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PubMed2003

Clinical manifestations of VX poisoning following percutaneous exposure in the domestic white pig.

Nerve agents are a class of organophosphorus chemicals that inhibit certain cholinesterase enzymes (ChE). If untreated, percutaneous exposure to nerve agents, such as VX (O-ethyl-S-[2(diisopropylamino)ethyl] methylphosphonothioate) can cause paralysis, apnoea and death. Much of the information concerning the percutaneous absorption and subsequent toxicity of nerve agents has been obtained using various rodent models. However, the most relevant 'skin model' is arguably the pig. Therefore, the purpose of this study was to examine the clinical manifestations of VX intoxication in the domestic white pig following a 2 LD50 (120 microg/kg) percutaneous challenge. There was a consistent onset of signs (where present) in each animal: mastication was followed by miosis, salivation, fasciculations and apnoea. Whilst ChE activity did not correlate with the onset of signs, there was a qualitative relationship in that mastication preceded substantial ChE inhibition, miosis lagged behind the linear decrease in acetylcholinesterase (AChE) activity and fasciculations and apnoea occurred after maximum ChE inhibition had been attained (5-10% of normal). These observations may be of use for the triage of patients exposed to VX. In comparison with similar studies with GD, VX did not affect glucose utilization. However, VX was similar to GD in that it caused a mild hyperkalaemia and hyperphosphataemia, although the significance of this observation was not clear. There was substantial lateral diffusion of the initial droplet of VX over the application site, indicating that, when decontaminating exposed skin, attention should also be directed to areas peripheral to the original site of exposure.

Acetylcholinesterase↗
PubMed1991

Computed tomography of maxillofacial infection.

Eighteen patients with maxillofacial infections, who had trismus and swelling of the masseteric region, were investigated by CT. Spread of infection was evaluated with particular reference to the fascial spaces. The masticator space was divided into four parts and the changes in each were assessed together with the surrounding fascial spaces. There were changes in the masseter muscle and infection had spread into the upper parts of the masticator space in more than half of the patients. There was a fall in the CT value in the affected muscles, whereas it was raised in the parotid gland and adipose tissue. The clinical importance of CT is shown to have a significant role in the diagnosis and follow-up of maxillofacial infections.

Adipose Tissue↗
PubMed2005

Fractal dimension and lacunarity analysis of dental radiographs.

OBJECTIVE: As the occlusal forces transmitted to the jaw bones during mastication might be different in dentate and edentulous regions, there might be different radiographical trabecular bone texture in these regions. Image analysis procedures are promising techniques which are used to detect structural changes of bone texture on radiographs. In this study, the differences of fractal dimension (FD) and lacunarity measurements of radiographical trabecular bone between dentate and edentulous regions were investigated. METHODS: Direct digital radiographs of premolar-molar region were taken from 51 patients who were included in our study. Two rectangular regions of interest (ROIs) with the same dimensions (37x119 pixels) were created on these radiographs; one in the edentulous region and the other one in the dentate region. The ROIs were segmented as black and white areas. Box-counting fractal dimension and lacunarity of these regions were calculated. RESULTS: Paired samples t-test and Pearson correlation coefficients were calculated. It was found that there were differences between dentate and edentulous regions for FD and lacunarity (P=0.000). There is a negative correlation between FD and lacunarity (-0.643, P<0.01), positive correlation between dentate and edentulous regions and FD (0.819, P<0.01), and a negative correlation between lacunarity and dentate and edentulous regions (-0.541, P<0.01). CONCLUSIONS: The differences of occlusal forces generated in dentate and edentulous regions during mastication cause some alterations in trabecular bone structure, and fractal dimension and lacunarity can reveal these alterations quantitatively.

Adult↗
PubMed1994

[Biting force and physical fitness in athletes].

The maximum biting force in 82 male athletes and 12 male subjects without any particular athletic activity (nonathletes) were measured in order to evaluate the relationship between biting force and physical fitness in athletes. The results obtained were as follows. 1. The maximum biting force in athletes (50.8 +/- 17.4kg) were significantly (p < 0.01) higher than that in the nonathletes (28.1 +/- 9.1kg). The maximum biting forces in the men who belonged to the rugby or judo clubs were predominantly higher than in other subjects. 2. In men who masticated on the left side of the mouth, the habitual (i. e., left) biting force was significantly higher than the nonhabitual (i. e., right) biting force. In men who masticated on the right side of the mouth, the habitual (i. e., right) biting force was also higher than the nonhabitual (i. e., left) biting force, but was not significantly so. 3. There was a significant positive correlation between the biting force and grip strength and back strength in athletes. In athletes, there was a significant correlation between biting force and the numbers of chin-ups, the numbers for the side-step tests and the time for 50m running.

Adult↗
PubMed1994

Bioceramic implantation in the intermandibular space in bilateral rostral mandibulectomy of the dog.

Effect of bioceramic implantation on the intermandibular space along with plating in rostral mandibulectomy was investigated in the dog. In this group, bioceramic beads consisting of a complex of hydroxyapatite and tricalcium phosphate were implanted in the intermandibular space between the lingual surfaces of the fracture ends. In two other groups, the dogs received only plating on the ostectomized end, or they received only rostal mandibulectomy without plating. No difficulty in mastication was observed in the implanted group after surgery. In the dogs which received plating, however, difficulty was noted only in the 4th week when wet food was replaced by dry food, and in the control group in the 6th week after the surgery. From the radiological and microscopical findings, in dogs with only plating or without the fixation there was no bony union in the intermandibular space at 16 weeks, though the increase in fibrous tissue and bony callus in the area was much greater in the plated dogs than in the control group. In the implanted group, on the other hand, the increase in callus formation was considerable compared to the other groups. Moreover, the lingual surfaces of the fracture ends were well ossified at 12 postoperative weeks. This suggests that in canine bilateral rostral mandibulectomy the stabilization of the fracture ends with plates and bioceramic implants filling a gap in the intermandibular space may enhance the ossification between the fracture ends and prevent postoperative difficulty in mastication.

Animals↗
PubMed1998

Chewing gum bezoars of the gastrointestinal tract.

Children have chewed gum since the Stone Age. Black lumps of prehistoric tar with human tooth impressions have been found in Northern Europe dating from approximately 7000 BC (Middle Stone Age) to 2000 BC (Bronze Age). The bite impressions suggest that most chewers were between 6 and 15 years of age. The Greeks chewed resin from the mastic tree (mastic gum). North American Indians chewed spruce gum. The first manufacturing patent for chewing gum was issued in 1869 for a natural gum, chicle, derived from the Sopadilla tree, indigenous to Central America. Chewing gum sold today is a mixture of natural and synthetic gums and resins, with added color and flavor sweetened with corn syrup and sugar. Chewing gum is big business. A significant amount of the $21 billion US candy industry sales is from chewing gums, many of which appeal almost exclusively to children. Despite the history and prevalence of gum chewing, the medical literature contains very little information about the adverse effects of chewing gum. In the present report, we briefly review gum-chewing complications and describe three children who developed intestinal tract and esophageal obstruction as a consequence of swallowing gum.

Bezoars↗
PubMed2002

The effect of feeding on the respiratory activity of the sloth.

The aim of the present study was to confirm whether feeding influences the resting breathing rate and to observe possible alterations in blood gas and pH levels produced by feeding in unanesthetized sloths (Bradypus variegatus). Five adult male sloths (4.1 +/- 0.6 kg) were placed daily in an experimental chair for a period of at least 4 h for sitting adaptation. Five measurements were made for each sloth. However, the sloths one, two and five were studied once and the sloths three and four were studied twice. Breathing rate was determined with an impedance meter and the output signal was digitized. Arterial blood samples were collected for blood gas analysis with a BGE electrolytes analyzer and adjusted for the animal's body temperature and hemoglobin content. The data are reported as mean +/- SD and were collected during the resting period (8:00-10:00 h) and during the feeding period (16:00-18:00 h). The mean breathing rate increased during mastication of ymbahuba leaves (rest: 5.0 +/- 1, feeding: 10 +/- 1 bpm). No significant alterations were observed in arterial pH (rest: 7.42 +/- 0.05, feeding: 7.45 +/- 0.03), PCO2 (rest: 35.2 +/- 5.3, feeding: 33.3 +/- 4.4 mmHg) or PO2 (rest: 77.5 +/- 8.2, feeding: 78.4 +/- 5.2 mmHg) levels. These results indicate that in unanesthetized sloths 1) feeding evokes an increase in breathing rate without a significant change in arterial pH, PCO2 or PO2 levels, and 2) the increase in breathing rate produced by feeding probably is due to the act of mastication.

Animals↗
PubMed2003

[Evaluation of condylar fractures treatment].

BACKGROUND: We analysed 40 patients with mandibular condylar process fractures, treated through the closed (intermaxilary fixation or conservatively) or open methods (wire internal fixation,titanium miniplates, bone reduction or articular exploration), from January 1993 to January 1999. METHODS: We evaluated these patients clinically with pre-determined criteria through the temporomandibular articulation touching (ATM), by observing the mandibular symmetry, dental oclusion, deviation to the mouth opening and maximum interincisal opening, besides the questionnaire about the complaints at ATM, disfunction of the mastication system and satisfaction of the treatment. We found an index of good clinical results of, at least, 70% (in the maximum interincisal opening) in the patients submitted to IMF. In the conservative method, we found an index of, at least, 42.9% and in the patients submitted to wire open reduction, at least, 28.6% (in the ATM touching exam) without significant difference in the clinical exams; the pain index at ATM in the closed method was 3.7% and in the open one was 15.4%; mastication disfunction was 22.2% in the closed method and 15.4% in the open one; we only found 7.1% dissatisfied patients in the closed method. There was no significant difference in the method results. CONCLUSIONS: The closed method - with IMF and conservative - and the open reduction - with ORIF - brought good clinical results in an evaluation up to 6 months. We could also conclude that there is no difference in the complaint results after the open or closed treatment according to the patients' opinion.

Adolescent↗
PubMed1989

[Prosthetic rehabilitation with the removable partial dentures using telescopic crowns after removal of unsuccessful dental implants].

It is well-known that unsuccessful dental implants sometimes give rise to pronounced inflammatory bone resorption of the upper and lower jaw, and that in such cases it is practically much difficult to attain adequate prosthodontic rehabilitation after removal of the implants. On this study it is completely reported that two patients suffering from implant-induced osteomyelitis could be finely compensated for with the removable partial dentures using telescopic crowns after removal of the implants, and then the results are shortly discussed from the view of pathology, oral surgery and prosthodontics. In the first case a 52-year-old woman had been suffering from osteomyelitis of the right mandible due to the both bladevent and endodontic-endosseous implant, and in another case a 43-year-old woman had been suffering from osteomyelitis of the right maxilla due to the endosseous subperiosteal implant, and they had borne insufficient mastication on the affected side of the jaws. Several months after removal of the unsuccessful dental implants, they were rehabilitated with the removable partial dentures using telescopic crowns to recover and maintain good functions such as occlusion, mastication, cosmetics and speech, and oral and general health.

Adult↗
PubMed2004

[Selection of occlusal scheme on the basis of pressure distribution on supporting structures under complete dentures].

In case of making complete dentures, we have to consider not only denture stability but also the restoration of aesthetics and function such as mastication and speech. However these are contradictory theoretically from the point of view of denture stability, and it is very difficult to satisfy both requirements in the case of a patient who has poor upper and lower alveolar ridges. We investigated the effect of artificial posterior teeth form and occlusal scheme on the distribution of pressure on supporting structures under complete dentures during mastication with upper and lower edentulous simulators. In this report, a guideline for the selection of occlusal scheme for complete dentures, based on our previous investigations, is described. The occlusal scheme remarkably affected the distribution of pressure under simulated complete dentures, as shown by comparing the distribution of pressure using two different occlusal schemes:fully balanced occlusion and lingualized occlusion. However other factors such as posterior teeth form and position affect the distribution of pressure as well, and are related to each other. Therefore, not only occlusal scheme but also posterior artificial teeth form has to be considered, and the form of posterior teeth should be carefully and comprehensively decided when making complete dentures.

English Abstract↗
PubMed1997

Imaging the temporal fossa.

OBJECTIVE: The purpose of our study was to delineate the interconnections in the temporal fossa that are visible on high-resolution clinical images. SUBJECTS AND METHODS: Thin-section MR images and CT scans of the temporal fossa in two normal volunteers were obtained in coronal and axial sections. MR images, CT scans, or both of 20 patients with demonstrable spread of disease were reviewed. RESULTS: The imaging studies of patients with disease proved more informative than images of the normal subject or the published anatomic and surgical descriptions of the temporal fossa. We recognized five discrete radiographically defined regions: the connective tissue layer, compartment of the superficial fat pad, compartment of the deep fat pad, compartment of the temporal muscle (superior recess of the suprazygomatic masticator), and subperiosteal zone. Important, tortuous, and to our knowledge undescribed interconnections between the scalp, posterior neck, eyelid, face, and the suprazygomatic masticator were delineated. CONCLUSION: Imaging studies of the temporal fossa can be used to formulate a clinically useful approach that simplifies the complex anatomy of the temporal fossa.

Adipose Tissue↗
PubMed1989

On the distribution of elastic fibers in the filiform papillae of Suncus murinus.

The distribution of elastic fibers in the filiform papillae of 1, 2, 3, 4 and 5 week-old and 6 month-old Suncus (Suncus murinus; insectivora) was examined by both Weigert's resorcin-fuchsin method and ultrastructural means. In the adult Suncus (6 months old), elastic fibers in the connective tissue core of the papillae were aligned perpendicularly to the epithelial surface and formed a palisade-like structure which encircled the margin of each connective tissue core. This characteristic structure was restricted to the filiform papillae in the anterior half of the lingual dorsum. In the filiform papillae of the posterior half, elastic fibers were markedly reduced and the palisade-like structure was not present. This characteristic pattern of elastic fiber distribution was established by 3 weeks of age. These observations reveal a characteristic structure consisting of elastic fibers in the connective tissue core of the filiform papillae and the regional distribution of this structure in the tongue. This suggests that the function of the structure in the connective tissue core is to protect against mechanical stress in mastication. The regional distribution of this structure may reflect the difference of mechanical strength between the anterior and posterior of the tongue caused by tongue movement during mastication.

Animals↗
PubMed1993

Forage quality and grazing steer performance from Tifton 85 and Tifton 78 bermudagrass pastures.

A new high-yielding bermudagrass hybrid, Tifton 85, produced 26% higher DM yield (P = .05) with 11% higher IVDMD (P = .05) than Coastal in two 3-yr yield trials. Tifton 78 and Tifton 85 were established in duplicate .81-ha pastures in 1988 and were grazed during 1989, 1990, and 1991 using a variable stocking rate method. Four tester steers per pasture with 269 kg initial BW grazed continuously for 169 d/yr beginning in April. Forage mass, targeted at 2,800 kg of DM/ha, was maintained by adjusting stocking rates at 14-d intervals to correspond with ground-level forage samples taken at 14-d intervals. Pastures received 84 kg of N/ha in March, June, and August of each year. Nutritive value was assessed using whole masticate samples from two esophageal cannulated steers grazing each pasture in late May, mid-July, or early September. The 3-yr mean masticate analyses revealed similar CP for Tifton 78 and Tifton 85 in May and July, but higher (P < .05) CP for Tifton 85 than for Tifton 78 in September. The IVDMD was higher (P < .05) in May and September for Tifton 85 than for Tifton 78; and, mean and medium particle sizes were greater (P < .05) for Tifton 85 than for Tifton 78 in May, July, and September samples.(ABSTRACT TRUNCATED AT 250 WORDS)

Animal Feed↗
PubMed1993

Forage intake and digestion by cattle grazing midgrass prairie rangeland or sideoats grama/sweetclover pasture.

In mid-May, beef cattle fitted with esophageal (four steers/pasture) or ruminal and duodenal cannulas (six heifers/pasture; 274 +/- 6 kg BW +/- SE) grazed midgrass prairie (excellent range condition; PRAIRIE) or a seeded mixture of sideoats grama (48% of pasture DM) and sweetclover (6% of pasture DM; Bouteloua curtipendula [Michx.] Torr./Melilotus officinalis [L.] Lam.; PASTURE). Masticate NDF, ADF, and in vitro OM disappearance did not differ (P > .11) between forage types (average = 66.6, 36.1, and 58.8% of OM). Only N differed (P = .02) between PRAIRIE (2.1) and PASTURE (2.4% of OM). Extents of in situ OM and N disappearance were greater (P < .05) and rate of N disappearance between 12 and 36 h was slower (P < .10) from PRAIRIE than from PASTURE masticate. Based on in situ data, the ruminally degraded N: ruminally degraded OM (grams/kilogram) ratio differed (P < .05) between PRAIRIE (22) and PASTURE (25). Ruminal ammonia N concentration (milligrams/deciliter) was less (P = .02) for PRAIRIE (2.8) than for PASTURE (3.8). Forage OM intake and fecal OM output did not differ (P > .72; average = 8,207 and 3,380 g/d), but duodenal OM flow tended (P = .13) to be greater (PRAIRIE = 4,892, PASTURE = 5,170 g/d) in cattle grazing PASTURE. Apparent and true ruminal OM digestion did not differ between forage types (P > .18; average = 38.3 and 48.5%). Nitrogen intake, nonammonia N, and forage N flow at the duodenum were greater (P < .04) for PASTURE (198 vs 171, 242 vs 210, and 162 vs 135 g/d) than for PRAIRIE. Microbial N flow (average = 78 g/d) and microbial efficiency (average = 20 g of microbial N/kg of OM truly fermented) did not differ (P > .25) between forage types. Apparent and true ruminal N digestion did not differ (P > .65; average = -26.6 and 19.3%) between forage types. Flow of nonammonia N was in excess relative to digestible OM intake; hence, digestible OM intake seemed to be first-limiting for performance by cattle grazing either forage type.

Animal Feed↗
PubMed1994

Steers grazing intermediate wheatgrass at various stages of maturity: effects on nutrient quality, forage intake, digesta kinetics, ruminal fermentation, and serum hormones and metabolites.

Six ruminally cannulated Holstein steers (average BW of 495 +/- 5 kg) grazed a 32-ha, nonirrigated, intermediate wheatgrass (Thinopyrum intermedium Host) pasture from April 10 through December 7. Sample collections were conducted in May, June, September, and November 1989. Total masticate N decreased (P < .05) and bound N increased (P < .05) with advancing forage maturity. Masticate in vitro OM disappearance was lower (P < .05) in November (40.5%) than in May (62.0%). Organic matter intake (grams/kilogram of BW) decreased (P < .05) at each sampling date (May = 35.7, June = 26.8, September = 20.0, November = 14.9). Correspondingly, particulate passage rate decreased and gastrointestinal mean retention time increased (P < .05) with advancing forage maturity. Extent and rate of NDF digestion were greater (P < .05) during May and June than during September and November. Ruminal NH3 N and total VFA concentrations were greater (P < .05) during May and June than during September and November. Advancing forage maturity did not alter (P > .10) serum growth hormone concentrations; however, nonesterified fatty acid concentrations were greater (P < .05) during September and November than during May and June. Serum insulin-like growth factor I decreased (P < .05) with advancing forage maturity. Seasonal changes in forage intake and ruminal fermentation suggest that animal performance might be increased if supplemental energy is provided early in the growing season of intermediate wheatgrass; however, supplemental protein would likely be needed as wheatgrass matures.

Animal Feed↗
PubMed2001

Supplemental soybean oil or corn for beef heifers grazing summer pasture: effects on forage intake, ruminal fermentation, and site and extent of digestion.

Nine Angus x Gelbvieh heifers (average BW = 347 +/- 2.8 kg) with ruminal and duodenal cannulas were used in a split-plot designed experiment to determine the effects of soybean oil or corn supplementation on intake, OM, NDF, and N digestibility. Beginning June 8, 1998, heifers continually grazed a 6.5-ha predominantly bromegrass pasture and received one of three treatments: no supplementation (Control); daily supplementation of cracked corn (Corn) at 0.345% of BW; or daily supplementation (0.3% of BW) of a supplement containing cracked corn, corn gluten meal, and soybean oil (12.5% of supplemental DM; Oil). Soybean oil replaced corn on a TDN basis and corn gluten meal was included to provide equal quantities of supplemental TDN and N. Three 23-d periods consisted of 14 d of adaptation followed by 9 d of sample collections. Treatment and sampling period effects were evaluated using orthogonal contrasts. Other than crude fat being greater (P = 0.01) for supplemented heifers, chemical and nutrient composition of masticate samples collected via ruminal evacuation did not differ (P = 0.23 to 0.56) among treatments. Masticate NDF and ADF increased quadratically (P < or = 0.003) and N decreased linearly (P = 0.0001) as the grazing season progressed. Supplementation did not influence (P = 0.37 to 0.83) forage OM intake, total and lower tract OM digestibility, ruminal and total tract NDF digestibility, or total ruminal VFA; however, supplemented heifers had lower ruminal molar proportions of acetate (P = 0.01), higher ruminal molar proportions of butyrate (P = 0.007), and greater quantities of OM digested in the rumen (P = 0.10) and total tract (P = 0.02). As the grazing season progressed, total tract OM and N and ruminal NH3 concentrations and NDF digestibility decreased quadratically (P < or = 0.04). Microbial N flow (P = 0.09) and efficiency (P = 0.04) and postruminal N disappearance (P = 0.02) were greater for Control heifers and declined linearly (P < or = 0.02) as the grazing season advanced. Depressed microbial N flow seemed to be more pronounced for Oil than for the Corn treatment. Although total digestible OM intake increased with supplementation, metabolizable protein supply was reduced in supplemented heifers. Therefore, feeding low levels of supplemental grain with or without soybean oil is an effective strategy to increase dietary energy for cattle grazing high-quality forages, but consideration should be given to reduced supply of metabolizable protein.

Animal Feed↗
PubMed2004

Effect of field pea-based creep feed on intake, digestibility, ruminal fermentation, and performance by nursing calves grazing native range in western North Dakota.

Two experiments evaluated digestive and performance effects of field pea-based creep feed in nursing calf diets. In Exp.1, eight nursing steer calves (145 +/- 27 kg initial BW) with ruminal cannulas were used to evaluate effects of supplementation and advancing season on dietary composition, intake, digestion, and ruminal fermentation characteristics. Treatments were unsupplemented control (CON) and field pea-based creep (SUP; 19.1% CP, DM basis) fed at 0.45% BW (DM basis) daily. Calves grazed native range with their dams from early July through early November. Periods were 24 d long and occurred in July (JUL), August (AUG), September (SEP), and October (OCT). Experiment 2 used 80 crossbred nursing calves, 48 calves in yr 1 and 32 calves in yr 2 (yr 1 = 144 +/- 24 kg; yr 2 = 121 +/- 20 kg initial BW), to evaluate effects of field pea-based creep on calf performance. Treatments included unsupplemented control (CON); field pea-based creep feeds containing either 8% (LS); or 16% (HS) salt; and soybean meal/field pea-based creep containing (as-fed basis) 16% salt (HIPRO). Masticate samples from SUP calves in Exp.1 had greater CP (P = 0.05) than those from CON calves. Forage CP and ADIN decreased linearly with advancing season (P = 0.01 and 0.03, respectively). In vitro OM digestibility of diet masticate decreased from JUL to OCT (P < 0.01; 58.5 to 41.3%). Forage intake did not differ (P = 0.33) between treatments but increased linearly with advancing season (1.67, 1.90, 3.12, 3.38 kg/d for JUL, AUG, SEP, and OCT, respectively; P < 0.01). Milk intake (percentage of BW) did not differ (P = 0.56) between CON and SUP calves but decreased linearly (P < 0.01) with advancing season. Supplemented calves had greater (P = 0.03) total intake (g/kg of BW; forage + milk + creep) compared with CON calves. Treatment did not affect (P < 0.30) rate of in situ disappearance of forage or creep. Forage DM, CP, and creep DM disappearance rate decreased linearly (P < or = 0.02) with advancing season. Supplementation decreased (P = 0.05) ruminal pH, whereas ruminal ammonia and VFA concentrations were greater (P < or = 0.02) in SUP calves. In Exp. 2, creep-fed calves had greater ADG and final BW than CON calves (P < 0.01). Calves offered HS tended (P = 0.07) to have increased gain efficiency above CON than LS calves. Field peas can be used as an ingredient in creep feed to increase calf weight gain without negatively affecting ruminal fermentation and digestion.

Animal Feed↗
PubMed2005

Models for estimating parameters of neutral detergent fiber digestion by ruminal microorganisms.

Model assumptions included number of concurrently degrading entities (or pools) and expected distributions of undegraded NDF. Degradation processes modeled included a single pool with ruminal age-constant rates (exponential distribution), a single pool with a ruminal age-dependent rate, two pools with age-constant rates, two pools with age-dependent and age-constant rates, and a continuum of pools with a gamma distribution of age-constant rates. Various sizes of ingestively masticated fragments of bermudagrass hay or corn silage were obtained via wet sieving of esophageal masticate and incubated in vitro with ruminal fluid for 0 h, every 6 h up to 48 h, and every 12 h up to 168 h. Models assuming a single pool of age-constant or age-dependent rates had larger mean residual mean squares (P < 0.05) than did the gamma mixture model or the two-pool models. Degradation rates estimated by the gamma mixture model indicated distribution of rates ranging from near exponential, age-constant distribution to a near normal bell-shaped distribution of age-constant rates for different datasets. Superior fit by the two-pool models in most datasets (83%) indicated that having two resolvable entities of potentially degradable NDF with different degradation rates was causal of a biphasic distribution of lifetimes. Increasing order of age-dependency modeled in the two-pool model improved fit and precision of estimation (standard error of estimate) for the limit parameters of time delay and indigestible NDF. Both the gamma mixture continuum of age-constant rate model and the two-pool, age-dependent models with a discrete time delay provided similar fit to data and flexibility for fitting data with lifetime distributions ranging from simple exponential to sigmodial. The two-pool, age-dependent and gamma-distributed, age-constant models were better in fitting the dominant biphasic lifetime distributions that occurred when the two pools of degrading entities were of similar size and in estimating the discrete time delay when strategic, quality data were available. Having fewer parameters (four), the gamma-distributed, age-constant model was superior when data quality was limited.

Animal Nutritional Physiological Phenomena↗