A review of new approaches to assessing hepatic function in animals

Performance, nutrient digestibilities, and metabolic profiles of Holstein calves fed whole milk or milk replacer at two feeding levels

The macronutrient composition of common milk replacers (MR) largely differs from bovine whole milk (WM). These differences are more nutritionally relevant when calves receive higher milk allowances. Therefore, the present study compared fresh WM with a conventional MR fed at 2 level of feeding allowances evaluating growth performance, apparent total-tract nutrient digestibilities, nitrogen (N) balance, and serum metabolite profiles in calves. Forty-eight newborn Holstein male calves (1.96 ± 0.99 d of age; 45.0 ± 4.37 kg BW) were blocked by arrival date and age. Calves in each block were then randomly assigned to the 4 treatments (n = 12/treatment): MR or WM at a high (9.0 L/d) or low feeding allowance (4.5 L/d) fed 3 times daily. Calves were weaned between wk 6 and 10 following the introduction of the starter feed in wk 6. The study ended 13 wk after the arrival at the facility. Blood and body weights were collected on arrival, and weekly thereafter. Total 24h-collection periods of feces and urine was performed at wk 2, 4, 5, 7, 9, 11, and 13. Remarkably, no interactions were observed between liquid feed and level of supply. Calves fed MR had higher ADG during the pre-weaning phase than to calves fed WM. However, calves fed WM had an increased growth rate post-weaning, resulting in no difference in BW at the end of the study. Calves fed WM had a higher apparent crude fat digestibility during the weaning period. Metabolic N efficiency, expressed as N balance relative to digestible N supply, was higher during the pre-weaning phase, but tended to be lower during the post-weaning phase for calves fed MR as compared with calves fed WM. In the pre-weaning period, serum glucose, BHB, nonesterified fatty acids (NEFA), total protein (TP), urea, albumin, globulin, triglyceride (TG), and cholesterol were influenced by liquid feed source. Carry-over effects of milk source on TG and TP were observed during the post-weaning period. As expected, calves fed a high-milk allowance showed better ADG at pre-weaning and were consistently heavier throughout the study than calves fed a low-milk allowance. Feeding a high-milk allowance did not negatively affect nutrient digestibility during the post-weaning phase. In the pre-weaning phase, milk allowance affected glucose and cholesterol metabolism, whereas TG, TP, albumin, and NEFA concentrations were affected during the post-weaning period. From a single oral dose of indigestible markers (Cr-EDTA, lactulose, and D-mannitol), calves fed a high-milk allowance showed greater urinary recovery of all markers after 6h of collection, but not after 24h. Calves fed a high-milk allowance had a higher proportion of days with lower fecal scores during the pre-weaning phase. In conclusion, the serum metabolite profiles of calves throughout the study were highly influenced by milk source. Higher milk allowance increased growth performance and had no adverse effects on starter feed intake or nutrient digestibility in the post-weaning phase. The multiple effects described for milk source and level of supply were overall independent, presenting no relevant interactions.

Effects of Fermentation on the Physicochemical Properties and Aroma of Lamb Liver Paste

The probiotic fermentation of lamb liver paste is a new method with which to utilize sheep by-products and address the issue of waste. In this study, a pH meter, chromaticity meter, texture analyzer, and gas chromatograph–mass spectrometer (GC–MS) were used to determine various indicators. The objective was to investigate the effect of fermentation on the physical properties and aroma of lamb liver paste. The results showed that the L* (brightness), a* (redness), and b* (yellowness) of the samples were significantly higher in the starter fermentation group than in the other two groups after storage for 0, 1, 7, 14, 21, and 28 days (p < 0.05). In addition, cohesiveness, adhesion, and chewiness were lower in the starter fermentation group after 7 days (p < 0.05). TVB-N and fat were lower in the starter fermentation group compared to the sterilization group at 28 days. pH was significantly lower in the starter fermentation group at the beginning of storage, and lactic acid bacteria numbers were significantly higher than in the sterilization groups (p < 0.05). Important aroma compounds, such as 2-undecenal, 1-octen-3-ol, and anethole, were significantly higher in the starter fermentation group than in the sterilization group (p < 0.05). Fermented lamb liver paste is a new by-product that exhibits a high degree of freshness and a low degree of fat oxidation during storage. This study provides a theoretical basis for future industrial production.

Measurements of caffeine and plasma metabolite/caffeine ratios as a test for hepatic drug-oxidizing capacity in goats

The aim of this investigation was to determine the pharmacokinetics and demethylation of caffeine (CF) and the metabolite/CF ratios that correlated best with CF clearance, which were used to evaluate hepatic drug-oxidizing capacity of CF after a single intravenous dose (5 mg/kg) in hair goats (n = 9). Pharmacokinetic parameters of CF and its metabolites, theobromine (TB), paraxanthine (PX) and theophylline (TP), were calculated. The plasma metabolic ratios TB/CF, PX/CF, TP/CF and TB+PX+TP/CF were determined at 6, 8 and 10 h after CF administration to evaluate their hepatic drug-oxidizing capacity. The plasma concentration-time data of CF were fit to a two-compartment model in all animals. The clearance of CF was 0.08 ± 0.02 L/h/kg, and the volume of distribution was 0.91 ± 0.16 L/kg. The demethylation fractions of CF to TB, PX and TP were 0.24, 0.37 and 0.39, respectively. Correlations between the metabolic ratios and CF clearance were quite high, except for the PX/CF ratio, particularly at 6 h (r = 0.650-0.750, P < 0.01, 0.05) and 10 h (r = 0.650-0.767, P < 0.01, 0.05). Plasma metabolite/CF ratios, except for the PX/CF ratio, may be useful as an alternative to measurements of CF clearance for the determination of the hepatic drug-oxidizing capacity in goats.

Pharmacokinetics of intravenously administered caffeine in healthy alpacas (Lama pacos) and llamas (Lama glama)

OBJECTIVE

To determine the pharmacokinetic disposition of IV administered caffeine in healthy Lama spp camelids.

ANIMALS

4 adult male alpacas and 4 adult female llamas.

PROCEDURES

Caffeine (3 mg/kg) was administered as an IV bolus. Plasma caffeine concentrations were determined by use of high-performance liquid chromatography in 6 animals and by use of liquid chromatography-mass spectrometry in 2 llamas.

RESULTS

Median elimination half-life was 11 hours (range, 9.3 to 29.8 hours) in alpacas and 16 hours (range, 5.4 to 17 hours) in llamas. The volume of distribution at steady state was 0.60 L/kg (range, 0.45 to 0.93 L/kg) in alpacas and 0.75 L/kg (range, 0.68 to 1.15 L/kg) in llamas. Total plasma clearance was 44 mL/h/kg (range, 24 to 56 mL/h/kg) in alpacas and 42 mL/h/kg (range, 30 to 109 mL/h/kg) in llamas.

CONCLUSIONS AND CLINICAL RELEVANCE

High-performance liquid chromatography and liquid chromatography-mass spectrometry were suitable methods for determination of plasma caffeine concentrations in alpacas and llamas. Plasma caffeine concentration-time curves were best described by a 2-compartment model. Elimination half-lives, plasma clearance, volume of distribution at steady state, and mean residence time were not significantly different between alpacas and llamas. Intravenous administration of caffeine at a dose of 3 mg/kg did not induce clinical signs of excitement.

Effect of DW2282 on the induction of methemoglobinemia, hypoglycemia or WBC count and hematological changes

DW2282,(S)-(+)-4-phenyl-1-[1-(4-aminobenzoyl)-indoline-5-sulfonyl] -4,5-dihydro-2-imidazolone hydrochloride, is a new anticancer agent which is thought to exhibit a characteristic mechanism of action in the inhibition of tumor growth. In this study, we estimated the toxicities of DW2282 in mice. When mice were orally dosed for five consecutive days at the dosages of 50, 100 and 150 mg/kg, DW2282 did not induce methemoglobinemia and hypoglycemia at any of these doses. However, increased ALT and AST values were observed in the 150 mg/kg dosing group, and white blood cells (WBC) were significantly decreased at all doses. However, the changes in WBC count, ALT and AST immediately reversed after the cessation of drug administration. In addition, we found that DW2282 did not cause an increase in hemolysis in human blood. Taken together, these data suggested that DW2282 may have a relatively low level of toxicity, and that there may be a quick recovery from any toxicity it does produce.

Clinical chemical diagnosis of diseases assisted by logistic regression illustrated by diagnosis of canine primary and secondary hepatobiliary diseases

OBJECTIVE

The purpose of the present study was to demonstrate the use of logistic regression models in the prediction of diseases using the prediction of canine primary and secondary hepatobiliary diseases as an example. Briefly, in a logistic regression model independent variables (i.e. the analytical results) are combined in a linear equation that is used to estimate the logarithm of the odds (logit) of an event (i.e. having primary or secondary hepatobiliary disease). From the estimated logit given by the logistic regression model, a conditional probability of the event (i.e. having primary or secondary hepatobiliary disease) can be calculated.

STUDY DESIGN

Twenty-six dogs with verified primary and secondary hepatobiliary diseases and 19 dogs, initially suspected to have hepatobiliary diseases, but with apparently other diseases, were included in the study. The following clinical chemical parameters were measured: alanine aminotransferase (ALAT), aspartate aminotransferase (ASAT), alkaline phosphatase (AP), bilirubin(Total) (TB), urea, glucose, retention of bromosulphthalein (BSP), fasting and postprandial total serum bile acid concentration (FSBA and PSBA). Logistic regression analysis, using the CATMOD procedure in SAS, was used to select which of the measured parameters should be included in the model, and to derive a logistic regression model using the selected parameters. To observe more closely the potential of the logistic regression model, the model was also used to classify a test group consisting of 13 dogs (6 dogs with hepatobiliary diseases and 7 dogs with other diseases).

RESULTS

By logistic regression analysis, ASAT and PSBA were selected to be included in the final model, and the final logistic regression model was Y = -3.194 + 0.044.PSBA + 3.251.ASAT. The logistic regression model classified correctly 38 (84%) of 45 dogs in the present study. Specifically, 21 (81%) of 26 dogs with verified primary or secondary hepatobiliary diseases and 17 (90%) of 19 dogs with various other diseases were correctly classified by the logistic regression model. When the model was used on the test group, 5 (83%) of 6 dogs with hepatobiliary diseases and 7 dogs (100%) of 7 dogs with other diseases were correctly classified.

CONCLUSIONS

Even though the logistic regression model derived in the present study only serves as an example, thus reducing the practical usefulness of the derived logistic regression model, the present study indicates a great potential of logistic models for the diagnosis of diseases.

Evaluation of diagnostic tests using relative operating characteristic (ROC) curves and the differential positive rate. An example using the total serum bile acid concentration and the alanine aminotransferase activity in the diagnosis of canine hepatobiliary diseases

The value of a diagnostic test depends on most cases on its ability to discriminate between patients with and without a certain disease. One way of evaluating a diagnostic test is to use the relative operating characteristic curve (ROC curve) and the differential positive rate (DPR). The ROC curve displays the relationship between the true positive ratio and the false positive ratio for a range of cutoff values and it can be used to compare various diagnostic tests under equivalent conditions (equal true positive ratios or false positive ratios) and over the entire range of cutoff values. The DPR is the difference between the true positive ratio and the false positive ratio at various cutoff values and it can be used to obtain the cutoff value associated with the highest sensitivity and specificity. The purpose of this study was to describe the evaluation and comparison of diagnostic tests using ROC curves and DPR. Eventually, the positive and negative predictive values were used to assess the differences between the sensitivity and specificity obtained when the upper limit of the reference interval, or the optimal cutoff value indicated by the DPR, was used as cutoff value. To illustrate the methods, the 2 h post-prandial total serum bile acid concentration (PSBA) and the alanine aminotransferase activity (ALAT) in the diagnosis of primary or secondary hepatobiliary diseases in dogs were used. The ROC curves showed, as expected from previous studies, that PSBA was superior to ALAT in diagnosing dogs with hepatobiliary diseases. Using DPR, the optimal cutoff value for PSBA was suggested to be 15.48 mumol/l. Compared to the traditionally used cutoff value of 22.24 mumol/l, no decisive difference in the positive predictive values were observed. However, the cutoff value of 15.48 mumol/l appeared to produce higher negative predictive values compared to a cutoff value of 22.24 mumol/l. Seemingly, ROC curves and DPR are simple methods useful to the evaluation of diagnostic tests and due to the simplicity, there seems to be a great potential for these methods in the evaluation of diagnostic tests in veterinary medicine.

Ancillary tests for assessment of the ruminant digestive system

This article reviews the ancillary tests that are available to evaluate disease and function of the gastrointestinal system. Procedures and tests such as abdominocentesis and peritoneal fluid cytology; rumen fluid analysis; abomasal pH and pepsinogen; upper digestive tract endoscopy; ultrasonography and radiology; hematologic and biochemical assessments; cytology, culture, and histopathology of aspirates; serology, liver function tests and biopsy; exploratory laparotomy; fecal examination; and microbiology are described.

Evaluation of fasting and postprandial total serum bile acid concentration in dogs with hepatobiliary disorders

The fasting and 2 h postprandial total serum bile acid concentrations (FSBA and PSBA), alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, bilirubin (Total), and retention of bromosulphthalein were determined in a group of dogs with various hepatobiliary disorders as well as in a group of dogs with other diseases than hepatobiliary disorders. Although FSBA and PSBA were generally elevated in cases of hepatobiliary disorders, no distinction between different disease groups could be made based solely on FSBA and PSBA. FSBA and PSBA were found to be relatively sensitive and specific parameters compared to the other hepatic tests. PSBA tended to be superior to the other parameters investigated in terms of sensitivity, specificity, positive predictive value, and negative predictive value.