Rapid Communication: Variance component estimates for Charolais-sired fed cattle and relative economic impact of bovine respiratory disease.

Variance components were estimated and relative economic importance of bovine respiratory disease (BRD) was derived from 3 yr of performance, morbidity, and mortality data collected from a single beef cattle finishing operation. One thousand one hundred eighty nine of 12,812 Charolais-sired calves were treated for BRD during the finishing period. Weaning weight (WW), DMI, days to harvest (D2H), HCW, yield grade (YG), and marbling score determined by image analysis (MARB) were collected to quantify the economic impact associated with treatment for BRD. Observed means and (co)variances for carcass and production traits were used to simulate populations of 10,000 healthy and 10,000 BRD treated calves. A bio-economic model was developed to derive the economic value associated with the incidence and number of treatments for BRD during the finishing period. Carcasses from healthy calves were worth $58.28 more on average compared to calves treated at least once for BRD. Heritability estimates for BRD were 0.15 when the trait was measured as number of treatments (0 to 4), and 0.14 when measured as incidence (0 or 1). The model indicated that D2H had the lowest relative economic importance in this system, with a cost of $1.91 per head for each additional day on feed. Furthermore, the relative economic value of BRD morbidity was approximately 10.65 greater than D2H when recording the BRD phenotype as the number of BRD treatments. The economic values of HCW, WW, and DMI were 11.47, 5.15, and 3.61 times more important than D2H, respectively. This indicates BRD morbidity has the second greatest relative economic value in this system, with a one percent increase in morbidity associated with an average loss of $2.08 per head. These results indicate that BRD morbidity can have an equal or greater economic importance when compared to carcass and production traits during the finishing period. Further, this indicates the opportunity exists to increase the genetic merit for profitability during the finishing period by incorporating BRD incidence into terminal-sire selection indexes.

Genetic parameters and genetic correlations among triacylglycerol and phospholipid fractions in Angus cattle.

The objective of this study was to estimate genetic parameters for intramuscular fatty acids from triacylglycerol (TAG) and phospholipid (PL) fractions in beef LM tissue. Longissimus muscle samples were obtained from 1,833 Angus cattle to determine the intramuscular fatty acid composition for 31 lipids and lipid classes from TAG and PL fractions and were classified by structure into saturated (SFA), monounsaturated (MUFA), polyunsaturated (PUFA), omega-3 (n-3), and omega-6 (n-6) fatty acids. An atherogenic index (AI) was also determined as a measure of the unsaturated fatty acid to SFA ratio. Restricted maximum likelihood methods combined with pedigree data were used to estimate variance components with the WOMBAT software package. Heritability estimates ranged from 0.00 to 0.63 for the major classes of fatty acids. Heritability estimates differed between the TAG and PL fractions, with higher estimates for TAG up to 0.64 and lower estimates for PL that ranged from 0.00 to 0.14. Phenotypic and genetic correlations among individual fatty acids were determined for the TAG fraction as well as among carcass traits, including rib eye area, numerical marbling score, yield grade, ether fat, and Warner-Bratzler shear force value. Strong negative or positive genetic correlations were observed among individual fatty acids in the TAG fraction, which ranged from -0.99 to 0.97 ( < 0.05). Moderate correlations between carcass traits and fatty acids from the TAG fraction ranged from -0.43 to 0.32 ( < 0.05). These results indicate that fatty acids prominent in beef tissues show significant genetic variation as well as genetic relationships with carcass traits.

Comparison of gene expression and fatty acid profiles in concentrate and forage finished beef.

Fatty acid profiles and intramuscular expression of genes involved in fatty acid metabolism were characterized in concentrate- (CO) and forage- (FO) based finishing systems. Intramuscular samples from the adductor were taken at slaughter from 99 heifers finished on a CO diet and 58 heifers finished on a FO diet. Strip loins were obtained at fabrication to evaluate fatty acid profiles of LM muscle for all 157 heifers by using gas chromatography fatty acid methyl ester analysis. Composition was analyzed for differences by using the General Linear Model (GLM) procedure in SAS. Differences in fatty acid profile included a greater atherogenic index, greater percentage total MUFA, decreased omega-3 to omega-6 ratio, decreased percentage total PUFA, and decreased percentage omega-3 fatty acids in CO- compared with FO-finished heifers (P<0.05). Fatty acid profiles from intramuscular samples were ranked by the atherogenic index, and 20 heifers with either a high (HAI; n=10) or low (LAI; n=10) atherogenic index were selected for gene expression analysis using real-time PCR (RT-PCR). Gene expression data for the 20 individuals were analyzed as a 2 by 2 factorial arrangement of treatments using the GLM procedure in SAS. There was no significant diet × atherogenic index interaction identified for any gene (P>0.05). Upregulation was observed for PPARγ, fatty acid synthase (FASN), and fatty acid binding protein 4 (FABP4) in FO-finished compared with CO-finished heifers in both atherogenic index categories (P<0.05). Upregulation of diglyceride acyl transferase 2 (DGAT2) was observed in FO-finished heifers with a HAI (P<0.05). Expression of steroyl Co-A desaturase (SCD) was upregulated in CO-finished heifers with a LAI, and downregulated in FO-finished heifers with a HAI (P<0.05). Expression of adiponectin (ADIPOQ) was significantly downregulated in CO-finished heifers with a HAI compared with all other categories (P<0.05). The genes identified in this study which exhibit differential regulation in response to diet or in animals with extreme fatty acid profiles may provide genetic markers for selecting desirable fatty acid profiles in future selection programs.

Effect of prolactin, beta-lactoglobulin, and kappa-casein genotype on milk yield in East Friesian sheep.

The effect of prolactin (PRL), beta-lactoglobulin (beta-LG), and kappa-casein (CSN3) on milk yield was estimated in an East Friesian dairy sheep population from Old Chatham Sheepherding Company, New York. Genotypes were determined by PCR amplification followed by digestion with HaeIII and RsaI for PRL and beta-LG, respectively, and by PCR amplification for CSN3. Monthly milking records and pedigree information were used to evaluate the effect of each polymorphism on milk yield. Results indicated that PRL genotype had a significant effect on milk yield. Ewes carrying one A allele produced 110.6g more milk per day than ewes with no A alleles. There was no statistical difference between ewes with only one A allele and ewes with 2 A alleles. No association among polymorphisms at the beta-LG and CSN3 loci and milk yield was found. The results presented in this study indicate that the PRL gene is a potential marker that could be used in selection programs for improving milk yield in dairy sheep.

Multiple vascular anomalies in a regurgitating German shepherd puppy.

Five cardio-thoracic vascular anomalies were detected in a German shepherd puppy. The patent ductus arteriosus (PDA) was detected on physical examination (5/6 continuous murmur) and confirmed by echocardiogram. The persistent right aortic arch (PRAA) was suspected by the signalment and history of the patient, and confirmed by survey thoracic radiographs (leftward deviation of the trachea cranial to the heart on the ventrodorsal projection). The ventrally deviated trachea cranial to the heart on the right lateral thoracic radiograph was suggestive of a persistent retroesophageal left subclavian artery and confirmed at surgery. The persistent left cranial vena cava and the left azygous vein were detected at surgery. This case report gives a thorough description of the clinical signs, diagnostics and treatments required for the detection and successful resolution of PRAA. The report describes the importance of having experienced surgeons who can recognize vascular anomalies associated with PRAA in order to successfully alleviate the arch and the coinciding oesophageal stricture without compromising vital blood supplies.

Vertebral scale system to measure heart size in growing puppies.

OBJECTIVE: To determine relative heart size in clinically normal puppies and assess whether relative heart size changes with growth. DESIGN: Prospective radiographic study. ANIMALS: 11 puppies without evidence of disease. PROCEDURE: Standardized measurements of the long and short axes of the heart, midthoracic vertebrae, and other structures were made at 3, 6, 12, and 36 months of age. Measurements were recorded in millimeters and number of thoracic vertebral lengths spanned by each dimension, measured caudally from T4 on lateral radiographic views. The long and short axis measurements of the heart, expressed in vertebral lengths, were added to yield vertebral heart size. RESULTS: Mean +/- SD vertebral heart sizes on lateral radiographic views at 3, 6, 12, and 36 months of age were 10.0 +/- 0.5, 9.8 +/- 0.4, 9.9 +/- 0.6, and 10.3 +/- 0.6 vertebrae, respectively. Significant differences were not detected. CONCLUSIONS AND CLINICAL RELEVANCE: Vertebral heart size measurements in puppies are within the reference range for adult dogs (9.7 +/- 0.5 vertebrae) and do not change significantly with growth to 3 years of age. Standards for determining cardiac enlargement are similar in puppies and adult dogs.

Pathogenesis of single right coronary artery and pulmonic stenosis in English Bulldogs.

English Bulldogs are the most common breed to have pulmonic stenosis. Previous studies showed that this congenital heart abnormality in Bulldogs frequently is caused by a circumpulmonary left coronary artery originating from a single right coronary artery. Fetal anasarca also occurs often in Bulldogs and might represent congestive heart failure, but the cause is unknown. To determine if fetal anasarca is associated with a coronary anomaly and pulmonic stenosis, major coronary arteries were studied in 6 bulldog puppies with fetal anasarca. Five of the puppies had normal coronary arteries, and this led to the conclusion that fetal anasarca usually is not associated with major coronary abnormalities or pulmonic stenosis. The 6th puppy had single right coronary artery with circumpulmonary left coronary artery and moderate subvalvular pulmonic stenosis. Serial section histology suggests that the underlying cause of this syndrome is malformation of the left aortic sinus (of Valsalva) and inversion of the proximal segment of the left main coronary artery.

Radiographic and echocardiographic measurement of the heart in obese cats.

A prospective study was undertaken to reconcile radiographic cardiomegaly and normal echocardiography in obese cats and to test a radiographic technique for better distinguishing between pericardial fat and the heart. Ten obese, but otherwise normal cats and 10 non-obese normal cats were used. A body condition scoring system was used to objectively group obese and non-obese normal cats. Two-dimensional echocardiograms were made to verify that all cats had a normal heart. Thoracic radiographs then were made using standard and altered exposure techniques. The hearts were measured on these radiographs using the metric and a vertebral scale system. Obese cats consistently had excessive fat around the heart especially if they also had a large amount of falciform fat. Altering exposure technique by increasing mAs and decreasing kVp sometimes enhanced the radiographic contrast between fat and myocardium. Enhanced radiographic contrast accentuated the double silhouette identifying the true cardiac silhouette within the fat expanded silhouette. Pericardial fat usually was distinguished more readily in lateral than in VD radiographs. In two cats, pericardial fat had a characteristic prominent square corner to the right cranial margin of the cardiac silhouette in VD radiographs. Obesity caused increased width and depth of the thoracic cage. 2D echocardiograms revealed normal cardiac dimensions in both groups of cats and increased precordial distance in the obese group.

Esophageal obstruction caused by a left aortic arch and an anomalous right patent ductus arteriosus in two German Shepherd littermates.

OBJECTIVE: To present details of surgical management of an unusual vascular ring anomaly in two German Shepherd littermates. STUDY DESIGN: Clinical case report. STUDY POPULATION: Three-month-old intact male and female German Shepherd littermates. RESULTS: In each dog, the esophagus was obstructed by a vascular ring comprised of the left aortic arch, an anomalous patent right ductus arteriosus, and the pulmonary artery ventrally. Surgical treatment consisted of dividing and oversewing the patent right ductus arteriosus. Neither dog has clinical signs of esophageal disease one year after treatment. CONCLUSION AND CLINICAL RELEVANCE: This vascular ring anomaly should be considered a possibility in any young dog with esophageal obstruction and a machinery murmur.

Vertebral scale system to measure heart size in radiographs.

This article describes a method for measuring heart size relative to vertebral length in radiographs. The lengths of the long and short axes of the heart are scaled against the length of vertebrae dorsal to the heart beginning with the fourth thoracic vertebra (v). The sum of the long and short axes of the heart is the vertebral heart size (VHS). In 100 normal dogs, VHS was 9.7 v +/- 0.5 SD. The differences between wide- and deep-chested dogs, males and females, and right or left lateral recumbency were not significant. In 100 normal cats, the average VHS was 7.5 v +/- 0.3. The short-axis dimension of the heart in ventrodorsal radiographs of cats was 3.4 v +/- 0.25.

Vertebral scale system to measure heart size in radiographs of cats.

OBJECTIVE: To determine absolute and relative heart size in clinically normal cats by correlating heart size and selected skeletal structures. DESIGN: Prospective radiographic study. ANIMALS: 100 cats that did not have thoracic radiographic abnormalities. PROCEDURE: Standardized measurements of the long and short axes of the heart, midthoracic vertebrae, and other structures were made. Measurements were recorded in millimeters and number of thoracic vertebral lengths spanned by each dimension, measured caudally from T4 in a lateral radiograph. The long- and short-axis measurements of the heart, expressed in vertebral lengths, were added to yield vertebral heart size. RESULTS: Mean +/- SD vertebral heart size in lateral radiographs was 7.5 +/- 0.3 vertebrae. The long-axis dimension correlated with the length of 3 sternebrae, measured from S2 to S4. The cardiac short-axis dimension correlated moderately with the length of 3.2 vertebrae, measured from T4 to T6. The cardiac short-axis dimension in ventrodorsal radiographs was 3.4 +/- 0.25 vertebrae. CONCLUSIONS AND CLINICAL RELEVANCE: The vertebral heart-size method is easy to use, allows objective assessment of heart size, and may be helpful in determining cardiomegaly and comparing heart size in sequential radiographs.

Circumferential suture of the mitral annulus for correction of mitral regurgitation in dogs.

OBJECTIVE: To develop a method for reducing mitral regurgitation in dogs by positioning and tightening a circumferential suture around the mitral valve annulus. STUDY DESIGN: Description of clinical cases. ANIMALS: 15 dogs with spontaneous mitral valve disease, annular dilation, and refractory congestive heart failure treated between 1962 and 1994. METHODS: A composite suture material was constructed using braided Teflon-impregnated polyester sternotomy suture, barium sulfate thread, and Silastic tubing. Through a left lateral thoracotomy, the suture was positioned around the mitral annulus by passing it through the coronary sinus, right atrium, and underneath the left coronary arteries before tightening it. RESULTS: Six dogs died during surgery because of hemorrhage from the left atrium, coronary sinus, or left coronary artery. Three dogs died postoperatively because of coronary artery compression by the suture. Satisfactory suture placement was achieved in six dogs, three of which were long-term survivors (6 to 26 months) before they were euthanatized for noncardiac reasons. CONCLUSIONS: Reduction of mitral annulus diameter with a circumferential purse-string suture does not require cardiopulmonary bypass. The surgery is technically difficult, and detailed knowledge of coronary artery anatomy is required. The current suture design is inexpensive, radiopaque, and biocompatible; no special instruments are required for placement. CLINICAL RELEVANCE: Mitral regurgitation is the most common cardiovascular disorder in dogs and the most common cause of congestive heart failure. Annular dilation occurs as a consequence of mitral regurgitation. Placement and tightening of a circumferential suture around the mitral annulus reduces the degree of mitral regurgitation.

Short-term hemodynamic evaluation of circumferential mitral annuloplasty for correction of mitral valve regurgitation in dogs.

OBJECTIVE: To determine the short-term hemodynamic effects associated with circumferential mitral annuloplasty (CMA) in dogs with mitral regurgitation. STUDY DESIGN: Prospective experimental study. Animals-Seven healthy adult mongrel dogs. METHODS: Mitral regurgitation was surgically induced, and annular dilation occurred. Echocardiography and cardiac catheterization were used to determine forward ejection fraction (FEF), regurgitant fraction (RF), pulmonary capillary wedge pressure (PCWP), and annular diameter before and immediately after CMA in five dogs. FEF and RF were also evaluated 7 days after annuloplasty. RESULTS: Mean annular diameter and PCWP were significantly reduced immediately after CMA. Significant increases in FEF of 19% and 22% were shown immediately and 7 days after CMA. Significant reductions in RF of 19% and 22% were also shown immediately and 7 days after annuloplasty. CONCLUSIONS: Sustained hemodynamic benefits and a reduction in annular diameter were achieved by CMA in a canine model of mitral regurgitation. CLINICAL IMPLICATIONS: CMA may be a suitable treatment for heart failure because of mitral regurgitation when early signs of cardiovascular decompensation persist despite appropriate medical management.

Femoral artery occlusion in Cavalier King Charles Spaniels.

OBJECTIVE: To investigate development of femoral artery occlusion in Cavalier King Charles Spaniels. DESIGN: Prospective study. ANIMALS: 954 Cavalier King Charles Spaniels. PROCEDURE: 1,750 cardiovascular examinations consisting of visual inspection of mucous membranes, thoracic auscultation in areas associated with the heart valves, thoracic palpation, and palpation of the femoral arteries were made at 10 dog shows on 954 dogs. Findings of clinically normal, weak, or undetectable femoral pulses were recorded. Pathologic changes in occluded femoral arteries of 2 dogs were examined histologically. RESULTS: Of the 954 dogs, 22 (2.3%) had an undetectable right or left femoral pulse on 1 or more examinations. Forty (4.2%) additional dogs had weak unilateral or bilateral femoral pulses. Only 1 dog had exercise intolerance, and it had coexistent congestive heart failure. Histologic examination of serial sections of an occluded femoral artery from 1 dog revealed intimal thickening with breaks in the internal elastic lamina proximal to the occluded segment. The occluded segment of the femoral artery was contracted and filled with an organizing, recanalizing thrombus. Similar histopathologic changes were found in sections of a femoral artery from another dog. CLINICAL IMPLICATIONS: Femoral artery occlusion is rare in other breeds and is not clinically important in dogs because of adequate collateral circulation; however, its rather common development in Cavalier King Charles Spaniels indicates a genetic predisposition and probable weakness in the femoral artery wall.

Vertebral scale system to measure canine heart size in radiographs.

A method for measuring canine heart size in radiographs was developed on the basis that there is a good correlation between heart size and body length regardless of the conformation of the thorax. The lengths of the long and short axes of the heart of 100 clinically normal dogs were determined with calipers, and the dimensions were scaled against the length of vertebrae dorsal to the heart beginning with T4. The sum of the long and short axes of the heart expressed as vertebral heart size was 9.7 +/- 0.5 vertebrae. The differences between dogs with a wide or deep thorax, males and females, and right or left lateral recumbency were not significant. The caudal vena cava was 0.75 vertebrae +/- 0.13 in comparison to the length of the vertebra over the tracheal bifurcation.

Electrical coupling and impulse propagation in anatomically modeled ventricular tissue.

Computer simulations were used to study the role of resistive couplings on flat-wave action potential propagation through a thin sheet of ventricular tissue. Unlike simulations using continuous or periodic structures, this unique electrical model includes random size cells with random spaced longitudinal and lateral connections to simulate the physiologic structure of the tissue. The resolution of the electrical model is ten microns, thus providing a simulated view at the subcellular level. Flat-wave longitudinal propagation was evaluated with an electrical circuit of over 140,000 circuit elements, modeling a 0.25 mm by 5.0 mm sheet of tissue. An electrical circuit of over 84,000 circuit elements, modeling a 0.5 mm by 1.5 mm sheet was used to study flat-wave transverse propagation. Under normal cellular coupling conditions, at the macrostructure level, electrical conduction through the simulated sheets appeared continuous and directional differences in conduction velocity, action potential amplitude and Vmax were observed. However, at the subcellular level (10 microns) unequal action potential delays were measured at the longitudinal and lateral gap junctions and irregular wave-shapes were observed in the propagating signal. Furthermore, when the modeled tissue was homogeneously uncoupled at the gap junctions conduction velocities decreased as the action potential delay between modeled cells increased. The variability in the measured action potential was most significant in areas with fewer lateral gap junctions, i.e., lateral gap junctions between fibers were separated by a distance of 100 microns or more.

Chronic mitral valve disease in cavalier King Charles spaniels: 95 cases (1987-1991)

Systolic heart murmurs caused by chronic mitral valve disease are particularly common in Cavalier King Charles Spaniels (CKCS) in Great Britain. To determine if American-bred CKCS have a similar high prevalence of chronic valve disease, results of stethoscopic examinations on 394 CKCS were analyzed. Left apical systolic heart murmurs were found in 22% of the dogs. The prevalence ranged from 9% in dogs < 1 year old to 100% in those > or = 10 years old; prevalence was 56% in dogs > or = 4 years old. Differences were not found in prevalence between sexes and among various coat colors. Reexamination of 79 dogs after 1 year revealed an incidence of new murmurs of 21%. Comparison of ages at initial examination in 128 referral hospital cases with chronic mitral valve disease revealed a mean age of 6.25 years in 17 CKCS, in contrast to a mean age of 12 years in other breeds. Echocardiographic and necropsy findings indicated that ruptured chordae tendineae and mitral valve prolapse are major components in the chronic valve disease process in CKCS.