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We investigated changes in rumen fermentation, peripheral blood metabolites and hormones, and hepatic transcriptomic dynamics in Holstein cows with and those without subacute ruminal acidosis (SARA) during the periparturient period. Sixteen multiparous Holstein cows were categorized in the SARA ( n = 8) or non-SARA ( n = 8) groups depending on whether they developed SARA during the 2 wk after parturition. Reticulo-ruminal pH was measured continuously throughout the study. Rumen fluid, blood, and liver tissue samples were collected at 3 wk prepartum and 2 and 6 wk postpartum, with an additional blood sample collected at 0 and 4 wk postpartum. The 1-h mean pH was depressed postpartum in both groups, whereas depression was more severe in the SARA group simultaneously with significantly longer duration of time (for pH <5.6 and 5.8). Significant expression of differentially expressed genes in liver tissue (DEGs; false discovery rate corrected P < 0.1) were identified only in the non-SARA group and were further analyzed by Ingenuity Pathway Analysis software. Among the top expressed DEGs, the hepatic genes encoding lipid and cholesterol secretion (APOA1, APOA4, and G0S2) and gluconeogenesis (PC, G6PC, and PCK1) were upregulated postpartum. In silico analysis revealed the significant postpartum activation of upstream regulators, such as INSR, PPARG, and PPARGC1A. These results suggested that hepatic transcriptomic responsiveness to postpartum metabolic load and hormones were likely discouraged in cows with SARA when compared with the significant activation of genes and signaling pathways for adequate metabolic adaption to postpartum high-grain diet feeding in Holstein cows without SARA.

This study reports findings from the pathological examination of the forestomach of an 11-month-old Japanese Black steer with severely retarded growth (41% of expected weight) and chronic ruminal tympany. The ruminal papillae were weakly formed (0.3-0.5 cm long) and unevenly distributed. The cellulae and cristae reticuli were underdeveloped; the cristae were 0.4-0.7 cm in height and milky white. The keratinized layer in the stratified squamous epithelium was thickened. Ruminal pH was 5.25, and ruminal volatile fatty acid concentration was 11.7 mM. The steer's severely retarded growth was considered to be caused by malnutrition due to developmental and functional failure of the forestomach.

During early lactation, both primiparous (PP) and multiparous (MP) cows are commonly fed diets rich in starch and low in forages to support their high energy requirements. Yet, the PP cows experience this dietary challenge for the first time, which might result in higher odds for them to develop rumen and systemic health disorders. The primary objective of this study was to evaluate the effect of decreasing the amount of forages in the diet on chewing and sorting behaviors and rumen and systemic health variables in PP and MP dairy cows. Twenty-four lactating Simmental cows [8 PP, average dry matter intake (DMI) of 19.1 ± 1.1 kg/d; 16 MP, average DMI of 22.5 ± 1.1 kg/d] with a body weight of 737 ± 90 kg and 50 ± 22 days in milk were used in this study. Cows were first fed a total mixed ration with 60% forage and 40% concentrate [on a dry matter (DM) basis] considered marginal in forages for 2 wk. Then, cows were switched to a diet low in forages with 40% forage and 60% concentrate (on a DM basis) for 4 wk. Reticular pH was measured continuously with wireless pH-sensors inserted into the reticulum to calculate the subacute ruminal acidosis (SARA) index. Chewing activity was measured with noseband-sensor halters, and feed sorting was measured weekly. Blood samples were collected weekly and analyzed for metabolic and inflammation markers. Switching PP and MP cows from a marginal to low-forage diet decreased the time spent eating and ruminating per kilogram of DM. Primiparous cows chewed longer per kilogram of DMI than MP cows. Also, the PP cows sorted more pronounced for longer particles and against fine particles than MP cows did. Despite higher rumination activity per kilogram of DMI and the adaptive sorting behavior, the PP cows spent on average 4.6 h/d longer below a pH of 5.8 and had a higher SARA index (i.e., area pH <5.8/DMI) than MP cows, especially during the first week of the low-forage diet (9.5 vs. 4.8). The concentration of liver enzymes increased with the low-forage diet, which was especially pronounced in the PP cows. In conclusion, this study demonstrated greater susceptibility of PP cows to SARA and liver damage than MP cows fed the same diets. Although PP cows demonstrated greater chewing and ruminating activity per kilogram of DMI, as well as adapted sorting behavior in favor of large particles during the low-forage high-starch feeding, they developed more severe signs of SARA. This suggests higher forage fiber requirements for PP cows and the need for improved feeding strategies to mitigate rumen fermentation disorders during early lactation in these cows., (Copyright © 2020 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The objectives were to nutritionally induce or blunt ruminal acidosis in young calves and to compare indicators of rumen and systemic health. Ten bull calves (n = 5/diet) were ruminally cannulated at 3 wk of age and received milk replacer and 1 of 2 calf starter diets that were designed to cause (AC; pelleted, 42.7% starch, 15.1% neutral detergent fiber, 57.8% nonfiber carbohydrates) or blunt (BL; texturized, 35.3% starch, 25.3% neutral detergent fiber, 48.1% nonfiber carbohydrates) ruminal acidosis. Mean birth weight was 38.7 ± 1.3 kg. Body weight and calf starter intake were measured weekly. Rumen contents were sampled at -8, -4, 0, 2, 4, 8, 12, and 24 h relative to starter feeding during wk 6, 8, 10, 12, 14, and 16 of age. Blood was collected from the jugular vein during the same weeks for complete blood cell count, blood pH, and partial pressures of oxygen and carbon dioxide. Rate of starter consumption was assessed during wk 16. Marker systems were used to estimate liquid passage and volatile fatty acid absorption rates. Calves were slaughtered at 17 wk, and rumen tissue was collected and assessed for papillae length, width, and degree of tissue degradation. Mean ruminal pH ± standard error was 5.37 ± 0.24 and 5.63 ± 0.24 for AC and BL calves, respectively. Lowest pH values were observed the week after weaning. Total ruminal volatile fatty acid concentrations were 131.5 and 124.8 ± 2.4 mM in AC and BL calves, respectively, and increased with age and time after feeding. Dry matter intake was lower in AC calves at wk 4 and remained lower through wk 16. Rate of starter consumption was also lower in AC calves at wk 16. Body weight also was also lower for AC calves from wk 5 through 16. Blood hemoglobin and hematocrit were lower in AC calves, but other blood characteristics were not different. Rumen volume increased with age and tended to be greater in BL calves. Passage rate and papillae length and width were not different between diets, but AC calves experienced a greater degree of tissue degradation. Ruminal acidosis symptoms in calves appear similar to those in adult cattle, and the etiology of the disease seems to follow similar mechanisms. It is clear from this study that symptoms can be moderated by diet, but further research is needed to determine whether symptoms can be nutritionally prevented or whether calves that experience ruminal acidosis are more susceptible to the disease as adults., (Copyright © 2020 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The transition from normal forage to a highly fermentable diet to achieve rapid weight gain in the cattle industry can induce ruminal acidosis. The molecular host mechanisms that occur in acidosis are largely unknown. Therefore, the histology and transcriptome profiling of rumen epithelium was investigated in normal and acidosis animals to understand the molecular mechanisms involved in the disease. The rumen epithelial transcriptome from acidosis (n=3) and control (n=3) Holstein steers was obtained using RNA-sequencing. The mean values of clean reads were 70,975,460&plusmn;984,046 and 71,142,189&plusmn;834,526 in normal and acidosis samples, respectively. In total, 1,074 differentially expressed genes were identified in the two groups (P&lt;0.05), of which 624 and 450 genes were up- and down-regulated in the acidosis samples, respectively. Functional analysis indicated that the majority of the up-regulated genes had a function in filament organization, positive regulation of epithelial and muscle fiber concentration, biomineral tissue development, negative regulation of fat cell differential, regulation of ion transmembrane transport, regulation of cell adhesion and butyrate, as well as short-chain fatty acid absorption that was metabolized as an energy source. Functional analysis of the down-regulated genes revealed effects in immune response, positive regulation of T-cell migration, regulation of metabolic processes, and localization. Furthermore, the results showed a differential expression of genes involved in the Map Kinase and Toll-like receptor signaling pathways. The IL1B, CXCL5, IL36A, and IL36B were significantly down-regulated in acidosis rumen tissue samples. The results suggest that rapid shifts to rich fermentable carbohydrates diets cause an increase in the concentration of ruminal volatile fatty acids, tissue damage, and significant changes in transcriptome profiles of rumen epithelial., (Copyright © 2020, Archives of Razi Institute. Published by Kowsar.)

The effectiveness of 7% hypertonic saline solution (HSS) and 6% hypertonic bicarbonate solution (HBS) followed by intraruminal water administration for the treatment of acute rumen lactic acidosis (ARLA) has not been evaluated yet. The hypothesis of the study is that treatment with HBS causes a faster correction of imbalances and clinical recovery than treatment with HSS. ARLA was induced in six healthy mature female sheep with sucrose twice. The sheep received both treatment regimens in a cross over design. After 18 h of induction, rumen lavage was performed and IV infusion of 7% HSS (4 mL/kg BW) or 6% HBS (6.7 mL/kg BW) was done over 5 min, followed by intraruminal administration of water (8% BW). The solutions provided 4.8 mmol/kg BW of sodium. Physical and laboratory tests were performed for 168 h. Both treatments increased plasma volume. After HSS treatment, pH and HCO 3 - returned to baseline values at 144 h and BE at 168 h. With HBS treatment, pH returned to baseline at 24 h, and HCO 3 - and BE at 48 h. In both treatments, the ruminal motility and the maximum hay intake were restored at 96 and 120 h, respectively. In conclusion, administration of HSS or HBS followed by intraruminal water corrects dehydration and mild-to-moderate metabolic acidosis in sheep with ARLA. Treatment with HBS promoted a faster correction of metabolic acidosis and could be indicated for the most severe cases., (Copyright © 2019 Elsevier Ltd. All rights reserved.)

Sub-acute ruminal acidosis is a type of metabolic disorder in which affected cattle show a considerable depression of rumen pH. This leads to a dramatic decline in productivity and consequent loss of income for many dairy farms. The objective of the present study is to identify and characterize novel long non-coding RNAs (lncRNAs) in Holstein cattle affected by sub-acute ruminal acidosis. Two replicates from six animals were sequenced that bioinformatically analyzed. Results showed 6679 novel lncRNAs among which 12 intergenic lncRNAs showed differential expression (p value ≤0.05). GO and KEGG analysis revealed that calcium signaling and G protein couple-receptor pathways may be involved in regulating metabolic processes during sub-acute ruminal acidosis. Furthermore, other biological processes including transmembrane transport, adult behavior, neuroactive ligand-receptor interaction, GABAergic synapse, cholinergic synapse were significantly enriched. The present data suggest that these differentially expressed lncRNAs may play regulatory roles in modulating biological processes associated with sub-acute ruminal acidosis in cattle rumen.

The increasing lactational performance of dairy cows over the last few decades is closely related to higher nutritional requirements. The decrease in dry matter intake during the peripartal period results in a considerable mobilisation of body tissues (mainly fat reserves and muscle mass) to compensate for the prevailing lack of energy and nutrients. Despite the activation of adaptive mechanisms to mobilise nutrients from body tissues for maintenance and milk production, the increased metabolic load is still a risk factor for animal health. The prevalence of production diseases, particularly subclinical ketosis is high in the early lactation period. Increased β-hydroxybutyrate (BHB) concentrations further depress gluconeogenesis, feed intake and the immune system. Despite a variety of adaptation responses to nutrient and energy deficit that exists among dairy cows, an early and non-invasive detection of developing metabolic disorders in milk samples would be useful. The frequent and regular milking process of dairy cows creates the ability to obtain samples at any stage of lactation. Routine identification of biomarkers accurately characterising the physiological status of an animal is crucial for decisive strategies. The present overview recapitulates established markers measured in milk that are associated with metabolic health of dairy cows. Specifically, measurements of milk fat, protein, lactose and urea concentrations are evaluated. Changes in the ratio of milk fat to protein may indicate an increased risk for rumen acidosis and ketosis. The costly determination of individual fatty acids in milk creates barriers for grouping of fatty acids into saturated, mono- and polyunsaturated fatty acids. Novel approaches include the potential of mid-IR (MIR) based predictions of BHB and acetone in milk, although the latter are not directly measured, but only estimated via indirect associations of concomitantly altered milk composition during (sub)clinical ketosis. Although MIR-based ketone body concentrations in milk are not suitable to monitor the metabolic status of the individual cow, they provide an estimate of the overall herd or specific groups of animals earlier in a particular stage of lactation. Management decisions can be made earlier and animal health status improved by adjusting diet composition.

A sudden decrease in feed intake (within 24 hours) without an impaired general condition occurred on a bull-rearing and -fattening farm in western Germany in December 2017. One day later, some of the bulls displayed signs of ruminal tympany (free gas bloat) and the reduction in feed intake became more severe. The maize silage was recognized as the cause of the observed symptoms, because clinical signs first appeared after taking the silage from a different localization within the bunker silo. Maize in this particular section was harvested from a separate area previously affected by wind damage (numerous bent maize plants), where no crop protection (herbicide application) was performed. Fruits and seeds of Jimson weed were identified in the incriminated maize silage samples. Following replacement of the contaminated parts of the maize silage with non-contaminated material and treatment of the clinically affected animals (anti-tympanic medication plus live yeast preparation), the feed intake returned to the normal level and the affected animals recovered within 6 days. The cause of the symptoms was probably the anti-nutritive properties of Datura stramonium that affect the motor function of the gastrointestinal tract., Competing Interests: Disclosure The authors report no conflicts of interest in this work., (© Georg Thieme Verlag KG Stuttgart · New York.)

Feeding dairy cows diets rich in grain often leads to subacute rumen acidosis (SARA), which might affect their responsiveness to immunogenic stimuli such as exogenous lipopolysaccharide (LPS), and can lead to metabolic alterations. The main objective of this study was to investigate if SARA affects the stress and metabolic health responses resulting from an intramammary LPS challenge. Before the intramammary LPS challenge, the SARA cows showed higher blood glucose and a tendency for higher lactate and aspartate aminotransferase as well as a trend toward lower β-hydroxybutyrate (BHBA) and γ-glutamyltransferase compared with control cows. After the LPS challenge, the serum cortisol concentration markedly increased and the calcium concentration decreased both in SARA and control cows. In SARA-LPS cows, however, the lactate concentration increased due to the LPS infusion, whereas it remained unchanged in the control cows. A lower serum BHBA concentration was found in SARA-LPS compared with control-LPS cows. Higher non-esterified fatty acid concentrations were found in control-LPS cows shortly before the LPS challenge compared with SARA cows, challenged or not with LPS, whereas it did not differ from SARA-LPS cows thereafter. In conclusion, the results suggest that intramammary LPS challenge induced stress and lowered calcium concentration in all dairy cows, whereby this challenge showed lower BHBA and higher lactate levels in cows with SARA conditions.

Subacute ruminal acidosis (SARA) of dairy cattle is a widely occurring but not very overt metabolic disorder thought to impair milk composition. The enzyme stearoyl-CoA desaturase 1 (SCD1) is rate-limiting for the formation of Δ-9 unsaturated fatty acids and thus crucially involved in controlling lipid metabolism in the liver. It is known that SCD1 expression is downregulated during SARA, but the underlying molecular mechanisms are unknown. To study these mechanisms, we enrolled 12 healthy multiparous mid-lactation Holstein cows into a diet-induced SARA experiment. Six cows were fed a high-concentrate diet for 18 weeks (60% content of high-concentrate to 40% forage; HC group), whereas the others received a low-concentrate diet ad libitum (40% high-concentrate content to 60% forage; LC group). Sustained low ruminal pH values (pH 5.6 maintained for 4 h/d) and reduced milk yield performance (2.07 kg/d less than LC cows) verified that SARA had been induced in the HC group. Results showed a significantly decreased concentrations of cis-9 monounsaturated long-chain fatty acids in plasma collected from hepatic but not portal veins. This was matched by reduced SCD1 mRNA and protein concentrations in HC livers. The expression levels of genes related to lipid formation (DGAT1 and PLIN2) were downregulated during SARA, whereas those of catabolic genes (CPT1A, CPT2, and ACOX1) and some inflammatory genes were upregulated. Expression of SCD1 was downregulated through reduced transcription and abundance of the transcription factor sterol regulatory element-binding protein 1 (SREBP1c).This effect was augmented by local chromatin tightening and DNA methylation at and around the SREBP1c binding site in the SCD1 promoter. Chromatin immunoprecipitation assays confirmed that SARA reduced SREBP1c binding at the SCD1 promoter; hence, epigenetic mechanisms are involved in regulating the expression of genes related to long-chain fatty acid modification, partially through downregulation of both SCD1 and SREBP1c in the liver. Our results suggest that in addition to inflammatory genes, SCD1 is also involved in SARA-induced epigenetic regulation and its associated metabolic changes. This knowledge might help to provide a target for intervening against the detrimental metabolic effects of SARA., (Copyright © 2018 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Rumen health is of vital importance in ensuring healthy and efficient dairy cattle production. Current feeding programs for cattle recommend concentrate-rich diets to meet the high nutritional needs of cows during lactation and enhance cost-efficiency. These diets, however, can impair rumen health. The term "subacute ruminal acidosis" (SARA) is often used as a synonym for poor rumen health. In this review, we first describe the physiological demands of cattle for dietary physically effective fiber. We also provide background information on the importance of enhancing salivary secretions and short-chain fatty acid absorption across the stratified squamous epithelium of the rumen; thus, preventing the disruption of the ruminal acid-base balance, a process that paves the way for acidification of the rumen. On-farm evaluation of dietary fiber adequacy is challenging for both nutritionists and veterinarians; therefore, this review provides practical recommendations on how to evaluate the physical effectiveness of the diet based on differences in particle size distribution, fiber content, and the type of concentrate fed, both when the latter is part of total mixed ration and when it is supplemented in partial mixed rations. Besides considering the absolute amount of physically effective fiber and starch types in the diet, we highlight the role of several feeding management factors that affect rumen health and should be considered to control and mitigate SARA. Most importantly, transitional feeding to ensure gradual adaptation of the ruminal epithelium and microbiota; monitoring and careful management of particle size distribution; controlling feed sorting, meal size, and meal frequency; and paying special attention to primiparous cows are some of the feeding management tools that can help in sustaining rumen health in high-producing dairy herds. Supplementation of feed additives including yeast products, phytogenic compounds, and buffers may help attenuate SARA, especially during stress periods when the risk of a deficiency of physically effective fiber in the diet is high, such as during early lactation. However, the usage of feed additives cannot fully compensate for suboptimal feeding management., (Copyright © 2018 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Subacute ruminal acidosis is induced by high concentrations of short-chain fatty acids (SCFA, mainly acetate, propionate, and butyrate) that release protons to decrease the pH of the ruminal digesta. This low pH, in turn, is thought to damage epithelial barrier function. The present study applied a model of simulated ruminal acidosis ex vivo to investigate if SCFA directly contribute to epithelial barrier failure beyond their role as proton donors. Epithelial tissues from the rumen of slaughtered sheep were mounted in Ussing chambers and incubated under 3 different conditions. Two groups were incubated in the absence of SCFA at mucosal pH 6.1 (control) and pH 5.1, respectively, for 7 h. A third group was first incubated in a mucosal solution containing 100 mM SCFA at pH 5.1 for 2 h and, thereafter, in a mucosal solution without SCFA at pH 6.1 for the remaining 5 h. Transepithelial conductance (G t ), short-circuit current (I sc ), and fluorescein fluxes were determined. After 7 h of incubation, the expression levels of claudin-1, claudin-4, claudin-7, and occludin were measured by quantitative reverse-transcription PCR and Western blot. Furthermore, the local distribution of these tight junction (TJ) proteins was examined by confocal laser scanning microscopy. A 7-h incubation at pH 5.1 in the absence of SCFA did not influence either G t or fluorescein flux rates of ruminal tissues ex vivo compared with the control. In contrast, incubation at pH 5.1 with SCFA for only 2 h induced increases in G t and fluorescein flux rates that continued even after tissues were returned back to pH 6.1. Expression analysis showed that pH 5.1 without SCFA for 7 h induced no changes in mRNA expression of claudin-1, claudin-4, claudin-7, and occludin and a selective decrease in protein expression of only claudin-4 compared with the control. However, a 2-h incubation at pH 5.1 in the presence of SCFA decreased the mRNA-expression of claudin-7, as well as the protein expression of claudin-4, claudin-7, and occludin. The decreased expression of these TJ proteins in the group incubated with SCFA was also evident in immunohistochemistry. Immunohistochemistry additionally evidenced a considerable retraction of all tested TJ proteins out of the TJ in that group. We conclude that a low mucosal pH of 5.1 is tolerated well by ruminal epithelia for several hours. However, a low pH in combination with SCFA induces damage to the TJ and disturbs barrier function, which is not immediately reversible upon the removal of the acidotic insult., (Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Three sources of sensory data: cow's individual rumination duration, activity and milk yield were evaluated as possible indicators for clinical diagnosis, focusing on post-calving health problems such as ketosis and metritis. Data were collected from a computerised dairy-management system on a commercial dairy farm with Israeli Holstein cows. In the analysis, 300 healthy and 403 sick multiparous cows were studied during the first 3 weeks after calving. A mixed model with repeated measurements was used to compare healthy cows with sick cows. In the period from 5 d before diagnosis and treatment to 2 d after it, rumination duration and activity were lower in the sick cows compared to healthy cows. The milk yield of sick cows was lower than that of the healthy cows during a period lasting from 5 d before until 5 d after the day of diagnosis and treatment. Differences in the milk yield of sick cows compared with healthy cows became greater from 5 to 1 d before diagnosis and treatment. The greatest significant differences occurred 3 d before diagnosis for rumination duration and 1 d before diagnosis for activity and milk yield. These results indicate that a model can be developed to automatically detect post-calving health problems including ketosis and metritis, based on rumination duration, activity and milk yield.

The objectives of this study were to explore changes of rumination time and reticuloruminal pH and temperature of dairy cows and heifers (means ± standard deviation; age = 5.8 ± 1.9; parity = 2.7 ± 1.4; body condition score = 3.2 ± 0.2) with eutocic (EUT, n = 10) and dystocic calving (DYS, n = 8). The recording period lasted from 3 d before calving until 7 d in milk. For the comparison of rumination time and reticuloruminal characteristics between groups, time to return to baseline (the time interval required to return to baseline from the delivery of the calf) and area under the curve (AUC; both for prepartum and postpartum periods) were calculated for each parameter. Rumination time decreased from baseline 28 h before calving both for EUT and DYS cows; after 20 h before calving, it decreased to 32.4 ± 2.3 and 13.2 ± 2.0 min/4 h between 8 and 4 h before delivery in EUT and DYS cows, respectively, and then it decreased below 10 and 5 min during the last 4 h before calving. Until 12 h after delivery, rumination time reached 42.6 ± 2.7 and 51.0 ± 3.1 min/4 h in DYS and EUT dams, respectively; however, AUC and time to return to baseline suggested lower rumination activity in DYS cows than in EUT dams for the 168-h postpartum observational period. Reticuloruminal pH decreased from baseline 56 h before calving both for EUT and DYS cows, but did not differ between groups before delivery. Reticuloruminal pH showed a decreasing tendency and clear diurnal variation after calving for both EUT and DYS cows, with slightly higher AUC values in DYS cows. In DYS cows, reticuloruminal temperature decreased from baseline 32 h before calving by 0.23 ± 0.02°C, whereas in EUT cows such a decrease was found only 20 h before delivery (0.48 ± 0.05°C). The AUC of reticuloruminal temperature calculated for the prepartum period was greater in EUT cows than in DYS cows. During the first 4 h after calving, reticuloruminal temperature decreased from 39.68 ± 0.09 to 38.96 ± 0.10°C and from 39.80 ± 0.06 to 38.81 ± 0.08°C in EUT and DYS cows, respectively, and reached baseline levels after 35.4 ± 3.4 and 37.8 ± 4.2 h after calving in EUT and DYS cows, respectively. Based on our results, continuous monitoring of changes in rumination time and reticuloruminal temperature seems to be promising in the early detection of cows with a higher risk of dystocia. Depressed rumination activity of DYS cows after calving highlights the importance of the postpartum monitoring of cows experiencing difficulties at calving. The effect of dystocia on postpartum reticuloruminal pH was not pronounced., (Copyright © 2017 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Indwelling rumen temperature bolus (RTB) systems have the potential to offer a convenient and timely method of detecting pyrexia, indicative of active infectious disease. The aim of this pilot study was to evaluate the utility of using RTB systems in preweaned dairy calves. First, an in vitro study was performed to evaluate the accuracy of the RTB in its immediate environment. Thirteen RTB were immersed in a hot water bath (WB). Variably collected RTB temperatures were then matched to WB temperatures, which varied from 36 to 41°C, with 1h spent at each temperature. Second, an in vivo study was performed to evaluate the ability of the RTB to predict a rectal thermometer (RT) temperature. Ten healthy heifer calves less than 1wk of age were administered an RTB. Rectal thermometer and matched RTB temperatures were taken hourly, over a 6-h period, 1 day per week during wk 1, 3, 5, 7, and 9 of age. During each 6-h observation period, calves were offered both water and milk feedings and temperatures recorded every 15min for 1h thereafter. For both studies, the relationship between RTB and one of WB (in vitro) or RT temperature (in vivo) was described by calculating a concordance correlation coefficient (CCC) and by use of a multivariable linear regression model with repeated measures. For the in vivo study, the model also controlled for week and breed. Diagnostic test characteristics were calculated for the ability of individual RTB measures to detect pyrexia (RT ≥39.5°C). For the in vitro study, the association between the RTB and a known temperature was strong (CCC=0.95), but the RTB measures underestimated the temperature of the water bath by 0.43±0.08°C. For the in vivo study, the association between RT and the RTB temperature measurement in a calf was weaker (CCC=0.29); the average RTB temperature was 0.33±0.06°C lower than the RT temperature. The sensitivity (29%) and positive predictive value (17%) of using individual RTB measures to detect a fever was low. The results of this pilot study suggest that an individual RTB measurement may not be a good diagnostic test to detect pyrexia in calves., (Copyright © 2016 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The objective of the current study was to evaluate if milk urea nitrogen (MUN) and milk fat content could be used as the noninvasive indicator to identify cows with greater or lower risk of subacute ruminal acidosis (SARA). Our hypothesis was that cows with lower MUN and milk fat content would have greater risk of SARA, whereas cows with higher MUN and milk fat content would have lower risk of SARA. In the screening study, 35 late-lactating Holstein cows (DIM=250±71.1; BW=601±45.4kg) were fed a high-grain diet containing 35% forage and 65% concentrate mix ad libitum for 21 d. Concentration of MUN ranged from 5.7 to 13.9Mg/dL among the 35 cows, and the average milk fat content was 3.5%. Then, 5 cows with highest MUN concentrations with milk fat higher than 3.5% were selected as animals that presumably have low risk of SARA, and 5 cows with lowest MUN concentrations with milk fat less than 3.5% were selected as animals that presumably have high risk of SARA. These 10 animals were ruminally cannulated during the subsequent dry period. As 1 low-risk cow was culled due to fatty liver, 9 animals (DIM=122±33.2; BW=615±49.1kg) were used in the subsequent study in the following lactation. All cows were fed a high-grain diet consisting of 35% forage and 65% concentrate mix ad libitum for 21 d. Ruminal pH was measured every 30 s for 72 h. Minimum (5.75 vs. 5.30) and mean ruminal pH (6.35 vs. 6.04) was higher for low- compared with high-risk animals. In addition, duration of rumen pH below 5.8 was shorter in low-risk animals (52.5 vs. 395min/d). These results suggested that MUN and milk fat content in late-lactating cows fed a high-grain diet may be used to identify cows that have higher or lower risk of SARA., (Copyright © 2015 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The effects of 18 essential oils, yeast, Quebracho tannin and Quillaja saponin on ruminal methane and gas production (GP) were studied in vitro. A lactating cow diet was incubated with rumen inoculum. Doses of the additives (mg/L) were: essential oils = 500; tannin = 67; yeast = 8.35 and 16.7; and saponin = 300. Lemongrass, estragole, eugenol, geraniol, limonen, thyme oil and thymol produced less gas (overall mean 33.8 mL/200 mg dry matter (DM)) than control (43.6 mL/200 mg DM; P < 0.001). Methane produced (mL/200 mg DM) by guaiacol (10.7), lemongrass (9.6), limonene (11.4), thyme oil (10.9) and thymol (2.1) was lower than control (12.5) (P < 0.001). Methane percentage on total GP was lower (P < 0.001) for cinnamic alcohol (25.4), guaiacol (24.5), thymol (19.7) and vanillin (26.3) than control (28.8). In a second experiment, thymol, guaiacol and yeast were added to the diet of dry fistulated cows to determine in situ neutral detergent fiber digestibility (NDFD) of six forages and in vivo dietary NDFD. Thymol and yeast decreased in situ NDFD after 24 h (33.9% and 33.5% vs. 38.1%; P = 0.008). Thymol decreased in vivo total tract NDFD (40.8% vs. 51.4%; P = 0.02). Differences in GP and methane levels were registered within classes of additives. A careful selection of additives may allow for the manipulation of ruminal fermentation., (© 2014 Japanese Society of Animal Science.)

The aims of the experiment were to investigate the variation in ruminal fermentation, milk performance and milk fatty acid profile triggered by induced subacute ruminal acidosis (SARA); and to evaluate the ability of beet pulp (BP) as a replacement for ground maize in order to alleviate SARA. Eight Holstein-Friesian cows were fed four diets (total mixed rations) during four successive periods (each of 17 d): (1) without wheat (W0); (2) with 10% finely ground wheat (FGW) (W10); (3) with 20% FGW (W20); (4) with 20% FGW and 10% pelleted BP (BP10). Inducing SARA by diet W20 decreased the daily mean ruminal pH (6.37 vs. 5.94) and the minimum ruminal pH (5.99 vs. 5.41) from baseline to challenge period. Ruminal concentrations of total volatile fatty acid, propionate, butyrate, valerate and isovalerate increased with the W20 compared with the W0 and W10 treatments. The substitution of BP for maize increased the minimum ruminal pH and molar percentage of acetate and decreased the molar percentage of butyrate. The diets had no effect on dry matter intake (DMI) and milk yield, but the milk fat percentage and yield as well as the amount of fat-corrected milk was reduced in the W20 and BP10 treatments. The cows fed the W20 diet had greater milk concentrations of C11:0, C13:0, C15:0, C14:1, C16:1, C17:1, C18:2n6c, C20:3n6, total polyunsaturated fatty acids (FA) and total odd-chain FA, and lower concentrations of C18:0 and total saturated FA compared with the cows fed the W0 diet. Therefore, it can be concluded that changes in ruminal fermentation, milk fat concentration and fatty acid profile are highly related to SARA induced by feeding high FGW diets, and that the substitution of BP for maize could reduce the risk of SARA in dairy cows.

Subacute ruminal acidosis (SARA) is a condition where the pH of the rumen becomes abnormally acidic because of increased and altered production of volatile fatty acids. The objective of this experiment was to determine how a SARA challenge affects total mixed ration selection in dairy cows. In this study, 8 multiparous, lactating, ruminally cannulated Holstein cows were given a choice between a long-forage-particle-size diet with slow-fermenting starch (LC) and a short-forage-particle-size diet with fast-fermenting starch in a crossover design. Cows were allowed to adapt to this feeding scheme and were then subjected to a rumen challenge to induce a bout of SARA. The rumen challenge successfully decreased rumen pH and altered rumen volatile fatty acid profiles. Daily average rumen pH decreased from 6.02 to 5.77, and average minimum rumen pH decreased from 5.59 to 5.28. In addition, following the rumen challenge, concentrations of acetate, butyrate, and valerate, and acetate-to-propionate ratio increased. In response to the rumen challenge, intake of LC increased from the baseline level of 18.1% of total daily dry matter intake to 38.3% for that day. During the first recovery day after the rumen challenge, LC intake moderated to 28.0% of total daily dry matter intake. On the second recovery day, LC intake returned to baseline levels at 18.6%. These results indicate that cows are able to alter their diet preference for higher physically effective fiber and slower starch fermentability during a bout of SARA and that they can effectively fully recover from this type of SARA within 72 h when appropriate diets are available., (Copyright © 2013 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Subacute rumen acidosis (SARA) is frequently encountered in ruminants on high-concentrate rations and characterized by mild to moderate rumen pH depression. Although the measurement of rumen pH is considered as a gold standard approach to diagnose SARA, rumen fluid collection is conceived as a cumbersome and invasive procedure. In the present study, the suitability of transabdominal ultrasonography to identify structural changes of the rumen mucosa associated with SARA was explored. Five adult rumen canulated bulls previously adjusted to a roughage-based ration were switched in 10-day intervals to rations with increasing concentrate content. Seven rations with a concentrate content ranging from 5% to 95% were fed. The rumen pH and rumen mucosal thickness were measured at the end of each 10-d feeding period. The left flank was divided into 12 acoustic windows and the mean rumen mucosal thickness for each acoustic window determined for each ration. Repeated measure ANOVA and stepwise regression analyses were conducted. Increasing the dietary concentrate content resulted in thickening of rumen mucosa which was most pronounced in the upper part of the ventral rumen sac and the least pronounced in the uppermost and lowermost parts of the rumen. The intersection of a horizontal line going through the costochondral junction and a vertical line coming from the third lumbar vertebra was found to be most suitable to identify animals with rumen pH < 5.5 at 4 h post feeding. We conclude that transabdominal ultrasonography of the rumen mucosa has the potential to be a suitable, non-invasive diagnostic tool to identify adult ruminants with SARA.

The objective of this study was to determine the efficacy of Prevotella bryantii 25A as a probiotic during a subacute ruminal acidosis (SARA) challenge using a commercial probiotic as a positive control. Six multiparous ruminally fistulated cows (BW=685 ± 65 kg; (mean ± SD) in the mid-phase of lactation (70 to 148 DIM) received the following treatments in a replicated 3×3 Latin square design: (1) total mixed ration (TMR; control, CON), (2) TMR + 2g/head per day of a probiotic combination of Enterococcus faecium and Saccharomyces cerevisiae (EFSC), or (3) TMR + Prevotella bryantii 25A. The Latin square consisted of 3 wk of adaptation to the respective treatments during which the animals were fed ad libitum once per day a conventional early-lactation TMR and 1.5 kg of hay. The adaptation was followed by 4 d of SARA (no hay) and 10d of rest (adaptation diet without probiotics). Dry matter intake and milk production were depressed during SARA (22.0 and 31.8 kg/d, respectively) compared with adaptation (24.4 and 34.0 kg/d, respectively) and did not recover during rest (22.3 and 30.7 kg/d, respectively). During SARA, P. bryantii 25A had no effect on rumen pH, whereas EFSC reduced the percentage of time with pH <6.0 (71%) compared with CON (85%) and increased maximum pH. The EFSC treatment tended to increase mean pH over 24h (5.65) compared with CON (5.45). Proportion of time with pH <5.6 tended to be lower with EFSC (46%) than with CON (62%). Populations of bacteria considered to be the most important cellulose digesters in the rumen (Ruminococcus flavefaciens, Ruminococcus albus, and Fibrobacter succinogenes) were also monitored during these treatments using culture-independent real-time PCR methods. The population of R. flavefaciens was similar between the 2 feeding phases, whereas F. succinogenes and R. albus were lower during SARA compared with rest. In light of the present study, P. bryantii 25A did not prove to be an effective preventative for SARA. The role of EFSC in regulating rumen pH was confirmed, with a possible effect of maintaining R. flavefaciens populations during SARA., (Copyright © 2012 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

The objective of this study was to determine whether subacute ruminal acidosis (SARA) could be diagnosed by continuous measurements of the reticular pH, as compared with the ruminal pH, using healthy cows fed a control diet and SARA cows fed a rumen acidosis-inducing diet. The reticular and ruminal pH were measured simultaneously by a radio transmission pH measurement system. The mean reticular pH at 1-h intervals decreased gradually from the morning feeding to the next feeding time in both healthy and SARA cows, though the decrease in the ruminal pH was observed to be more drastic as compared with that observed in the reticular pH. The threshold of the 1-h mean pH in the reticulum for a diagnosis of SARA was considered to be 6.3, and a significant positive correlation was observed between the reticular and ruminal pH. No differences in the concentrations of lactic acid, ammonia nitrogen, and volatile fatty acids were noted between the reticular and ruminal fluids in SARA cows. These results demonstrate that the reticular pH can be used to detect SARA in cows, as opposed to using the ruminal pH.

Background: Ruminal disbiosis induced by feeding is the cause of ruminal acidosis, a digestive disorder prevalent in high-producing ruminants. Because probiotic microorganisms can modulate the gastrointestinal microbiota, propionibacteria- and lactobacilli-based probiotics were tested for their effectiveness in preventing different forms of acidosis., Results: Lactic acidosis, butyric and propionic subacute ruminal acidosis (SARA) were induced by feed chalenges in three groups of four wethers intraruminally dosed with wheat, corn or beet pulp. In each group, wethers were either not supplemented (C) or supplemented with Propionibacterium P63 alone (P) or combined with L. plantarum (Lp + P) or L. rhamnosus (Lr + P). Compared with C, all the probiotics stimulated lactobacilli proliferation, which reached up to 25% of total bacteria during wheat-induced lactic acidosis. This induced a large increase in lactate concentration, which decreased ruminal pH. During the corn-induced butyric SARA, Lp + P decreased Prevotella spp. proportion with a concomitant decrease in microbial amylase activity and total volatile fatty acids concentration, and an increase in xylanase activity and pH. Relative to the beet pulp-induced propionic SARA, P and Lr + P improved ruminal pH without affecting the microbial or fermentation characteristics. Regardless of acidosis type, denaturing gradient gel electrophoresis revealed that probiotic supplementations modified the bacterial community structure., Conclusion: This work showed that the effectiveness of the bacterial probiotics tested depended on the acidosis type. Although these probiotics were ineffective in lactic acidosis because of a deeply disturbed rumen microbiota, some of the probiotics tested may be useful to minimize the occurrence of butyric and propionic SARA in sheep. However, their modes of action need to be further investigated.

The use of reticulo-rumen temperature boluses to detect bovine respiratory disease (BRD) was investigated in young bulls following their entry into a fattening unit. Twenty-four bulls received a bolus at entry and were observed for 40 days. As soon as a reticulo-rumen hyperthermia (RH) episode was detected using the bolus, clinical examination was performed by a veterinarian and then repeated every 12-24h until the end of RH episode. Fifty-two RH episodes were detected in 22 animals. High rectal temperatures (40.1±0.6°C) were observed during these episodes. BRD was diagnosed on the basis of clinical examination during 38/52 RH episodes in 21 animals (positive predictive value 73%). The onset of BRD signs always occurred after the onset of RH episodes, with a time-lag from 12 to 136 h, depending on BRD signs. Monitoring reticulo-rumen temperature permits early detection of BRD; however, clinical examination is required to confirm BRD., (Copyright © 2010 Elsevier Ltd. All rights reserved.)

The objective of this study was to validate the efficacy of a radiotelemetric bolus (RTB) to detect changes in ruminal temperature resulting from (1) systemic illnesses that are associated with febrile responses and (2) subacute ruminal acidosis (SARA). Eight rumen-fistulated, lactating Holstein cows (586±37 kg of body weight, 106±18 d in milk) were used in a replicated 4 × 4 Latin square design with a 2 × 2 factorial arrangement. Each period consisted of 21 d. The factors were 2 diets, a moderate forage:concentrate [MFC; 52:48; % of dry matter (DM)] or a high forage:concentrate (HFC; 65:35, % of DM) total mixed ration, and a challenge with a single intramammary injection of lipopolysaccharide (LPS; 100 μg derived from Escherichia coli 0111:B4) or no LPS (sterile saline). Thus, the 4 resulting treatments were (1) MFC with LPS challenge, (2) MFC with saline, (3) HFC with LPS challenge, and (4) HFC with saline. Cows were fed at 0800 and 1400 h daily. Cows received the intramammary injections at 0900 h of d 21. Ruminal pH and ruminal temperature were also measured on d 21 every minute via an indwelling logging system that resided in the ventral sac of the rumen and via a radiotelemetric bolus that resided in the reticulum. Vaginal temperature was also recorded every minute via temperature loggers. Prior to LPS injection, the duration of rumen pH below 5.6 (indicative of SARA) was higher in cows receiving MFC than cows receiving HFC (148±24 and 62±24 min/d, respectively). The temperature measured at the same time via RTB was higher for MFC than HFC cows (167±21 vs. 104 vs. 21 min/d above 38.8°C, respectively). The following day, cows challenged with LPS showed signs of mastitis within the injected quarters, depressed DM intake, decreased milk yield, and a peak vaginal temperature of 41.3±0.1°C 5.5h after the LPS injection. The RTB system successfully detected a fever response parallel to that measured by the vaginal loggers but temperature peak detected by RTB was, on average, 0.5°C lower than that detected by the vaginal logger. Although the RTB system was able to detect a temperature response to the diet effect before LPS challenge, it was unable to detect this effect during the LPS challenge, likely because cows receiving the LPS challenge had decreased feed consumption. In conclusion, radiotelemetry has the potential to improve the detection of SARA and fever on farm., (Copyright © 2011 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

Twenty-four German Merino sheep (72.3±10.1 kg of body weight) were fed an all-hay diet and assigned to either the subacute ruminal acidosis (SARA) treatment (n=17) or sham treatment (n=7). The SARA sheep were orally dosed with a 2.2 M glucose solution to supply 5 g of glucose/kg of body weight, whereas sham sheep received an equal volume of water. Ruminal pH was measured for 48 h before and 3 h after the oral dose. Sheep were then killed and ruminal epithelia from the ventral sac were mounted in Ussing chambers. The serosal-to-mucosal flux rate of partially (3)H-labeled mannitol (J(mannitol-SM)), an indicator of barrier function, was measured while epithelia were exposed to 3 sequential in vitro measurement periods lasting 1 h each. The measurement periods consisted of baseline, challenge, and recovery periods and were interspersed by 30-min periods for treatment equilibration. Baseline conditions were pH 6.1 (mucosal solution) and pH 7.4 (serosal solution) with a bilateral osmolarity of 293 mOsm/L. During the challenge period, the mucosal side of the epithelia was exposed to either an acidotic challenge (pH 5.2, osmolarity 293 mOsm/L) or an osmotic challenge (pH 6.1, osmolarity 450 mOsm/L); a third group served as control (pH 6.1, osmolarity 293 mOsm/L). The mucosal buffer solution was replaced for the recovery period. In vivo, sheep on the SARA treatment had lower mean (5.77 vs. 6.67) and nadir (5.48 vs. 6.47) ruminal pH for the 3h following the oral drench compared with sham sheep, indicating the successful induction of SARA with the oral glucose dose. Despite the marked reduction in pH in vivo, induction of SARA had no detectable effects on the baseline measurements of J(mannitol-SM), tissue conductance (G(t)), and short-circuit current (I(sc)) in vitro. However, reducing mucosal pH to 5.2 in vitro had negative effects on epithelial barrier function in the recovery period, including increased J(mannitol-SM), increased G(t), and decreased I(sc). The osmotic challenge increased J(mannitol-SM) and G(t) and decreased I(sc) during the challenge period, which was reversible in the recovery period except for slight reduction in I(sc). Interactions between the in vitro treatment and measurement period were detected for J(mannitol-SM), G(t), and I(sc). These data indicate that a mild episode of SARA (nadir pH, 5.48; duration ruminal pH <5.8, 111 min relative to the 180-min measurement period) does not affect ruminal epithelial barrier function immediately after the episode but that a rapid and more severe acidification (pH 5.2) in vitro increases epithelial permeability following the insult., (Copyright © 2010 American Dairy Science Association. Published by Elsevier Inc. All rights reserved.)

A study was conducted to determine if subacute ruminal acidosis (SARA) induced by feeding alfalfa pellets results in increases in free bacterial lipopolysaccharide (LPS) in rumen fluid and peripheral blood, and acute phase proteins in plasma, and to determine the effect of alfalfa pellet-induced SARA on feed intake, rumen fermentation characteristics, milk production and composition, and blood metabolites. Eight lactating Holstein cows, 4 of which were ruminally cannulated, were used in a 6-wk experiment and were fed once daily at 0900 h. During wk 1, cows received a diet containing 50% of DM as concentrate and 50% of DM chopped alfalfa hay. Between wk 2 and wk 6, alfalfa hay was gradually replaced with alfalfa pellets at the rate of 8% per week to reduce rumen pH. Rumen pH was monitored continuously in the ruminally cannulated cows using indwelling pH probes. Rumen fluid and peripheral blood were sampled 15 min before feed delivery and at 6 h after feed delivery. Based on adopted threshold of SARA of at least 180 min/d below pH 5.6, SARA was induced from wk 3 onwards. Replacing 40% of alfalfa hay with alfalfa pellets quadratically increased the DMI from 18.1 kg/d in wk 1 to 23.4 kg/d in wk 6. This replacement linearly decreased milk yield (32.7 vs. 35.9 kg/d) and milk fat percentage and yield (2.32 vs. 3.22%, and 0.77 vs. 1.14 kg/d, respectively), but increased milk protein percentage and yield (3.80 vs. 3.04%, and 1.23 vs. 1.07 kg/d, respectively). This gradual replacement also linearly increased the daily averages of total volatile fatty acids (90 to 121.9 mM), acetate (53.9 to 66.8 mM), propionate (21.5 to 39.6 mM), and osmolality (277.7 to 293.8 mmol/kg) in the rumen and decreased the acetate to propionate ratio from 2.62 to 1.73. Replacing alfalfa hay with alfalfa pellets linearly increased blood lactate from 1.00 mM in wk 1 to a peak of 3.46 mM in wk 5. Induction of SARA in this study increased free rumen LPS concentration from 42,122 endotoxin unit (EU)/mL in wk 1 to 145,593 EU/mL in wk 6. However, this increase was not accompanied by an increase in LPS (<0.05 EU/mL) and in acute phase proteins serum amyloid-A, haptoglobin, and LPS-binding protein in peripheral circulation. Results suggest that SARA induced by alfalfa pellets increased LPS in the rumen without causing translocation of LPS and an immune response.

The primary objective of this experiment was to determine whether lactating dairy cows that are at high (HR) or low (LR) risk for experiencing ruminal acidosis, because of their diet and stage of lactation, differ in their response to an acidosis challenge. A secondary objective was to determine whether the severity of acidosis changes with repeated challenges. The experiment was a completely randomized design with 2 groups (risk scenarios, HR vs. LR) and 3 periods corresponding to 3 repeated acidosis challenges. Eight lactating ruminally cannulated cows were assigned to 1 of 2 groups: HR, early lactation cows fed a 45% forage diet, or LR, midlactation cows fed a 60% forage diet. Cows were exposed to 3 acidosis challenges, each separated by 14 d. The challenge consisted of restricting total mixed rations to 50% of ad libitum intake for 24 h, followed by a 1-h meal of 4 kg of ground barley-wheat before allocating the total mixed rations. Ruminal pH was measured continuously for 9 of the 14 d each period using an indwelling system. Subacute acidosis (SARA) was described at 2 thresholds: pH <5.8 and pH <5.5. As expected, HR cows had lower ruminal pH profiles (curves) compared with LR cows: mean pH (5.81 vs. 6.21) and nadir pH (5.13 vs. 5.53). The HR cows also experienced SARA to a greater extent than LR cows during the experiment (pH <5.8, 10.6 vs. 3.5 h/d; pH <5.5, 5.9 vs. 1.6 h/d). The pH profiles of cows in both risk categories decreased with each challenge period; mean pH was 6.13, 6.03, 5.77, and nadir pH was 5.52, 5.34, and 5.14 in periods 1, 2, and 3, respectively. The challenges caused a similar decrease in pH for cows in both risk categories, but because the HR cows had a lower baseline pH, they experienced more severe SARA with each subsequent challenge. Feed restriction the day before administering the acidosis challenge caused ruminal pH to gradually increase. On the challenge day, the entire grain allotment was consumed by all cows in period 1, six cows in period 2, and only 3 cows in period 3. The pH plummeted immediately after each grain challenge. Ruminal pH remained very low during the first day after the challenge for all cows, but LR cows began their recovery more quickly than HR cows. Regardless of risk category, with each successive challenge, the pH decrease on the challenge day was more severe: nadir pH on the challenge day was 5.19, 5.07, and 4.90 and duration of SARA (pH <5.8) was 12.2, 13.4, and 15.8 h/d in periods 1, 2, and 3. This study indicates that cows become more prone to acidosis over time even though they decrease intake of the challenge grain to avoid acidosis. The severity of each subsequent bout of acidosis increases, especially for cows fed diets low in physically effective fiber and at high acidosis risk. Therefore, a bout of acidosis that occurs due to improper feed delivery or poor diet formulation can have long-term consequences on cow health and productivity.

The effects of grain-induced subacute ruminal acidosis (SARA) in lactating dairy cows on free ruminal lipopolysaccharide (LPS) and indicators of inflammation were determined. Four mid lactation dairy cows were divided into 2 groups of 2 cows and used in a repeated switchover design. During each period, SARA was induced in 2 animals for 5 subsequent days by replacing 25% of their total mixed ration (dry matter basis) with a concentrate made of 50% wheat and 50% barley. The other 2 cows acted as controls and were fed a total mixed ration diet in which 44% of dry matter was concentrate. On average, inducing SARA did not affect milk composition, increased the duration of rumen pH below 5.6 from 187 to 309 min/d, and increased free ruminal LPS concentration from 24,547 endotoxin units (EU)/mL to 128,825 EU/mL. Averaged across treatments, milk fat yield and milk protein yield were 0.66 and 1.00 kg/d, respectively. Rumen pH and milk fat data suggest that control cows also experienced ruminal acidosis, albeit a milder form of this disease than SARA cows. Serum LPS concentration in both control and SARA cows was less than the detection limit of <0.01 EU/mL for the assay. Induction of SARA elevated serum amyloid A concentration from 286.8 to 498.8 mug/mL, but did not affect other markers of inflammation including haptoglobin, fibrinogen, serum copper, or white blood cells. These results suggest that grain-induced SARA in mid lactation dairy cows increases the lysis of gram-negative bacteria and activates an inflammatory response.

In ruminal drinkers (RD) ingested milk is transported into the rumen and not into the abomasum. Because this is followed by changes in digestibility and absorption, we have tested whether this is associated with postprandial metabolic and endocrine changes. Unweaned, bucket-fed calves (one RD, two controls) were studied on seven farms. On d 1, after metabolic and endocrine 12-h profiles were studied, RD and one control calf were fed for 10 d by nipple, whereas the other control calf was fed by bucket. On d 11, metabolic and endocrine 12-h profiles were again studied. On d 1, mean plasma concentrations of glucose, triglycerides, urea, insulin, insulin-like growth factor-1 (IGF-1), 3,5,3'-triiodothyronine (T3), thyroxine (T4) and leptin were significantly different between RD and controls, whereas mean concentrations of non-esterified fatty acids (NEFA), total protein, albumin, and glucagon did not differ significantly among groups. In RD concentrations of glucose, NEFA, insulin, growth hormone, IGF-1, and T4 were higher, and of urea were lower on d 11 than on d 1. Glucose and insulin concentrations increased postprandially in healthy calves on d 1, but barely in RD and remained lower than in controls, and there was no rise of NEFA and triglyceride concentrations on d 1 after the initial postprandial decrease in RD, in contrast to controls. But on d 11 postprandial responses of these four traits were similar in RD and controls and urea and T4 concentrations on d 11 became normalized. However, glucose and T3 concentrations in RD on d 11 were still lower than in one or both control groups. In conclusion, various metabolic and endocrine traits in RD differed from healthy controls. Drinking by floating nipple instead of drinking from bucket for 10 d normalized several metabolic and endocrine traits in RD.

Objective: To report on spontaneous clinical and subclinical acidosis in a large dairy herd, to evaluate the diets and feeding strategies involved, and to report on measures of rumen function in the cows affected., Design: A Gippsland dairy herd was sampled as part of a wider randomised cross-sectional study that examined the prevalence, risk factors for, and effects of, acidosis on rumen function of dairy cattle. Three herds on the farm were involved in the study: the transition herd (cows 3 weeks prior to calving), the very fresh lactating herd (1 < days in milk < 10, herd 1) and the fresh lactating herd (10 < days in milk < 120, herd 2) including a small lame herd fed separately. The transition cows were fed 2 kg dry matter triticale per cow per day and hay with an estimated total dry matter intake of 4.8 kg per cow per day. The lactating cow diet included 6.75 kg dry matter triticale per cow per day with total concentrate fed being 8.1 kg dry matter per cow per day in the milking parlour. Silage, lucerne cubes, hay and pasture (herd 2 only) was also fed to the lactating cows with the estimated total dry matter intake for cows in herds 1 and 2 being 13.7 kg and 20.8 kg per cow per day respectively. Three primiparous and five multiparous cows in early lactation (< 100 days in milk) were randomly selected from each of two lactating herds: herds 1 and 2. Rumen fluid was sampled from each cow by both rumenocentesis and stomach tube. The rumenocentesis samples were tested for pH at the time of sampling. Stomach tube samples were frozen and subsequently tested for volatile fatty acid, ammonia, and D- and L-lactate concentration., Results: In the very fresh herd, there was a high prevalence of severe lameness and scouring, coupled with a mean rumen pH 5.67, low mean total volatile fatty acid concentration 71.0 mM and high mean concentrations of L- and D-lactate, (7.71 mM and 7.31 mM), respectively. Cows in the fresh herd had moderate signs of scouring and lameness. A lame herd comprising approximately 50 cows separated from the fresh herd was also present on the farm. The mean rumen pH of the fresh herd was 5.74 and mean rumen concentrations of volatile fatty acids, ammonia, L- and D-lactate were within ranges considered normal., Conclusions: The transition diet failed to supply sufficient energy and protein for maintenance of cows of this live weight in late gestation. The diet fed to the very fresh herd was low in effective fibre and contained an excessive content of non-structural carbohydrate in the form of processed, rapidly fermentable grain. The sudden change from the transition diet to the diet fed to the very fresh herd probably also precipitated the outbreak of acidosis. This case report provides unique detail, including information on diets and rumen parameters, of an outbreak of acidosis in a pasture-fed herd.

The effect of intravenous administration of the steroidal drug isoflupredone acetate on lactating dairy cows with mastitis induced using gram-negative bacterial endotoxin was investigated. Cows were randomly assigned to one of four treatment groups: untreated controls, isoflupredone acetate only, mastitis only, and mastitis plus isoflupredone acetate. Isoflupredone acetate was given to treated groups at a dose of 20 mg intravenously, once. Mastitic cows receiving treatment were given isoflupredone acetate after the development of clinical signs. When compared with untreated mastitic controls, cows with endotoxin-induced mastitis treated with isoflupredone acetate did not exhibit measurable differences in heart rate, rectal temperature, rumen motility, or changes in mammary gland surface area in the 14 h following the administration of intramammary endotoxin. Healthy cows treated with isoflupredone acetate had a higher heart rate over the 14 h after drug administration than did untreated healthy controls. When compared with untreated mastitic controls, cows treated with isoflupredone acetate did not exhibit statistically significant differences in milk production following endotoxin-induced mastitis.

The effects of a single intramuscular injection of a drug product containing ampicillin, colistin and dexamethasone, as a suspension in a diester of propylene glycol of medium-chain fatty acids, on the clinico-pathological course of experimental Escherichia coli-endotoxin mastitis was examined in 30 dairy cows. Cows were divided into five groups, six cows per group, and 24 of them were infused with E. coli endotoxin into two quarters of their udders. The drug product was injected at 25,000 IU colistin sulphate, 10.0 mg ampicillin anhydrate and 0.025 mg dexamethasone acetate.kg-1 body weight as follows: Group 2 cows, immediately post-endotoxin infusion (PEI); Group 3 cows, 2 h PEI and, Group 4 cows, 4 h PEI. Group 1 cows were not treated with the product and served as a positive (endotoxin only) control while Group 5 cows were not challenged with endotoxin and were not treated with the product. A clinical mastitis score (CMS) was developed to quantitatively assess the degree of inflammation. Blood biochemistry and hematological parameters were used to monitor the immediate effects of treatment on several conventional inflammatory markers. Milk somatic cell counts (MSCC), milk electrical conductivity and daily milk production were among the parameters used to monitor systemic and local inflammatory reactions. Administration of the drug product immediately PEI and 2 h PEI clearly nullified some of the most severe early systemic reactions to inflammation but the effect of therapy on the local inflammatory markers was not as obvious. Notewhorthy, however, were the effects of the treatment on reducing the duration of elevated quarter MSCC and the increase in the speed of return to pre-endotoxin challenge daily milk production levels.

Liver abscesses in slaughtered beef cattle result from aggressive grain-feeding programs. The incidence, averaging from 12 to 32% in most feedlots, is influenced by a number of dietary and management factors. Liver abscesses represent a major economic liability to producers, packers, and ultimately consumers. Besides liver condemnation, economic impacts include reduced feed intake, reduced weight gain, decreased feed efficiency, and decreased carcass yield. Fusobacterium necrophorum, a member of the ruminal anaerobic bacterial flora, is the primary etiologic agent. Actinomyces pyogenes is the second most frequently isolated pathogen. Ruminal lesions resulting from acidosis generally are accepted as the predisposing factors for liver abscesses. F. necrophorum possesses or produces a number of virulence factors that participate in the penetration and colonization of the ruminal epithelium and subsequent entry and establishment of infection in the liver. However, only a few virulence factors have been characterized well. Control of liver abscesses in feedlot cattle generally has depended on the use of antimicrobial compounds. Five antibiotics (i.e., bacitracin methylene disalicylate, chlortetracycline, oxytetracycline, tylosin, and virginiamycin) are approved for prevention of liver abscesses in feedlot cattle. Tylosin is the most effective and the most commonly used feed additive. Tylosin feeding reduces abscess incidence by 40 to 70%. The mode of action of antibiotics in preventing liver abscesses is believed to be via inhibition of ruminal F. necrophorum. Protective immunity against F. necrophorum induced by a variety of antigenic components has ranged from ineffectual to significant protection.

Diagnosis of deaths due to digestive disorders can be a difficult task. It is helpful if the carcass can be viewed for condition, position, and location before being moved from the pen in which it was found. A complete necropsy is absolutely necessary even though postmortem decomposition may be advanced. All thoracic and abdominal organs must be examined for gross lesions. If one believes that the central nervous system was involved, the brain should be removed and examined. Checking the ruminal pH is important. If indicated, samples should be obtained and submitted to a diagnostic laboratory. Salient lesions include congestion of the anterior portion of the carcass, especially the cervical muscles and tissues adjacent to the esophagus and trachea, paleness of the posterior portion of the carcass, edema between the muscle groups of the hindquarters, scrotal, or mammary area, and a lack of other gross lesions. Many cases have congestion and(or) edema in the submucosa of the dorsal portion of the trachea extending from the thoracic inlet cranially. One must list the cause of death as unknown or undetermined when it is not apparent.

Rumen motility was recorded on an experimental cow by means of telemetric signal transfer from strain gauge force transducers fixed surgically on the peritoneal surface of the rumen wall in the left flank. The normocalcaemic cow was given a standard milk fever treatment with calcium borogluconate (400 ml with 14 mg Ca/ml) intravenously. Transient clinical signs were: decreased rumination, muscle ticks, salivation and a heart rate reduction of 20%. Rectal temperature remained unaltered. Frequency of rumen contractions was reduced up to 40% whereas amplitude of contractions did not deviate from baseline values. Hypocalcaemia was induced in a second experiment by iv infusion of Na2EDTA. At 0.60 mmol/l ionized blood calcium periods of no motility were recorded whereas inactivity of rumen activity was persistent at 0.55 mmol/l ionized blood calcium. The cow went down at 0.45-0.48 mmol/l ionized blood calcium at which point the heart rate was increased by 40%. The high sensitivity of the method employed allowed the conclusion that already at a concentration of ionized blood calcium at 1.0 mmol/l both frequency and amplitude of rumen contractions decreased rapidly although eating behaviour and rumination appeared unaffected during the short term observation periods. Implications of this finding towards health and production in transition cows are discussed.

The influence of dried yeast on the in-vitro-fermentation of chronic acidotic bovine rumen fluid was investigated using the longterm rumen simulation technique (RUSITEC). Five investigation periods keeping 21 days each were carried out. After a control period of eight days a five days lasting test phase followed. During this time 2 g of dried yeast were added to two reaction vessels and two reaction vessels remained as controls. The following effects of dried yeast during the investigation period on rumen fluid and rumen gas, respectively, could be noted: negligible increase of pH for 0.1 units (ns) increase of short volatile fatty acids concentrations up to 10% (p < 0.01), (acetate +1.5% [ns], propionate +6.0% [ns], i-butyrate up to +180% [p < 0.001], n-butyrate 0%, i-valerinate +39%, [p < 0.05], n-valerinate +17.6% [p < 0.001], hexanat +33% [p < 0.001]) increase of gas production up to 29% (p < 0.001) decrease of methane production up to 30% (ns) increase of hydrogen production up to 10% (ns) increase of protein concentrations up to 23% (p < 0.05) increase of ammonia concentrations up to 385% (p < 0.001). The fermentation patterns became normal during 6 days after withdrawal of the yeast.

The clinical, ultrasonographic and radiographic findings in three cows and one bull with pleuropneumonia are described. All the animals had fever, indigestion, tachypnoea and abnormal lung sounds. Percussion of the thoracic wall elicited signs of pain and tests for foreign bodies were positive. Ultrasonographic examination revealed an accumulation of anechogenic to hypoechogenic fluid in the pleural space in the ventral thorax of all the animals. In one animal, echogenic bands of fibrin were observed between the thoracic wall and pulmonary surface. In another, parts of the right lung were not inflated because of severe bronchopneumonia. Radiographic examination revealed a pleural effusion, apparent as a horizontal fluid line, in three animals. In addition, the increased radiopacity in parts of the dorsal lung fields and increased bronchial and peribronchial markings suggested bronchopneumonia. In three animals, the radiographs revealed linear foreign bodies in the reticulum, suggesting that the pleuropneumonia was caused by the penetration of the foreign body into the thoracic cavity. A diagnosis of pleuropneumonia was made in all the animals on the basis of the clinical, ultrasonographic and radiographic findings and the analysis of the pleural fluid. The diagnosis was confirmed at slaughter in three of them; the fourth animal was treated and was clinically healthy when it was discharged.

Most of the metabolic diseases of dairy cows-milk fever, ketosis, retained placenta, and displacement of the abomasum-occur within the first 2 wk of lactation. The etiology of many of those metabolic diseases that are not clinically apparent during the first 2 wk of lactation, such as laminitis, can be traced back to insults that occurred during early lactation. In addition to metabolic disease, the overwhelming majority of infectious disease, in particular mastitis, becomes clinically apparent during the first 2 wk of lactation. Three basic physiological functions must be maintained during the periparturient period if disease is to be avoided: adaptation of the rumen to lactation diets that are high in energy density, maintenance of normocalcemia, and maintenance of a strong immune system. The incidence of both metabolic and infectious diseases is greatly increased whenever one or more of these physiological functions are impaired. This paper discusses the etiological role of each of these factors in the development of common diseases encountered during the periparturient period.

A study was undertaken to provide further information on the ruminal, cardiorespiratory and hypothalamo-pituitary-adrenocortical (HPAC) physiological sequelae of hypocalcaemia in dairy calves. The functional picture observed in standing calves experiencing Na2EDTA-induced progressive hypocalcaemia showed a biphasic pattern. During the first phase (Ca2+ varying between 1.20 +/- 0.09 and 0.64 +/- 0.15 mmol/L, mean +/- SD), the animals became dull and lethargic, shifting their weight from one hind limb to the other, with cool extremities and hypersalivation. Their ventilation was slightly increased but their heart rate, thoracoabdominal pressure, pulmonary mechanics, haemoglobin and temperature remained constant. Conversely, their systemic arterial pressure (SAP) and the amplitude of their ruminal contractions (RCA) were severely decreased. During the second phase (Ca2+ < 0.64 +/- 0.15 mmol/L), there was restlessness, tachycardia, hypertension, polycythaemia and, finally, inability to stay upright. It is suggested that the diminished Ca2+ availability caused smooth-muscle and myocardial dysfunctions which could explain the RCA and SAP changes recorded during the first phase, whereas neural and/or humoral sympathetic discharge probably accounted for the reversal in SAP and heart rate when Ca2+ was decreased further. Serum cortisol increased regularly and remained significantly correlated with Ca2+ in each animal. Moreover, regression of delta cortisol/delta Ca2+ on delta Ca2+/delta Na2EDTA was significant (p < or = 0.001). It was concluded that mild asymptomatic hypocalcaemia severely impairs ruminal function, which will progressively worsen the Ca2+ deficit; that the inability to maintain posture in hypocalcaemia is not due to hypotension; and that the higher the HPAC response to hypocalcaemia, the higher the resistance to its effects. An asymptomatic periparturient cow with barely detectable ruminal activity may merit preventive calcium borogluconate therapy. Also, the physiological role of hypotension in explaining the clinical picture may be less important than other processes, such as neuromuscular failure. Finally, the present results imply a possible HPAC exhaustion in cows with periparturient paretic hypocalcaemia.

Twenty crossbred wethers (41.9 +/- 4.0 kg BW), each fitted with a ruminal cannula and a jugular catheter, were used in a completely randomized design to examine the effects of ruminal acidosis on plasma activities of pancreatic enzymes and fractional rates of VFA absorption. Lambs had ad libitum access to a 50% concentrate diet. Acidosis was induced by an intraruminal dose of glucose at 0, 6, 12, or 18 g/kg BW via the ruminal cannula. Ruminal fluid and plasma were collected 0, 4, 8, 12, 18, 24, 36, 48, and 72 h after dosing. Ruminal fluid pH was reduced (linear, P < .001) with increasing ruminal glucose. Total ruminal VFA concentration decreased (linear, P < .01) and D(-)-lactate (linear, P < .01) and L(+)- lactate (linear, P = .07) concentrations increased with increasing ruminal glucose. Activities of amylase and lipase in plasma were not affected by ruminal glucose (P > .10). Ten days after the acidosis insult, rumens were evacuated and contents were replaced with an isotonic Cr:VFA solution to measure ruminal VFA absorption. Ruminal fluid was collected hourly from 0 to 6 h. Fractional rate of acetate absorption was 13% lower for lambs receiving 18 g/kg BW glucose than for control lambs. In addition, fractional liquid passage rate was lower (P < .05) in lambs receiving 18 g/kg BW glucose 6 mo after the insult of acidosis. These data suggest that a short-term, severe insult of acute acidosis does not result in pancreatic tissue damage but may result in reduced ruminal VFA absorption for an extended period of time.

The effects of protein supplementation and infection with Trichostrongylus colubriformis on production responses and immune function in young sheep and on nematode population dynamics were assessed. Eighty-four 3-month-old Merino wether sheep were housed in individual pens and fed ad libitum chopped oaten hay containing 0.5% urea, together with 50 g day-1 lucerne meal. Fish meal (FM) was given as a source of protected protein at 0, 50 or 100 g day-1 (FM0, FM50, FM100; from Days --28 to 140). From Days 1 to 140, 0 or 1000 T. colubriformis infective larvae were given on Mondays, Wednesdays and Fridays. Infected sheep were slaughtered after 35, 70, 105, or 140 days of infection. Live-weight gain was reduced significantly by infection with T. colubriformis in sheep given FM0, but not in sheep given FM50 or FM100. Greasy wool production and fibre diameter were increased by FM, whereas the effects of infection with T. colubriformis on wool measurements depended on the level of FM given. Worm egg concentrations in faeces were significantly lower for sheep given FM100 than for those given FM0 or FM50 during the last 28 days of infection. Similarly, the apparent rate of worm expulsion was considerably higher in sheep given FM than in those not given FM. The rate of expulsion of T. colubriformis correlated with levels of circulating eosinophils as well as with the concentration of intestinal sheep mast cell proteases. Levels of parasite-specific and non-specific circulating antibodies were either unaffected or reduced as a result of supplementation with FM, although lymphocyte stimulation in vitro in response to T. colubriformis third stage larval antigen was enhanced significantly in infected animals given FM100. It was concluded that supplementary feeding with FM substantially reduced the production losses attributable to infection with T. colubriformis and was associated with enhanced expulsion of the parasite burden.

Mortalities due to digestive disturbances occur in homozygous grey and white lambs after they have reached weaning age. Milk-filled, distended rumens, due to malfunctioning of the oesophageal groove, are found 24 h after birth. Scanning electron microscopical studies revealed that milk caused sloughing of the luminal cells in the forestomachs of the affected lambs, while no sloughing of cells was apparent in control black lambs. The purpose of this study was to compare the ultrastructure of the forestomach mucosa of grey, white and black Karakul lambs; to determine whether the sloughing of luminal cells was evident in sections; and, if possible, to find a reason for the desquamation of the cells. Samples of the forestomach of grey, white and black Karakul lambs were prepared routinely for electron microscopy and studied with a Phillips electron microscope. In all the lambs the mucosa of the forestomach was a stratified squamous epithelium consisting of a stratum basale, stratum spinosum and stratum corneum. In the grey and white lambs the luminal cells of the stratum corneum were electron dense, non-nucleated and vacuolated. Sloughing of luminal cells was observed. In the black lambs no sloughing of cells was evident and the luminal cells were moderately electron-dense, nucleated elements. Desquamation of the luminal cells in the affected lambs revealed the underlying layer with its exposed desmosomal attachment sites. This explained the differences in the appearance of the luminal cells in the three groups of lambs as revealed by the scanning electron microscope.

Health disturbances of ruminal origin in cattle are summed up. The problems are classified in those caused by special feed (NPN for example), those caused by insufficient ruminal detoxication capacity (poisoning by nitrate or aliphatic N-derivates) and belonging to ruminal toxin production (3-methyl-indole, S-methyl-cysteine-sulfoxide, glucosinolates) and arranged in pathophysiological sense.

Methscopolamine was used to induce ruminal stasis in calves. Clinical and blood biochemical parameters were studied to judge the possible role of gastro-intestinal endotoxins from Gram-negative bacteria. Two trials were carried out where one injection of 100 mg and 3 consecutive injections of 70 mg of methscopolamine were administered. The animals showed signs of ruminal stasis. General clinical signs and changes in blood biochemical parameters were similar to what is found in endotoxaemia or in induced ruminal acidosis. Relevant parameters such as prostaglandin F2 alpha metabolite, endotoxin, iron, zinc, calcium and glutamate dehydrogenase changed significantly indicating exposure of endotoxins.