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PubMed1989

Estimating salivary flow and ruminal water balance of intake, diet, feeding pattern, and slaframine.

Three experiments with ruminally fistulated cattle fed 12 times daily were conducted to study the role of saliva secretion in ruminal water balance when intake, diet, and feeding pattern were altered. Water balance data were determined from continuously infused Co-EDTA and pulse-dosed Cr-EDTA with saliva flow estimated by difference between water intake and ruminal outflow. Any net transruminal water flux would be included in the estimate of salivary flow. When the concentration of bluestem hay in the diet was increased from 50 to 90%, ruminal fluid volume, saliva secretion, water intake, dilution rate, and total ruminal outflow increased. At equal intake, the higher forage diet increased ruminal liquid volume, outflow, and saliva secretion but had no effect on dilution rate. Intake, but not forage concentration, affected ruminal pH when 50 and 90% hay diets were fed. Increasing feeding frequency of forage in a 65% bluestem hay diet from 4 to 12 times daily (the grain portion was fed 12 times daily) increased dilution and ruminal outflow; however, the latter was only significant with data from Cr-EDTA. Ruminal volatile fatty acids were not altered by feeding frequency of forage. Nycterohemeral patterns were seen in water intake, ruminal dilution rate, outflow, and salivary flow in both studies. Slaframine increased saliva flow by 29% and was accompanied by increased ruminal liquid volume, dilution rate, and outflow.

Animals↗
PubMed1996

Effect of the degradation of organic matter and crude protein on ruminal fermentation in dairy cows.

The potential of the dacron bag technique to assess fluctuations in ruminal metabolites was studied using 40 Israeli-Friesian dairy cows assigned to an experiment with a 2 x 2 factorial design. Diets contained a low (62%) or high (65%) percentage of ruminally degradable CP and a low (55%) or high (59%) percentage of ruminally degradable OM. Metabolites were monitored before feeding and at 3 and 6 h postfeeding. Before feeding, total VFA and propionate were higher, and acetate and pH were lower, in diets containing a high percentage of ruminally degradable OM than in diets containing a low percentage of degradable OM. By 3 H postfeeding, acetate, butyrate and pH were lower, and propionate was higher, in the diets containing a high percentage or ruminally degradable OM than in the diets containing a low percentage of ruminally degradable OM. By 6 h postfeeding, propionate was higher, and acetate was lower, in diets containing a high percentage of ruminally degradable OM than in diets containing a low percentage of ruminally degradable OM. In the diets with a high percentage of ruminally degradable OM, before feeding and by 3 h postfeeding, ammonia concentrations were higher and lower, respectively, relative to the diets containing a low percentage of degradable OM. Milk yield and composition and DMI were similar among treatments. The correlation was good between the degradability data obtained by the dacron bag technique and the meal-induced variations in ruminal metabolites. The lack of a positive yield response to controlled fluctuations in ruminal metabolites may be related to surplus CP intake.

Ammonia↗
PubMed2002

In vitro ruminal biotransformation of benzimidazole sulphoxide anthelmintics: enantioselective sulphoreduction in sheep and cattle.

The comparative in vitro sulphoreduction of the (+) and (-) enantiomers of albendazole sulphoxide (ABZSO) and oxfendazole (OFZ) by ruminal fluid obtained from sheep and cattle, was investigated, under anaerobic conditions, in this study. Ruminal fluid samples were obtained from Holstein steers fitted with a permanent rumen fistula and from Corriedale lambs via an oesophageal tube. Albendazole sulphoxide, incubated as either the racemic (rac) mixture or as each individual enantiomeric form, was extensively sulphoreduced to form albendazole (ABZ) by ruminal fluid from both species. The concentrations of ABZ formed at different incubation times were between 55 and 158% greater after the incubation of cattle ruminal fluid with (+) ABZSO, compared with that produced when (-) ABZSO was the incubated substrate. Similarly, the concentrations of ABZ were 1.3--3.0-fold higher when (+) ABZSO was incubated with sheep ruminal fluid. Significantly higher rates of depletion were observed for the (+) enantiomeric form when ABZSO was incubated with ruminal fluid from both species. The rates of ABZ formation from both ABZSO enantiomeric forms were significantly higher in sheep compared with cattle ruminal fluid. Fenbendazole (FBZ) was the metabolite formed after the incubation of the racemic form of OFZ with ruminal fluid obtained from both species. The metabolic profile of both OFZ enantiomers followed a similar pattern to that observed for ABZSO enantiomers. A bi-directional chiral inversion of one enantiomer into its antipode was observed. The (+) enantiomer appeared in the incubation medium when (-) ABZSO was the incubated substrate, and also the (-) antipode was detected after (+) ABZSO incubation with ruminal fluid obtained from both species. The results reported here demonstrate an enantioselective ruminal sulphoreduction of ABZSO and OFZ (substrate enantioselectivity). These findings contribute to interpret the chiral behaviour of benzimidazole-sulphoxide anthelmintics.

Administration, Oral↗
PubMed1995

Leucaena toxicosis and its control in ruminants.

Leucaena (Leucaena spp., especially L. leucocephala) is an arboreal, tropical legume that ranges into the cool subtropics and equatorial elevations up to 1,000 m. One of its uses includes forage for livestock, but introduction of leucaena outside its indigenous range often has led to acute and chronic toxicosis. The major toxic constituents of leucaena are the nonprotein free amino acid mimosine and its ruminal degradation product, 3-hydroxy-4(1H)-pyridone (3,4-dihydroxypyridine; 3,4-DHP). Leucaena also contains appreciable quantities of condensed tannins. In ruminants, mimosine is a depilatory agent and 3,4-DHP is a potent goitrogen. In the 1980s, Australian workers demonstrated that the geographical limits of leucaena toxicosis were due to the absence of ruminal bacteria capable of degrading 3,4-DHP, and successfully introduced 3,4-DHP degrading ruminal bacteria from a Hawaiian goat into goats and cattle in Australia. Simple in vitro screening methods have been developed for detection of 3,4-DHP degraders in ruminal samples and feces. Also, several strains of 3,4-DHP degrading ruminal bacteria have been characterized and have been given the genus and species designation, Synergistes jonesii. Ruminal inoculation with ruminal contents from adapted animals, enriched cultures of 3,4-DHP-degrading ruminal bacteria, and pure cultures of S. jonesii have all been used successfully to establish ruminal populations that are capable of degrading 3,4-DHP and preventing leucaena toxicosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed2007

Rumination in posttraumatic stress disorder.

Recent studies have shown that rumination is a powerful predictor of persistent posttraumatic stress disorder (PTSD). However, to date, the mechanisms by which rumination maintains PTSD symptoms are little understood. Two studies of assault survivors, a cross-sectional (N = 81) and a 6-month prospective longitudinal study (N = 73), examined several facets of ruminative thinking to establish which aspects of rumination provide the link to PTSD. The current investigation showed that rumination is not only used as a strategy to cope with intrusive memories but it also triggers such memories. Certain characteristics of rumination, such as compulsion to continue ruminating, occurrence of unproductive thoughts, and "why" and "what if" type questions, as well as negative emotions before and after rumination, were significantly associated with PTSD, concurrently and prospectively. These characteristics explained significantly more variance in PTSD severity than the mere presence of rumination, thereby indicating that not all ways of ruminative thinking are equally maladaptive.

Adult↗
PubMed2004

Rumination, mood and social problem-solving in major depression.

BACKGROUND: Ruminating when depressed is thought to lower mood and impair problem-solving, while distraction is thought to alleviate mood and assist problem-solving. The present study investigates each of these proposals using both naturally occurring and experimentally induced rumination and distraction in a sample of patients with major depression. METHOD: Thirty-six patients with major depression and 36 control participants were randomly allocated to either a rumination or distraction induction condition. Levels of trait rumination and distraction were measured at baseline, mood and problem-solving were measured before and after the inductions. RESULTS: In terms of trait measures, depressed patients with higher levels of trait rumination reported poorer mood and gave less effective problem solutions than those who were less ruminative. Trait distraction was not associated with mood or problem-solving. In terms of induced responses, depressed patients who were made to ruminate experienced a deterioration in their mood and gave poorer problem solutions. For those receiving the distraction induction, mood improved in all patients and problem-solving improved in patients who were not naturally ruminating at a high level. Neither induction had an impact on mood or problem-solving in control participants. CONCLUSIONS: Treatment for depression associated with adverse life events may need to target rumination as well as problem-solving deficits if interventions are to be effective. The differential effects of self-applied versus experimentally induced distraction require further investigation. Future research will need to consider that high levels of trait rumination may interfere with the impact of experimental inductions.

Adolescent↗
PubMed1992

Developmental changes in glucose and butyrate metabolism by isolated sheep ruminal cells.

The ontogeny of glucose and butyrate metabolism in developing sheep ruminal epithelium was determined using an isolated ruminal cell system. Ruminal cells were isolated from 21 lambs at seven ages before weaning. Rumen weight increased in proportion to increases in body weight, except between 28 and 42 d, when rumen weight increased threefold, whereas body weight increased only 33%. Glucose oxidation rates [expressed as nmol/(1 x 10(6) ruminal cells.120 min)] by ruminal cells were low at birth (14.2 +/- 5.08), increased sharply by 14 d (71.38 +/- 16.71), and remained elevated until 42 d. Following 42 d, glucose oxidation declined to rates lower than those observed at birth (6.11 +/- 0.83). Butyrate oxidation to CO2 increased from birth (20.03 +/- 3.41) to a peak at 4 d (134.0 +/- 31.71) and decreased throughout the remainder of the preweaning period (56 d; 36.32 +/- 7.48). Butyrate inhibited glucose oxidation by ruminal cells isolated at 14, 28 and 42 d. Similarly, glucose inhibited butyrate oxidation by ruminal cells isolated from 4 d to 28 d following birth. beta-Hydroxybutyrate production [nmol/(1 x 10(6) ruminal cells.120 min)] from butyrate by ruminal cells was undetectable at birth, but measurable by 4 d (3.28 +/- 2.15). Rates of beta-hydroxybutyrate production remained unchanged through 42 d; however, by 56 d, production had increased 10-fold (36.71 +/- 0.67). The metabolic adaptations of the ruminal epithelium are intimately associated with the physical development of the tissue, and major shifts in the fate of glucose and butyrate carbon occur prior to weaning.

Aging↗
PubMed2002

Rumination and executive function in depression: an experimental study.

BACKGROUND: Major depression is associated with cognitive deficits, particularly those requiring central executive functioning. Depressed patients also tend to focus on and think about their symptoms and problems ("ruminate") more than non-depressed controls. Although an association has been found between rumination and impaired performance on a central executive processing task, the causal relation between impaired executive functioning and rumination has not been determined. This study sought to directly manipulate rumination and assess the impact on executive functioning in depression as measured by random number generation. METHODS: Depressed patients (n=14) and non-depressed controls (n=14) were compared on a random number generation task, performed after both a rumination induction and after a distraction induction, with order of inductions counter balanced within each group. RESULTS: Compared with the distraction induction, the rumination induction produced a significant increase in both ruminations and the tendency towards stereotyped counting responses (thought to reflect a failure of inhibitory executive control) in depressed patients but not in controls. However, after distraction, no difference in random number generation or rumination was found between the two groups. CONCLUSIONS: The aspects of executive function involved in random number generation are not fundamentally impaired in depressed patients. In depressed patients, the rumination induction seems to trigger the continued generation of ruminative stimulus independent thoughts, which interferes with concurrent executive processing.

Adult↗
PubMed2004

Rumination and future thinking in depression.

OBJECTIVES: Future thinking is an important domain of cognitive functioning, with reduced ability to imagine positive future events associated with hopelessness in depression and parasuicide. Rumination has been shown to exacerbate negative cognitive biases in depression, and to reduce likelihood estimations for positive future events. We examine the hypothesis that, in depressed patients, rumination would reduce the ability to imagine positive future events, whilst increasing the ability to imagine negative future events. METHOD: The ability to imagine positive and negative future events was assessed using the future thinking paradigm (MacLeod, Rose, & Williams, 1993). Depressed and nondepressed participants completed the future thinking task after being randomly allocated to either a rumination or distraction manipulation (Nolen-Hoeksema & Morrow, 1993). Mood was measured before and after the manipulation. Participants also completed a standard verbal fluency task. RESULTS: In the depressed group, compared to distraction, rumination increased both negative and positive future thinking, although the effect was only significant for negative future thinking once baseline levels of hopelessness were controlled for. These findings are consistent with the prediction that rumination would increase negative future thinking, but inconsistent with the prediction that rumination would reduce positive future thinking. Previous findings that, compared to controls, depressed patients generated fewer positive future events were replicated. CONCLUSION: Ruminative self-focus leads to greater negative future thinking in depressed patients, further confirming that rumination exacerbates negative cognitive biases in depression. The relationship between rumination and positive future thinking was unexpected, but might potentially reflect a general priming of self-related information by rumination.

Adult↗
PubMed1990

Characterizing rumination patterns of dairy cows using spectral analysis.

Spectral analysis techniques were used to characterize the cyclical variation in rumination behavior of cows. Four Holstein cows were fed twice daily a diet of 60% high-moisture shelled corn-based concentrate, 15% first-cut alfalfa-grass hay and 25% second-cut alfalfa silage. The number of minutes that each cow spent ruminating was determined for 15-min intervals during six consecutive days. Rumination data then were characterized using Fourier harmonic analysis to decompose the total sum of squares into 288 orthogonal components due to different rumination wavelengths. Rumination patterns for all cows consisted mainly of wavelengths that were harmonics of a 24-h cycle, indicating a circadian pattern of rumination. Differences in rumination patterns between cows occurred mainly at wavelengths of less than 2 h. Rumination patterns of two of the four cows were more complex, and consisted of high-frequency, non-24-h harmonic wavelengths in addition to the circadian pattern. Spectral analysis can be used to identify the component cycles of rumination patterns of individual animals, which can then be used to determine the effects of dietary or other manipulations on rumination behavior.

Animals↗
PubMed1991

Effect of water-filled bags in the rumen of wethers on ruminal digesta kinetics and total tract nutrient digestibility.

Four ruminal cannulated wethers (65 +/- 2.4 kg) were used in a Latin square design experiment to determine the effects of water-filled bags on ruminal liquid and particulate dilution rates. Treatments consisted of ratios of water volume (liters) in bags to pretrial ruminal volume (liters) and were A) 0, B) .22, C) .44, and D) .66. Diet DM, consisting of 75% concentrate and 25% chopped alfalfa hay, was offered once daily at 2.3% of each wether's pretrial live weight. The largest water-filled bag decreased ruminal liquid volume by 68%, increased ruminal liquid dilution rate by 64%, and increased ruminal pool size of non-water soluble concentrate (NWSC) by 137% compared with the control. Ruminal dilution rate of ytterbium-marked NWSC decreased by 37% compared with the control. Ruminal fluid concentrations of NH3 N, pH, and molar ratios of acetate, propionate, butyrate, and isovalerate and plasma urea nitrogen varied over time postfeeding depending on water-filled bag size. Total tract apparent digestibility of DM, OM, ADF, starch, and energy were decreased (P less than .05) with increasing water-filled bag size in the rumen. In this study, water-filled bags acted to increase ruminal liquid dilution rate and decrease ruminal liquid volume and total tract nutrient digestibility but to retard passage of NWSC and hay fiber.

Animal Feed↗
PubMed1989

Eating and ruminating behavior of steers fed Coastal Bermudagrass hay at four levels.

Effects of feeding level on chewing behavior and physical reduction of particles during ingestive mastication and rumination were examined in four ruminally cannulated steers fed Coastal bermudagrass (Cynodon dactylon [L.] Pers.) hay in the long form. The experimental design was a 4 x 4 latin square with 18-d periods. Treatments based on previous intakes were set at 50, 70, 90 and 110% of feed consumed per animal. Steers were fed at 12-h intervals. Chewing behavior was monitored over 4 d with a computerized system. Boli of ingested, masticated hay (MH), collected at the cardia, and serial samples of digesta taken from the ruminal upper strata (RUS) were wet-sieved. Dimensions of MH particles retained on 4.0- and 2.0-mm sieves were determined by image analysis. Increasing feeding level resulted in a linear increase in the number of boli ruminated (P less than .01) and in linear increases in eating (P less than .01), ruminating (P less than .05) and total chewing time (P less than .01). Linear increases in number of eating (P less than .01), ruminating (P less than .01) and total chews (P less than .01) also were observed. Feeding level had no effect on bolus duration, number of chews/bolus, number of boli/min rumination time and number of chews/min rumination time. The extent of particle breakdown during ingestive mastication was a determinant of the number of boli ruminated daily and their associated number of chews. Number of boli ruminated daily also was related to the RUS mean particle size. Eating time did not provide a reliable indication of how well feed was chewed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed2002

Prediction of ruminal pH from pasture-based diets.

This study identified suitable predictors of ruminal pH and identified relationships between ruminal pH and animal measures for diets based on fresh pasture. Animal and dietary variables (121 treatment means from six countries) were collated from 23 studies of lactating dairy cows fed pasture. Mean daily ruminal pH ranged from 5.6 to 6.7 across studies. Within studies, a low ruminal pH was associated with higher (P < 0.05; r2 > 0.40) microbial N flow from the rumen, total and individual volatile fatty acid concentrations, milk and milk component yields, and dry matter intake, and with lower (P < 0.05; r2 > 0.30) concentrations of milk fat, fat:protein, and acetate:propionate. Large variation between studies meant that these ruminal and production variables could not be used to make reliable predictions of ruminal pH in future pasture-based studies or feeding scenarios. Ruminal pH was positively related (P < 0.05; r2 < 0.15) to forage neutral detergent fiber (NDF) and NDF content within study, and negatively related (P = 0.001; r2 = 0.14) to nonstructural carbohydrate across studies. No single dietary variable, or group of variables, could be used to make a reliable prediction of ruminal pH. Estimates of effective fiber for diets containing only pasture were made using the Cornell Net Carbohydrate and Protein System ruminal pH equation. Mean effectiveness of fiber in pasture was 43% of NDF, and ranged from 17 to 78% across studies. High flows of microbial nitrogen, milk, milk fat yield, and dry matter intake suggested that the performance of cows fed high quality pasture was not limited when mean ruminal pH decreased to 5.8.

Acetates↗
PubMed2007

Severity of ruminal acidosis in primiparous holstein cows during the periparturient period.

The objectives of this study were: 1) to determine the effect of providing additional prepartum concentrate on the occurrence and severity of ruminal acidosis (RA) and lactational performance during the periparturient period in primiparous cows; and 2) to characterize the occurrence and severity of RA during the periparturient period. We hypothesized that providing additional concentrate prepartum would reduce postpartum RA. Fourteen ruminally cannulated Holstein heifers were paired by expected calving date and body condition score. The heifers were assigned to 1 of 2 prepartum feeding regimens: 1) a control treatment consisting of a far-off diet (forage:concentrate, F:C = 80:20) fed from d -60 to d -25 and a close-up diet (F:C = 54:46) fed from d -24 until parturition; or 2) a high-concentrate (HC) feeding program consisting of 4 prepartum diets, HC-1 (F:C = 68:32) fed from d -60 to d -43, HC-2 (F:C = 60:40) fed from d -42 to d -25, HC-3 (F:C = 52:48) fed from d -24 to d -13, and HC-4 (F:C = 46:54) fed from d -12 until parturition. All cows received the same lactation diet postpartum. Ruminal pH was measured continuously from d -5 to d +5, and for 3 consecutive days starting on d +17 +/- 1.2, d +37 +/- 1.4, and d +58 +/- 1.5 relative to parturition using an indwelling ruminal pH system. Ruminal acidosis was considered to occur when ruminal pH was <5.8 (total RA). Ruminal acidosis was further partitioned into: 1) mild RA (5.8 > ruminal pH > 5.5), 2) moderate RA (5.5 > ruminal pH > 5.2), and 3) acute RA (ruminal pH < 5.2). Feeding additional concentrate prepartum did not reduce postpartum RA. In fact, cows fed the HC treatment had more daily episodes of acute RA than cows fed the control treatment. Day relative to parturition affected the occurrence and severity of RA; RA increased following parturition and was sustained thereafter. The DM intake during the last 5 d of gestation was lower for cows fed the HC treatment compared with cows fed the control treatment, but lactational performance was not affected. We conclude that, under the conditions imposed, feeding additional concentrate prepartum does not reduce postpartum RA. Furthermore, the incidence and severity of RA increases immediately postpartum, emphasizing the need to develop and implement feeding strategies that reduce this risk.

Acidosis↗
PubMed1992

Influence of dietary fiber and buffer value index on the ruminal milieu of lactating dairy cows.

The influence of dietary buffer value index and dietary ADF content on ruminal fluid pH, buffering capacity, and buffer value index was measured. Four lactating Holstein cows (two primiparous) averaging 72 +/- 60 DIM were used in a 4 x 4 Latin square with 3-wk experimental periods. Treatments were a 2 x 2 factorial arrangement of TMR containing two ADF concentrations (16 and 21% of DM) and two buffer value indexes (calculated from analysis of individual dietary ingredients to be -200 and 0). Milk fat content and milk fat yield tended to be increased by high ADF, and protein yield tended to increase with low buffer value index and low ADF. Although the high ADF diets increased ruminal fluid pH, they reduced buffering capacity; because the magnitude of the pH increase was greater than the reduction in buffering capacity, ruminal fluid buffer value index was increased by added ADF. The high buffer value index diets reduced ruminal fluid pH and increased ruminal fluid buffering capacity; effects on pH outweighed those on buffering capacity so that the ruminal fluid index paradoxically decreased as the dietary index increased. Ruminal fluid acetate increased and propionate decreased as ADF increased. We conclude that ruminal fluid buffer value index increases with dietary ADF, likely because of reduced ruminal concentrations of fermentation acids. Because diets with the highest index produced the lowest ruminal indexes, dietary buffer value index must be studied further before it can be included in any model purporting to predict the need for supplemental dietary buffers.

Acetates↗
PubMed1997

Production and composition of milk from Jersey cows administered bovine somatotropin and fed ruminally protected amino acids.

Eight multiparous and 4 primiparous Jersey cows averaging 92 d of lactation were utilized in a replicated 4 x 4 Latin square design with 28-d periods to determine responses to bovine somatotropin (bST) and ruminally protected Met and Lys when diets were fed that contained supplemental fat. Treatments were 1) control [no bST or ruminally protected amino acids (AA)], 2) control plus bST, 3) control plus ruminally protected AA, and 4) control plus bST plus ruminally protected AA. Dry matter intake was increased by bST but was unaffected by ruminally protected AA. Milk yield was increased by bST but was not altered by ruminally protected AA compared with the control diet. The bST tended to increase percentages of fat and total solids in milk and increased yields of fat, protein, 3.5% fat-corrected milk, and total solids. Ruminally protected AA increased percentages of fat, protein, and total solids in milk; however, yields of milk components were unaffected by ruminally protected AA. Body weight and body condition scores were unaffected by treatment. Concentrations of essential AA in plasma were unaffected by bST administration. Ruminally protected Met and Lys increased the concentration of Met and tended to increase the concentration of Lys in plasma. The lack of an increase in yields of milk and milk protein when ruminally protected AA were fed suggests that adequate amounts of Met and Lys were supplied by the control diet and protein reserves of the cows to meet the AA requirements for synthesis of milk and milk components.

Amino Acids↗
PubMed1999

Diagnostic methods for the detection of subacute ruminal acidosis in dairy cows.

Two experiments were conducted 1) to validate a field protocol for the determination of ruminal pH and 2) to develop a strategy to interpret ruminal pH data from groups of cows. In the first experiment, ruminal fluid was collected from 30 lactating dairy cows. Ruminal fluid pH was 0.28 pH units lower for fluid collected by rumenocentesis than for fluid collected through a ruminal cannula. Concentrations of volatile fatty acids were correspondingly higher in samples collected by rumenocentesis. A portable pH meter capable of measuring pH of a very small volume of ruminal fluid yielded very similar pH readings as did a standard meter with a pH probe. Filtration or aspiration of ruminal fluid had no effect on pH. In the second experiment, a strategy was developed to use ruminal pH values from a subsample of cows to distinguish between groups fed either a low or higher forage diet. Groups could be distinguished using a cut point of 5.5 ruminal pH, a sample size of 12 cows, and a critical value of 3 or more cows below the cut point. This strategy had the lowest theoretical error rate for herds with either a high or low prevalence of cows with a low ruminal pH.

Acidosis↗
PubMed1989

[Salivary microbial flora of mentally retarded persons with rumination].

The salivary microflora of institutionalized mentally retarded persons with chronic rumination was investigated, especially emphasizing the occurrence of the aciduric microorganisms such as mutans streptococci, lactobacilli and yeasts. 10 of those subjects together with 10 control subjects resident in the same institution were selected at random. The control subjects were mentally retarded but without rumination. Samples of saliva were collected about 2 hours after lunch. The results obtained were as follows: 1. Dental caries was more prevalent and advanced in those ruminating than the control subjects. 2. The mean salivary pH-value in the ruminating subjects was significantly lower than the control subjects. 3. The proportional distribution of the genera or species of salivary microorganisms cultivated on the blood agar plates was similar for both the ruminating and non-ruminating subjects. The only difference was observed in the genus of Actinomyces, which was less frequently isolated from the ruminating subjects. 4. Mutans streptococci, lactobacilli and yeasts recovered from their respective selective media were significantly predominant in those ruminating compared with control subjects. 5. Positive correlations among the cell count of mutans streptococci, lactobacilli and yeasts were found in the ruminating subjects. The yeasts isolated were classified exclusively into Candida albicans. 6. The results described above suggest that long-lasting acidic milieu in the oral cavities of the ruminating subjects favors the proliferation of mutans streptococci, lactobacilli and yeasts, resulting in the prevalence of dental caries in those subjects.

Adolescent↗