Multipolar endocardial mapping of the right heart using a basket catheter: acute and chronic animal studies

The development of catheter-based ablative techniques for primary atrial and ventricular arrhythmias is likely to be assisted by improved techniques for systematic endocardial activation sequence mapping. RA mapping using a multielectrode basket catheter has been shown to be feasible with minimal acute toxicity in a prior study. The objectives of the current study are to investigate: (1) the utility of the basket catheter for mapping RV activation; and (2) the evolution of acute endocardial lesions produced by basket catheter use in both the RA and RV over 4-8 weeks time. A flexible, 5-spoke basket catheter bearing 25 electrode pairs was placed in the RA (n = 9) or the RV (n = 13) in 22 juvenile sheep (22-56 kg). The catheter was deployed for 0.1-4.1 hr (RA) and 0.3-3.9 hr (RV). In 20 of these 22 animals, 32 recordings were made of filtered (30-250 Hz) bipolar electrograms and surface ECG. Electrograms were timed and used to construct activation sequences based on a schematic of catheter geometry. Hearts were examined either acutely (4 RA and 9 RV studies) or 4-8 weeks after the procedure (5 RA and 4 RV studies). One animal undergoing RA placement had an air embolism resulting in cardiac arrest immediately prior to basket placement; all other animals were stable during placement. RA electrograms of sufficient quality to determine activation time were recorded from 82% of pairs in RA maps, and RV electrograms from 89% of pairs in RV maps. Mean activation sequence duration in RV was 16 ms versus 47 ms in RA (P < 0.0001), making construction of RV maps more difficult. Acute postmortem studies of RV placement revealed a silent apical RV puncture in one animal. Superficial abrasion or ecchymosis of RV endocardium and/or tricuspid valve were noted in six animals. Postmortem exams in both RA and RV chronic studies showed healed endocardial lesions, with only superficial scarring. Rapid RV activation mapping using a basket catheter is feasible, but requires precision recording techniques. Endocardial abrasions produced in lambs both by RA and RV placement of the catheter are healed in < 4-8 weeks, with trivial residua. The multielectrode basket catheter may be applicable to the mapping of tachycardias originating in or involving the right ventricle.

High-density endocardial activation mapping of the right atrium in three dimensions by composition of multielectrode catheter recordings

The use of radiofrequency ablation for treatment of complex arrhythmia substrates has prompted interest in transcatheter endocardial activation mapping. Technical constraints on catheter fabrication and the intention to use such maps to guide ablation both demand innovative approaches to mapping. A fluoroscopically based endocardial mapping technique is proposed to improve the ability of electrophysiologists to interpret large amounts of data acquired using multielectrode catheter arrays, improving their ability to visualize the data and act on its content. This technique addresses previous limitations imposed by the number of electrodes that can be deployed and by the difficulty in determining their relative spatial locations. It is based on the composition of multiple activation sequence mappings made in a single rhythm, with the spatial locations of recording electrode pairs determined in orthogonal fluoroscopic views referenced to stable intrathoracic markers. Rather than imposing a geometry determined primarily by the measurement apparatus, the spatial locations of only those electrodes in proximity to the endocardial surface, as determined by their ability to record bipolar electrograms, are measured. In this manner, the geometry of the endocardium may be approximated by measurements made of electrode position. Using this approach, the number of endocardial sites that can be sampled in a stable rhythm is theoretically unlimited, resulting in the realization of high-resolution activation maps. Spatiotemporal data may be used to create three-dimensional activation sequence maps, displayed as animated sequences. This technique was used in anatomically normal and diseased human right atria to create activation maps of sinus and paced rhythms, classic atrial flutter, and postoperative intraatrial reentrant tachycardia, using a median of 108 electrode positions (range, 27-197) in 25 maps. The activation sequences represented by these maps were diverse, but qualitatively concordant with known mechanisms of atrial activation. High-density catheter-based activation mapping of the right atrium is feasible and may improve understanding of complex arrhythmias and assist in the development of ablative techniques. Further research is needed on the spatial correlation between cardiac anatomy and fluorography, suppression of spatial artifact, and optimal mapping densities.

In-hospital mortality for surgical repair of congenital heart defects: preliminary observations of variation by hospital caseload

OBJECTIVE

To examine the impact of hospital caseload on in-hospital mortality for pediatric congenital heart surgery.

DESIGN

Population-based, retrospective cohort study.

SETTING

Acute care hospitals in California and Massachusetts.

PATIENTS

Children undergoing surgery for congenital heart disease, identified by the presence of procedure codes indicating surgical repair of a congenital heart defect in computerized statewide hospital discharge abstract databases. Cases were grouped into four categories based on the complexity of the procedure.

MAIN OUTCOME MEASURES

Adjusted odds ratios (OR) for in-hospital death were estimated using generalized estimating equations that account for the intra-institutional correlation among patients.

RESULTS

A total of 2833 cases at 37 centers were identified. Compared with centers performing > 300 cases per year, after controlling for patient characteristics, centers performing < 10 cases per year had an OR for in-hospital death of 7.7 (95% confidence interval (CI) [1.6-37.8]); 10 to 100 cases, OR = 2.9 (95% CI [1.6-5.3]); 101 to 300 cases, OR = 3.0 (95% CI [1.8-4.9]). Independent risk factors for mortality included procedure complexity category (P < .0001), use of cardiopulmonary bypass (P < .0001), young age at surgery (P = .001), and transfer from another acute care hospital (P < .0001). Few differences were found by hospital caseload in length of stay or total hospital charges.

CONCLUSIONS

For children with a congenital heart defect who underwent surgery in California in 1988 or Massachusetts in 1989, the risk of dying in-hospital was much lower if the surgery was performed at an institution performing > 300 cases annually. This study was limited by the absence of clinical detail in discharge abstract databases. If these findings are corroborated by other studies, health care delivery strategies that direct children requiring surgical correction of congenital heart defects to high-volume centers may substantially reduce overall mortality.

Influence of right heart size on outcome in pulmonary atresia with intact ventricular septum

BACKGROUND

Neonates with pulmonary atresia and intact ventricular septum (PA-IVS) are frequently born with hypoplastic right heart structures that must grow after right ventricular decompression (RVD) procedures for a complete two-ventricle physiology to be achieved. Previous authors have asserted that neonatal right heart size or morphology will predict right heart growth potential. Since 1983, our bias has favored early RVD regardless of initial right heart size. In 1986, we recognized a subset of patients with coronary artery abnormalities associated with poor outcome after RVD and have defined these patients as having a right ventricular-dependent coronary circulation (RVDCC).

METHODS AND RESULTS

To assess the influence of right heart size on outcome independent of the presence of RVDCC, we measured echocardiographic right ventricular (RV) dimensions in 37 neonates with adequate studies presenting between 1983 and 1990. Coronary artery anatomy was adequately assessed by angiography in 36. RV volume and tricuspid valve (TV) diameter were significantly smaller in patients with RVDCC than in those without. However, there was no statistically significant association between RV volume or TV diameter and survival among patients with or without RVDCC: Among 29 patients without RVDCC, 23 of 24 (95.8%) who achieved RVD are alive compared with 1 of 5 (20%) who did not achieve RVD (P = .001). Twenty-one of the 23 survivors have a complete two-ventricle physiology with low right atrial pressure. Among 7 patients with RVDCC, 2 patients who underwent RVD died early of left ventricular failure, whereas 4 of 5 who did not undergo RVD have survived single ventricular palliation.

CONCLUSIONS

Small right heart size is associated with RVDCC but is not associated with survival in PA-IVS. Patients without RVDCC have improved survival after RVD regardless of neonatal right heart size.

Multipolar endocardial mapping of the right atrium during cardiac catheterization: description of a new technique

OBJECTIVES

Using a new mapping system that allows the simultaneous acquisition of data from 25 right atrial bipolar electrodes during cardiac catheterization, we mapped normal sinus rhythm and atrial reentrant tachycardia in 24 sheep (20 to 49 kg) and 7 pigs (25 to 35 kg).

BACKGROUND

Rapid, high resolution mapping during cardiac catheterization may shorten ablation procedures and permit ablation of otherwise refractory arrhythmias.

METHODS

A flexible, elliptic, basket-shaped recording catheter has five spokes, each with 10 electrodes arranged as 5 bipolar pairs. Catheter shape, electrode spacing and introduction technique were modified in response to the results of experiments in the first 23 animals. In the most recent eight animals, retraction of a string attached to the distal tip distended the basket, providing safe tissue contact. Filtered (30 to 250 Hz) bipolar recordings from all 25 electrode pairs, as well as a surface electrocardiogram, were recorded and digitized at 1,000 Hz using custom software. An activation map was digitally constructed and superimposed on anteroposterior and lateral fluoroscopic catheter images. Bipolar recordings were made in normal sinus rhythm (31 animals), with adequate signals recorded from > 95% of electrode pairs. Rapid burst pacing and intentional right atrial air embolus (30 to 50 ml) induced sustained atrial reentrant tachycardia in five animals, which was also adequately recorded.

RESULTS

Catheter positioning and complete atrial mapping required < 10 min after venous access in the most recent eight experiments. The catheter was left in position for up to 4 h. Postmortem evaluation revealed minor superficial abrasion of the venae cavae or right atrial endocardium in six animals and moderate abrasion in two. No other damage was observed.

CONCLUSIONS

This new system may ultimately assist in mapping simple or complex atrial arrhythmias during cardiac catheterization.

Individual pulmonary vein size and survival in infants with totally anomalous pulmonary venous connection

OBJECTIVES

We investigated whether mortality in totally anomalous pulmonary venous connection could be predicted from preoperative individual pulmonary vein size.

BACKGROUND

Some infants with this anomaly die with or without surgical repair because of stenosis of individual pulmonary veins.

METHODS

Individual pulmonary vein, vertical vein and pulmonary venous confluence diameters were retrospectively measured from preoperative echocardiograms in 32 infants with totally anomalous pulmonary venous connection presenting to Children's Hospital, Boston over a 4 1/2-year period. Data on body surface area, other cardiac anomalies, presence of initial pulmonary venous obstruction and early surgery and outcome were also recorded.

RESULTS

Of 32 patients, 6 (18.8%) died before hospital discharge, and 8 (25.0%) died subsequently. Six (75.0%) of the eight patients who died late had individual pulmonary vein stenosis at sites remote from the surgical anastomosis to the left atrium. The remaining 18 patients (56.3%) are alive at a mean follow-up period of 9.7 months. A Cox proportional hazards model revealed that small sum of individual pulmonary vein diameters (p = 0.0004), small confluence size (p = 0.02) and presence of heterotaxy syndrome (p = 0.008) were each significant univariate predictors of survival. Multivariate analysis showed that small pulmonary vein sum was a strong predictor of survival (p = 0.008), independent of the presence of heterotaxy syndrome. An analysis stratified by the presence of heterotaxy syndrome showed that the predictive effect of small pulmonary vein sum on survival was strongest in patients without heterotaxy syndrome.

CONCLUSIONS

These data show that individual pulmonary vein size at diagnosis is a strong, independent predictor of survival in patients with totally anomalous pulmonary venous connection. In patients with this anomaly and small individual pulmonary veins, the anomaly may not be correctable by surgical creation of an anastomosis between the pulmonary venous confluence and the left atrium.

Research note: efficacy of various flavonoids and simple phenolics in prevention of nutritional myopathy in the chick

A 33-day feeding experiment was conducted with 3-day-old broiler chicks to assess the efficacy of various flavonoid and simple phenolic antioxidants in preventing nutritional muscular dystrophy (NMD) resulting from vitamin E deficiency. None of the flavonoids or simple phenolics at a dietary concentration of 1,000 ppm completely prevented NMD but quercetin reduced (P less than .05) its incidence and quercetin, morin, and ferulic acid reduced (P less than .05) the severity of the disorder. The low-selenium, low-vitamin E diet also promoted the development of a mild exudative diathesis (ED) in many of the birds, which was inhibited (P less than .05) by the rutin and silymarin treatments, but exacerbated (P less than .05) by quercetin, morin, and ferulic acid. Changes in concentrations of vitamin E in plasma, liver, or muscle, caused by the various treatments (other than vitamin E), were not related to protection against NMD or ED.

Changes in lipid composition of calf tissues by excess dietary zinc

In a previous study, very high Zn (1000 ppm) prevented most of the tissue lipid increases caused by very high Cu (1000 ppm), and this investigation was conducted to study whether Zn had a direct effect on lipid metabolism or simply acted indirectly by inhibiting excess Cu activity. Calves were fed basal dietary Cu (10 ppm), and lipid composition of heart, liver, and blood plasma was measured as affected by control (40 ppm in DM), high (500 ppm), or very high (1000 pm) Zn intakes. Supplementation with 1000 ppm of Zn did not cause any marked quantitative changes in tissue lipids (e.g., lipid classes, oleic, or stearic acids), suggesting that, in the previous study, Zn had mainly interfered with excess Cu effects on lipids rather than with lipid metabolism directly. However, there were two exceptions. Adding 1000 ppm of Zn to basal Cu ration 1) reduced concentration and changed the fatty acid composition of plasma cholesterol esters, both of which are indicative of excess Zn inhibiting lecithin:cholesterol acyltransferase activity, and 2) altered the desaturation and elongation of the essential fatty acids and their concentration in tissue phospholipids. This latter effect of excess Zn conceivably could be important in changing the structure and function of cell membranes and in the production and activity of prostanoids and leukotrienes.

Function of the anatomic pulmonary valve in the systemic circulation

The anatomic pulmonary valve, which has thin leaflets with little elastic tissue in the normal heart, must function as the neoaortic valve after arterial switch operation (ASO) for transposition of the great arteries, palliative surgery for hypoplastic left heart syndrome (HLHS), and pulmonary artery-to-aortic (P-A) anastomosis for complex heart disease with subaortic obstruction. The long-term function of this valve under these circumstances is not known. To investigate the function of this valve in the systemic circulation, the follow-up echocardiograms, catheterization data, and angiograms were reviewed for 189 patients at our institution after an ASO (n = 112), palliative surgery for HLHS (n = 45), or P-A anastomosis (n = 32). In addition, the effect on valve function of preoperative anatomy, prior placement of a pulmonary artery band (PAB), and length of follow-up was examined. Neoaortic regurgitation was present in 41% of patients after an ASO (mean +/- SD) follow-up (20 +/- 20; range, 2.2-80.5 months), 60% of patients after an HLHS repair (21 +/- 15; range, 3.7-62.4 months) and 50% after a P-A anastomosis (27 +/- 21; range, 2.6-89.4 months). Only eight patients had more than trivial/mild regurgitation. No neoaortic stenosis was observed. Minor preoperative valve abnormalities did not influence postoperative valve function. Prior PAB placement significantly increased the likelihood of postoperative neoaortic regurgitation after a two-stage ASO but not after a P-A anastomosis. In the ASO group, patients with an intact ventricular septum had a significantly higher prevalence of neoaortic regurgitation than those with a ventricular septal defect.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of excess dietary manganese on lipid composition of calf blood plasma, heart, and liver

Preruminant calves were fed milk replacer containing control (40 ppm) or two high concentrations (200 and 1000 ppm) of Mn to assess the effect of excessive Mn intakes on plasma, heart, and liver lipids. The two higher Mn intakes had no effect on lipid classes in liver and heart, except for elevated triglycerides in liver and lower sphingomyelin in heart (for 1000 ppm of Mn). At 1000 ppm of Mn intake, but not at 200 ppm, marked increases occurred in plasma total lipids, phosphatidylcholine, cholesterol, cholesterol esters, sphingomyelin, and triglycerides. The highest intake altered the essential fatty acid composition of liver phosphatidylcholine. Linoleic and linolenic acids were increased, but arachidonic and eicosapentaenoic acids were decreased, suggesting that very high excess of Mn interfered with hepatic desaturation and elongation of the essential fatty acids. Thus, high Mn intake (200 ppm) caused relatively few tissue lipid changes, whereas very high intake (1000 ppm) markedly increased plasma lipid classes and apparently interfered with essential fatty acid metabolism in liver.

Tolerance of the preruminant calf for excess manganese or zinc in milk replacer

In two experiments, calves were fed milk replacer containing 40, 200, 500, 1000, or 5000 ppm Mn or 40, 200, 500, 700, or 1000 ppm Zn in DM, from 3 to 38 d of age, to estimate the minimum toxic concentrations of Mn and Zn. Starting at 1000 ppm Mn, weight gains and feed efficiencies were decreased slightly; none of the calves fed 5000 ppm Mn survived the 5-wk experiment. Liver and bile showed the largest increases in Mn concentration. In the Zn experiment, only at 700 and 1000 ppm Zn were weight gains, DM intake, and feed efficiency reduced. Largest Zn increases were in liver, kidney, and plasma. Thus, performance of the preruminant calves was not affected adversely by 500 ppm Mn or 500 ppm Zn in milk replacer, concentrations that are markedly higher than the NRC recommendations of 40 ppm Mn and 40 ppm Zn. However, Mn and Zn concentrations increased in some tissues, and toxicities might have arisen if the trial had been continued. Evidence was not obtained indicating that the calf benefits from Mn or Zn intakes above the NRC recommendations.

Effects of dietary corn oil and fish oil concentrate on lipid composition of calf tissues

Lipid composition of calf blood plasma, liver platelets, muscle, heart, and brain was measured, as affected by high dietary intake of linoleic acid from corn oil or of polyunsaturated fatty acids from fish oil concentrate. Plasma total lipids, phosphatidylcholine, and cholesteryl esters were reduced by corn oil and fish oil concentrate. Dietary fatty acid composition had no influence on percentage distribution of the major phospholipid components of liver, heart, muscle, and brain, but did alter the polyunsaturated fatty acid composition of major phospholipids in plasma, liver, platelets, muscle, and heart. In general, high linoleic acid intake increased linoleic acid and decreased oleic, arachidonic, and linolenic acids in tissue phospholipids, and fish oil concentrate high in eicosapentaenoic and docosahexaenoic acids increased phospholipid concentrations of these fatty acids. The fatty acid composition of brain phosphatidylcholine and phosphatidyl-ethanolamine was relatively resistant to dietary lipid alterations. The fatty acid changes in tissue phospholipids that resulted from dietary lipid alterations may have important implications in eicosanoid metabolism, and in the structure and function of cell membranes.

Lipid compositional changes in calves fed excess iodine

Calves were fed milk replacer containing .57, 10, or 200 ppm iodine (from ethylenediaminedihydriodide) to determine the effects of excess dietary iodine on composition of lipids in blood plasma, liver, and heart. High iodine intakes had no effect on plasma total lipids or lipid classes, but caused lipid class concentration changes in liver and heart. Both 10 and 200 ppm iodine increased concentration of liver phosphatidylethanolamine and heart phosphatidylcholine, cholesterol, and total lipids, and the 200 ppm intake also increased concentration of liver phosphatidylcholine, total lipids, and heart phosphatidylethanolamine. Both iodine treatments tended to increase all the other minor lipid classes in liver and heart as well. Both 10 and 200 ppm iodine treatments increased some of the n-3 polyunsaturated fatty acids in the major phospholipids of plasma, liver, and heart. For the preruminant calf, liver and heart may be more useful than blood plasma for indicating excess iodine effects on lipid metabolism.

Effects of elevated iodine in milk replacer on calf performance

Calves were fed milk replacer containing .57, 10, 50, 100, or 200 ppm iodine (from ethylenediaminedihydroiodide) in DM, from 3 to 38 d of age, to estimate the minimum toxic concentration of iodine. Only the 200 ppm iodine intake reduced weight gains, DM intake, feed efficiency, and DM digestibility. At the 100 and 200 ppm iodine intakes, protein digestibility was reduced, and calves showed typical symptoms of iodine toxicity (nasal discharge, excessive tear and saliva formation, and coughing from tracheal congestion). Thyroid iodine increased with every elevation in iodine intake. Iodine in plasma, bile, and non-thyroid tissues started to increase at the 50 ppm intake and, except for muscle, tended to increase again at the 100 and 200 ppm intakes. Thus, the preruminant calf tolerated up to 50 ppm iodine in milk replacer DM for 5 wk postpartum. However, as iodine concentrations in plasma and nonthyroid tissues started to increase at 50 ppm iodine, an upper limit of 10 ppm would be more preferable.

Influence of excess dietary copper on lipid composition of calf tissues

Lipid composition of calf liver, heart, and skeletal muscle was measured, as affected by control Cu (10 ppm in DM), high Cu (1000 ppm), or high Cu plus high Zn (1000 ppm) in milk replacer. High dietary Cu increased all lipid classes in liver, some in the heart, and decreased all lipid classes except cholesterol in muscle. Zinc inhibited many of the changes in tissue lipid classes by excess copper. High Cu intake increased fatty acid unsaturation (palmitoleic, oleic, linoleic acids) and decreased stearic acid in phosphatidylcholine and phosphatidylethanolamine of liver and heart. Excess Cu tended to have an opposite effect in changing fatty acid concentrations in liver and muscle. Activities of various desaturases and elongases were estimated in liver, heart, and muscle using ratios of fatty acid precursors to products in combined phosphatidylcholine and phosphatidylethanolamine. High Cu intake frequently altered activities of these enzymes in all three tissues with additional high Zn usually coregulating activity in the direction opposite to Cu.

Effect of copper loading of preruminant calves on intracellular distribution of hepatic copper, zinc, iron, and molybdenum

The subcellular distribution of Cu, Zn, Fe, and Mo was investigated in liver homogenates from preruminant calves fed control Cu (10 ppm), high Cu (1000 ppm), or high Cu plus high Zn (1000 ppm) milk replacer. For controls, Cu was located primarily in the nuclei and large granule fractions, Zn mainly in the cytosol, and Fe in the cytosol and nuclei fraction; Mo was present in all compartments but least in microsomes. Calves fed high Cu had markedly increased hepatic Cu concentration in the nuclei and cytosol fractions, reduced cytosol Zn, increased nuclei Fe, and decreased Mo concentration in all cell compartments. Feeding high Zn with high Cu (which prevented deaths from high Cu) reversed some changes in hepatic trace element patterns caused by high Cu while initiating new alterations. The marked increase in hepatic Cu and reduced Mo in nuclei and cytosol after Cu loading indicate that these compartments may have a predominant role in the development of Cu toxicity in the preruminant calf.

Tolerance of the calf for excess copper in milk replacer

Calves were fed milk replacer containing 10, 50, 200, 500, or 1000 ppm Cu, from 3 d to 45 d of age, to estimate the Cu concentration that would adversely affect calf performance. Weight gains and feed efficiency were similar for 10 and 50 ppm Cu but were reduced at 200 and 500 ppm Cu. All calves survived 500 ppm Cu and lower intakes, but only 4 of 7 calves survived the 1000 ppm concentration. Typical clinical symptoms of chronic Cu toxicity and hemolytic crisis were evident for the 1000 ppm calves before death. Additional 1000 ppm Zn prevented deaths for 1000 ppm Cu, but calf performance was poor. Increased Cu intakes elevated plasma ceruloplasmin and glutamic oxalacetic transaminase activity, reduced packed cell volume (hematocrit), markedly increased fecal excretion of Mo and Zn, increased Cu concentration of liver, muscle, heart, blood, and bile, and decreased Mo and Zn in liver. We found 50 ppm Cu a safe intake where milk replacer contained 48 ppm Zn and 1.1 ppm Mo. However, at lower intakes of these elements, and for longer feeding periods than 6 wk, the calf may be much more susceptible to Cu toxicity.

Plasma lipoproteins in neonatal, preruminant, and weaned calf

This study compared plasma lipoprotein fraction profiles and lipid composition in the calf at 3 d, 3 wk, and 12 wk (weaned). For all ages the major plasma lipoprotein fraction was high density lipoproteins (52 to 73%), followed by very high density lipoproteins (10 to 22%), low density lipoproteins (13 to 18%), and chylomicrons plus very low density lipoproteins (5 to 9%). Most plasma lipid was cholesterol esters (41 to 49%) and phosphatidylcholine (21 to 29%). Most cholesterol esters (66 to 81%) and phosphatidylcholine (68 to 80%) were in high density lipoproteins; free fatty acids (83 to 96%) and lysophosphatidylcholine (75 to 85%) in very high density lipoproteins; and triglycerides (93 to 98%) in the remaining lipoprotein fractions. Of the three ages studied, 3-d-old calves had comparatively low plasma total lipids, high density lipoproteins, cholesterol esters, phosphatidylcholine, and linoleic acid in all lipid classes; they had relatively high plasma very high density lipoproteins, triglycerides, free fatty acids, phosphatidylethanolamine, and 20:3 n-9 fatty acid (indicative of essential fatty acids deficiency). Lipoprotein classes and lipid composition were similar at wk 3 and 12. Comparison of fatty acid profiles for phosphatidylcholine with those for lysophosphatidylcholine and cholesterol esters indicated plasma lecithin-cholesterol acyltransferase was active in calves at all three ages studied.

Factors affecting poor performance and scours in preruminant calves fed corn oil

A 4-wk study with 12 3-d-old calves compared the effect of feeding tallow, corn oil, or corn oil plus aspirin on calf performance, feed utilization, incidence of scours, and composition of blood plasma lipids. Aspirin treatment was to inhibit a possible role of prostaglandins in promoting scours. Calves given both corn oil treatments had lower average daily gain, feed efficiency, and higher incidence of scours than those fed tallow. Unexpectedly, corn oil produced appreciably less scours in calves than encountered in previous studies. This appeared to be related to the fat dispersion method used here, which produced much smaller fat globules (less than 1 micron vs. 10 to 20 microns). Over-production of prostaglandins from corn oil was not a causative factor in scours development. Arachidonic acid and other linoleic acid prostaglandin precursors in blood plasma cholesteryl esters and phosphatidylcholine were reduced by dietary corn oil. Aspirin, a potent inhibitor of prostaglandin biosynthesis, was ineffective in reducing scours.

Binding of selenium-75 to blood and liver cytosolic proteins in the preruminant calf

Labeled selenite (75Se) administered to calves in milk replacer, containing .2 or 5 ppm Se, was rapidly absorbed with peak blood 75Se at 6 h. Gel filtration and dialysis treatment of plasma and erythrocyte hemolysates showed that initially 75Se was transported in blood as 75SeO3= or loosely bound to plasma and erythrocyte proteins. At high Se intake, albumin became a transport protein for some of the plasma 75Se, and proportionately more blood radioactivity was carried in the erythrocytes. At 72 h after dosing, most plasma 75Se was tightly bound to protein in glutathione peroxidase fraction with low peroxidase activity, possibly Se transport protein. At 72 h, distribution of 75Se in erythrocyte was 35 to 40% in glutathione peroxidase, 50% in hemoglobin, and 5% in a selenite plus selenopolypeptide fraction. Erythrocyte peroxidase activity was mostly in the glutathione peroxidase fraction (57%) and hemoglobin (38%). Molecular weight estimate for erythrocyte glutathione peroxidase was 84,200 daltons; about 90% of blood peroxidase activity was in erythrocytes. High Se intake had no marked effect on distribution of 75Se among liver cytosolic proteins. About 35% of 75Se was in glutathione peroxidase fraction, having most of the peroxidase activity, 25% in void volume, 11 to 18% in a selenite plus selenopolypeptide fraction, and small amounts in selenoproteins of about 12,000 and 50,000 daltons.

Effect of excess dietary iron on lipid composition of calf liver, heart, and skeletal muscle

Effect of excess dietary iron on lipid composition of calf liver, skeletal muscle, and heart was assessed. High dietary iron (5000 versus 100 ppm in milk replacer DM) had no effect on the relative proportion of lipid classes in liver or their unsaturated fatty acid composition. In muscle some minor lipid components were reduced and cholesterol and sphingomyelin increased. Excessive iron had a marked effect, however, on heart lipid composition, reducing total lipids and almost all lipid classes; triglycerides, sphingomyelin, and lysophosphatidylcholine were increased. Characteristically, sphingomyelin increases in cell membranes in response to aging and numerous pathological conditions. High dietary iron reduced linolenic acid in phosphatidyl-ethanolamine and phosphatidylcholine of both skeletal and cardiac muscle. This may have resulted from iron-caused ethane production from autoxidation of linolenic acid or other n-3 family fatty acids, an effect known to occur in the rat. Linoleic and arachidonic fatty acids appeared to be unaffected. Plasmalogens in muscle and heart phosphatidylethanolamine and phosphatidylcholine were increased by high iron intake. As these alk-1-enyl ethers protect cells from oxidation and radiation damage, their synthesis may have been increased in response to stress from excessive iron. The results indicate that a relatively high concentration of vitamin E may be required in calf milk replacer when excessive iron is present.

Effect of excess iron in milk replacer on calf performance

Milk replacers containing 100, 500, 1000, 2000, or 5000 ppm iron were fed to 3-d-old calves for 6 wk to estimate the lowest amount of dietary iron (added as ferrous sulfate) that would reduce calf performance. Calves tolerated all iron treatments except 5000 ppm. At this intake calves showed reduced weight gains, DM intake, feed efficiency, and digestibility of DM and protein. There were no other signs of iron toxicity and no gross abnormalities were found on postmortem examination. Percent of dietary iron in feces increased with higher dietary iron and ranged from 65 to 84%. Elevated iron intakes caused relatively small increases in iron concentration of blood plasma, bile, kidney, heart, and muscle but marked increased in spleen and liver iron, particularly in liver for the 2000 and 5000 ppm treatments. At 100 ppm iron intake, nonheme iron in liver, spleen, and kidney was composed of similar proportions of ferritin and hemosiderin, but at 5000 ppm iron intake, hemosiderin predominated in these tissues. Thus, the preruminant calf tolerated between 2000 and 5000 ppm iron in milk replacer. At toxic iron intake, calf performance and feed efficiency were reduced; there was a characteristic change to higher liver than spleen iron; and hemosiderin became the predominant iron storage compound in both tissues.

Performance of calves fed combinations of whole milk and reconstituted skim milk powder

A 52-d study with 24 3-d-old calves compared the effect of feeding whole milk (controls) or milk diluted 1:1 or 1:3 with reconstituted skim milk powder (10%, wt/wt) on calf performance to weaning at 38 d. Skim powder diets were supplemented with vitamins and trace minerals. Liquid diet was fed at 5% body weight twice daily for 24 d, then once daily for 14 d followed by abrupt weaning. Starter was provided for ad libitum intake from 14 to 52 d. For the first 13 d, controls had the greatest weight gains, but at 38 and 52 d, gains were similar for all groups. Three-quarters of the whole milk diet could be replaced with reconstituted skim milk powder (10% wt/wt) without any reduction in calf gain to weaning because starter intake increased 23%.