Effects of dietary forage neutral detergent fiber and rumen degradable starch ratios on chewing activity, ruminal fermentation, ruminal microbes and nutrient digestibility of Hu sheep fed a pelleted total mixed ration.

Pelleted total mixed ration (P-TMR) feeding, which has become a common practice in providing nutrition for fattening sheep, requires careful consideration of the balance between forage neutral detergent fiber (FNDF) and rumen degradable starch (RDS) to maintain proper rumen functions. The present study aimed to investigate the effects of the dietary FNDF/RDS ratio (FRR) on chewing activity, ruminal fermentation, ruminal microbes, and nutrient digestibility in Hu sheep fed a P-TMR diet. This study utilized eight ruminally cannulated male Hu sheep, following a 4 × 4 Latin square design with 31 d each period. Diets consisted of four FRR levels: 1.0 (high FNDF/RDS ratio, HFRR), 0.8 (middle high FNDF/RDS ratio, MHFRR), 0.6 (middle low FNDF/RDS ratio, MLFRR), and 0.4 (low FNDF/RDS ratio, LFRR). Reducing the dietary FRR levels resulted in a linear decrease in ruminal minimum pH and mean pH, while linearly increasing the duration and area of pH below 5.8 and 5.6, as well as the acidosis index. Sheep in the HFRR and MHFRR groups did not experience subacute ruminal acidosis (SARA), whereas sheep in another two groups did. The concentration of total volatile fatty acid and the molar ratios of propionate and valerate, as well as the concentrate of lactate in the rumen linearly increased with reducing dietary FRR, while the molar ratio of acetate and acetate to propionate ratio linearly decreased. The degradability of NDF and ADF for alfalfa hay has a quadratic response with reducing the dietary FRR. The apparent digestibility of dry matter, organic matter, neutral detergent fiber, and acid detergent fiber linearly decreased when the dietary FRR was reduced. In addition, reducing the dietary FRR caused a linear decrease in OTUs, Chao1, and Ace index of ruminal microflora. Reducing FRR in the diet increased the percentage of reads assigned as Firmicutes, but it decreased the percentage of reads assigned as Bacteroidetes in the rumen. At genus level, the percentage of reads assigned as Prevotella, Ruminococcus, Succinivibrio, and Butyrivibrio linearly decreased when the dietary FRR was reduced. The results of this study demonstrate that the dietary FRR of 0.8 is crucial in preventing the onset of SARA and promotes an enhanced richness of ruminal microbes and also improves fiber digestibility, which is a recommended dietary FRR reference when formulating P-TMR diets for sheep.

Forage neutral detergent fiber (FNDF) and rumen degradable starch (RDS) are key components of carbohydrates in the diet for ruminants, which would reflect saliva secretion and the acid production potential of feed. However, appropriate FNDF to RDS ratios (FRR) applicable to ruminants under the condition of pelleted total mixed ration (P-TMR) feeding have not been reported. In this study, we investigated the effects of the dietary FRR on chewing activity, ruminal fermentation, ruminal microbial communities, and nutrient digestibility of Hu sheep under P-TMR feeding. The results indicate that reducing dietary FRR levels would induce acidosis in sheep, which negatively affected fiber utilization and ruminal bacterial communities. The FRR of 0.8 was a recommended dietary FRR when formulating a P-TMR diet for fattening sheep, as indicated by decreased ruminal acidosis risk and increased richness of ruminal microbes in the rumen as well as nutrient digestibility.

Metabolomics and proteomics insights into subacute ruminal acidosis etiology and inhibition of proliferation of yak rumen epithelial cells in vitro.

BACKGROUND: Untargeted metabolomics and proteomics were employed to investigate the intracellular response of yak rumen epithelial cells (YRECs) to conditions mimicking subacute rumen acidosis (SARA) etiology, including exposure to short-chain fatty acids (SCFA), low pH5.5 (Acid), and lipopolysaccharide (LPS) exposure for 24 h. RESULTS: These treatments significantly altered the cellular morphology of YRECs. Metabolomic analysis identified significant perturbations with SCFA, Acid and LPS treatment affecting 259, 245 and 196 metabolites (VIP > 1, P < 0.05, and fold change (FC) ≥ 1.5 or FC ≤ 0.667). Proteomic analysis revealed that treatment with SCFA, Acid, and LPS resulted in differential expression of 1251, 1396, and 242 proteins, respectively (FC ≥ 1.2 or ≤ 0.83, P < 0.05, FDR < 1%). Treatment with SCFA induced elevated levels of metabolites involved in purine metabolism, glutathione metabolism, and arginine biosynthesis, and dysregulated proteins associated with actin cytoskeleton organization and ribosome pathways. Furthermore, SCFA reduced the number, morphology, and functionality of mitochondria, leading to oxidative damage and inhibition of cell survival. Gene expression analysis revealed a decrease the genes expression of the cytoskeleton and cell cycle, while the genes expression associated with inflammation and autophagy increased (P < 0.05). Acid exposure altered metabolites related to purine metabolism, and affected proteins associated with complement and coagulation cascades and RNA degradation. Acid also leads to mitochondrial dysfunction, alterations in mitochondrial integrity, and reduced ATP generation. It also causes actin filaments to change from filamentous to punctate, affecting cellular cytoskeletal function, and increases inflammation-related molecules, indicating the promotion of inflammatory responses and cellular damage (P < 0.05). LPS treatment induced differential expression of proteins involved in the TNF signaling pathway and cytokine-cytokine receptor interaction, accompanied by alterations in metabolites associated with arachidonic acid metabolism and MAPK signaling (P < 0.05). The inflammatory response and activation of signaling pathways induced by LPS treatment were also confirmed through protein interaction network analysis. The integrated analysis reveals co-enrichment of proteins and metabolites in cellular signaling and metabolic pathways. CONCLUSIONS: In summary, this study contributes to a comprehensive understanding of the detrimental effects of SARA-associated factors on YRECs, elucidating their molecular mechanisms and providing potential therapeutic targets for mitigating SARA.

Development of an experimental model for liver abscess induction in Holstein steers using an acidotic diet challenge and bacterial inoculation.

Holstein steers (n = 40; initial BW = 84.9 ±â€…7.1 kg) were used to study the genesis of liver abscesses (LA) using an acidotic diet challenge with or without intraruminal bacterial inoculation. Steers were housed in individual pens inside a barn and randomly assigned to one of three treatments: (1) low-starch control diet comprised primarily of dry-rolled corn and wet corn gluten feed (CON); (2) high-starch acidotic diet with steam-flaked corn (AD); or (3) acidotic diet plus intraruminal inoculation with Fusobacterium necrophorum subsp. necrophorum (9.8 × 108 colony forming units [CFU]/mL), Trueperella pyogenes (3.91 × 109 CFU/mL), and Salmonella enterica serovar Lubbock (3.07 × 108 CFU/mL), previously isolated from LA (ADB). Steers in AD and ADB were fed the acidotic diet for 3 d followed by 2 d of the CON diet, and this cycle was repeated four times. On day 23, ADB steers were intraruminally inoculated with the bacteria. At necropsy, gross pathology of livers, lungs, rumens, and colons was noted. Continuous data were analyzed via mixed models as repeated measures over time with individual steer as the experimental unit. Mixed models were also used to determine the difference in prevalence of necropsy scores among treatments. Ruminal pH decreased in AD and ADB steers during each acidotic diet cycle (P ≤ 0.05). LA prevalence was 42.9% (6 of 14) in ADB vs. 0% in AD or CON treatments (P < 0.01). Ruminal damage was 51.1% greater in ADB than in AD (P ≤ 0.04). Culture of LA determined that 100% of the abscesses contained F. necrophorum subsp. necrophorum, 0% contained T. pyogenes, 50% contained Salmonella, and 50% contained a combination of F. necrophorum subsp. necrophorum and Salmonella. The F. necrophorum subsp. necrophorum was clonally identical to the strain used for the bacterial inoculation based on phylogenetic analysis of the whole genome. This experimental model successfully induced rumenitis and LA in Holstein steers and confirms the central dogma of LA pathogenesis that acidosis and rumenitis lead to the entry of F. necrophorum into the liver to cause abscesses. Our findings suggest that an acidotic diet, in conjunction with intraruminal bacterial inoculation, is a viable model to induce LA. Further research is needed to determine the repeatability of this model, and a major application of the model will be in evaluations of novel interventions to prevent LA.

Liver abscesses (LA) in feedlots are costly to the beef industry. At harvest, LA cause an increase in liver condemnations, carcass trimming, and a decrease in quality grade. The objective of this research was to develop an experimental LA model in Holstein steers using an acidotic diet with and without intraruminal inoculation of bacteria involved in LA formation. These data suggest acidotic diet challenges in conjunction with bacterial inoculation were able to induce LA in Holstein steers. The acidotic diet alone caused reduced rumen content pH and caused rumen wall inflammation and damage, observed at harvest. Nonetheless, the addition of bacteria had a compounding effect on rumen damage. Both bacteria inoculated were isolated from 57% of LA suggesting they may work in synergy to form LA.

Elucidating the factors and consequences of the severity of rumen acidosis in first-lactation Holstein cows during transition and early lactation.

First-lactation cows are particularly prone to subacute ruminal acidosis (SARA) during transition. Besides common risk factors of SARA, such as feeding of starch-rich diets, an individual severity of SARA in cows has been recently evidenced. Yet, the factors that play a role in SARA severity have not been elucidated. The main goal of this research was to evaluate the factors of SARA severity in first-lactation cows during transition and early lactation, which go beyond high-grain feeding, and to explore their impact on behavior, health, and fermentation in the rumen and hindgut. Twenty-four first-lactation Holstein cows with the same feeding regime were used starting from 3 wk before the expected calving day until 10 wk postpartum. Cows received a close-up diet (32% concentrate) until calving and were then transitioned to a lactation diet (60% concentrate) within 1 week. The SARA severity was assessed by cluster analysis of several rumen pH metrics, which revealed exceptionally longer and more severe SARA in cows denominated as high (n = 9), as compared to moderate (n = 9) and low (n = 6) SARA severity cows (P < 0.01). The logistic analysis showed that the length of close-up feeding, age at parturition, and the level of dry matter intake (DMI) were the main factors that influenced the cows' odds for high SARA severity (each P ≤ 0.01). Moreover, the ANOVA hinted differences in the metabolic activity of the ruminal microbiome to promote SARA severity, as indicated by highest ruminal propionate proportions (P = 0.05) in high SARA severity cows, also with similar DMI. The distinct SARA severity was marginally reflected in behavior and there were no effects of SARA severity or high-grain feeding on blood inflammation markers, which peaked at parturition regardless of SARA severity (P < 0.01). Still, ongoing high-grain feeding increased liver enzyme concentrations from 6 wk postpartum on, compared to weeks before (P < 0.01), yet irrespectively of SARA severity. In conclusion, first-lactation cows differed in SARA severity under the same feeding regime, which was ascribed to management factors and differences in ruminal fermentation. Further research is warranted to validate these findings and to understand the mechanisms behind differences in the metabolic function of rumen microbiome, in particular in terms of evaluating markers for various SARA severity, as well as to evaluate potential long-term effects on health, performance, fertility, and longevity of dairy cows.

The present study reports a high variation of severity of subacute rumen acidosis in first-lactation dairy cows with the same feeding regimen close to parturition and until 10 weeks after parturition. Six significant factors influencing this severity were identified, including in particular length of close-up period, age at parturition, and dry matter intake. Therefore, management factors seem to play a key role for the development of a severe subacute rumen acidosis. Cows with high severity showed marginally altered behavior but distinct rumen fermentation patterns compared to cows with low severity, suggesting also a key role of the ruminal microbiome for subacute rumen acidosis risk in cows. The higher severity was not associated with systemic inflammation and all cows remained healthy.

Perianesthetic metabolic acidosis is associated with 2% dorzolamide eye drops in dogs that underwent ophthalmic surgery: a retrospective study (2019-2022).

OBJECTIVE: To evaluate whether the administration of 2% dorzolamide ophthalmic solution in dogs undergoing ophthalmic surgery is associated with perianesthetic metabolic acidosis. ANIMALS: 60 dogs, with or without dorzolamide administration, underwent arterial blood gas analysis immediately after anesthesia for ophthalmic surgery between 2019 and 2022; a total of 60 surgeries were evaluated. METHODS: This was a retrospective cross-sectional study. Logistic regression analysis was performed to investigate the association between the administration of 2% dorzolamide ophthalmic solution in dogs and the development of metabolic acidosis. Additionally, the influence of various potential risk factors, including age, body weight, sex, use of topical or systemic NSAIDs, and preoperative medications on the occurrence of metabolic acidosis, was evaluated. RESULTS: A significant association was found between the use of 2% dorzolamide ophthalmic solution and perianesthetic metabolic acidosis (OR, 6.79; 95% CI, 2.00 to 23.02; P = .002). Furthermore, topical dorzolamide administration was significantly associated with both perianesthetic hypokalemia (OR, 3.52; 95% CI, 1.11 to 11.20; P = .033) and perianesthetic hyperchloremia (OR, 9.25; 95% CI, 1.71 to 50.01; P = .010). CLINICAL RELEVANCE: The use of 2% dorzolamide ophthalmic solution is associated with perianesthetic metabolic acidosis, hypokalemia, and hyperchloremia in dogs. It is prudent to be aware of these risks, especially before anesthesia.

Acidosis defense mechanisms in the preimplantation stages of embryos in BALB/c strain mice.

Regulation of intracellular pH (pHi) is an important homeostatic function of cells. There are three major pHi regulatory mechanisms: the HCO3-/Cl- exchanger (AE), which alleviates alkalosis, and the Na+/H+ exchanger (NHE) and Na+,HCO3-/Cl- exchanger (NDBCE), both of which counteract acidosis. NHE activity, which is high at the germinal vesicle stage of oocyte, is inhibited during meiotic maturation, while this inhibition is abolished when the oocyte reaches the pronuclear (PN) stage of the zygote. On the other hand, we have previously found that NDBCE performs complementary regulation against acidosis during meiotic maturation. Additionally, we found that AE activity, which is a defense mechanism against alkalosis, gradually decreases during preimplantation period of embryonic development. Considering that NHE activity is inhibited during meiotic maturation and AE activity gradually decreases during embryonic development stages, we investigated whether NHE and NDBCE activities, both of which act against acidosis, functionally change from the PN zygote to the blastocyst stage of the embryo and identified these pH-regulating proteins at the molecular level in mice of the Balb/c strain. PN zygotes, two-cell (2-c), four-cell (4-c), morula and blastocyst stage embryos were obtained from 5-8-week-old, sexually mature female Balb/c mice by using the classical superovulation procedure. pHi was recorded by using the microspectrofluorometric technique on zygotes and embryos simultaneously loaded with the pH-sensitive fluorophore, 2',7'-Bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF). The activities of NHE and NDBCE were determined from the recovery curve of induced-acidosis in bicarbonate-free and bicarbonate-containing media, respectively. Specific inhibitors such as cariporide (1 µM), S3226 (1 and 10 µM), EIPA (1, 5, and 25 µM), and amiloride (1 mM) were used to functionally identify NHE isoforms, and the nonspecific inhibitor 4,4'-diisocyanatostilbene-2,2' disulphonic acid, disodium salt (DIDS) was used to confirm NDBCE activity. The isoforms of the pHi-regulatory proteins were also identified by molecular biology using real-time PCR. We found that NHE activity was high at all embryonic stages, and differences between stages were not significant. Functional and molecular findings indicated that isoforms of NHE 1 and 5 are present in the blastocyst, whereas isoforms of NHE 1, 3, and 4 are functional at earlier embryonic stages. Although the contribution of NDBCE activity to recovery from induced-acidosis was detected at all embryonic stages, it was significant only in the PN zygote and the 2-c embryo. This finding was confirmed by molecular analysis, which detected the expression of SLC4A8 encoding NDBCE at all embryonic stages. In conclusion, NHE is an active and important defense mechanism against acidosis and is encoded by at least two protein isoforms in all stages of the Balb/c strain of mice. NDBCE has a supportive function in all embryonic stages, especially in the PN zygote and the 2-c embryo. Preimplantation stage embryos have effective mechanisms to defend against acidosis in response to their metabolic end products (increased acid load) and the acidic environment in utero.

Effects of two oral electrolyte solutions in healthy newborn lambs.

This study aimed to evaluate the effects of two oral electrolyte solutions (OES), commercialized for the hydration of calves, on the water, electrolyte, and acid-base balance of newborn lambs. Twenty healthy crossbred Santa Inês lambs, 10 days old, 4-5 kg of body weight (BW), and fed on mother's milk, were included. The OES tested were slightly hyposmolar (OES 1: 279 mOsm/L; and OES 2: 283 mOsm/L) and had an alkalizing potential with an effective strong ion difference (SID3) of 76 mmol/L (OES 1) and 58 mmol/L (OES 2). In a crossover design, all lambs received the two OES, one at a time, with an interval of 7 days. On the day of treatment, the lambs received a volume corresponding to 5% of BW administered by esophageal tube at 0 and 6 h. Physical examinations were performed and venous blood samples were taken at 0, 6, 12, 24, and 48 h. Packed cell volume, total plasma protein, pH, partial pressure of carbon dioxide, bicarbonate ion, base excess, sodium (Na+), potassium, chloride (Cl-), SID3, L-lactate, glucose, anion gap, total concentration of non-volatile weak acids, and percentage change in plasma volume were measured. Data were analyzed by two-way repeated measures ANOVA. OES caused iatrogenic imbalances characterized by expansion of plasma volume, change in the Na+ and Cl- ratio with increase in plasma SID3, and strong ion metabolic alkalosis. These imbalances were mostly reversed 24 h after the start of treatment and did not differ (P > 0.05) between the two tested OES. The absence of side effects indicates that the tested commercial OES are safe for use in newborn lambs. Further studies are needed to prove the therapeutic efficacy of these OES in dehydrated sick lambs with metabolic acidosis.

Characterization of a model of hindgut acidosis in mid-lactation cows: A pilot study.

The objective of this pilot study was to generate data to support the development of an experimental model of hindgut acidosis to further understand its systemic consequences independently of rumen acidosis. Four ruminally fistulated multiparous Holstein cows (213 ± 11 d in milk) were subjected to 2 consecutive experimental periods (P1 and P2), separated by a 3-d washout. Experimental periods were 96 h long from the baseline to the final measurements but expanded over 5 calendar days (d 0-4). Abomasal infusions of saline and corn starch (2.8 kg/d) were performed for the first 72 h (d 0-3) of P1 and P2, respectively. Final measurements were performed 24 h after the end of the infusions (d 4). Each cow was used as its own control by comparing P2 to P1. Postruminal-intestinal permeability was assessed by Cr appearance in blood after a pulse dose administration of Cr-EDTA into the abomasum on d 2 (48 h after infusion initiation) of each period. Starch infusion during P2 was associated with a milk protein yield increase (3.3%) and a decrease in milk urea nitrogen (11%). Fecal dry matter increased (8.8%), and starch content tended to increase (∼2 fold) during P2. There was a period-by-day interaction for fecal pH as it decreased during starch infusion (1.3 pH points) but remained constant during P1. Although fecal lactate was not detectable during P1, it consistently increased during starch infusion. Fecal alkaline phosphatase activity also increased (∼17 fold) in association with starch infusion. Two hours after Cr-EDTA administration, blood Cr concentration was higher during starch infusion, resulting in a tendency for a treatment-by-hour interaction. Furthermore, blood d-lactate increased (∼2.5 fold), serum Cu decreased (18%), and blood urea nitrogen, cholesterol, and Ca tended to decrease (9.4%, 1.2%, and 2.4%, respectively), relative to P1. The current results suggest that hindgut acidosis was successfully induced by postruminal starch infusion, leading to gut damage and increased intestinal permeability. However, indications of systemic inflammation were not observed. The herein described preliminary results will require confirmation in a properly powered study.

Can computerized rumen mucosal colorimetry serve as an effective field test for managing subacute ruminal acidosis in feedlot cattle?

Subacute ruminal acidosis (SARA) is one of the major nutritional disorders in the dairy and beef industries, leading to significant financial losses. Diagnosing SARA is challenging due to the need to evaluate multiple parameters, such as milk fat/protein ratio, ruminal lactate, and hemogram, instead of relying on a single definitive symptom or diagnostic method. This study aimed to evaluate the effectiveness of computerized rumen colorimetry in detecting SARA in beef cattle. Over one year, 75 cattle aged 8-10 months from five farms were periodically monitored for rumen pH prior to slaughter. Samples of rumen wall and rumen content were obtained at slaughter for analysis. The study found a positive correlation coefficient between rumen pH and color components, particularly for Red (0.853) and color lightness (L) (0.862). The darkening of the rumen epithelium's color was attributed to the effect of rumen pH on the keratinized layer of the epithelium. Furthermore, an increase in the thickness of ruminal epithelium layers, particularly non-keratinized and total epithelium, was observed in animals with a history of SARA. It is possible that the lower rumen pH increases the rate of replacement of the keratinized epithelium, and the non-keratinized epithelium overgrows to compensate for the need to of produce keratinized layers. In conclusion, computerized rumen colorimetry shows promise as a reliable method for managing SARA in bovine farms by monitoring the condition in the slaughterhouse. Further research is needed to evaluate its effectiveness in detecting SARA in live animals.

Association of the type of metabolic acidosis and non-survival of horses with colitis.

Background: Metabolic acidosis (MA) is the most common acid-base disorder reported in horses with colitis but its association with survival is yet to be determined. Objective: Investigate the types of MA in horses with colitis to determine effects of various anions on fatality rates. Animals and procedures: We studied 158 horses with colitis. Horses were classified into 4 groups depending on the anion contributing to MA: i) no MA, ii) lactic acidosis (LA), iii) unmeasured strong ion (USI) acidosis, and iv) hyperchloremic acidosis (HA). Results: Sixty percent (95/158) of horses had no MA, 22% (34/158) had LA, 12% (19/158) had HA, and 6% (10/158) had USI acidosis. The fatality rate of horses without MA was 20% (20/95), whereas the rates for those with LA, USI, and HA were 53% (18/34), 30% (3/10), and 16% (3/19), respectively. Horses with LA were more likely to die or be euthanized than horses without MA (OR: 4.2, 95% CI: 1.83 to 9.72, P < 0.001) and HA (OR: 5.9, 95% CI: 1.47 to 24.4, P < 0.01). Conclusion and clinical relevance: Lactic acidosis was the most common type of MA in horses with colitis, and it was associated with non-survival.

Association du type d'acidose métabolique et de non-survie des chevaux atteints de colite. Historique: L'acidose métabolique (AM) est le trouble acido-basique le plus fréquemment signalé chez les chevaux atteints de colite, mais son association avec la survie reste à déterminer. Objectif: Étudier les types d'AM chez les chevaux atteints de colite pour déterminer les effets de divers anions sur les taux de mortalité. Animaux et procédures: Nous avons étudié 158 chevaux atteints de colite. Les chevaux ont été classés en 4 groupes en fonction de l'anion contribuant à l'AM : i) pas d'AM, ii) acidose lactique (LA), iii) acidose à ions forts non mesurés (USI) et iv) acidose hyperchlorémique (HA). Résultats: Soixante pour cent (95/158) des chevaux n'avaient pas d'AM, 22 % (34/158) avaient une LA, 12 % (19/158) avaient une HA et 6 % (10/158) avaient une acidose USI. Le taux de mortalité des chevaux sans AM était de 20 % (20/95), tandis que les taux de ceux avec LA, USI et HA étaient de 53 % (18/34), 30 % (3/10) et 16 % (3/19), respectivement. Les chevaux atteints de LA étaient plus susceptibles de mourir ou d'être euthanasiés que les chevaux sans AM (OR : 4,2, IC à 95 % : 1,83 à 9,72, P < 0,001) et HA (OR : 5,9, IC à 95 % : 1,47 à 24,4, P < 0,01). Conclusion et pertinence clinique: L'acidose lactique était le type d'AM le plus courant chez les chevaux atteints de colite et elle était associée à la non-survie.(Traduit par Dr Serge Messier).

Effects of feed additives on rumen function and bacterial and archaeal communities during a starch and fructose challenge.

The objective of this study was to improve understandings of the rumen microbial ecosystem during ruminal acidosis and responses to feed additives to improve prudent use strategies for ruminal acidosis control. Rumen bacterial and archaeal community composition (BCC) and its associations with rumen fermentation measures were examined in Holstein heifers fed feed additives and challenged with starch and fructose. Heifers (n = 40) were randomly allocated to 5 treatment groups: (1) control (no additives); (2) virginiamycin (VM; 200 mg/d); (3) monensin (MT; 200 mg/d) + tylosin (110 mg/d); (4) monensin (MLY; 220 mg/d) + live yeast (5.0 × 1012 cfu/d); (5) sodium bicarbonate (BUF; 200 g/d) + magnesium oxide (30 g/d). Heifers were fed twice daily a 62% forage:38% concentrate total mixed ration at 1.25% of body weight (BW) dry matter (DM)/d for a 20-d adaptation period with their additive(s). Fructose (0.1% of BW/d) was added to the ration for the last 10 d of adaptation. On d 21 heifers were challenged once with a ration consisting of 1.0% of BW DM wheat and 0.2% of BW fructose plus their additive(s). A rumen sample was collected from each heifer via stomach tube weekly (d 0, 7, 14) and 5 times over a 3.6 h period at 5, 65, 115, 165, and 215 min after consumption of the challenge ration (d 21) and analyzed for pH, and ammonia, d- and l-lactate, volatile fatty acids (VFA), and histamine concentrations and total bacteria and archaea. The 16S rRNA gene spanning the V4 region was PCR amplified and sequenced. Alpha and ß diversity and associations of relative abundances of taxa with rumen fermentation measures were evaluated. Rumen BCC shifted among treatment groups in the adaptation period and across the challenge sampling period, indicating the feed additives had different modes of action. The monensin-containing treatment groups, MT and MLY often had similar relative abundances of rumen bacterial phyla and families. The MLY treatment group was characterized in the challenge period by increased relative abundances of the lactate utilizing genera Anaerovibrio and Megasphaera. The MLY treatment group also had increased diversity of ruminal bacteria which may provide resilience to changes in substrates. The control and BUF treatment groups were most similar in BCC. A redundancy analysis showed the MLY treatment group differed from all other treatment groups and concentrations of histamine and valerate in the rumen were associated with the most variation in the microbiota, 5.3% and 4.8%, respectively. It was evident from the taxa common to all treatment groups that cattle have a core microbiota. Functional redundancy of rumen bacteria which was reflected in the greater sensitivity for the rumen BCC than rumen fermentation measures likely provide resilience to changes in substrate. This functional redundancy of microbes in cattle suggests that there is no single optimal ruminal microbial population and no universally superior feed additive(s). In summary, differences in modes of action suggest the potential for more targeted and improved prudent use of feed additives with no single feed additive(s) providing an optimal BCC in all heifers.

Effect of short-term abomasal corn starch infusions on postruminal fermentation and blood measures.

It is possible that some of the systemic responses to subacute ruminal acidosis (SARA) may be caused by increased intestinal starch fermentation. The objective of this experiment was to evaluate the effect of abomasal infusion of up to 3 g of corn starch/kg body weight (approximately 1.6 kg of starch/d) on fecal measures of fermentation, plasma acute phase proteins, and white blood cell populations. Six ruminally cannulated cows in late lactation were randomly assigned to duplicate 3 × 3 Latin squares with 21-d periods. Cows were fed a 20.6% starch TMR twice daily and during the last 7 d of each period cows were abomasally infused with corn starch at 0 (CON), 1 (ST1), or 3 (ST3) g/kg body weight split into 2 bolus infusions, provided every 12 h. Fecal samples were collected at 0, 6, 12, and 18 h following feeding on d 21 and were analyzed for pH, VFA, lactic acid, and lipopolysaccharide (LPS). Composite fecal samples were used to estimate apparent total-tract nutrient digestibility using undigested neutral detergent fiber as an internal marker. Blood samples were collected at 0 and 6 h relative to feeding on d 14, 18, and 21 of each period. Concentrations of haptoglobin and serum amyloid A in plasma were measured in all samples, 0 h samples on d 14 and 21 were used to measure white blood cell populations, and 0 h samples from d 14, 18, and 21 were used for flow cytometric analysis of γδ T cells. Data were analyzed in SAS using models that included fixed effects of treatment and period and the random effects of cow and square. For blood measures, d 14 samples collected before the initiation of abomasal infusions were included as covariates. Time (d or h) was added as a repeated measure in variables that included multiple samples during the abomasal infusion period. A contrast was used to determine the linear effect of increasing abomasal corn starch. Abomasal corn starch linearly decreased fecal pH and linearly increased fecal total VFA and LPS, but effects were modest, with fecal pH, total VFA, and LPS changing from 6.96, 57.7 mM, and 4.14 log10 endotoxin units (EU) per gram for the CON treatment to 6.69, 64.1 mM, and 4.58 log10 EU/g for the ST3 treatment, respectively. This suggests that we did not induce hindgut acidosis. There were no effects of treatment on apparent total-tract starch digestibility or fecal starch content (mean of 96.9% and 2.2%, respectively). Treatment did not affect serum acute phase proteins or most circulating white blood cells, but the proportion of circulating γδ T cells tended to linearly decrease from 6.69% for CON to 4.61% for ST3. Contrary to our hypothesis, increased hindgut starch fermentation did not induce an inflammatory response in this study.

Acid-base and electrolyte evaluation in dogs with upper GI obstruction: 115 dogs (2015-2021).

OBJECTIVES: Metabolic alkalosis, although uncommon in small animals, has been previously associated with gastrointestinal obstructions. Depending on the population and disease process evaluated, previous prevalence of metabolic alkalosis is reported as ranging from 2% to 45% in canine patients. The objective of this study was to determine the prevalence of metabolic alkalosis and other acid-base and electrolyte disorders in a cohort of dogs with a confirmed upper gastrointestinal obstruction. MATERIALS AND METHODS: Electronic medical records were reviewed to identify dogs who presented for vomiting with evidence of an upper gastrointestinal obstruction from January 2015 to October 2021. Patients were enrolled only if a preoperative venous blood gas was obtained and analysed in house. Traditional acid-base analysis was utilised to determine an acid-base status before relieving the obstruction. When available, post-operative venous acid-base status was determined within 24 hours after surgery, and compared to preoperative results. RESULTS: A total of 115 dogs were included in the study. Twenty-five out of 115 (22%) dogs displayed either a simple metabolic alkalosis or a mixed acid-base disturbance before surgery. Twenty-seven out of 115 dogs (37%) had a normal acid-base status at entry. Seventy-one dogs had pre- and post-operative venous blood gas results available. Metabolic alkalosis was resolved in nearly all patients post-operatively, with no patients displaying a simple metabolic alkalosis. A mixed metabolic acidosis and respiratory alkalosis was the most common condition post-operatively, found in 25 of 71 (35%) dogs. Severe derangements of electrolytes were infrequent preoperatively (3/115; 2.6%). A majority of patients in this study exhibited hypokalaemia (64.4%), hypochloraemia (72.8%) and hyponatraemia (77.4%) on preoperative venous blood gases. Venous pH, Pv CO2 , bicarbonate and base excess were significantly higher preoperatively when compared to the post-operative results. CLINICAL SIGNIFICANCE: This study found the prevalence of pre-operative metabolic alkalosis in dogs with a documented upper gastrointestinal obstruction to be lower than previously reported. Surgical or endoscopic alleviation of the upper gastrointestinal obstruction resulted in resolution of metabolic alkalosis in nearly all patients.

Variability in chewing, ruminal fermentation, digestibility and bacterial communities between subacute ruminal acidosis-susceptible and acidosis-tolerant sheep.

Sorting behaviour is a common phenomenon observed in ruminants when they are provided with a total mixed ration, which contributes to variations in the severity of subacute ruminal acidosis (SARA). Pelleted total mixed ration (PTMR) reduces sorting, but high-grain content increases acidosis risk. However, whether the variability in the severity of SARA exists in sheep fed the same high-grain PTMR is less understood. This study aimed to investigate SARA variability among individual sheep offered a high-grain PTMR, considering chewing activity, ruminal fermentation, bacterial communities and nutrient digestibility. Twenty ruminally cannulated male Hu sheep were individually housed in cages and fed a PTMR comprising 80% concentrate mix and 20% roughage. A 14-day adaptation period to the diet and facilities was provided before a 10-day sample collection period. Continuous monitoring of ruminal pH was conducted for 48 h, during which time chewing activity was also recorded. Ruminal fluid samples were collected for analysis of volatile fatty acid and microbial DNA extraction. Faecal samples were collected to measure nutrient digestibility. Based on their acidosis index, the sheep were classified into two groups: SARA-susceptible group (n = 6) and SARA-tolerant group (n = 6). The SARA-susceptible sheep exhibited a lower ruminal mean pH and minimum pH than the SARA-tolerant sheep (P < 0.05). Additionally, the SARA-susceptible group increased the acidosis index, duration and areas of pH below 5.8 and 5.6 compared to the SARA-tolerant group (P < 0.05). The SARA-susceptible group also exhibited a longer ruminating time than the SARA-tolerant group (P < 0.05). The SARA-susceptible group exhibited a tendency to increase the relative abundance of Firmicutes (P = 0.089), while simultaneously decreasing the copy number of Fibrobacter succinogenes in the rumen, as well as the digestibility of NDF and ADF compared to the SARA-tolerant group (P < 0.05). The acidosis index was found to be positively correlated with ruminating time (min/kg DM intake (DMI)) and total chewing time (min/kg DMI), but negatively correlated with the copy number of Fibrobacter succinogenes and Ruminococcus albus in the rumen. These findings indicate that there exists variability in the SARA severity among sheep when fed a high-grain PTMR, as evidenced by varied chewing activity, bacterial communities and nutrient digestibility. Ruminating time, total chewing time per kilogram of DMI as well as the copy number of Fibrobacter succinogenes and Ruminococcus albus in the rumen hold potential as indicators for assessing the severity of SARA.

The effects of antibiotic-free supplementation on the ruminal pH variability and methane emissions of beef cattle under the challenge of subacute ruminal acidosis (SARA).

Subacute ruminal acidosis (SARA) in feedlot cattle during the feed transition to grain-based diets is a significant constraint to animal health and productivity. This experiment assessed an antibiotic-free supplement (ProTect®) effects on ruminal pH variability and methane (CH4) emissions of cattle during the challenge of SARA. Ten 18-month-old Angus steers (472 ± 4.8 kg) were randomly allocated into monensin (n = 5) and ProTect® groups (n = 5) and progressively introduced to grain diets incorporating monensin or ProTect® for 36 days of the experiment [starter (7 days; 45% grain), T1 (7 days; 56% grain), T2 (7 days; 67% grain), finisher (15 days; 78% grain)]. The pH variability on the finisher period was reduced by the ProTect® supplement (6.6% vs. 5.2%; P < 0.01), with CH4 emissions being significantly higher relative to the monensin group [88.2 g/day (9.3 g CH4/kg DMI) vs. 133.7 g/day (14.1 g CH4/kg DMI); P < 0.01]. There was no difference between treatments in the time spent on the ruminal pH < 5.6 or < 5.8 (P > 0.05). The model evaluation for the ruminal pH variation indicated that the mean absolute error (MAE) proportion for both groups was good within the same range [4.05% (monensin) vs. 4.25% (ProTect®)] with identical root mean square prediction error (RMSPE) (0.34). It is concluded that the ProTect® supplement is an effective alternative to monensin for preventing SARA in feedlot cattle by managing ruminal pH variation during the transition to high-grain diets. Both monensin and ProTect® supplemented cattle exhibited lower CH4 yield compared to cattle fed forages and low-concentrate diets.

Evaluation of circulating microRNA profiles in blood as potential candidate biomarkers in a subacute ruminal acidosis cow model - a pilot study.

BACKGROUND: Subacute ruminal acidosis (SARA) is a metabolic disorder often observed in high-yielding dairy cows, that are fed diets high in concentrates. We hypothesized that circulating miRNAs in blood of cows could serve as potential candidate biomarkers to detect animals with metabolic dysbalances such as SARA. MicroRNAs (miRNAs) are a class of small non-coding RNAs, serving as regulators of a plethora of molecular processes. To test our hypothesis, we performed a pilot study with non-lactating Holstein-Friesian cows fed a forage diet (FD; 0% concentrate, n = 4) or a high-grain diet (HG; 65% concentrate, n = 4) to induce SARA. Comprehensive profiling of miRNA expression in plasma and leucocytes were performed by next generation sequencing (NGS). The success of our model to induce SARA was evaluated based on ruminal pH and was evidenced by increased time spent with a pH threshold of 5.8 for an average period of 320 min/d. RESULTS: A total of 520 and 730 miRNAs were found in plasma and leucocytes, respectively. From these, 498 miRNAs were shared by both plasma and leucocytes, with 22 miRNAs expressed exclusively in plasma and 232 miRNAs expressed exclusively in leucocytes. Differential expression analysis revealed 10 miRNAs that were up-regulated and 2 that were down-regulated in plasma of cows when fed the HG diet. A total of 63 circulating miRNAs were detected exclusively in the plasma of cows with SARA, indicating that these animals exhibited a higher number and diversity of circulating miRNAs. Considering the total read counts of miRNAs expressed when fed the HG diet, differentially expressed miRNAs ( log2 fold change) and known function, we have identified bta-miR-11982, bta-miR-1388-5p, bta-miR-12034, bta-miR-2285u, and bta-miR-30b-3p as potential candidates for SARA-biomarker in cows by NGS. These were further subjected to validation using small RNA RT-qPCR, confirming the promising role of bta-miR-30b-3p and bta-miR-2285. CONCLUSION: Our data demonstrate that dietary change impacts the release and expression of miRNAs in systemic circulation, which may modulate post-transcriptional gene expression in cows undergoing SARA. Particularly, bta-miR-30b-3p and bta-miR-2285 might serve as promising candidate biomarker predictive for SARA and should be further validated in larger cohorts.

Systematic review of the relationship between rumen acidosis and laminitis in cattle.

Laminitis is usually considered a consequence of digestive disorders that reduce ruminal pH. However, it is still not clear the direct relation between low ruminal pH provoked by excessive fast-digesting carbohydrate ingestion and laminitis, considering indicators, signs, and diagnosis aspects. This study aimed to clarify the association between different clinical presentations of laminitis with ruminal acidosis provoked by diet using the systematic review methodology. Three electronic databases were used: ISI Web of Science, PubMed, and Scopus. A total of 339 manuscripts were identified and only 16 were included. Manuscripts were published between 2000 and 2021 in 11 different peer-reviewed journals. Fifteen studies confirmed the occurrence of ruminal acidosis. The main indicators used were ruminal pH and clinical signs, such as anorexia, depression, discomfort and diarrhea. Two of the studies that administered oligofructose to induce acidosis and acute laminitis did not observe clinical signs of laminitis, using lameness score or hooves' sensitivity as an indicator. Various diagnostic methods were used to describe laminitis, like thermography, hoof biopsy, sensitivity test, and visual inspection. Although the variety of laminitis indicators used in the included studies, we evidence the existence of an association between diet (high level of fast-digesting carbohydrates), ruminal acidosis, and acute laminitis, mostly in the short-term acidosis' induction protocols, but the mechanism of action is still not clear.

A high-concentrate diet induces mitochondrial dysfunction by activating the MAPK signaling pathway in the mammary gland of dairy cows.

Subacute rumen acidosis can lead to mastitis in dairy cows. Mitochondrial dysfunction is closely related to the inflammatory response. This experiment was conducted to investigate the effects of a high-concentrate diet on mammary gland inflammation and mitochondrial damage in dairy cows. Twelve Holstein dairy cows in mid-lactation were randomly divided into 2 groups and fed a 40% concentrate (low concentrate, LC) diet or a 60% concentrate (high concentrate, HC) diet. Cows were fed individually, and the experiment lasted for 3 wk. After the experiment, mammary gland tissue, blood, and rumen fluid were collected. Compared with the LC diet, the HC diet significantly decreased rumen pH; the pH was <5.6 for more than 3 h. The HC diet also increased the concentration of LPS in the blood (7.17 ± 1.25 µg/mL vs. 12.12 ± 1.26 µg/mL), which indicated that feeding the HC diet successfully induced subacute rumen acidosis. The HC diet also increased the concentration of Ca2+ (34.80 ± 4.23 µg/g vs. 46.87 ± 7.24 µg/g) in the mammary gland and upregulated the expression of inflammatory factors IL-6 (1,128.31 ± 147.53 pg/g vs. 1,538.42 ± 241.38 pg/g), IL-1ß (69.67 ± 5.86 pg/g vs. 90.13 ± 4.78 pg/g), and tumor necrosis factor-α (91.99 ± 10.43 pg/g vs. 131.75 ± 17.89 pg/g) in mammary venous blood. The HC diet also increased the activity of myeloperoxidase (0.41 ± 0.05 U/g vs. 0.71 ± 0.11 U/g) and decreased the content of ATP (0.47 ± 0.10 µg/mL vs. 0.32 ± 0.11 µg/mL) in the mammary gland. In addition, phosphorylation of JNK (1.00 ± 0.21 vs. 2.84 ± 0.75), ERK (1.00 ± 0.20 vs. 1.53 ± 0.31), and p38 (1.00 ± 0.13 vs. 1.47 ± 0.41) and protein expression of IL-6 (1.00 ± 0.22 vs. 2.21 ± 0.27) and IL-8 (1.00 ± 0.17 vs. 1.96 ± 0.26) were enhanced in cows of the HC group, indicating that the mitogen-activated protein kinase (MAPK) signaling pathway was activated. Compared with the LC diet, the HC diet reduced the protein expression of mitochondrial biogenesis-related proteins PGC-1α (1.00 ± 0.17 vs. 0.55 ± 0.12), NRF1 (1.00 ± 0.17 vs. 0.60 ± 0.10), TFAM (1.00 ± 0.10 vs. 0.73 ± 0.09), and SIRTI (1.00 ± 0.44 vs. 0.40 ± 0.10). The HC diet promoted mitochondrial fission and inhibited mitochondrial fusion by reducing protein expression of MFN1 (1.00 ± 0.31 vs. 0.49 ± 0.09), MFN2 (1.00 ± 0.19 vs. 0.69 ± 0.13), and OPA1 (1.00 ± 0.08 vs. 0.72 ± 0.07), and by increasing that of DRP1 (1.00 ± 0.09 vs. 1.39 ± 0.10), MFF (1.00 ± 0.15 vs. 1.89 ± 0.12), and TTC1/FIS1 (1.00 ± 0.08 vs. 1.76 ± 0.14), leading to mitochondrial dysfunction. The HC diet increased mitochondrial permeability by upregulating the protein expression of VDAC1 (1.00 ± 0.42 vs. 1.90 ± 0.44), ANT (1.00 ± 0.22 vs. 1.27 ± 0.17), and CYPD (1.00 ± 0.41 vs. 1.82 ± 0.43). Taken together, these results indicated that feeding the HC diet induced mitochondrial damage via the MAPK signaling pathway in the mammary gland of dairy cows.

Canine hypoadrenocorticism: Insights into the Addisonian crisis.

Objective: Primary objectives of this study were to determine presenting complaints, physical examination, clinicopathologic findings, and hospitalization time of dogs with spontaneous hypoadrenocorticism presenting with critical disease; and to compare those end points to dogs with a more stable presentation. Secondary objectives were to evaluate the shock index and to identify precipitating stressors. Animals: Eighty-four dogs at the Western College of Veterinary Medicine between 1998 and 2018 were included. Procedure: Data were retrieved from the medical records. Results: Collapse and depression were more common among critically ill dogs. Hyperlactatemia was rare despite a diagnosis of hypovolemic shock, and a shock index was ineffective in this patient subset. Isosthenuria, total hypocalcemia, and more severe acidosis were more common (P < 0.05) in critical dogs. Owner separation was the most common precipitating stressor. Conclusion and clinical relevance: We concluded that the critical Addisonian dog has unique characteristics that may aid in early disease identification.

Hypoadrénocorticisme canin : aper ç u de la crise Addisonienne. Objectif: Les principaux objectifs de cette étude étaient de déterminer les motifs de présentation, l'examen physique, les résultats clinico-pathologiques et la durée d'hospitalisation des chiens atteints d'hypoadrénocorticisme spontané présentant une maladie critique; et de comparer ces paramètres aux chiens avec une présentation plus stable. Les objectifs secondaires étaient d'évaluer l'indice de choc et d'identifier les facteurs de stress déclencheurs. Animaux: Quatre-vingt-quatre chiens du Western College of Veterinary Medicine entre 1998 et 2018 ont été inclus. Procédure: Les données ont été extraites des dossiers médicaux. Résultats: L'effondrement et la dépression étaient plus fréquents chez les chiens gravement malades. L'hyperlactatémie était rare malgré un diagnostic de choc hypovolémique, et un indice de choc était inefficace dans ce sous-groupe de patients. L'isosthénurie, l'hypocalcémie totale et l'acidose plus grave étaient plus fréquentes (P < 0,05) chez les chiens critiques. La séparation du propriétaire était le facteur de stress déclencheur le plus courant. Conclusion et pertinence clinique: Nous avons conclu que le chien addisonien critique a des caractéristiques uniques qui peuvent aider à l'identification précoce de la maladie.(Traduit par Dr Serge Messier).

Transient distal renal tubular acidosis with nephrogenic diabetes insipidus after general anaesthesia in a dog.

A 3-year-old, 3.5 kg, female spayed Pomeranian was referred due to persistent vomiting, anorexia, polyuria and polydipsia, 7 days after receiving general anaesthetic for a medial patellar luxation correction. Physical examination revealed lethargy, tachypnoea and 7% dehydration. Complete blood count and serum chemistry results were unremarkable, and venous blood gas analysis revealed hypokalaemia and hyperchloraemic metabolic acidosis with a normal anion gap. Urinalysis revealed a urine specific gravity (USG) of 1.005, pH of 7.0 and proteinuria, and the bacterial culture was negative. Based on these results, the dog was diagnosed with distal renal tubular acidosis, and potassium citrate was prescribed to correct metabolic acidosis. In addition, concurrent diabetes insipidus (DI) was suspected because the dog showed persistent polyuria, polydipsia and a USG below 1.006 despite dehydration. After 3 days of initial treatment, acidosis was corrected, and vomiting resolved. Desmopressin acetate and hydrochlorothiazide were also prescribed for DI, but the USG was not normalized. Based on the insignificant therapeutic response, nephrogenic DI was highly suspected. DI was resolved after 24 days. This case report describes the concomitant presence of RTA and DI in a dog after general anaesthesia.