Predicting fecal nutrient concentrations and digestibilities and growth performance in feedlot cattle by near-infrared spectroscopy.

Fecal nutrients and apparent total tract digestibility (ATTD) were predicted using near-infrared spectroscopy (NIRS) of feces collected from the pen floor or the rectum of feedlot cattle in 2 studies, and pen floor samples were assessed for their ability to predict NE, ADG, and G:F. In study 1, 160 crossbred beef steers in 16 pens (4 pens per treatment) were fed dry-rolled barley or wheat (89% of diet DM) processed at 2 levels. Study 2 utilized 160 crossbred beef steers in 20 pens (5 pens per treatment) that were fed dryrolled barley with 4 levels of barley silage (0%, 4%, 8%, and 12% of diet DM). Both studies fed steers to a target weight of 650 kg. Differences in composition of feces collected from the rectum and the pen floor of a subset of steers (3 to 7) were examined. Fecal pats from the pen floor of each pen were collected throughout the feeding period and composited by pen. Except for DM, which was higher ( 0.01) in pen floor than rectal fecal samples, there were minimal differences in fecal constituents between collection methods. In study 1, interactions between grain type and processing index ( ≤ 0.05) were observed, with a reduction in DM, OM, and starch and an increase in NDF and ADL concentrations being associated with more extensively processed wheat than barley. As grain was more extensively processed, ATTD of all nutrients increased ( 0.01). In study 2, fecal ADF and ADL linearly increased ( 0.01) with increasing silage in the diet, whereas fecal DM and N linearly decreased ( 0.01). Digestibility of all nutrients except starch linearly decreased ( 0.01) with increasing silage. Apparent total tract digestibility of GE predicted using NIRS was related to NEg of the diets as estimated by performance for the wheat-fed steers in study 1 ( = 0.58, = 0.03) and those fed increasing silage in study 2 ( = 0.43, < 0.01). Similarly, observed ADG could be predicted using NIRS for steers fed wheat in study 1 ( = 0.48, = 0.05) and silage in study 2 ( = 0.40, < 0.01), but G:F could not. Using NIRS of feces collected from multiple cattle off the feedlot pen floor demonstrated potential for predicting growth performance of finishing cattle. However, grain type and stage of maturity of the cattle impacted the predictability of equations. Increasing the sample size and sampling frequency may be necessary to improve predictions.

Effect of diastatic power and processing index on the feed value of barley grain for finishing feedlot cattle.

The objective of this study was to assess the nutritional value of barley grain differing in diastatic power (DP; high vs. low; a malt trait) and processing index (PI; 75 vs. 85). One hundred sixty Angus × Hereford crossbred yearling steers (467 ± 38 kg; 144 intact and 16 rumen cannulated) were used in a complete randomized 2 × 2 factorial experiment. Steers were assigned to 16 pens, 8 of which were equipped with the GrowSafe system to measure individual feed intake. Cannulated steers (2 per pen) were randomly assigned to the 8 GrowSafe pens. Diets consisted of high- or low-DP barley grain (80.0% of diet DM) processed to an index of either 75 or 85% (PI-75 and PI-85, respectively). Ruminal pH in cannulated steers was measured over four 5-d periods using indwelling electrodes. Fecal samples were collected every 28 d from the rectum of each steer to assess digestibility using AIA as a marker. No differences ( > 0.10) in rumen pH were observed among cattle as measured by the indwelling pH meters. However, lower ( < 0.05) rumen pH was observed for steers fed low- as opposed to high-DP barley in rumen samples collected just prior to feeding and measured in the laboratory. Intake of DM and OM were not affected ( ≥ 0.24) by DP but were lower ( < 0.01) with more severe processing (PI-75 vs. PI-85). Low-DP barley tended to exhibit higher ( = 0.09) total tract DM digestibility than high-DP barley. Steers fed PI-75 barley also had higher ( = 0.06) G:F and NEg. Digestibility of DM, OM, CP, NDF, and starch was higher ( < 0.05) for PI-75 barley than for PI-85 barley. Low-DP barley increased ( < 0.05) carcass dressing percentage by 0.5% compared with high-DP barley, with a lower PI tending to increase ( = 0.06) rib eye area. Compared with steers fed high-DP diets, steers fed low-DP diets had more ( = 0.01) total (41.7 vs. 19.4%) and severe liver abscesses (22.2 vs. 9.7%). Results suggest that although low-DP barley increased liver abscesses, differences in DP did not alter digestion or growth performance but low-DP barley did improve dressing percentage. Barley with different DP responded similarly to processing, with more intensive processing (PI-75) of barley improving starch digestion, feed efficiency, and NEg without negatively affecting rumen pH.

Evaluation of in vitro models for predicting acidosis risk of barley grain in finishing beef cattle.

Our objective was to develop a model to predict the acidosis potential of barley based on the in vitro batch culture incubation of 50 samples varying in bulk density, starch content, processing method, growing location, and agronomic practices. The model was an adaptation of the acidosis index (calculated from a combination of in situ and in vitro analyses and from several components of grain chemical composition) developed in Australia for use in the feed industry to estimate the potential for grains to increase the risk of ruminal acidosis. Of the independent variables considered, DM disappearance at 6 h of incubation (DMD6) using reduced-strength (20%) buffer in the batch culture accounted for 90.5% of the variation in the acidosis index with a root mean square error (RMSE) of 4.46%. To evaluate our model using independent datasets (derived from previous batch culture studies using full-strength [100%] buffer), we performed another batch culture study using full-strength buffer. The full-strength buffer model using in vitro DMD6 (DMD6-FS) accounted for 66.5% of the variation in the acidosis index with an RMSE of 8.30%. When the new full-strength buffer model was applied to 3 independent datasets to predict acidosis, it accounted for 20.1, 28.5, and 30.2% of the variation in the calculated acidosis index. Significant ( < 0.001) mean bias was evident in 2 of the datasets, for which the DMD6 model underpredicted the acidosis index by 46.9 and 5.73%. Ranking of samples from the most diverse independent dataset using the DMD6-FS model and the Black (2008) model (calculated using in situ starch degradation) indicated the relationship between the rankings using Spearman's rank correlation was negative (ρ = -0.30; = 0.059). When the reduced-strength buffer model was used, however, there were similarities in the acidosis index ranking of barley samples by the models as shown by the result of a correlation analysis between calculated (using the Australian model) and predicted (using the reduced-strength buffer DMD6 model) acidosis index (ρ = 0.67; < 0.001). Results suggest that our model, which is based on a reduced-strength buffer in vitro DMD6, has the potential to predict acidosis risk and can rank barley samples based on their acidotic risk. Nonetheless, the model would benefit from further refinement by expanding the database.

A noncalibration spectroscopic method to estimate ether extract and fatty acid digestibility of feed and its validation with flaxseed and field pea in pigs.

Digestibility of ether extract (EE) or fatty acids (FA) is traditionally measured by chemical analyses for EE or GLC methods for FA combined with marker concentration in diet and digesta or feces. Digestibility of EE or FA may be predicted by marker concentrations and spectral analyses of diet and digesta or feces. On the basis of Beer's law, a noncalibration spectroscopic method, which used functional group digestibility (FGD) determined with marker concentration and peak intensity of spectra of diets and undigested residues (digesta or feces), was developed to predict the apparent ileal digestibility (AID) of total FA and apparent total tract digestibility (ATTD) of EE. To validate, 4 diets containing 30% flaxseed and field pea coextruded with 4 extruder treatments and a wheat and soybean basal diet with predetermined AID of total FA and ATTD of EE were used. Samples of ingredients, diets, and freeze-dried digesta and feces were scanned on a Fourier transform infrared (FT-IR) instrument with a single-reflection attenuated total reflection (ATR) accessory. The intensity of either the methylene (CH2) antisymmetric stretching peak at 2,923 cm(-1) (R(2) = 0.90, P < 0.01) or the symmetric stretching peak at 2,852 cm(-1) (R(2) = 0.86, P < 0.01) of ingredients, diet, and digesta spectra was related strongly to the concentration of total FA. The AID of total FA of diets measured using GLC was predicted by the spectroscopic method using FGD at 2,923 and 2,852 cm(-1) (R(2) = 0.75, P < 0.01) with a bias of 0.54 (SD = 3.78%) and -1.35 (SD = 3.74%), respectively. The accumulated peak intensity in the region between 1,766 and 1,695 cm(-1) of spectra was related to EE concentration in ingredients and diets (R(2) = 0.61, P = 0.01) and feces (R(2) = 0.88, P < 0.01). The relation was improved by using second-derivative spectra of the sum of peak intensities at 1,743 and 1,710 cm(-1) for ingredients and diets (R(2) = 0.90, P = 0.01) and at 1,735 and 1,710 cm(-1) for feces (R(2) = 0.92, P < 0.01). The ATTD of EE of test diets determined with proximate analysis was estimated by the FGD of nonderivative spectra with or without baseline (R(2) = 0.90, P < 0.01) with a bias of 3.15 (SD = 3.14%) and 3.50 (SD = 3.24%), respectively. In conclusion, instead of using GLC methods or predictions based on calibrations, the AID of total FA and ATTD of EE can also be estimated directly from ATR FT-IR spectra, provided the ratio of marker in the diet and undigested residue is known.

Evaluation of energy digestibility of canola coproducts by in vitro analyses and characterization of fat digestion using spectroscopy.

In vitro methods did not accurately predict in vivo apparent total tract digestibility of energy for canola coproducts (r = -0.81; P = 0.002). We scanned 153 samples of digesta, feces, and in vitro digestion residues (ivR) on a Fourier transform midinfrared instrument with a single-reflection attenuated total reflectance attachment. The second derivative spectral net intensities of the carbonyl ester peak at 1745 cm(-1) and olefinic hydrocarbon (=C-H) peak at 3008 cm(-1) were both higher in ivR than in feces (3.83 × 10(-04) vs. 3.46 × 10(-05) and 7.92 × 10(-05) vs. 5.17 × 10(-06), respectively; P < 0.001), indicating poor enzymatic digestion of unsaturated fat. In conclusion, fat digestion of in vitro procedure for canola coproducts requires improvement to adequately mimic in vivo digestion in pigs.

Development and validation of a spectroscopic method to predict wheat protein digestibility.

The CP digestibility is traditionally measured by chemical analyses of CP and marker concentration in digesta and diets. Potentially, CP digestibility can also be predicted by marker concentrations and spectral analyses of digesta and diet. Spectroscopy is a rapid, nondestructive method to ascertain qualitative and quantitative chemical information. Based on Beer's law, a spectroscopic method was developed to predict in vivo CP digestibility. To validate, samples of digesta and diet of wheat grain with predetermined apparent ileal digestibility (AID) of CP were scanned on a Fourier transform midinfrared (FTIR) instrument with a single-reflection attenuated total reflectance attachment. The AID of CP was calculated from peak intensities of spectra and measured marker concentrations in digesta and diet and then compared with in vivo AID of CP. The AID of CP of a wheat-based diet was predicted accurately with a deviation of 0.68 ± 0.86% from in vivo AID of CP ranging from 60.4 to 87.8%. Functional group digestibility based on the peak at 1,643 cm(-1) or the Amide I region was strongly correlated (r ≥ 0.99; P < 0.001) with in vivo AID of CP. In conclusion, instead of predictions based on calibrations, CP digestibility can also be potentially predicted directly from FTIR spectra.

Effects of rumen-undegradable protein sources and supplemental 2-hydroxy-4-(methylthio)-butanoic acid and lysine-HCl on lactation performance in dairy cows.

One hundred primiparous and multiparous Holstein cows were used in an experiment to evaluate the effect of supplementing diets with either a plant- or an animal-based source of rumen-undegradable protein (RUP), with or without AA supplementation, during the transition period and early lactation on milk production response. The experimental design was a randomized block design with approximately one-third of the cows being primiparous. Cows were assigned to 1 of 4 prepartum diets introduced 3 wk before the expected calving date and switched to the corresponding postpartum diet at calving. Diets 1 (AMI) and 2 (AMI+) included a vegetable RUP source (heat- and lignosulfonate-treated canola meal), with diet 2 containing supplemental Lys x HCl and Met hydroxy analog sources [D,L-2 hydroxy-4-(methylthio)-butanoic acid; Alimet feed supplement]. Diets 3 (PRO) and 4 (PRO+) consisted of a blend of animal RUP sources (blood meal, fish meal, feather meal, and porcine meat and bone meal), with diet 4 containing supplemental Lys x HCl and Met hydroxy analog sources [D,L-2 hydroxy-4-(methylthio)-butanoic acid; Alimet]. During the first 4 wk of lactation, dry matter intake was less when synthetic Lys x HCl and Alimet were supplemented, but this effect was no longer evident in wk 5 to 9 of the experiment. Interestingly, despite the initial decrease in dry matter intake in the cows fed AA-supplemented diets, there was no effect of treatment on milk production or the ratio of fat-corrected milk to dry matter intake throughout the 17 wk of the study. Undegradable protein source (vegetable vs. animal) did not affect dry matter intake, milk production, or 3.5% fat-corrected milk production for the first 17 wk of lactation. The results of this study indicate that heat- and lignosulfonate-treated canola meal can be used as a source of undegradable protein in place of high-quality rumen-undegradable animal protein sources without negative effects on milk production when diets are equivalent in rumen degradable protein, RUP, and metabolizable Met and Lys. Despite other reports citing clear benefits to feeding supplemental synthetic Lys or Met in diets fed to high-producing lactating dairy cows, we were unable to provide additional evidence to support these findings. Additionally, there was a trend for whole-blood Lys concentrations to be greater for diets supplemented with Lys x HCl.

The effect of formulation and amount of potassium fertilizer on macromineral concentration and cation-anion difference in tall fescue.

This study investigated the feasibility of altering the dietary cation-anion difference (DCAD) in grass by altering the grass variety and the amount and formulation of K fertilizer application. In experiment 1, treatments were combinations of 2 varieties (Barcel and Hi-Mag) of tall fescue (Festuca arundinacea Schreb); 2 rates of K (0 and 250 kg/ha), supplied as KCl; and 2 rates of Mg (0 and 60 kg/ha), supplied as MgO. In experiment 2, K fertilizer was applied at 0 or 125 kg/ha as KCl or K2SO4. There was no difference between HiMag and Barcel tall fescue in the concentrations of Mg, S, and Cl. Application of K fertilizer decreased concentrations of Mg, but the magnitude of the decrease was not consistent across harvests. Conversely, application of Mg fertilizer increased Mg concentrations, but again, the magnitude of the increase was not consistent across harvests. The concentrations of Ca were higher in HiMag than in Barcel tall fescue, with the magnitude of the difference increasing from first to last harvest. Potassium fertilizer decreased Ca concentrations in the first, fourth, and fifth harvests only. Calcium concentration was decreased by a greater magnitude in HiMag tall fescue as a result of Mg fertilization. The HiMag tall fescue contained lower concentrations of K than did Barcel tall fescue in the first, second, and third harvests. Application of K fertilizer increased the K concentration in all 5 harvests but did not affect Na concentrations except in the last harvest. The HiMag tall fescue contained less Na than did Barcel, but the magnitude of the difference was affected by K and Mg fertilization. Application of K fertilizer decreased S concentrations in first-harvest grass, increased concentrations in second-and third-harvest grasses, and had no effect in fourth-or fifth-harvest grasses. Application of Mg fertilizer decreased S concentrations of tall fescue. Application of K fertilizer increased DCAD values for grass harvested from the second through fifth harvests. The increase in DCAD attributable to K fertilizer was less in HiMag than in Barcel tall fescue. Application of K fertilizer as K2SO4 increased dry matter yield and S concentrations of HiMag tall fescue, whereas K applied as KCl increased concentrations of K and Cl. There was no effect of fertilizer formulation on Na concentrations. The DCAD was lower in HiMag tall fescue fertilized with K2SO4 compared with that fertilized with KCl. This study showed that DCAD of grass can be manipulated by the choice of grass variety, fertilizer formulation, and fertilizer application rate.

Heat- and lignosulfonate-treated canola meal as a source of ruminal undegradable protein for lactating dairy cows.

This experiment used 18 lactating Holstein cows in a 3 x 3 Latin square replicated 6 times to determine the effectiveness of processing with moist heat or moist heat combined with lignosulfonate (LSO3) for increasing the ruminal undegradable fraction of canola meal for use as a protein supplement for lactating dairy cows. Diets were formulated to be isonitrogenous and contained one of 3 forms of canola meal; untreated canola meal (UCM), heat-treated canola meal (HTCM) or heat-and LSO3-treated canola meal (LSO3CM). Total collection of urine and feces was taken from each cow during the last 5 d of each 42-d experimental period. Milk production was greater for cows fed the LSO3CM diet (36.6 kg/d) than for cows fed the UCM diet (34.8 kg/d) but did not differ from cows fed the HTCM diet (35.3 kg/d). Digestibility of crude protein was lower for cows supplemented with LSO3CM and they had reduced concentrations of ruminal ammonia N, blood urea N, and milk urea N compared with cows supplemented with UCM or HTCM. Dry matter intake and apparent digestibilities of neutral and acid detergent fiber were increased in cows fed the LSO3CM diet. Urinary N excretion (as % of N intake) was reduced in cows fed the LSO3CM diet. These results indicate that moist heat combined with LSO3 treatment of canola meal was effective in increasing the proportion of crude protein digested in the lower digestive tract of lactating cows and was therefore used more effectively as a source of protein than UCM or HTCM.

A broiler chick bioassay for measuring the feeding value of wheat and barley in complete diets.

Energy is an important component of poultry feed and is derived principally from cereal grains. Unfortunately, all of the chemical energy is not available to the bird, and biological assays must be used to determine the digestible energy value of a cereal grain. The bioassay described uses four pens of six male broiler chicks, complete diets containing 80% of a test cereal grain (with or without an appropriate commercial enzyme), and ad libitum feed intake. Apparent metabolizable energy values (kilocalories per kilogram of cereal grain, DM basis) values are calculated from gross energy and acid insoluble ash measurements of diet and excreta collected for 24 h at 16 d of age. To monitor variation between broiler chick assays, due to bird, environment, etc., common control samples of Hard Red Spring (HRS) and Canadian Prairie Spring (CPS) wheat were tested in each of 15 separate assays over 2 yr. Similarly, for barley, control samples of hulled and hulless barley were repeatedly tested in five assays. Broiler performance in this study was lower than expected for commercial broilers, in part due to a high dietary cereal grain component and the fine mash texture. However, AME values as determined were comparable to those reported in the literature for wheat and barley. The CV for AME measured among pens, representing the intra-assay CV, was between 1.2 and 3.4% and was lower with enzyme supplementation. The interassay CV was only slightly higher than the intra-assay CV. This assay provides precise estimations of ME in cereal grains fed to young broilers that can be used for diet formulation or for verification of laboratory measures of feeding value of cereal grains.

Comparison of sample source (excreta or ileal digesta) and age of broiler chick on measurement of apparent digestible energy of wheat and barley.

The broiler chick bioassay measures AME of wheat- or barley-based diets, with or without an enzyme, from excreta (24-h collections at 8 or 16 d) and ileal digesta (17 d). The objective was to discuss the merits and accuracy of sample source (excreta vs ileal digesta) and bird age for determining the feeding value of wheat and barley. The bioassay utilized 80% of a test cereal grain, 20% basal diet containing 1.1% acid insoluble ash marker, and fed with or without an enzyme to four pens of six male broilers from 4 to 17 d. A total of 138 wheat and 97 barley samples (with and without an enzyme) were tested in 15 and five bioassays, respectively. Within each wheat or barley bioassay two control wheat and barley samples were measured. The among-pens and between-assays CV for AME were calculated for these control samples, and correlation coefficients between the measures were calculated for the controls and for all of the 138 wheat and 97 barley samples included in the assays. For wheat samples, values for AME were lowest for excreta samples collected at 8 d, and similar for excreta and ileal digesta samples collected at 16 and 17 d, respectively. For barley samples, the three values were significantly different. The among-pens and between-assay CV were low for AME among both wheat and barley samples. Correlation coefficients between several measures of AME at 8 and 16 d were significant for the control samples with enzyme supplementation. When all samples were included in the analysis, correlation coefficients between AME measures were moderate to high. On the basis of accuracy, precision, and cost, these data favor measuring AME on excreta samples at 16 d of age. Comparisons of number of pens of broilers used to determine AME would suggest that much of the variability predicted with four pens of six broilers each could be achieved with three, and possibly two pens of six broilers each, thereby greatly increasing the capacity of the assay to screen large numbers of samples.

In situ disappearance of amino acids from grass silages in the rumen and intestine of cattle.

Nineteen grass silages were evaluated using the in situ rumen and mobile nylon bag techniques to determine the amino acid (AA) composition of rumen-undegradable protein and the possibility of predicting the concentrations of individual AA presented to the duodenum from the dietary AA profiles. All feeds and residues from the nylon bags were analyzed for diaminopimelic acid to correct for contamination by microbial proteins. All essential AA behaved similarly; the initial feed had the highest concentrations, and the material remaining in the mobile nylon bag had the lowest concentrations. The reduction in the concentration of methionine between the 12-h rumen residue and the residue in the mobile nylon bag was significant. With the exception of arginine (r2 = 0.76) and serine (r2 = 0.82), the relationship was poor between the concentrations of AA in the grass silage and those in the residue in the nylon bag following 12 h of rumen incubation. The lack of reliable relationships between concentrations of individual AA in the silages and concentrations of AA in the 12-h rumen residue indicated that degradability characteristics of AA in grass silage were not alike. This poor relationship was likely the reason that prediction equations could not be developed between the AA composition of the initial feed and the pattern of AA presented to the duodenum following 12 h of rumen incubation. The AA composition of the rumen-undegradable portion of grass silages differs from the AA composition of grass silages.

Giardia and Cryptosporidium in dairy calves in British Columbia.

A study was undertaken to determine the prevalence of Giardia infections in dairy calves and to compare Giardia and Cryptosporidium infections in calves of different ages. Fresh fecal samples were collected from 386 male and female Holstein calves (newborn to 24 wk) in 20 dairies located in the lower Fraser river valley area of British Columbia. Giardia intestinalis, Cryptosporidium parvum, and Cryptosporidium muris were enumerated in each sample after concentration by sucrose gradient centrifugation and immunofluorescent staining. Giardia was identified at all farm locations. The overall prevalence of Giardia in calves was 73% with a geometric mean cyst count of 1180 cysts per gram of feces (CI, 41 to 5014). Cryptosporidium parvum and C. muris were identified in 80% and 40% of the farms, respectively. The prevalence of C. parvum was 59%, and the geometric mean for oocysts was 457 oocysts per gram of feces (CI, 18 to 160). The prevalence of C. muris was only 2% and the mean oocyst counts were 54 oocysts per gram of feces. Giardiasis was not age dependent, and approximately 80% of the calves from 2 to 24 wk were infected. In contrast, C. parvum infections were predominant in calves 2 to 4 wk, while C. muris was demonstrated in calves older than 4 wk. Fourty-seven percent of calves with diarrhea had high numbers of Giardia cysts in their feces. Giardia infections are highly prevalent in dairy calves and should be considered in animals with diarrhea or failure to thrive.

Effect of ageing on responses of nerve fibres to pulpal inflammation in rat molars analysed by quantitative immunocytochemistry.

The response of sensory nerve fibres to inflammation in young adult rat molars has recently been shown to include increases in nerve sprouting and neuropeptide content. The objective was to evaluate neural responses to class V dental preparations in molars of old (1-2 yr) as compared with young adult rats (3-4 months). Tissues were investigated immunocytochemically 4 days post-injury for the sensory neuropeptides calcitonin gene-related peptide (CGRP) and substance P. Quantitative image analysis of the material demonstrated that more immunoreactivity was present for CGRP than for substance P in intact control teeth for each age group. Four days after injury, both immunoreactivities were increased in pulp adjacent to the injury in both young and old teeth. The increase depended on at least three factors: (1) enhanced immunoreactivity of the nerve fibres; (2) increased terminal nerve sprouts near the injury and (3) elevated peptide content of the pulp tissue. Although the incidence of CGRP- and substance P-immunoreactive nerve fibres had decreased in older teeth, the proportional increases in both neuropeptides near the injury were greater in old than in young teeth, owing to a reduction in pulpal volume during ageing. Pulpal tissue was also immunostained for the low-affinity nerve growth factor receptor (p75-NGFR) as an index of pulpal ageing; and an extensive decrease was found in the old adult as compared to young adult rats. These results indicate that old rats maintain the capacity for nerve sprouting despite the decreases in p75-NGFR labelling of pulp cells, pulp volume and nerve fibre numbers that occur as part of dental ageing.

Reactions of sensory nerves to dental restorative procedures.

The reactions of sensory nerves to restorative procedures can be classified as immediate, early and late. For each of these, the neural response depends upon the severity of pulpal injury and the stages of inflammation and healing. Immediate responses in the first few minutes include destruction of nerve fibers in the injured dentin and pulp, hypersensitivity of surviving fibers, release of neuropeptides into the pulp and neurogenic inflammation. Early responses occur during the first few days after cavity preparation, with nerve fibers sprouting in the surviving pulp and gaining increased axonal transport and neuropeptide contents. Sensory fibers containing calcitonin gene related peptide (CGRP) greatly outnumber those with substance P (SP); but both types grow toward the surviving odontoblasts and associated pulp tissue surrounding the lesion. Later during subsequent weeks the nerve fibers accompany granulation tissue as it replaces acute inflammation; and nerve sprouting subsides when inflammation is reduced and when reparative dentin covers the injury site. An important response to tooth injury that may regulate nerve sprouting reactions is the increased production of nerve growth factor (NGF) by pulpal fibroblasts near the lesion. The timing of the nerve sprouting reactions suggests that they may contribute to tooth hypersensitivity after restorative procedures.

Endodontic retreatment in small and large curved canals.

This study used a special jig system, photography, and a sonic digitizer to evaluate the change in canal size and location after retreatment in 20 teeth with small or large curved canals (greater than 23 degrees). During initial instrumentation, small canals enlarged twice as much as large canals in the coronal and middle areas. During retreatment, small and large canals showed 30 to 85% enlargement compared with that of the initial instrumentation. There was a trend, primarily during retreatment, for small canals to deviate more than large canals away from the original canal location.

Interaction between insulin and thyroid hormones on the control of carbohydrate and lipid metabolism in rat adipose tissue.

Adipose tissue segments excised from normal rats and from rats rendered experimentally hypothyroid and hyperthyroid retained insulin responsiveness when studied in vitro. Basal rates of glucose oxidation to CO2, conversion into glyceride-glycerol, fatty acids, and total lipids, and the activities of pyruvate dehydrogenase and fatty acid synthetase were enhanced in fat pads from hyperthyroid rats when compared with values seen with tissue from euthyroid animals. The response of each of these parameters was further enhanced by treating tissue from hyperthyroid rats in vitro with insulin. Basal rates of glucose oxidation and the activities of pyruvate dehydrogenase and fatty acid synthetase were depressed as a result of hypothyroidism. However, all of these values could be restored to levels approaching the values seen in the basal state for euthyroid rats when tissue segments from hypothyroid rats were incubated in vitro with insulin. The basal rates for glucose conversion into glyceride-glycerol, fatty acids, and total lipids were not changed by hypothyroidism but retained insulin responsiveness. These data suggest that the insulin-effector system in adipose tissue is not altered by thyroid status and that thyroid hormones may act independently with insulin to regulate glucose and lipid metabolism in this tissue at multiple intracellular metabolic sites.

Analysis of molluscan sterols: Colorimetric methods.

The wide variety of sterols normally found in extracts of bivalve molluscs leads to high variability in analytical data obtained with colorimetric (chole)sterol methods. Total sterol levels in oyster (Crassostrea virginica) extracts were determined using the Liebermann-Burchard reagent, an acid-FeCl3 reagent and a cholesterol oxidase procedure. The data from the latter two agreed to within 5.4% and yielded about 30% higher estimates of sterol content than the Liebermann-Burchard test. Gas-liquid chromatographic data also are compared.Several pure sterols, selected because of their presence in oyster sterol fractions or because of their structural similarities to such sterols, were examined using each of the three procedures. Sterols, differing from cholesterol only with regard to the side chain, reacted 80-102% as well as cholesterol with the acid-FeCl3 reagent and cholesterol oxidase. The Liebermann-Burchard reaction was more specific for cholesterol. The colorimetric cholesterol oxidase method is recommended for the estimation of total molluscan sterol content.