Chronic indigestion in milk-fed calves]

Calves with chronic indigestion have disturbed general attitude and condition, decreased appetite, loss of hair, clay-like faeces and ruminal and metabolic acidosis. Possible causes include dysfunction of the oesophageal-groove reflex, reflux of abomasal contents into the rumen and abnormal ruminal motility. The anion gap may be increased or within normal limits. Metabolic acidosis is significantly more severe in calves that are unable to stand than in calves that can stand. Treatment of chronic indigestion consists primarily of intravenous administration of sodium bicarbonate, transfaunation of the rumen and oral administration of electrolyte solutions.     

A review of the physiological significance of hypertonic body fluids on feed intake and ruminal function: salivation, motility and microbes

Mechanisms exist in the ruminant to detect changes in osmolality and volume of plasma during feeding to maintain fluid and electrolyte homeostasis. Feed intake during a meal can be limited by the rise in osmolality of ruminal fluid, which is sensed in the wall of the rumino-reticulum. Ruminal microbes appear to be resilient to the short-term changes in ruminal fluid tonicity, but in vitro growth rates are inhibited when the tonicity of the culture medium is increased beyond physiological levels. Although mixing contractions of the rumen are not inhibited by the normal increases in tonicity of ruminal fluid, time to first rumination is increased. This aspect of motility requires further research. The tonicity of plasma increases toward the end of a large meal as a consequence primarily of absorption of VFA and Na+ from the rumen and fluid shifts into the gut. This hypertonicity is sensed centrally to inhibit parotid secretion by a reduction in the parasympathetic stimulation to the gland. Increases in animal production may result from future research directed toward developing ways of counteracting these negative effects of hypertonicity in body fluids on feed intake and ruminal function.     

Inhibitory action of intravenously administered ammonium acetate on the motility of the rumen in sheep

Summary

The effect of 60 minutes’ intravenous infusions, before morning feeding, of ammonium acetate (18.6 micromole/min/kg of body weight) and ammonium acetate with propranolol (11 μg/min/kg of body weight) on the ruminal motility of sheep was examined. Ammonia has an adrenaline‐like action therefore propranolol, a beta‐receptor blocking agent, was administered in order to eliminate the possible effect of adrenaline on ruminal motility. The contractions of the dorsal sack of the rumen were registered by means of the balloon method, with the gauge inserted through the rumen fistula. The infusion of ammonium acetate caused an increase of the ammonia concentration in the blood to 0.6 mmolel/at the end of 60 minutes’ infusion. Already during the first 5 minutes of the intravenous infusion of ammonium acetate there was a decreased frequency of ruminal contractions, which was observed throughout the infusion. After the infusion there was a radical decrease of the concentration of ammonia in the blood, and at the same time an increase in the frequency of rumen contraction was observed.

Blocking of the beta‐adrenergic receptors by propranolol did not eliminate the inhibiting action of ammonium ion on rumen motility. The infusion of the ammonium acetate caused an increase of adrenaline and glucose concentration. This response was eliminated by propranolol in the case of adrenaline but not glucose. It is assumed that the action of ammonium ion on the rumen motility is derived primarily by the central nervous system.     

Evaluation of the therapeutic efficacy of rumen transfaunation

Transfaunation is supposed to stimulate normal rumen function and has been used as an ancillary treatment for indigestion. Although it is widely recommended, there are little research data on the efficacy and the necessary volume. The objective of the prospective clinical trial was the evaluation of the therapeutic efficacy of two different transfaunation volumes which can be obtained under practical conditions. Forty-five cattle suffering from indigestion were included in the study. A scoring system for the classification of rumen fluid was used. Scores were given in accordance with the importance of the parameter as an indication of microbial dysfunction. Animals with disturbed rumen fluid composition and activity were randomly assigned into 3 groups. Group 1 received 1 L of rumen fluid, group 2 received 5 L of rumen fluid and group 3 (control group) received 5 L of body temperature water. Rumen fluid analysis was repeated on days 1 and 4 after transfaunation. The feed intake of the animals was recorded. After the transfaunation of 1 L and 5 L, the rumen fluid score improved significantly from day 0 to days 1 and 4. Rumen fluid samples in the control group showed no significant improvement from day 0 to day 1. No significant differences were observed between the two treatment groups. But significant differences between the improvement of group 1 and the control group on days 1 and 4 and significant differences between group 2 and the control group on day 1 were detected. Small volumes of rumen fluid are easily obtainable by stomach tubes fitted with suction pumps. In summary, the transfaunation of as little as 1 L of rumen fluid caused significant improvement in the activity of rumen flora in cows suffering from indigestion.     

Forestomach epithelial receptor activation by rumen fluids from sheep given intraruminal infusions of volatile fatty acids

Forty-four reticuloruminal epithelial receptors were tested with rumen fluids obtained from 12 sheep before they were intraruminally infused with 4.0M acetic acid (8 sheep) or 4.0M butyric acid (4 sheep; preinfusion rumen fluid) and with rumen fluids obtained at the onset of ruminal stasis (abolition rumen fluid). The preinfusion rumen fluids from the 8 acetic acid-infused sheep (mean pH, 6.55) contained 1.7 mM nondissociated volatile fatty acids (VFA)/L and excited none of the 25 receptors tested. Preinfusion rumen fluids from the 4 butyric acid-infused sheep (mean pH, 6.98) contained 0.3 mM nondissociated VFA/L and also did not evoke responses in any of the 19 receptors tested. Abolition rumen fluids from sheep treated with acetic acid excited 17 of the 25 receptors tested and contained 89.4 mM nondissociated VFA/L, of which nondissociated acetic acid comprised 85.0 mM/L. Abolition rumen fluids from sheep treated with butyric acid activated 14 of the 19 receptors tested and contained 61.1 mM nondissociated VFA/L, of which 38.7 mM/L was nondissociated butyric acid. Preinfusion rumen fluids whose pH values were adjusted to that of abolition rumen fluids with HCl contained nondissociated VFA levels ranging from 16.3 mM/L (acetic acid-treated sheep) to 20.6 mM/L (butyric acid-treated sheep) and elicited responses in 4 of 30 receptors tested. Preinfusion rumen fluids whose pH values were adjusted to the pH value of abolition rumen fluid with acetic acid contained 29.5 mM nondissociated VFA/L and excited 7 of 13 tested receptors.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of a hay and a grain diet on the rate of hydrolysis of ochratoxin A in the rumen of sheep

The hydrolysis of ochratoxin A (OA) and the corresponding formation of its hydrolysis product, alpha ochratoxin (O alpha), by ruminal digesta and in the rumen of hay-fed and grain-fed sheep were compared. Ruminal contents from sheep fed diets with hay or with grain hydrolyzed OA in vitro; the majority of the activity was associated with the particulate fraction of the ruminal contents. The rate of hydrolysis of OA by ruminal fluid that was adjusted to different pH values was not influenced (P greater than .6) by the pH of the samples (pH was from 5.5 to 7.0). Ruminal fluid obtained from hay-fed animals (pH 7.0) was able to hydrolyze OA in vitro and to produce the hydrolyzed product, O alpha, at a much greater rate (fivefold) than ruminal fluid obtained from grain-fed animals (pH 5.5) (P less than .01). Ochratoxin A was administered intraruminally at a concentration of .5 mg/kg of BW to hay-fed and grain-fed sheep. The half-lives for disappearance of OA from the rumen of sheep fed grain (normal feed intake, rumen pH 5.7), fed grain at a low level (30% of normal feed intake, pH 6.5), and fed hay (pH 7.1) were 3.6, 1.3, and .6 h, respectively. The results suggest that OA is hydrolyzed much faster in the rumen of sheep fed hay than in sheep fed grain, presumably because of the different ruminal microbial population, which in turn influenced the rate of hydrolysis of OA.     

Secondary indigestion as a cause of functional pyloric stenosis in the cow

In 23 cows suffering from a secondary indigestion, in most cases with septicaemia, the syndrome of functional pyloric stenosis or vagal indigestion developed. The signs were anorexia, ruminal distension with fluid material, abomasal reflux into the ruminoreticulum, dehydration, hypochloraemic, hypokalaemic metabolic alkalosis and uraemia. These signs often disappeared after treatment of both the primary causative disease and the secondary indigestion. The importance of recognising this condition is emphasised, because the serious signs of the secondary indigestion may dominate the causative disease. The prognosis depends upon the causative disease and is not necessarily bad.     

Ruminal lactic acidosis: forestomach epithelial receptor activation by undissociated volatile fatty acids and rumen fluids collected during loss of reticuloruminal motility

Forty-three reticuloruminal epithelial receptors, with excitatory receptive fields within the reticulum, were isolated in 19 anaesthetised sheep. The responsiveness of these receptors to acetic, propionic, butyric and DL-lactic acids were assessed as well as their ability to be activated by rumen fluids obtained from sheep with induced ruminal lactic acidosis. Eighteen (41.9 per cent) receptors were excited by all three volatile fatty acids (VFAs) and 17 (39.5 per cent) responded to two VFAs. Butyric acid was the most potent volatile fatty acid eliciting responses in 41 (95.3 per cent) receptors. Acetic acid activated 33 (76.7 per cent) receptors and propionic acid excited 22 (53.5 per cent) receptors. DL-lactic acid only activated 13 (30.2 per cent) receptors, six of which required concentrations of 200 mM to be activated. Rumen fluids obtained when forestomach motility was impaired, activated 37 (81.1 per cent) of the 43 receptors, whereas rumen fluids obtained when forestomach motility was normal did not activate any receptors. Despite the high levels of lactic acid in rumen fluids which activated epithelial receptors, this acid was not responsible for receptor excitation.     

Current ideas on the pathophysiology and treatment of lantana poisoning of ruminants

Lantana poisoning in ruminants results from the ingestion of toxic varieties of the plant Lantana camara, which contain the triterpene acids lantadene A and lantadene B. Poisoning results in intrahepatic cholestasis and the consequences of the liver injury include jaundice, photosensitisation and ruminal stasis. The decreased ruminal motility causes toxic material to be retained in the rumen and continuous absorption of toxins from the rumen maintains the disease. Lantana poisoning can best be treated by preventing further absorption of toxins. This can be achieved by giving a large quantity of activated charcoal into the rumen together with a large volume of a multiple electrolyte solution to stimulate ruminal motility and rehydrate the animal. Treatment for photosensitive dermatitis should also be given.     

The effects of high levels of rumen degradable protein on rumen pH and histamine concentrations in dairy cows

An experiment was conducted to test the hypothesis that the supplementation of crude protein (CP) results in rumen acidosis and increased histamine concentrations in dairy cows. Six ruminally fistulated, non-pregnant dry cows were fed three experimental rations in a replicated 3 × 3 Latin square design. The CP contents in the low-CP, the high rumen undegradable protein (high-RUP) and the high rumen degradable protein (high-RDP) rations were 112, 259 and 266 g/kg dry matter (DM) respectively. The cows were fed 7.7 kg DM of the concentrates and 2.7 kg DM of rice straw. High levels of RDP in the ration significantly increased the ammonia, total volatile fatty acid (VFA) and histamine concentrations in the rumen fluid. However, supplemental CP, whether degradable or undegradable, did not significantly affect the pH of rumen fluid. Plasma urea nitrogen concentration was higher in both high-RDP and high-RUP in relation to cows fed the low-CP ration. The rise in ruminal histamine concentrations was physiologically non-relevant, most likely because rumen pH was not affected by supplemental CP at the installed level of DM intake. Therefore, it can be concluded that the issue of supplemental CP, rumen pH and ruminal histamine concentrations has not yet been settled. Further research is warranted to understand these relationships.     

Theoretical turnover rate of the rumen liquid fraction in dairy cows and its relationship to feed intake,rumen fermentation,and milk production

Ruminant animals are able to convert plant materials (grain and the human‐indigestible portion of carbohydrates) to milk and meat. In this conversion, most of the plant materials are digested by rumen fermentation and are changed to short‐chain fatty acids, microbial cells, and methane, which is released into the atmosphere. The relationships among feed, rumen fermentation, and milk production are poorly understood. Here we report a novel indicator of characteristics of rumen fermentation, theoretical turnover rate (TTOR) of the rumen liquid fraction. The TTOR was calculated from the presumed rumen volume (PRV) which is estimated by dividing the methane yield by the methane concentration of rumen fluid. The formula for the TTOR is: TTOR = PRV/body weight^0.75. Our present analyses confirm that the TTOR as an indicator is capable of connecting feed, rumen fermentation, and milk production, because dry matter intake/TTOR showed a strong correlation with milk yield/TTOR. In addition, the TTOR may be related to ruminal pH, as we observed that the ruminal pH decreased as the TTOR increased. We propose that the TTOR is a factor characterizing rumen fermentation and a good indicator of the productivity of ruminants and dysbiosis of the rumen microbiome.     

Factors that limit maintenance of recombinant rumen bacterium in sheep rumen

Factors limiting the maintenance of recombinant ruminal bacterium in the rumen were evaluated in vitro , using batch culture prepared from rumen fluid of sheep. Butyrivibrio fibrisolvens expressing a foreign xylanase gene ( B. fibrisolvens NO4) was used as a tested recombinant that was selectable on an erythromycin-containing agar medium. The recombinant tended to reduce its level slowly in the rumen fluid of sheep on a high hay diet, while its initial decrease was more apparent in the rumen fluid of sheep on a high concentrate diet. Incubation with cell-free ruminal fluid revealed a significant decrease of inoculated recombinant, suggesting the presence of antibacterial factors limiting maintenance of the recombinant. In particular, during the first 12 h of incubation this inhibition was more notable in culture prepared from rumen fluid of sheep given the high concentrate diet. Autoclaving the cell-free rumen fluid inactivated the inhibition. Numbers of the recombinant for inoculation did not influence the final level of survived recombinant, that is, the initial depression was larger as more recombinant was inoculated. Subculturing with xylan before inoculation and/or direct addition of xylan to the batch culture did not improve survival of the recombinant. From these results it is suggested that the level of survived recombinant is limited to 10^2–4/mL of in vitro batch culture with restricted energy supply and that initial depression of the recombinant is mainly caused by the heat-sensitive antibacterial factors not associating with microbial cells in the rumen.     

Effect of dietary protein level on nitrogen metabolism in the growing bovine: II. Diffusion into and utilization of endogenous urea nitrogen in the rumen

Six Angus heifer calves (234 kg) were assigned to either a high (HP; 126.1 g N/d) or low (LP; 66.5 g N/d) protein intake to evaluate ruminal criteria associated with movement of blood urea-N (BUN)-derived NH3-N from the rumen wall into interior ruminal digesta. Calves received 4.8 kg DM/d of diets containing 30% cottonseed hulls and 70% cornsoybean meal in equal portions at 4-h intervals. Following single i.v. injections of 15N-urea, ruminal fluid was collected serially for 4 h postinjection from digesta located adjacent to the rumen wall (wall-proximate digesta; WPD) and from the center of the rumen digesta mass after manual agitation (center mixed digesta; CMD). Mean ruminal NH3-N (RAN) concentrations were higher (P less than .05) for HP than for LP, but were not affected (P greater than .05) by digesta sampling site. Ruminal urease activity was higher (P less than .05) for LP than for HP and tended (P = .14) to be higher for WPD than for CMD. Area under the 15N enrichment curve (AUC) ratios between sampling sites (WPD/CMD x 100) for RAN were greater (P less than .05) for LP than for HP. However, AUC ratios for bacterial N were not affected (P greater than .05) by protein level. Whereas BUN-derived 15NH3 appeared to thoroughly equilibrate with RAN in interior ruminal digesta with HP, there appeared to be a declining enrichment gradient for RAN from the rumen wall to the interior ruminal digesta with LP. Data are interpreted to suggest that bacteria at or near the rumen wall may preferentially utilize some BUN-derived NH3-N entering through the rumen wall in calves fed LP diets.     

Ammonia and urea transport across the rumen epithelium: a review

The transport of nitrogen across the rumen epithelium is characterized by absorption of ammonia from the rumen and by an influx of urea into the rumen. The transport rates of both compounds are large and exhibit wide variation. The transport of ammonia occurs in two forms: in the lipophilic form as NH3, the magnitude of which is linearly related to the pH in the ruminal fluid at pH values above 7, while at a physiological pH of 6.5 or lower, ammonia is predominantly absorbed as NH4+ via putative potassium channels in the apical membrane. The uptake of NH4+ depends on the potential difference of the apical membrane, Pda, and shows competition with K uptake. The pathway for basolateral exit of NH4+ is unknown. Hence, the relative transport rates of NH3 or NH4+ are determined by the ruminal pH according to the Henderson-Hasselbalch equation. Transport of ammonia interacts with the transport of Na and Mg mainly via changes of the intracellular pH. Urea recycling into the rumen has been known for many years and the transport across the rumen epithelium is mediated via urea transporters in the luminal and basolateral membrane of the epithelium. Transport of urea occurs by simple diffusion, but is highly variable. A significant increase of urea influx is caused by the fermentation products CO2 and short-chain fatty acids. Conversely, there is some evidence of inhibition of urea influx by ruminal ammonia. The underlying mechanisms of this modulation of urea transport are unknown, but of considerable nutritional importance, and future research should be directed to this aspect of ruminal transport.     

不同精料补饲水平对藏绵羊瘤胃内环境参数的影响

选择1.2岁左右藏绵羊30只,随机分3组,采用单因子分组设计,以青干草为基础日粮,按每只150,300,450 g/d 3种精料水平补饲,研究不同精料补饲水平对藏绵羊瘤胃代谢参数变化规律的影响。结果表明;随精料补饲水平提高,藏绵羊瘤胃液pH值下降,NH3-N浓度、NH3-N浓度平均值、总挥发性脂肪酸(VFA)浓度显著增加(P<0.05)。在本试验条件下,从藏绵羊瘤胃内环境的稳定方面考虑,藏绵羊每日补饲精料300 g效果最佳。     

Effect of intravenous infusion of proglumide on ruminal motility in conscious sheep (<Emphasis Type="Italic">Ovis aries</Emphasis>)

The effects of intravenous infusion of proglumide on regular ruminal contractions were examined in conscious sheep using doses that inhibit pancreatic exocrine secretion. After a control period of 20 min, proglumide was infused intravenously for 40 min at a dose of 15, 30 or 60 μmol/kg per min and venous blood was collected. The intravenous infusion of proglumide significantly increased the frequency of ruminal contractions at 15 μmol/kg per min without altering the amplitude, while it significantly decreased the frequency and amplitude of ruminal contractions at 30 and 60 μmol/kg per min in a dose-dependent manner. Proglumide did not increase contractile activity of the omasum, abomasum and duodenum or the plasma concentration of immunoreactive cholecystokinin (CCK). Application of proglumide at 1–30 mmol/L inhibited bethanechol-induced contraction in both longitudinal and circular muscle strips of the dorsal sac of the rumen. These results suggest that proglumide at a low dose acts indirectly on the rumen as a CCK receptor antagonist to increase the frequency of contractions, whereas at higher doses it inhibits cholinergic-induced contraction of the ruminal muscles or acts as an agonist to inhibit contractions in sheep. Hence, proglumide at high doses seems unsuitable for research or therapeutic use as a CCK receptor blockade in sheep.     

Ruminal lactic acidosis in sheep and goats.

The clinical findings in 37 sheep and goats with acute ruminal lactic acidosis included a disturbed general condition characterised by anorexia, apathy, teeth grinding and muscle twitching, ruminal stasis, and the excretion of soupy or watery faeces. The ruminal fluid of affected animals was milky, had a sour odour and a low pH. There was a predominance of Gram-positive bacteria in smears of ruminal fluid. In comparison with 10 control animals, the rumen fluid of 23 sheep with ruminal lactic acidosis had higher lactic acid and lower volatile fatty acid concentrations. In addition, the affected animals often had haemoconcentration and metabolic acidosis. Treatment included single or repeated transfer of ruminal fluid from healthy cows and, depending on the severity, the administration of antacids, yeast and chlortetracycline, and the intravenous infusion of isotonic sodium chloride and 5 per cent sodium bicarbonate solutions. Of the 37 treated sheep and goats, four died within 24 hours, and three others were euthanased after one, two and three days because their condition rapidly deteriorated. Thirty animals were discharged one to nine days after treatment. Twenty-nine of them (78.4 per cent) recovered completely but one was euthanased later.     

Relationship between pH and Temperature in the Ruminal Fluid of Cows, Based on a Radio-Transmission pH-Measurement System

To assess the relationship between pH and temperature in the ruminal bottom fluid, circadian changes were monitored using cows fed a control diet (C diet) or a rumen acidosis-inducing diet (RAI diet) by using a wireless radio-transmission pH- measurement system. These two parameters were measured simultaneously at 10-min intervals on day 14 after commencement of feeding. Compared to the mean ruminal pH for 60 min immediately after the morning feeding (0 hr), significantly lower pH was noted 3-13 hr later (P<0.05) and 4-19 hr later (P<0.01) in cows fed the C and RAI diets, respectively, although the reduction in the latter was much higher than that in the former. In contrast, significantly higher ruminal temperature was found at 8 and 12-14 hr later (P<0.05) and 6, 8, and 10-19 hr later (P<0.01) in cows fed the C and RAI diets, respectively. A significant negative correlation was observed between the lowest ruminal pH and its corresponding ruminal temperature in cows fed the C and RAI diets (r=-0.722 and -0.650, P<0.01, respectively), suggesting active fermentation and volatile fatty acid production in the rumen. However, ruminal pH profiles may not be predictable by measuring only ruminal temperature because decreases in ruminal pH were preceded by increases in ruminal temperature, and circadian changes in pH and temperature were associated with ruminal fermentation.     

Signals for identifying cows at risk of subacute ruminal acidosis in dairy veterinary practice

Controlling rumen disorders is critical to ensure successful dairy herd health management. Lactation diets of dairy cows are commonly rich in concentrates and low in physically effective fibre. Feeding of these diets increases the risk of rumen disorders with far‐reaching consequences for cattle health, welfare and sustainability of dairy production. The term subacute ruminal acidosis or SARA is often used as a synonym for poor rumen health. Being subclinical, SARA lacks of clear symptoms and is therefore difficult to diagnose and to control in the practice. This review article summarises common and identifies new direct and indirect cow signals related to SARA. We have performed a scientific evaluation and interpretation of each of these cow signals by highlighting their advantages and disadvantages from the practitioner's point of view. The gold standard of SARA cow signals still remains direct measurement of ruminal pH. However, continuous pH monitoring is cost‐intensive and often biased by sensor drift. Single‐point ruminal pH measurements by oral stomach tubing or rumenocentesis have strong limitations. Therefore, there is a need for reliable and robust markers of SARA that are easily accessible and inexpensive. Such indirect parameters are the observation of chewing and feeding activities, as well as the monitoring of milk, faecal, urine and blood variables. Also, novel technologies that allow rapid and non‐invasive measurement of the rumen mucosa thickness and ruminal motility patterns might provide advantages in SARA diagnosis. Due to several constraints of these indirect diagnostic tools, such as limited specificity and sensitivity, we strongly recommend using a combination of the signals to reliably identify cows at risk of SARA in a dairy herd.     

Occurrence of 2-aminoethylphosphonic acid in feeds, ruminal bacteria and duodenal digesta from defaunated sheep

A quantitative method of analysis for 2-aminoethylphosphonic acid (AEP) was developed using reverse-phase HPLC. The detection limit for AEP was 15 nM, and the detector response (peak area) was linear from AEP levels up to 100 microM (R = .99). Mean recovery of AEP added to strained ruminal fluid from faunated sheep was 98.2%. When AEP was added to a fermentation mixture at a concentration of 22.6 micrograms/ml, 78% disappeared during a 24-h incubation. 2-Aminoethylphosphonic acid was readily detected in preparations of mixed ruminal ciliate protozoa as well as in mixed and pure strains of ruminal bacteria, feedstuffs, and ruminal fluid and duodenal digesta from defaunated sheep. The occurrence of AEP in feed and bacterial hydrolysates was confirmed by organic phosphorus analyses. The concentration of AEP in mixed ruminal protozoa was three times greater than its concentration in mixed ruminal bacteria (4,304 vs 1,383 micrograms/g DM, respectively). The AEP values for pure ruminal bacterial cultures ranged from 733 micrograms/g DM in Bacteroides succinogenes B21a to 1,166 micrograms/g DM in Butyrivibrio fibrisolvens H17c. Ruminal fluid and duodenal digesta from defaunated sheep contained AEP concentrations of 30 micrograms/ml and 90 micrograms/g DM, respectively. The concentration of AEP in feedstuffs ranged from 25 micrograms/g DM in wheat straw to 263 micrograms/g DM in oats. Because AEP occurrence is not limited to ruminal ciliate protozoa, it is of little value as a marker for protozoal presence in or passage out of the rumen.