Relationship between reticular pH parameters and potential on-farm indicators in the early lactation of dairy cows.

Subacute ruminal acidosis (SARA) is an important nutritional disorder affecting animal welfare and economy of milk production. Definitions rely on ruminal pH but due to limitations of its measurement, indicators reflecting low pH are highly desirable. The aim of this study was to investigate the relationship between reticular pH and 18 on-farm indicators in milk, blood, faeces, urine and chewing behaviour in early lactating dairy cows. Ten farms were visited for 3 weeks and in total samples of 100 cows (10 per farm) were taken. The statistics and graphical visualization were performed using Pearson correlation and linear regression models on an animal individual level as well as with linear mixed models. Eight indicators (milk fat, fat-to-protein ratio, rumination time, feed intake time, rumination frequency, rumination boluses, lying time and faecal pH) were statistically significant associated with the daily animal individual reticular pH average. However, none of the models including the potential explanatory variables explained more than 5% of the pH variations. The study confirms the necessity of pH measurement to detect SARA risk animals in early lactation dairy cows.

Determining the predictive capability of a Clinical Assessment Scoring Chart to differentiate severity of the clinical consequences of neonatal calf diarrhea relative to gold-standard blood gas analysis.

Neonatal calf diarrhea (NCD) is a major problem to calf health worldwide, in terms of both morbidity and mortality. A five-point ordinal scale clinical assessment scoring (CAS) chart was utilized to assess calves suffering from NCD-related clinical abnormalities (acidosis and dehydration) on commercial farms. The objective of this research was to determine the predictive capability of this CAS chart against gold standard blood gas parameters, designed to assist farmers in the accurate assessment of the clinical consequences of NCD. A total of 443 diarrheic and non-diarrheic calves were enrolled in the study. The CAS chart rated a calf's health from no clinical signs to varying degrees of clinical severity on a 0 (clinically normal) to 4 (grave) scale, based on clinical indicators including calf demeanour, ear position, mobility, suckle reflex, desire-to-feed, and enophthalmos. Blood gas analysis was conducted for individual calves, consisting of pH, base excess, Na+, K+, Ca2+, Cl-, glucose, total hemoglobin, bicarbonate, anion gap, and strong ion difference. Statistical evaluation was performed by comparison of the CAS score with blood gas profiles using ordinal logistic regression and a non-parametric estimation of the Receiver Operating Characteristics (ROC). The ROC analysis indicated that the CAS chart had acceptable specificity (>95%) with low sensitivity (<60%) in differentiating clinically normal from acidotic/dehydrated cases. Assessment of individual severity classes indicated that the chart can predict and differentiate both clinically normal and advanced cases from the other severity classes (peak estimations >80%) but had reduced accuracy in differentiating mild and moderate cases (peak estimations >50%). The chart, as presented, provides a simple tool to differentiate clinically normal from calves suffering the consequences of diarrhea, but fails to accurately differentiate severity for NCD related acidosis and dehydration. Further efforts are required to enhance the sensitivity and differential diagnostic value of this type of chart.

Review: Metabolic challenges in lactating dairy cows and their assessment via established and novel indicators in milk.

The increasing lactational performance of dairy cows over the last few decades is closely related to higher nutritional requirements. The decrease in dry matter intake during the peripartal period results in a considerable mobilisation of body tissues (mainly fat reserves and muscle mass) to compensate for the prevailing lack of energy and nutrients. Despite the activation of adaptive mechanisms to mobilise nutrients from body tissues for maintenance and milk production, the increased metabolic load is still a risk factor for animal health. The prevalence of production diseases, particularly subclinical ketosis is high in the early lactation period. Increased ß-hydroxybutyrate (BHB) concentrations further depress gluconeogenesis, feed intake and the immune system. Despite a variety of adaptation responses to nutrient and energy deficit that exists among dairy cows, an early and non-invasive detection of developing metabolic disorders in milk samples would be useful. The frequent and regular milking process of dairy cows creates the ability to obtain samples at any stage of lactation. Routine identification of biomarkers accurately characterising the physiological status of an animal is crucial for decisive strategies. The present overview recapitulates established markers measured in milk that are associated with metabolic health of dairy cows. Specifically, measurements of milk fat, protein, lactose and urea concentrations are evaluated. Changes in the ratio of milk fat to protein may indicate an increased risk for rumen acidosis and ketosis. The costly determination of individual fatty acids in milk creates barriers for grouping of fatty acids into saturated, mono- and polyunsaturated fatty acids. Novel approaches include the potential of mid-IR (MIR) based predictions of BHB and acetone in milk, although the latter are not directly measured, but only estimated via indirect associations of concomitantly altered milk composition during (sub)clinical ketosis. Although MIR-based ketone body concentrations in milk are not suitable to monitor the metabolic status of the individual cow, they provide an estimate of the overall herd or specific groups of animals earlier in a particular stage of lactation. Management decisions can be made earlier and animal health status improved by adjusting diet composition.

Evaluation of reticuloruminal pH measurements from individual cattle: Sampling strategies for the assessment of herd status.

The application of pH observations to clinical practice in dairy cattle is based on criteria derived primarily from single time-point observations more than 20 years ago. The aims of this study were to evaluate these criteria using data collected using continuous recording methods; to make recommendations that might improve their interpretation; and to determine the relationship between the number of devices deployed in a herd and the accuracy of the resulting estimate of the herd-mean reticuloruminal pH. The study made use of 815,475 observations of reticuloruminal pH values obtained from 75 cattle in three herds (one beef and two twice-daily milking herds) to assess sampling strategies for the diagnosis of sub-acute rumen acidosis (SARA), and to evaluate the ability of different numbers of bolus devices to accurately estimate the true herd-mean reticuloruminal pH value at any time. The traditional criteria for SARA provide low diagnostic utility, the probability of detection of animals with pH values below specified thresholds being affected by a strong effect of time of day and herd. The analysis suggests that regardless of time of feeding, sampling should be carried out in the late afternoon or evening to obtain a reasonable probability of detection of animals with pH values below the threshold level. The among-cow variation varied strongly between herds, but for a typical herd, if using reticuloruminal pH boluses to detect a predisposition to fermentation disorders while feeding a diet that is high in rapidly fermentable carbohydrates, it is recommended to use a minimum of nine boluses.

Radiographic assessment of pulmonary fluid clearance and lung aeration in newborn calves delivered by elective Caesarean section.

The aim of this study was to develop a radiographic standard for the assessment of pulmonary fluid clearance and lung aeration in newborn calves. Caesarean-delivered mature calves (n = 9) underwent lung assessment by thoracic radiography as well as arterial and venous blood gas analysis within the first 30 min, 1, 2, 3, 6, 12 and 24 hr after birth. The results indicated that newborn calves delivered by elective Caesarean section suffered from a physiological combined respiratory and metabolic acidosis with the dominance of respiratory acidosis, and an improvement in these conditions was recorded within 24 hr after birth. Concerning the radiographic results, clear lung fields, improvement in lung expansion, air content of the lung and absence of lung opacification occurred within 24 hr of birth. Furthermore, the ventral lung quadrant showed an improvement in radiographic opacification and lung expansion earlier than the dorsal lung regions. The findings of this study support the potential role of thoracic radiography in the assessment of pulmonary fluid clearance and lung aeration in newborn calves.

Indicators of induced subacute ruminal acidosis (SARA) in Danish Holstein cows.

BACKGROUND: The prevalence of subacute ruminal acidosis (SARA) in dairy cows is high with large impact on economy and welfare. Its current field diagnosis is based on point ruminal pH measurements by oral probe or rumenocentesis. These techniques are invasive and inaccurate, and better markers for the diagnosis of SARA are needed. The goal of this study was to evaluate clinical signs of SARA and to investigate the use of blood, faecal and urinary parameters as indicators of SARA. Six lactating, rumen cannulated, Danish Holstein cows were used in a cross-over study with three periods. The first and second periods included two cows on control diet and two cows on nutritional SARA challenge. The third period only included two cows on SARA challenge. Control diet was a conventional total mixed ration [45.5% dry matter (DM), 17.8% crude protein, 43.8% neutral detergent fibre, and 22.5% acid detergent fibre (DM basis)]. SARA challenge was conducted by substituting control diet with grain pellets (50% wheat/barley) over 3 days to reach 40% grain in the diet. Ruminal pH was measured continuously. Blood samples were collected once daily at 7 h after feeding. Samples of faeces and urine were collected at feeding, and at 7 and 12 h after feeding. Blood samples were analysed for pCO2, pO2, pH, electrolytes, lactate, glucose, packed cell volume (PCV), and total plasma protein concentration. Milk composition, ruminal VFA, and pH of faeces and urine were measured. RESULTS: SARA was associated with decreased (P < 0.05) minimum ruminal, faecal and urinary pH. Daily times and areas of ruminal pH below 5.8, and 5.6 were increased to levels representative for SARA. Significant differences were detected in milk composition and ruminal VFAs. Blood calcium concentration was decreased (P < 0.05), and pCO2 tended to be increased (P = 0.10). Significant differences were not detected in other parameters. CONCLUSIONS: SARA challenge was associated with changes in faecal and urinary pH, blood calcium concentration and pCO2. These may be helpful as indicators of SARA. However changes were small, and diurnal variations were present. None of these parameters are able to stand alone as indicators of SARA.

Acid-base assessment: when and how to apply the Henderson-Hasselbalch equation and strong ion difference theory.

The Henderson-Hasselbalch equation is probably the most famous equation in biology but is more descriptive than mechanistic. The traditional approach to acid-base assessment using the Henderson-Hasselbalch equation provides a clinically useful and accurate method when plasma protein concentrations are within the reference range. The simplified strong ion approach is a mechanistic acid-base model that can provide new insight into complicated acid-base disturbances. The simplified strong ion approach should be used to evaluate acid-base balance whenever plasma protein concentrations are abnormal.

Dietary electrolyte balance affects the nutrient digestibility and maintenance energy expenditure of Nile tilapia.

Acid-base disturbances caused by environmental factors and physiological events including feeding have been well documented in several fish species, but little is known about the impact of dietary electrolyte balance (dEB). In the present study, we investigated the effect of feeding diets differing in dEB (-100, 200, 500 or 800 mEq/kg diet) on the growth, nutrient digestibility and energy balance of Nile tilapia. After 5 weeks on the test diet, the growth of the fish was linearly affected by the dEB levels (P< 0·001), with the lowest growth being observed in the fish fed the 800 dEB diet. The apparent digestibility coefficient (ADC) of fat was unaffected by dEB, whereas the ADC of DM and protein were curvilinearly related to the dEB levels, being lowest and highest in the 200 and 800 dEB diets, respectively. Stomach chyme pH at 3 h after feeding was linearly related to the dEB levels (P< 0·05). At the same time, blood pH of the heart (P< 0·05) and caudal vein (P< 0·01) was curvilinearly related to the dEB levels, suggesting the influence of dEB on postprandial metabolic alkalosis. Consequently, maintenance energy expenditure (MEm) was curvilinearly related to the dEB levels (P< 0·001), being 54 % higher in the 800 dEB group (88 kJ/kg(0·8) per d) than in the 200 dEB group (57 kJ/kg(0·8) per d). These results suggest that varying dEB levels in a diet have both positive and negative effects on fish. On the one hand, they improve nutrient digestibility; on the other hand, they challenge the acid-base homeostasis (pH) of fish, causing an increase in MEm, and thereby reduce the energy required for growth.

Construction and validation of a decision tree for treating metabolic acidosis in calves with neonatal diarrhea.

BACKGROUND: The aim of the present prospective study was to investigate whether a decision tree based on basic clinical signs could be used to determine the treatment of metabolic acidosis in calves successfully without expensive laboratory equipment. A total of 121 calves with a diagnosis of neonatal diarrhea admitted to a veterinary teaching hospital were included in the study. The dosages of sodium bicarbonate administered followed simple guidelines based on the results of a previous retrospective analysis. Calves that were neither dehydrated nor assumed to be acidemic received an oral electrolyte solution. In cases in which intravenous correction of acidosis and/or dehydration was deemed necessary, the provided amount of sodium bicarbonate ranged from 250 to 750 mmol (depending on alterations in posture) and infusion volumes from 1 to 6.25 liters (depending on the degree of dehydration). Individual body weights of calves were disregarded. During the 24 hour study period the investigator was blinded to all laboratory findings. RESULTS: After being lifted, many calves were able to stand despite base excess levels below -20 mmol/l. Especially in those calves, metabolic acidosis was undercorrected with the provided amount of 500 mmol sodium bicarbonate, which was intended for calves standing insecurely. In 13 calves metabolic acidosis was not treated successfully as defined by an expected treatment failure or a measured base excess value below -5 mmol/l. By contrast, 24 hours after the initiation of therapy, a metabolic alkalosis was present in 55 calves (base excess levels above +5 mmol/l). However, the clinical status was not affected significantly by the metabolic alkalosis. CONCLUSIONS: Assuming re-evaluation of the calf after 24 hours, the tested decision tree can be recommended for the use in field practice with minor modifications. Calves that stand insecurely and are not able to correct their position if pushed require higher doses of sodium bicarbonate, if there is clinical evidence of a marked D-lactic acidosis. In those calves, determining the degree of loss of the palpebral reflex was identified as a useful decision criterion to provide an additional amount of 250 mmol sodium bicarbonate. This work demonstrates the clinical relevance of the discovery that D-lactate is responsible for most of the clinical signs expressed in neonatal diarrheic calves suffering from metabolic acidosis.

Development of a diagnostic diagram for rapid field assessment of acidosis severity in diarrheic calves.

OBJECTIVE: To develop a diagnostic diagram for rapid field assessment of acidosis severity in diarrheic calves. DESIGN: Prospective cross-sectional study. ANIMALS: 148 Piedmontese calves (38 calves in preliminary experiments; 83 diarrheic calves and 27 healthy control calves in the primary experiment). PROCEDURES: Physical examination was performed and a standard data collection form was completed for each calf. Blood samples were obtained and submitted for evaluation of acid-base balance, performance of a CBC, and measurement of electrolyte and total protein concentrations. RESULTS: Severe metabolic acidosis (extracellular base excess more negative than -10 mmol/L) was associated with abnormal mental status, delayed or absent suckle reflex, abnormal posture or gait, enophthalmos, and cold oral mucosal membranes. Clinical signs associated with severe metabolic acidosis were arranged into a grid to create a diagnostic diagram. Sensitivity and specificity of the diagnostic diagram for the prediction of severe metabolic acidosis were 88% and 79%, respectively. CONCLUSIONS AND CLINICAL RELEVANCE: Use of the diagnostic diagram may aid differentiation between severe and nonsevere acidosis patterns as determined on the basis of clinical signs.

Metabolic acidosis in neonatal calf diarrhea-clinical findings and theoretical assessment of a simple treatment protocol.

BACKGROUND: Clinical assessment of metabolic acidosis in calves with neonatal diarrhea can be difficult because increased blood concentrations of d-lactate and not acidemia per se are responsible for most of the clinical signs exhibited by these animals. OBJECTIVES: To describe the correlation between clinical and laboratory findings and d-lactate concentrations. Furthermore, the theoretical outcome of a simplified treatment protocol based on posture/ability to stand and degree of dehydration was evaluated. ANIMALS: A total of 121 calves with diagnosis of neonatal diarrhea admitted to a veterinary teaching hospital during an 8-month study period. METHODS: Prospective blinded cohort study. Physical examinations were carried out following a standardized protocol. Theoretical outcome of treatment was calculated. RESULTS: Type and degree of metabolic acidosis were age dependent. The clinical parameters posture, behavior, and palpebral reflex were closely correlated to base excess (r = 0.74, 0.78, 0.68; P < .001) and d-lactate concentrations (r = 0.59, 0.59, 0.71; P < .001), respectively. Thus, determining the degree of loss of the palpebral reflex was identified as the best clinical tool for diagnosing increase in serum d-lactate concentrations. Theoretical outcome of treatment revealed that the tested dosages of sodium bicarbonate are more likely to overdose than to underdose calves with diarrhea and metabolic acidosis. CONCLUSIONS AND CLINICAL IMPORTANCE: The degree of metabolic acidosis in diarrheic calves can be predicted based on clinical findings. The assessed protocol provides a useful tool to determine bicarbonate requirements, but a revision is necessary for calves with ability to stand and marked metabolic acidosis.

[Qualification of the Stewart variables for the assessment of the acid-base status in healthy dogs and dogs with different diseases]. / Eignung der Stewart-Variablen zur Beurteilung des Säuren-Basen-Status bei gesunden und unterschiedlich erkrankten Hunden.

Peter Stewart criticized the traditional theory of the acid-base status by Henderson-Hasselbalch as too simple and incomplete. He developed a new model with 3 independent variables: (1) pCO2, (2) SID (strong ion difference) and (3) Atot (Acid total). In healthy and ill dogs the diagnostic usefulness of both acid-base models were compared. This study included n=58 healthy dogs and 3 clinical cases of sick dogs. The age of the healthy dogs was 5.0 (2.0-7.0) years (= median (1.-3. quartil)). The 3 clinical cases included (1) a dog with septic shock, (2) with acute renal insufficiency, and (3) with hypovolaemic shock due to gastric torsion. Venous blood was taken of all dogs and the acid-base parameters were determined within < or =30 minutes. Electrolytes and albumin were determined in blood serum and used for calculation of the Stewart variables. Limits of reference intervals (x+/-1.96 - s) were determined for the healthy dogs yielding pCO2 = 3.6-6.5 kPa, [SID3] = 33.1-50.9 mmol/l resp. [SID4] = 31.8-49.6 mmol/l and [Al = 8.5-13.1 mmol/l. In Case 1 the Henderson-Hasselbalch parameters demonstrated the presence of a strong metabolic acidosis with mild respiratory influence (pH, [HCO3-], [BE] and PCO2 at upper range of normal). Analysis of the Stewart variables [SID3] resp. [SID4] revealed an electrolyte imbalance with [Cl-] and [lactate-] as the reason for metabolic acidosis. Case 2 showed a metabolic acidosis with respiratory compensation (pH, [HCO3-], [BE] and PCO2). Analysis of the Stewart variables with [SID3] resp. [SID4 caused by [K+], [Na+] and [lactate-]demonstrated the acidotic metabolism due to a renal malfunction. Case 3 had a metabolic acidosis (pH-value in the lower range) caused by electrolyte imbalances ([SID4]. The Stewart variables allow a better understanding of the causes of acid-base-disturbances in animals with implications for successful therapy via infusion.

Assessment of acid-base status of cats with naturally occurring chronic renal failure.

Metabolic acidosis is reported to be a common complication of feline chronic renal failure (CRF) but acid-base status of feline patients with this disease is rarely assessed by general practitioners. A cross-sectional study involving 59 cases of naturally occurring feline CRF was conducted to determine the prevalence of acid-base disturbances. Cases were categorised on the basis of their plasma creatinine concentrations as mild, moderate or severe. A group of 27 clinically healthy, age-matched cats was assessed for comparison. A low venous blood pH (<7.270) was found in 10 of the 19 severe cases (52.6 per cent), three of the 20 moderate cases (15 per cent) and none of the 20 mild cases. Acidaemia was associated with an increased anion gap contributed to by both low plasma bicarbonate and low chloride ion concentrations. Biochemical analysis of urine samples showed urine pH to decrease with increasing severity of renal failure. Urinary loss of bicarbonate was not associated with the occurrence of acidaemia and there was a tendency for urinary ammonium ion excretion to decrease as the severity of renal failure increased. Cats with naturally occurring CRF do not show plasma biochemical evidence of acid-base disturbances until the disease is advanced.

Assessment of rumen processes by selected-ion-flow-tube mass spectrometric analysis of rumen gases.

This work investigated the potential to use measurement of the concentration of certain gases in the rumen headspace to gain information about rumen processes and as a potential diagnostic tool. We used new equipment (selected-ion-flow-tube mass spectrometer) that allows rapid and precise analysis of many of the gases present in a sample. Samples of rumen headspace gas and corresponding samples of rumen liquor were taken from three lactating cows, prepared with rumen fistulae, at intervals after receiving their morning feed allocation (grass silage and concentrates). Hydrogen sulfide, methyl sulfide, and dimethyl sulfide, were the predominant gases that were measured in the rumen headspace by this technique. The concentrations of these sulfur compounds declined over the interval after feeding, mirroring ammonia concentrations measured in rumen liquor, reflecting their common dependence on the fermentation of sulfur amino acids. Ammonia concentrations in rumen headspace gas varied in the opposite direction to the concentration of ammonia in rumen liquor and likely depend more on the pH of rumen liquor. Consideration of the pKa of ammonia suggests that ammonia concentrations in rumen gas will be very low below pH 6, representing a useful diagnostic for subacute ruminal acidosis. Low concentrations of volatile fatty acids were detected in rumen gas. The molar proportions of volatile fatty acids were similar in gas and liquor samples, with rumen gas containing slightly less acetic acid and disproportionately more valeric and caproic acids.

A practitioner's views on fluid therapy in calves.

This article is aimed to persuade most bovine practitioners that FET is a therapeutic tool that can easily be used under field conditions, and that by following the right protocol, one can provide a cost-effective treatment for the farmer, a rewarding experience for us, and a boost for our professional image. Based on the excellent current publications, the scheme of work to put FET into practice is presented. Controversial decisions must be made (such as oral vs. parenteral fluids, removing milk from diet vs. continued feeding, oral fluids with bicarbonate vs. those with metabolizable bases, and so forth). Practicality, economy, and owner compliance are critical components of a successful protocol. This work protocol is based on the current literature, considers controversial subjects, such as route of administration, alkalinizing agents, and fasting, employs simple yet effective techniques, and is successful in a high percentage of cases.

Malate content of forage varieties commonly fed to cattle.

The objective of this study was to determine the concentration of malate in forage varieties at different stages of maturity. Five alfalfa varieties (Alfagraze, Apollo Supreme Cimarron, Crockett, and Magnum III) and three bermudagrass varieties (Coastal, Tifton-78, and Tifton-85) were collected at different stages of maturity. Samples were collected from replicate plots (n = 3) of each alfalfa variety at 9, 18, 28, 35, and 42 d of maturity; bermudagrass hay samples were composited from six bales of each variety from two cuttings staged to be harvested at 27 and 41 d of maturity. Malate was extracted from the samples and quantitated by high performance liquid chromatography using an organic acid column. As maturity increased, the concentration of malate declined in both plant species. Concentrations of malate were numerically higher in two alfalfa varieties (Crockett and Magnum III) at 35 and 42 d of maturity than in all other alfalfa varieties. Concentrations of malate in bermudagrass at 41 d of maturity were lower than concentrations of malate in all alfalfa varieties at 42 d of maturity. Malate declined as maturity increased in the Coastal and Tifton-78 varieties. Because malate stimulates the utilization of lactate by the predominant ruminal bacterium Selenomonas ruminantium, some of the benefits associated with alfalfa in the diets of dairy cattle may be due to the malate in this forage.

The interval between birth and sternal recumbency as an objective measure of the vitality of newborn calves.

The time from birth to attaining sternal recumbency (T-SR) was recorded for 219 newborn calves in order to evaluate its use as a parameter for diagnosing vitality. Calves were defined as vital if they received routine care without medical treatment and survived seven days from birth without any symptom of illness (n = 192). Those which did not fulfil these conditions were categorised as non-vital (n = 27). Ten calves were born spontaneously and the others were delivered either by caesarean section (n = 105), normal extraction (n = 78) or forced extraction (n = 26). The mean (+/- sd) T-SR values of the vital calves in these delivery groups were: 4.0 +/- 2.2, 4.5 +/- 3.1, 5.4 +/- 3.3 and 9.0 +/- 3.3 minutes, respectively. Jugular blood gas and pH measurements were performed at several fixed times after birth until pH and base excess had reached values of over 7.2 and more than -5.0 mmol/litre, respectively. Mean pH and base excess values of vital calves 10 minutes post partum were significantly higher and lower, respectively, than those of non-vital calves. Forcefully extracted calves had longer T-SR, more serious acidosis, recovered more slowly from acidosis, died more, and exhibited trauma more frequently. A T-SR of at least 15 minutes had a predictive value of 84 per cent for non-vitality, while 10 minute pH values of less than 6.9 had a lower predictive value, namely 68 per cent, for non-vitality. Correlations between T-SR values and 10 minute pH and base excess values were moderate, whereas correlations between T-SR values and PCO2 values were weaker still and much more dependent on the type of delivery. It is concluded that T-SR determination is a valuable, practicable and objective diagnostic tool for estimating the condition of newborn calves during the first 15 minutes of life. The diagnostic value of a single pH measurement on the jugular blood of a neonatal calf is doubtful.

Rates of diseases and their associated costs in two Colorado sheep feedlots (1985-1986).

Data related to rates of disease and their associated costs were collected for 12 months from 2 sheep feedlots in northern Colorado. There was an apparent seasonal occurrence of many of the diseases. Pneumonia, enterotoxemia, acidosis, and transport tetany accounted for most of the diseases seen in these feedlots and were responsible for most of the economic losses. There was a large difference in the incidence of diseases between the 2 feedlots and in the expenditures for disease prevention between the 2 feedlots.

Economical preparation of fluids for intravenous use in cattle practice.

The equipment and materials necessary to prepare and safely administer fluids intravenously to cattle are described. The preparation and clinical uses of Hartmann's solution are discussed, together with modifications of the solution to permit its application to different disease states.

A rapid quantitative colorimetric determination of blood acetone applied to the assessment of ketosis in fasted pregnant ewes.

A simple, accurate, colorimetric method for determining blood acetone as an adjunct to the enzymic method of estimating the other ketones was developed and tested on a group of fasted pregnant ewes. Acetone reacted with 2-hydroxybenzaldehyde to form a stable coloured complex that followed Beer's Law up to an acetone concentration of at least 4 mg/100 ml of the test solution at 490 nm. While the optimum incubation time of the reaction mixture was found to be 3 h at 40 degrees C, it could also be left to incubate overnight at room temperature. When tested in a blood matrix, the method gave a mean within-batch coefficient of variation of 0,7%, and a day to day variation of 0,3-1,2%, while an overall recovery of 100, 6+/-1,4% was achieved over 5 concentration ranges (2,86-10,53 mg/100 ml). The values obtained from this method corresponded closely to those from the diffusion technique previously employed and it considerably simplified the procedure. A direct linear relationship, y = 2,594x + 2,917 with a coefficient of determination r2 = 0,958 for 49 pairs of data, was found between the acetone (= x mg/100 ml) and total ketone (= y mg/100 ml) concentrations in blood samples drawn from fasted pregnant sheep. This relationship can therefore be used to estimate accurately the degree of ketosis from the blood acetone concentration alone.