms. Whereas, further studies using primary cell lines and animal models are needed. Our combined data suggest that HDAC1/2‐specific inhibitors may prove efficacious for the treatment of bovine mastitis. Histone deacetylases (HDACs) 1 and 2 regulate extracellular signal‐regulated kinase and c‐Jun N terminal kinase phosphorylation in bovine mammary epithelial (MAC‐T) cells. HDAC1/2‐selective inhibition attenuated mitogen‐activated protein kinase signaling, which contributed to normalization of tumor necrosis factor α‐mediated inflammatory gene expression. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the effects of different sources of cobalt in a lactating dairy cow diet on in vitro ruminal fermentation. All diets provided the same amount of supplemental Co (1 mg per kg of diet DM) included in a premix with a targeted inclusion level of 2.5% of diet DM. Treatments were cobalt carbonate (CON), and three alternative Co sources; alternative source 1 (AS1), alternative source 2 (AS2), and alternative source 3 (AS3). Eight dual-flow continuous culture fermenters were used in a replicated 4 × 4 Latin square. Experimental periods were 10 d (7 d adaptation and 3 d sample collection). Composite samples of daily effluents were collected and analyzed for NH3-N, lactate, and VFA concentration as well as for nutrient digestibility. Samples of ruminal content were collected from each fermenter at 0, 1, 2, 4, 6, and 8 h after feeding to determine lactate, NH3-N, and pH kinetics. All data were analyzed using PROC MIXED of SAS and the repeated variable of time was included for pH, lactate, and NH3-N. There were neither treatment effects nor interactions between treatment and time for pH, NH3-N, and lactate concentrations, indicating a similar Co kinetics across treatments. With regards to lactate pool, we did not observe treatment effects for L-lactate; however, we observed treatment effects for D-lactate and total-lactate as seen in Table 1. Analyses of total and individual VFA, N utilization, and nutrient degradation are still undergoing, hence, it is possible that Co sources have effects on ruminal fermentation. [ABSTRACT FROM AUTHOR]