A preliminary study on the feasibility of two different cow-calf contact systems in a pasture-based, seasonal calving dairy system: effects on cow production and health.

Internationally, consumer dissatisfaction with cow-calf separation at birth has led to increased interest in alternative calf-rearing methods, specifically cow-calf contact (CCC) systems. The objectives of this preliminary study were to estimate whether CCC could be incorporated into an Irish spring-calving, pasture-based system, and to investigate the effects on cow milk production and health. Three systems were compared: the conventional Irish system (CONV;18 cows), cow and calf were separated < 1 h postbirth, cows were pasture-based and milked twice-a-day; a full-time access system (FT;14 cows), cow and calf were allowed constant, unrestricted access, were pasture-based, and cows were milked twice-a-day; and a part-time access system (PT;18 cows), cow and calf had unrestricted access when indoors at night, cows grazed outdoors by day while calves remained indoors, and cows were milked once-a-day in the morning. Cows were blocked and balanced across the three systems by previous lactation machine milk yield (MMY), BW, and body condition score (BCS). Following an 8-week CCC period, all calves were weaned (FT and PT underwent a 7-d gradual weaning and separation process) and all cows were milked twice-a-day. Cow MMY was recorded daily and milk composition was recorded weekly; milk data were analysed from weeks 1 to 8 (CCC period), weeks 9 to 35 (post-CCC period), and weeks 1 to 35 (cumulative lactation). Cow BW and BCS were taken weekly for weeks 1-12, and at the end of the lactation. During the CCC period, all systems differed (P < 0.001) in MMY (mean ± SEM; 24.0, 13.6, and 10.3 ± 0.50 kg/d for CONV, FT, and PT cows, respectively). After the CCC period, CONV MMY (20.2 ± 0.48 kg/d) remained higher (P < 0.001) than the FT (16.6 kg/d) and PT cows (15.7 kg/d). The FT and PT cows yielded 24 and 31% less in cumulative lactation MMY and 26 and 35% less in cumulative lactation milk solids yield, respectively, compared to CONV (5 072 ± 97.0 kg and 450 ± 8.7 kg). During the CCC period, somatic cell score was higher (P = 0.030) in PT cows (5.15 ± 0.118) compared to FT cows (4.70 ± 0.118), while CONV (4.94 ± 0.118) were inconclusive to both. The PT cows (523 ± 4.9 and 520 ± 6.8 kg) were heavier than the CONV (474 ± 4.9 and 479 ± 6.8 kg) and FT (488 ± 4.9 and 487 ± 6.8 kg) cows at week 4 and week 8 (both P < 0.001). The PT cows had higher BCS than CONV and FT at all observed times. This preliminary research suggests that although CCC was incorporated without impacting cow health, the two CCC systems investigated negatively affected cow production.

Exploring individual responses to welfare issues in growing-finishing pig feeding behaviour.

The feeding behaviour of individual growing-finishing pigs can be continuously monitored using sensors such as electronic feeding stations (EFSs), and this could be further used to monitor pig welfare. To make accurate conclusions about individual pig welfare, however, it is important to know whether deviations in feeding behaviour in response to welfare issues are shown only on average or by each individual pig. Therefore, this study aimed (1) to quantify the individual variation in feeding behaviour changes in response to a range of welfare issues, and (2) to explain this individual variation by quantifying the responses to welfare issues for specific subgroups of pigs. We monitored four rounds of 110 growing-finishing pigs each (3-4 months per round). We collected feeding behaviour data using IVOG® EFSs and identified health issues and heat stress using climate sensors and twice-weekly health observations. For each pig, a generalised additive model was fitted, which modelled feeding behaviour through time and estimated the effect of each welfare issue that the pig had suffered from. The range of these effect estimates was compared between pigs to study the individual variation in responses. Subsequently, pigs were repeatedly grouped using physical and feeding characteristics, and, with meta-subset analysis, it was determined for each group whether a deviation in response to the welfare issue (i.e. their combined effect estimates) was present. We found that the range in effect estimates was very large, approaching normal distributions for most combinations of welfare issues and feeding variables. This indicates that most pigs did not show feeding behaviour deviations during the welfare issue, while those that did could show both increases and reductions. One exception was heat stress, for which almost all pigs showed reductions in their feed intake, feeding duration and feeding frequency. When looking at subgroups of pigs, it was seen that especially for lameness and tail damage pigs with certain physical characteristics or feeding strategies did consistently deviate on some feeding components during welfare issues (e.g. only relatively heavier pigs reduced their feeding frequency during lameness). In conclusion, while detection of individual pigs suffering from heat stress using feeding variables should be feasible, detection of (mild) health issues would be difficult due to pigs responding differently, if at all, to a given health issue. For some pigs with specific physical or behavioural characteristics, nevertheless, detection of some health issues, such as lameness or tail damage, may be possible.

Review: Towards an integrated concept of animal welfare.

Animal welfare is an important field of study due to animal sentience, yet there is to date no consensus on the definition of animal welfare. There have been four key developments in the field of animal welfare science since its birth: the theoretical and empirical study of affective states, and hence our understanding thereof, has increased; there has been a shift from a primary focus on unpleasant experiences towards an inclusion of pleasant experiences; there has been an increasing mention and investigation of the notion of cumulation of experiences in time, and with this, the importance of the time component of both affective states and animal welfare has come forward. Following others, we define welfare as a balance or cumulation of pleasant and unpleasant experiences over time. The time period of welfare depends on when welfare considerations are necessary, and may range from the duration of single and relatively short-term experiences to the entire life of an animal. We further propose that animal welfare conceptualised in this way can be assessed at three levels: level 1 represents the assessment of the environment and 'internal factors' such as health and personality, which interact in their impact on the affective experiences of animals; level 2 represents the assessment of affective states; and level 3 represents the assessment of the balance or cumulation of these affective states in time. The advancement of research necessitates studies to be more or less comparable, and this would be facilitated by researchers mentioning which concept of animal welfare they are basing their work on, at which level of assessment they are working, which assumptions they might be drawing from to infer welfare and which time period of interest they are focusing on, even if this is not mirrored by the timing of the assessment in practice. Assessment at levels 2 and 3 still needs much study, at both the theoretical and empirical levels, including agreements on validation tools.

Impact of early dam contact on veal calf welfare.

Dairy calves, including surplus calves, are typically separated from their dam within hours of birth. The aim of this study was to assess the welfare impacts of raising surplus calves destined for veal with their dam for 2 or 4 weeks until transport. Surplus calves from one dairy farm were separated from their dam at birth (n = 39) or kept with the dam (n = 37) until transport to the veal farm at either 2 (n = 50) or 4 (n = 26) weeks of age, with abrupt separation for dam-reared calves. Calf measures of body weight, health, immunity, haematology and behaviour were recorded at the dairy and veal farms. Dam-reared calves had higher body weights in weeks 3, 4 and 5 at the DF, as well as at arrival at the veal farm, but by slaughter this advantage was lost. More dam-reared calves had fever in week 3 and showed signs of disease in week 5 at the dairy farm. Dam-reared calves did not differ in IgG, IgA or IgM levels but had higher counts of white blood cells, which could reflect a higher pathogen exposure rather than improved immunity. Dam-reared calves displayed more fear towards humans in a human approach test at 5 and 7 weeks after arrival at the veal farm, and more frequent social behaviours at the veal farm at 9 and 16 weeks of age. In conclusion, it seems that there may be both advantages and disadvantages to keeping veal calves with the dam in terms of welfare in the current system.

The nuts and bolts of animal emotion.

The study of animal emotion, as with its human equivalent, can be confusing due to the complicated and inconsistent use of terminology, and the number of interlinked fields and topics it encompasses. With this review, we aim to provide an up-to-date and, to the best of our knowledge, complete overview of the field of animal emotion, especially intended for new-comers to the field who wish to get a grasp of this field. We start by tackling the terminology and proposing definitions of commonly used terms, and present the different frameworks used for the study of animal emotion. Here, we heavily draw from human literature, as the definitions of animal emotion are derived originally from human research. We follow-up with an overview of current methodologies for the study of animal emotion, in particular the valence dimension of emotion, and include some of the associated limitations linked to these methodologies. We end by pointing out key areas for future research.

Invited review: Abomasal damage in veal calves.

Within all cattle production systems, veal calves are the most severely affected by abomasal damage, with current prevalence at slaughter ranging from 70 to 93% of all animals affected. Although most damage is found in the pyloric region of the abomasum, fundic lesions are also found. Despite past research into the etiology of abomasal damage and the many risk factors that have been proposed, consensus on the causal factors of abomasal damage in veal calves has not yet been reached. The aim of this review was to integrate and analyze available information on the etiology of, and possible risk factors for, abomasal damage in veal calves. We describe various proposed pathways through which risk factors may contribute to damage formation and conclude that the etiology of abomasal damage is most likely multifactorial, with diet being a main contributor. Pyloric lesions, the most common type of damage in veal calves, are likely the result of large and infrequent milk and solid feed meals, whereas fundic lesions may be caused by stress, although the evidence for this is inconclusive. Providing calves with multiple smaller milk and solid feed meals (or ad libitum provision) may decrease abomasal damage. In future research, ulcers, erosions, and scars as well as fundic and pyloric lesions should be recorded separately, because etiologies of these may differ. Further research is required to understand the exact pathway(s) by which milk replacer causes abomasal damage in veal calves; that is, whether low abomasal pH, overloading, or composition are important. Further research is also required to elucidate whether rapid intake of milk replacer and solid feed, which is influenced by restricted amounts fed, inter-calf competition, and calf breed, increases abomasal damage. Research is also needed into the effect of medication and nutrient deficiencies other than iron. The types of experimental designs that can be used for future research could be enhanced if a means to assess abomasal damage antemortem is developed. We conclude that it is unlikely that abomasal or ruminal hairballs, iron deficiency, water provision, and various infections and diseases are significant contributors to abomasal damage in veal calves.

Understanding oral stereotypies in calves: alternative strategies, hypothalamic-pituitary-adrenal axis (re)activity and gene by environment interactions.

Stereotypies are used as indicators of poor animal welfare and it is, therefore, important to understand underlying factors mediating their development. In calves, two oral stereotypies, that is, tongue playing and object manipulation, result mostly from insufficient structure in the diet. Three hypotheses were studied: (1) oral stereotypies in calves are one of two alternative strategies, the alternative being hypo-activity; (2) stereotyping and non-stereotyping calves differ in terms of cortisol secretion; (3) oral stereotypy development in calves rests on a gene by environment interaction. Eight-week-old bull calves (n=48) were assigned to one of four solid feed allowances (0, 9, 18 or 27 g dry matter/kg metabolic weight per day) with the following composition: 50% concentrate, 25% maize silage and 25% straw on dry matter basis. The calves received milk replacer in buckets, the provision of which was adjusted to achieve equal growth rates. At 14 to 18 weeks of age, calves were exposed to a challenge, that is, tethering inside cages. Oral stereotypies and inactivity were recorded in the home pens in the 4 weeks before the challenge using instantaneous scan sampling. Salivary cortisol levels were measured at -120, +40, +80, +120 min and +48 h relative to the challenge. Individual differences in behaviour were recorded in the first 30 min after challenge implementation using focal animal sampling and continuous recording, and these elements were entered into a principal component (PC) analysis to extract PCs. Regression analyses were performed to find relationships between stereotypies and inactivity, stereotypies and cortisol, and stereotypies and PCs (individual differences, genes) and solid feed (environment). Relationships between PCs and cortisol were also investigated to help with the interpretation of PCs. Hypotheses 1 and 2 were rejected. Hypothesis 3, however, was supported: calves with a zero solid feed allowance, that is, in the most barren environment, showed links between stereotypies and two of the PCs. Calves that displayed high levels of idle and rapid locomotion and low levels of oral contact with the cage during the challenge also displayed high levels of object manipulation in the home pens. Calves that displayed low levels of stepping and turning attempts during the challenge also displayed high levels of tongue playing in the home pens. This study corroborates the gene by environment interaction on the development of oral stereotypies in calves.

The role of solid feed amount and composition and of milk replacer supply in veal calf welfare.

Diets used in veal production were linked with welfare problems: that is, behavioral and gastrointestinal health disorders. This study aimed to determine how indicators of calf welfare, that is, behavior and some characteristics of the feces reflecting gastrointestinal health status, are affected by (1) different amounts and compositions of solid feed (SF), (2) the addition of ad libitum long straw to a typical veal diet, and (3) milk replacer (MR) being fed via automated milk dispensers (AMD). Two-week-old Holstein-Friesian bull calves (n=270) were used in this study. In a 4×2 factorial design, 32 pens (5 calves per pen) were allocated to different levels of SF (SF1, SF2, SF3, or SF4) and roughage-to-concentrate ratios (20:80 or 50:50). The experimental period (13 to 29wk of age) was preceded by an adaptation period (3 to 12wk of age). Targeted total dry matter (DM) intake from SF during the experimental period was 20 kg of DM for SF1, 100 kg of DM for SF2, 180 kg of DM for SF3, and 260 kg of DM for SF4. The roughage part of the SF was 50% maize silage and 50% chopped wheat straw (on a DM basis). Ten additional pens were allocated to 2 treatments with ad libitum SF, with either (1) SF components in separate troughs (SEP) or (2) SF components mixed, with the composition being equal to the choice of SEP calves in the preceding week (MIX). Another 4 pens were fitted with racks filled with long wheat straw (STR) and fed SF2 with a roughage-to-concentrate ratio of 20:80. All the aforementioned pens received MR in buckets. Finally, 8 pens were allocated to 1 of 2 SF levels: SF1 or SF2 (with a roughage-to-concentrate ratio of 50:50) and fed MR via an AMD. Milk replacer provision was adjusted every 2wk to achieve similar rates of carcass gain across treatments (excluding SEP, MIX, and STR). Behavior was recorded at 15 and 24wk using instantaneous scan sampling. The prevalence of diarrhea and clay-like feces, which signal ruminal drinking, was monitored at 14 and 25wk. More roughage, but not concentrate, increased rumination and decreased tongue playing. The STR calves had higher rumination and lower abnormal behavior levels compared with calves without ad libitum straw. Offering MR via an AMD reduced tongue playing at 15wk. Tongue playing frequency was related to both roughage amount and AMD feeding, suggesting 2 separate motivations (i.e., rumination and sucking) underlying the development of this behavior. Only SF amount affected aspects of feces: SF1 calves had the highest diarrhea incidence. No effect of diet was found on clay-like feces.

Effects of roughage source, amount, and particle size on behavior and gastrointestinal health of veal calves.

The European Union 1997 Directive, stipulating that veal calves should be fed a minimum of 50 to 250 g of fibrous feed from 8 to 20 wk of age, is vague. A fibrous feed ration maximum of 250 g has been implicated in welfare issues, namely the occurrence of abnormal oral behaviors and poor gastrointestinal health. Past research suggests that this amount is insufficient to prevent the development of abnormal oral behaviors and enabling good rumen development. Different sources and particle sizes of roughage could lead to very different welfare outcomes. In a 3×2 × 2 factorial design, 240 group-housed calves (10±1 d; 46.1±0.1 kg) were fed different roughage sources (straw, maize silage, or maize cob silage; the latter 2 were dried and provided no extra moisture compared with straw) in 2 amounts (250 or 500 g of dry matter per day), and 2 particle sizes (chopped or ground). Roughage was supplemented to milk replacer (MR) from 2 wk after arrival. In addition, 60 calves were fed 1 of 3 additional control treatments: MR only (n=20), MR plus an iron supplement (n=20), or MR plus ad libitum hay (n=20). Oral behaviors were recorded using instantaneous scan sampling at 2-min intervals for 2 h in 3 periods per day, at 12 and 22 wk of age. Calves were slaughtered at 24 wk of age and rumen and abomasal health parameters were recorded. Limited provision of straw resulted in behavior comparable with that from unlimited provision of hay, with reduced tongue playing and oral manipulation of the environment, as well as increased chewing compared with diets with no roughage supplement. Straw prevented ruminal hairballs, but impaired rumen development and increased abomasal damage. A higher ration of roughage increased chewing (12 wk), decreased oral manipulation of the trough (12 and 22 wk) and the pen (22 wk), and increased rumen weight. However, more roughage led to increased abomasal damage for certain parameters. Longer feed particles had no obvious benefits for behavior, but decreased hairball prevalence. Overall, unlimited hay had the highest benefit for both behavior and gastrointestinal health. Adding iron to the MR did not alter behavior or gastrointestinal health compared with MR without iron supplement. This study demonstrated that different roughage sources, amounts, and particle sizes have different effects on veal calf behavior and gastrointestinal health, and hence on veal calf welfare.

Elevation of whole-blood glutathione in peritoneal dialysis patients by L-2-oxothiazolidine-4-carboxylate, a cysteine prodrug (Procysteine).

Glutathione is a major cellular antioxidant that protects protein thiols and inhibits cellular damage due to oxygen free radicals. It has been reported previously that patients undergoing dialysis have low levels of blood glutathione, which may lead to increased susceptibility to oxidant stress. L-2-oxothiazolidine-4-carboxylic acid (OTZ) is a cysteine prodrug that raises cellular glutathione levels by increasing delivery of cysteine, the rate-limiting substrate for glutathione synthesis. This study investigates the effect of OTZ on blood glutathione in a blinded, placebo-controlled study of patients with chronic renal failure treated by peritoneal dialysis. Twenty patients were randomly selected to receive OTZ (0.5 g three times a day orally with meals) or placebo for 14 d. Patients visited the clinic for predose blood collection and safety evaluation at baseline (days 3, 7, and 14 and again at 14 d from the last dose [follow-up]). Glutathione concentrations were determined in whole blood by HPLC. OTZ resulted in a significant rise in whole-blood glutathione at days 7 (594 +/- 129 mumol/L) and 14 (620 +/- 108 mumol/L) compared with baseline (544 +/- 139 mumol/L) (P < 0.01 and P < 0.05, respectively). Glutathione was also significantly increased at days 7 and 14 when normalized by hematocrit (Hct) or hemoglobin to correct for anemic status (e.g., 20.7 +/- 5.7 mumol/L per % Hct [day 7] and 20.9 +/- 4.0 mumol/L per % Hct [day 14] versus 18.0 +/- 4.2 mumol/L per % Hct [baseline]; P < 0.05). Glutathione levels did not change in the placebo group at any patient visit, and levels in the OTZ-treated group returned to baseline at follow-up. There were no serious adverse events attributable to OTZ, and the drug appeared to be well tolerated by patients with renal failure treated by continuous ambulatory peritoneal dialysis. Our results show that OTZ increases blood glutathione levels, which may improve antioxidant status in dialysis patients.

Mycobacterium hodleri sp. nov., a new member of the fast-growing mycobacteria capable of degrading polycyclic aromatic hydrocarbons.

A bacterial strain isolated from a fluoranthene-polluted soil was characterized with respect to its metabolic and chemotaxonomic properties, and its phylogenetic position was determined. This bacterium exhibits all of the genus-specific properties of the genus Mycobacterium and clusters phylogenetically with the group of fast-growing mycobacteria. On the basis of its unique fatty acid pattern, the distinctness of its physiological properties and the uniqueness of the primary structure of its 16S ribosomal DNA, we propose that the new isolate should be assigned to a new species, Mycobacterium hodleri. This novel species is phylogenetically closely related to Mycobacterium diernhoferi and Mycobacterium neoaurum. The type strain of M. hodleri is strain EM12 (= DSM 44183).

Determination of L-2-oxothiazolidine-4-carboxylic acid (Procysteine) in human plasma by high-performance liquid chromatography.

A new high-performance liquid chromatographic (HPLC) method has been developed for the determination of the cysteine prodrug, L-2-oxothiazolidine-4-carboxylic acid (Procysteine), in human plasma. Samples were mixed with 5% metaphosphoric acid and the supernatants chromatographed using a reversed-phase analytical column. Procysteine was detected spectrophotometrically at 230 nm and quantitated by comparison with a standard curve of known amounts of Procysteine (20-1000 microM) in plasma. The coefficients of variation for 48.6 microM and 676 microM control pools were 6.5 and 4.0% respectively (n = 46). Deviations from the expected concentrations were less than 2%. The method has been utilized to evaluate the pharmacokinetics of a wide range of oral and intravenous doses.

A rapid high performance liquid chromatographic method for the analysis of choline in human plasma and peritoneal dialysis effluent: application in the assessment of choline loss in continuous ambulatory peritoneal dialysis.

Mesothelial cells lining the peritoneal cavity utilize choline in the synthesis of a phosphatidylcholine-rich material thought to play a role in peritoneal homeostasis. This function is particularly important for patients undergoing continuous ambulatory peritoneal dialysis (CAPD). To assess choline loss in these patients, we measured choline in plasma and peritoneal dialysis effluent (PDE) by a rapid high performance liquid chromatography (HPLC) procedure that combined electrochemical detection with an immobilized enzyme reactor. Chromatography was performed directly on plasma and PDE ultrafiltrates. In 30 patients, the amount of choline lost to the dialysate was 129 +/- 49 mumol per day and 32 +/- 8 mumol per dwell (mean +/- SD). The average plasma choline concentration was 22.5 mumol/L, a value somewhat higher than the mean value reported for normal adults (9 mumol/L). The average PDE choline concentration was 14 mumol/L. There was a positive correlation between daily choline loss of dialysate and plasma choline concentrations (r = 0.826).

Choline levels in human peritoneal dialysate.

The average free choline level was determined to be 14 mumol/L in peritoneal dialysates and 22 mumol/L in the plasma of 30 patients on continuous ambulatory peritoneal dialysis (CAPD). Daily choline loss via dialysate averaged 129 mumol with 32 mumol choline lost per dwell. Daily choline loss via the dialysate was positively correlated with plasma choline concentrations. Choline levels in dialysate during CAPD exceed plasma levels of choline 9 mumol/L in healthy individuals.

Choline levels in human peritoneal dialysate.

The average free choline level was determined to be 14 M in peritoneal dialysates and 22 M in plasma of thirty patients on continuous ambulatory peritoneal dialysis (CAPD). Daily choline loss via dialysate averaged 129 moles with 32 moles choline lost per dwell. Daily choline loss via the dialysate was positively correlated with plasma choline concentrations. Choline levels in dialysate during CAPD exceed plasma levels of choline (9 M) in healthy individuals.

The effects of perfluorochemicals on tumor growth and chemotherapy response.

Hypoxia, leading to cells in resting or slow replication phases may be a cause of chemotherapy and radiation therapy resistance in some tumors. Perfluorochemicals (PFC) may potentiate response to these therapies by increasing oxygen delivery to the tumor, forcing cells into more therapy-responsive replicating phases. To assess the effects of PFC on tumor growth and chemotherapy response, 91 ACI rats bearing 1 cc flank Morris hepatoma tumors were divided into groups: Group I, control; Group II, Adriamycin (ADR) 10 mg/kg intraperitoneally (IP); Group III, Cytoxan (CTX) 100 mg/kg IP; Group IV, PFC 20 mL/kg IV; Group V, ADR and PFC; Group VI, CTX and PFC. Animals were kept in 0.5 FiO2 for 24 hours after treatment, and mortality and tumor volumes determined 2 weeks later. Tumor DNA turnover was measured using opposing pathways assay of 14C-thymidine uptake and degradation. In a separate group, tumor tissue pO2 was measured polarographically with an oxygen microelectrode before and after injection of PFC (20 mL/kg). The survival was significantly reduced in group IV (4%) compared with group I, control (73%). Both ADR and CTX slowed the growth of the tumor, while PFC alone significantly accelerated tumor growth. The tumor response to ADR was potentiated by the addition of PFC. These results were confirmed by DNA synthesis evaluation. The mean pO2 level prior to injection was 6.6 +/- 1.96 mmHg compared with 18.92 +/- 1.00 mmHg after PFC injection (P less than or equal to .01).(ABSTRACT TRUNCATED AT 250 WORDS)

Choline in plasma measured by liquid-chromatography with electrochemical detection.

We have developed a simple, specific, and sensitive method for plasma choline measurement based on the HPLC procedure of Potter et al. (J Neurochem 1983; 41: 188) for the measurement of acetylcholine and choline in neuronal tissue. The effluent from a reverse-phase column is mixed with choline oxidase in a post-column reaction coil to produce hydrogen peroxide which is monitored electrochemically. Plasma samples are prepared by deproteinization with perchloric acid. Choline is recovered quantitatively from the plasma, but an internal standard (homocholine) is added to compensate for any variation in electrode response. Choline can be measured in plasma samples containing less than 1 mumole per litre of plasma; the method response is linear in the 1-20 mumol/L range. Catecholamines and ascorbic acid do not interfere. The chromatography, enzymatic reactions, and electrochemistry all contribute to the specificity of the method.

Micromethod for lipid-chromatographic determination of cholesterol in lipemic sera.

A micromethod involving "high-performance" lipid chromatography was developed for determining cholesterol in sera obtained from animals that has been infused with high doses of lipid emulsions. Only 50 micro L of serum is required, and there is no interference from turbidity, bilirubin, fat-soluble vitamins, and sterols. Correlation with the commonly used Abell-Kendall method was good at cholesterol concentrations as great as 10.0 g/L (r = 0.998). The assay is ideal for determinations on samples from pediatric and hyperlipidemic patients. It is particularly useful for monitoring patients on lipid-emulsion therapy and for toxicological studies with small animals.