Pathophysiology and pathological remodelling associated with dilated cardiomyopathy in broiler chickens predisposed to heart pump failure

Broiler chickens selected for rapid growth are highly susceptible to dilated cardiomyopathy (DCM). In order to elucidate the pathophysiology of DCM, the present study examines the fundamental features of pathological remodelling associated with DCM in broiler chickens using light microscopy, transmission electron microscopy (TEM), and synchrotron Fourier Transform Infrared (FTIR) micro-spectroscopy. The morphological features and FTIR spectra of the left ventricular myocardium were compared among broiler chickens affected by DCM with clinical signs of heart pump failure, apparently normal fast-growing broiler chickens showing signs of subclinical DCM (high risk of heart failure), slow-growing broiler chickens (low risk of heart failure) and Leghorn chickens (resistant to heart failure, used here as physiological reference). The findings indicate that DCM and heart pump failure in fast-growing broiler chickens are a result of a complex metabolic syndrome involving multiple catabolic pathways. Our data indicate that a good deal of DCM pathophysiology in chickens selected for rapid growth is associated with conformational changes of cardiac proteins, and pathological changes indicative of accumulation of misfolded and aggregated proteins in the affected cardiomyocytes. From TEM image analysis it is evident that the affected cardiomyocytes demonstrate significant difficulty in the disposal of damaged proteins and maintenance of proteostasis, which leads to pathological remodelling of the heart and contractile dysfunction. It appears that the underlying causes of accumulation of damaged proteins are associated with dysregulated auto phagosome and proteasome systems, which, in susceptible individuals, create a milieu conducive for the development of DCM and heart failure. RESEARCH HIGHLIGHTS The light and electron microscopy image analyses revealed degenerative changes and protein aggregates in the cardiomyocytes of chickens affected by DCM. The analyses of FTIR spectra of the myocardium revealed that DCM and heart pump failure in broiler chickens are associated with conformational changes of myocardial proteins. The morphological changes in cardiomyocytes and conformational changes in myocardial proteins architecture are integral constituents of pathophysiology of DCM in fast-growing broiler chickens.

Temperature gradients in trailers and changes in broiler rectal and core body temperature during winter transportation in Saskatchewan

Temperature conditions inside commercial trailers transporting market-age broilers during four winter journeys were measured, and changes in the rectal and core body temperature of birds were quantified. Pre-selected modules were equipped with data loggers recording temperature every 72 s. Rectal temperatures were taken from eight birds in each of four modules immediately before and after each trip, and two or three birds, with temperature recording implants, were placed in each of two selected modules. Temperature heterogeneity was found among modules on all loads with average crate temperatures ranging from 10.9 to 30.7, 8.9 to 28.1, 2.5 to 26.1 and -0.7 to 16.5°C for transportation times of 191, 193, 178 and 18 min and ambient temperatures of -7.1, -27.1, -28.2 and -18.4°C, respectively. Wet birds, condensation and frost provided evidence for moisture accumulation during transportation. Body temperature recordings indicated the potential for the development of both hypothermia and hyperthermia, showing that cold stress can occur near air inlets and heat stress in poorly ventilated areas. Passive ventilation inside trailers resulted in crate temperatures 17.7 to 55.2°C above outside temperature. Mortality ranged from 0.7 to 1.4% but several deaths occurred during lairage, prior to processing. A heterogeneous distribution of airflow resulted in undesirable temperate and humidity conditions for some birds. Key words: Broiler, transportation, temperature gradient, mortality, cold weather

Congenital intestinal incarceration in broiler chickens

The present work describes specific congenital intestinal accidents found in commercial broiler chickens where the affected individuals have their intestinal loops translocated outside the abdomen. These anomalies have been observed in many embryos that failed to hatch, in newly hatched chicks, as well as in broilers at various stages of growth. It appears that these lesions stem from incomplete closure of the abdominal cavity during the last stages of embryonic development.

Effects of peripartum propylene glycol supplementation on nitrogen metabolism, body composition, and gene expression for the major protein degradation pathways in skeletal muscle in dairy cows

Early-lactating dairy cows mobilize body protein to provide amino acids that are directed toward gluconeogenesis and milk protein synthesis. Propylene glycol (PG) is a precursor of ruminal propionate, and feeding PG has been reported to improve energy supply by increasing blood glucose. Our hypothesis was that feeding PG could spare body protein by providing an alternative source of carbon for gluconeogenesis. The major objectives of this study were 1) to delineate the effects of pre- and postpartum PG supplementation in transition dairy cows on whole-body nitrogen balance, urinary 3-methylhistidine (3-MH) excretion, body composition, and gene expression profiles for the major protein degradation pathways in skeletal muscle; and 2) to characterize the changes in body protein metabolism during the periparturient period. Sixteen pregnant cows (7 primiparous and 9 multiparous) were paired based on expected calving dates and then randomly assigned within each pair to either a basal diet (control) or basal diet plus 600 mL/d of PG. Diets were fed twice daily for ad libitum intake, and PG was fed in equal amounts as a top dress from d -7 to d 45. All measurements were conducted at 3 time intervals starting at d -14 +/- 5, d 15, and d 38 relative to calving. Propylene glycol had no effect on whole-body N balance, urinary 3-MH excretion, or body composition. However, N balance was lower at d 15 and 38, compared with d -14. Urinary excretion of 3-MH was lower at d -14 than at d 15 and 38. Supplemental PG had no effect on body weight (BW) and all components of empty BW. On average, cows fed both diets mobilized 19 kg of body fat and 14 kg of body protein between d -14 and d 38. Supplemental PG had no effect on mRNA abundance in skeletal muscle for m-calpain, and the 14-kDa ubiquitin-carrier protein E2 (14-kDa E2) and proteasome 26S subunit-ATPase components of the ubiquitin-mediated proteolytic pathway; however, PG supplementation downregulated mRNA expression for mu-calpain at d 15, and tended to downregulate mRNA expression for ubiquitin at d 15 and 38. Relative to calving, mRNA abundance for m- and mu-calpain, ubiquitin, and 14-kDa E2 were greater at d 15 compared with d -14 and d 38. In summary, these results indicate that transitional effects on whole-body metabolism and gene expression for the Ca(2+)-dependent and ubiquitin-mediated proteolytic pathways in skeletal muscle were more pronounced than those elicited by PG supplementation.

A study on pathogenesis of sudden death syndrome in broiler chickens

Sudden death syndrome (SDS) in fast growing broiler chickens has been recognized as a patho-physiological entity for four decades, but its pathogenesis still remains unknown. More recent investigations provided evidence that link SDS to cardiac arrhythmia, but the mechanism triggering arrhythmogenesis and factors responsible for fatal outcome are poorly understood. In order to understand the chain of events leading to SDS in broilers, the present study focused on putative mechanisms that trigger arrhythmia and mechanisms that predispose the myocardium to fatal arrhythmia. Susceptibility of broilers to cardiac arrhythmia under stress conditions was evaluated using a simulated stress test with epinephrine. Detailed histopathological evaluation of the broiler heart was undertaken to identify structural features that may predispose the myocardium to fatal arrhythmia. The simulated stress challenge revealed that many broilers are highly susceptible to stress induced cardiac arrhythmia. In some broilers the stress challenge induced severe ventricular arrhythmia, and the life threatening nature of this arrhythmia was evidenced by the fact that several birds showing the most severe arrhythmic responses, died suddenly within several days after the stress challenge. Examination of hearts of broilers that died of SDS revealed microscopic lesions in the cardiomyocytes, and widespread changes in the sub-endocardial and mural His-Purkinje system (HPS). Immune staining for Caspase-3 confirmed that numerous Purkinje cells in the left ventricular myocardium from broiler chickens that died of SDS were undergoing apoptosis. The observed lesions suggest that the electrical stability of the myocardium was compromised. Taken together, our findings indicate that stress is a most likely trigger of cardiac arrhythmia in broilers, whereas the pathological changes seen in the myocardium and in the HPS in fast growing broilers provide a very conducive milieu for sustained ventricular arrhythmia. In cases where the electrical stability of the myocardium is compromised, even an episodic arrhythmic event may readily degenerate to catastrophic ventricular fibrillation and sudden death. We conclude that the combination of stress and changes in the cardiomyocytes and HPS are the key requisite features in the pathogenesis of SDS.

The effect of dietary sinapic acid (4-hydroxy-3, 5-dimethoxy-cinnamic acid) on gastrointestinal tract microbial fermentation, nutrient utilization, and egg quality in laying hens

Plant-based simple phenolics are natural antimicrobial and antioxidant compounds that may possess biological activity when included in animal diets. Previous work in our lab has shown that sinapic acid (SA) found in canola meal improves nutrient retention and alters gut microbiota when fed at low levels (0 to 0.10%) to broiler chickens. It was of interest to investigate the effect of dietary SA in laying hens that possess a more mature intestinal microbiota. Therefore, 2 experiments were conducted to determine the effects of dietary SA on performance, nutrient digestibility, and egg quality in laying hens. Sinapic acid (Sigma-Aldrich, 98% purity) was included in diets at 0, 0.025, 0.050, and 0.075% in experiment 1, and 0 and 0.5% in experiment 2. Both experiments were conducted for 21 d. Dietary treatment did not affect production traits and gastrointestinal tract volatile fatty acid production in either experiment. Apparent metabolizable energy and protein digestibility were also unaffected by treatment in experiment 1, but in experiment 2, feeding 0.5% SA increased both AME(n) and protein digestibility in comparison to the unsupplemented control. Egg weight, albumen weight, yolk weight, egg specific gravity, shell thickness, and Haugh units were not significantly affected by dietary treatments in either of the experiments. Sinapic acid was not detected in eggs from experiment 1 but in experiment 2, low levels of SA were detected in both the yolk and albumen of eggs from hens fed 0.5% SA. Further research is needed to more completely define the relationship between dietary SA level and nutrient utilization as well as the accumulation of SA in egg components.

Biochemical factors limiting myocardial energy in a chicken genotype selected for rapid growth

Broiler chickens (Gallus gallus) genetically selected for rapid growth are inherently predisposed to heart failure. In order to understand the biochemical mechanisms associated with the deterioration of heart function and development of congestive heart failure (CHF) in fast-growing chickens, this study examined several factors critical for myocardial energy metabolism. Measured variables included cardiac energy substrates [creatine phosphate (CrP), adenosine triphosphate (ATP), l-carnitine], activity of selected cytosolic enzymes [creatine kinase (CK; EC 2.7.3.2), lactate dehydrogenase (LDH; EC 1.1.1.27)] and mitochondrial enzymes [pyruvate dehydrogenase (PDH; EC 1.2.4.1), alpha-ketoglutarate dehydrogenase (alpha-KGDH; EC 1.2.4.2)]. The CK activities were higher in fast-growing and CHF broilers as compared to slow-growing broilers (p<0.05). Cardiac LDH and alpha-KGDH activities were not changed (p>0.05), whereas PDH activity was highest (p<0.05) in broilers with CHF. Deterioration of heart function is correlated with lowered cardiac ATP, CrP, and l-carnitine levels (all p<0.05). Depletion of high energy phosphate substrates, ATP and CrP, is evident in fast-growing chickens and those that developed CHF. Increased activity of CK suggests that cardiac energy management in fast-growing broilers and those with CHF largely depends on contribution of this pathway to regeneration of ATP from CrP. In this scenario, inadequate level of CrP is a direct cause of ATP insufficiency, whereas low cardiac l-carnitine, because of its role in fatty acid transport, is most likely an important factor contributing to shortage of key substrate required for synthesis of cardiac ATP. The insufficiencies in cardiac energy substrate synthesis provide metabolic basis of myocardial dysfunction in chickens predisposed to heart failure.

Comparative study of myocardial high energy phosphate substrate content in slow and fast growing chicken and in chickens with heart failure and ascites

In order to explain the biochemical mechanisms associated with deteriorating heart function in broiler chickens, this study compared myocardial high energy phosphate substrates in leghorns, feed restricted (Broilers-Res) broilers, ad libitum fed broilers (Broilers-AL), and in broilers that developed heart failure and ascites. The profile of adenine nucleotide content in the heart tissue did not differ between leghorns and Broilers-Res, but there were significant differences among Broilers-Res, Broilers-AL, and broilers with ascites. During intensive growth periods, leghorns and Broilers-Res showed increasing trends in heart ATP levels, whereas in fast growing broilers the heart ATP declined (p<0.021). ATP:ADP and ATP:CrP ratios increased with age in both leghorn and Broilers-Res, declined in fast growing broilers, and were the lowest in broilers that developed heart failure. The changes in heart high energy phosphate profile in broilers suggest that the energy demand of the heart during a rapid growth phase may exceed the bird's metabolic capacity to supply adequate levels of high energy phosphate substrate. The insufficiency of energy substrate likely contributes to the declining heart rate. In some individuals this may lead to impaired heart pump function, and in more severe cases may progress to heart pump failure.

Pathophysiology of heart failure in broiler chickens: structural, biochemical, and molecular characteristics

Modern strains of fast-growing meat type poultry are highly susceptible to heart failure. Heart-related mortalities are observed predominantly in fast-growing broiler chickens, with ascites and sudden death syndrome being the most common heart-related conditions in modern broiler flocks. This paper examines the role of structural, molecular, and biochemical factors pertinent to the pathophysiology of heart failure in fast-growing broilers. Evidence explaining the pathogenesis of acute and chronic heart failure, in the context of the underlying molecular and biochemical changes in the cardiomyocytes, contractile apparatus, and extracellular matrix in the ventricular myocardium are critically evaluated and discussed with reference to the clinical signs associated with deterioration of heart pump function. The secondary pathophysiological effects on the cardiovascular system, resulting from hemodynamic changes associated with the failing heart pump, are also reviewed and critically discussed.

Response of Turkey Poults to Soybean Lectin Levels Typically Encountered in Commercial Diets. 2. Effect on Intestinal Development and Lymphoid Organs

Lectins are capable of altering intestinal morphology by binding to and disrupting the intestinal brush border membrane. They are also known to alter the weight of lymphoid organs. Therefore, we evaluated the effect of soybean lectin (SBL) on intestinal morphology and lymphoid organ weights of poults fed diets containing SBL. Dietary treatments evaluated in this study included a cornstarch and casein-based control (lectin-free) semipurified diet (PD) and semipurified diets containing 0.024 or 0.048% SBL (PDL and PDH, respectively). Experimental diets were fed from hatch to 14 d. Morphological evaluation of the intestine involved measurement of the villi height and perimeter, crypt depth, villus:crypt, and thickness of the muscle layer in the jejunum. Intestinal physical characteristics were also determined by measuring intestinal weight, length, and volume. Results indicated that 0.048% SBL in PDH increased villus:crypt and reduced total intestinal length in turkey poults. In addition, both the 0.024 and 0.048% dietary SBL levels reduced thymus weights. It was concluded that dietary SBL up to 0.048% enhanced intestinal development by increasing villus:crypt, but might alter the structural integrity of lymphoid organs.

Responses of broiler chickens orally challenged with Clostridium perfringens isolated from field cases of necrotic enteritis

The present study examines the responses of broiler chickens to oral administration of Clostridium perfringens freshly isolated from field cases of necrotic enteritis (NE). The challenge studies included long-term exposure and short-term exposure, factored in with dietary and management variables including high levels of dietary components such as fish meal, meat meal, abrupt change of feed, and fasting. In the long-term exposure trials, the birds were orally inoculated daily, with 1 ml (1.0 or 2 x 10(8) CFU/ml) of an overnight culture of C. perfringens for 7 days. Short-term exposure trials involved challenge with 1 ml (3 x 10(10) CFU/ml) administered as a single dose. The responses of broilers to orally administered C. perfingens under laboratory controlled conditions are presented and discussed in the context of authentic field cases of necrotic enteritis. None of the challenge trials produced overt clinical signs of NE and there were no mortalities associated with oral exposure to high doses of C. perfringens. However, many of the challenged birds showed distinctly pronounced pathological changes in the intestinal tissue. On gross examination the responses in birds challenged orally with C. perfringens could be placed into two categories: (1) no apparent pathological changes in the intestinal tissue and (2) sub-clinical inflammatory responses with focal, multi-focal, locally extensive, or disseminated distribution throughout various sections of duodenum, jejunum, ileum, and ceca. In birds that responded with intestinal lesions, hyperemia and occasional hemorrhages were the main gross changes. In some birds, the mucosa was covered with a brownish material, but typically, the mucosa was lined by yellow or greenish, loosely adherent material. Mild gross changes were seen in some control birds, but both qualitatively and quantitatively, the lesions were distinctly more pronounced in the challenged birds. Upon histological examination, none of the experimentally exposed birds showed overt mucosal necrosis typical of field cases of NE, but typically the lamina propria was hyperemic and infiltrated with numerous inflammatory cells. Most significant changes were seen at the interface of the basal domain of enterocytes and lamina propria. Multifocally, these areas were extensively edematous, allowing for the substantial disturbance of the structural integrity between the lamina propria and the enterocytes. The lesions observed in the present study were consistently reproduced in all of our challenge trials, hence these responses may signify newly emerging patterns of sub-clinical enteric disorders in contemporary strains of poultry. The pathological changes observed in broilers challenged orally with C. perfringens in the present study, differ significantly from those reported previously, and must be clearly differentiated from those described in cases of NE or ulcerative enteritis. Although no overt necrosis of the intestinal mucosa typical of field cases of NE were observed in the present study, the birds challenged with C. perfringens showed strong inflammatory reaction to the introduced pathogens. The distinct features of the microscopic lesions were changes involving apparently normal enterocytes at the interface of the basal domain of villar epithelia and lamina propria. Although the pathological changes in the intestinal tissues observed in our trials appear to be rather subtle when compared to field cases of NE, the nature of these lesions suggest a significant negative effect on the digestive physiology of intestinal mucosa.

Effect of dietary Ca manipulation, anionic salts and supplemental vitamin D3 on calcium homeostasis of finishing steers

The objective of this study was to evaluate the effects of a low-Ca diet, followed by a high-Ca diet in combination with feeding of anionic salts and/or vitamin D3 on Ca and acid-base homeostasis of finishing steers. Twenty Hereford steers (448 _ 26 kg) were individually penned and fed at 0800 and 1600 with a ration consisting of 90% barley grain-based concentrate and 10% barley silage (DM basis). The experimental protocol included a 19-d adaptation period, a 14-d period of low Ca feeding, a 10-d supplemental period and a 5-d withdrawal period. During the supplemental period, anionic salts (MgSO4 and NH4Cl) were incorporated into the diet at -1500 and -3000 mEq steer-1 d-1 for 3 and 7 d, respectively. The cattle were also supplemented with one of four vitamin D3 treatments: 0, 0.6, 1.2 and 2.4 million IU (MIU) of vitamin D3 steer-1 d-1. Blood samples were obtained for measurement of total and ionized Ca, parathyroid hormone (PTH) and calcitonin, vitamin D3, 25(OH)D3 and 1,25(OH)2D3. Feed intake was depressed (P < 0.05) by anionic salt feeding but not vitamin D3 treatment. Cattle supplemented with vitamin D3 had higher total (P < 0.05) and ionized (P < 0.05) serum Ca levels than the control cattle that were only supplemented with anionic salts. Higher (P < 0.04) ionized Ca levels were seen in cattle fed 2.4 versus those fed 0.6 MIU vitamin D3. Maximum total serum Ca values were 10.11, 10.97, 11.43 and 12.24 mg dL-1 for the 0, 0.6, 1.2 and 2.4 MIU vitamin D3 treatments, respectively. Respective maximum values for ionized Ca were 5.43, 5.90, 5.98 and 6.25 mg dL-1. These values represent increases, relative to the adaptation period of 3, 12, 16 and 25% for total and 9, 18, 20 and 31% for ionized Ca for the 0, 0.6, 1.2 and 2.4 MIU D3 treatments, respectively. Circulating concentrations of vitamin D3, 25(OH)D3, and 1,25(OH)2D3 were increased (P < 0.05) by vitamin D3 feeding, however, PTH was decreased (P < 0.05), while calcitonin was not affected (P > 0.05). Anionic salt feeding induced (P < 0.05) a mild systemic acidosis. The results indicate that anionic salt feeding enhanced the response of serum Ca to vitamin D3 supplementation. Higher serum Ca levels prior to slaughter may increase intra-muscular Ca levels and enhance postmortem activity of Ca-dependant proteases responsible for myofibril degradation. The results point to a dietary strategy that with further research may prove useful in enhancing beef tenderness. Of particular interest is that serum Ca levels were elevated when vitamin D3 was supplemented at levels 25 to 50% or less than levels used in previous research. Key words: Calcium homeostasis, vitamin D3, anionic salts, beef tenderness

The Role of First Line of Defence Mechanisms in the Pathogenesis of Cellulitis in Broiler Chickens: Skin Structural, Physiological and Cellular Response Factors

The present study examined several basic attributes of first-line defence mechanisms in the skin as potential factors that may explain the susceptibility of broiler chickens to cellulitis. The variables including structural characteristics of the skin, physicochemical properties and cellular responses to the challenge with pathogens were compared between two categories of chickens, a strain of fast-growing commercial broiler chickens (susceptible to cellulitis) and leghorn chickens (resistant to cellulitis). There were substantial differences between leghorns and broilers with regard to physiological characteristics of the skin. Broiler skin was more amenable to injury and the wound-healing process was slow. Compared with leghorns, the lesions resulting from sub-dermal challenge in broilers were more severe and disseminated over a larger area. Mobilization of phagocytic cells (heterophils and macrophages) in leghorns was brisk even in the areas distant from the site of infection, whereas only few heterophils were recruited in the skin of broilers. The functional competence of heterophils in broilers was inferior when compared with leghorns. Based on the present finding, the predisposition of broilers to cellulitis appears to be primarily associated with the inferior first line of defence of their skin. Broilers in commercial situations may be at higher risk to succumb to even minor infection and eventually develop cellulitis because: (1) structural weaknesses of the skin may predispose broilers to skin injury and thus the risk of skin infection by pathogens is increased; (2) broiler skin surface is more likely to provide a conducive environment for colonization of Escherichia coli; (3) in the event of infection, poor recruitment of phagocytic cells to the site of infection may readily lead to widespread colonization of the tissue by pathogens causing cellulitis and (4) poor functional quality of the phagocytic cells that are mobilized compromise the ability of the host to contain the spread of infection.

Feeding high levels of lupine seeds to broiler chickens: plasma micronutrient status in the context of digesta viscosity and morphometric and ultrastructural changes in the gastrointestinal tract

This work examines the effects of lupine-based diets on the status of the host's riboflavin and zinc. Test diets contained 35% soybean meal (control) or raw (40%) or dehulled (35%) lupine seed meal and were isocaloric (13.4 MJ of AME/kg) and isonitrogenous (23% crude protein). Each diet was offered ad libitum to a group of 16 male commercial broiler chicks for 21 d, starting at 1 d of age. Broilers fed lupine diets had lower feed intakes and growth rates. All sections of the intestinal tract were significantly enlarged (P < 0.01) in all groups fed lupine-based diets in comparison with broilers fed the soybean meal diet, but there were no differences in the morphologies of the mucosa, submucosa, muscularis, or serosa. Increased size of the duodenum, jejunum, and ileum was predominantly attributed to the increase in length rather than intestinal tissue mass. Hence, the enlargement of the intestinal tract was consistent with physiological hyperplasia and not pathological remodeling and hypertrophy. Overall, broilers fed lupine-based diets had more viscous digesta than those fed the soybean meal diet, but the differences were statistically not significant. Blood plasma Zn concentration did not differ between broilers fed lupine-based diets and those fed soybean-meal-based diets, and all broilers fed lupine-based diets had significantly higher (P < 0.001) riboflavin concentrations. In this context, it is apparent that the bioavailability of these micronutrients from lupine diets is not compromised. Intestinal tissue hyperplasia may be interpreted as physiological adaptation to increase absorptive capacity and thus maximize absorption of essential nutrients in the face of antinutritional factors in the diet.

Pathogenesis of Ascites in Broilers Raised at Low Altitude: Aetiological Considerations Based on Echocardiographic Findings

This study reports novel insight into the aetiology of pulmonary hypertension and ascites in broiler chickens. The scope of measurements was focused on anatomical and functional parameters, and blood flow patterns in leghorns (resistant to ascites), fast-growing broilers (susceptible to ascites), broilers developing ascites, and ascitic broilers evaluated in vivo using echocardiography, and further examined in the context of postmortem findings. Both, in vivo observed features and postmortem findings, showed clear differences between broilers and leghorns, and between normal and ascitic broilers. Abnormalities in the heart chamber geometry and blood flow patterns were detected upon echocardiographic examination in all ascitic broilers. Right and left atrio-ventricular (AV) valve regurgitation were common findings in ascitic broilers and some apparently normal broilers, with left AV valve insufficiency being a predominant feature with respect to degree and frequency of occurrence. Blood flow disturbances were not detected in leghorns. Left ventricular fractional shortening (functional parameter) was considerably reduced (P < 0.01) in ascitic birds (mean: 21.7 +/- 2.0 SE) in comparison with normal broilers (mean: 39.1 +/- 3.6 SE), or leghorns (mean: 43.3 +/- 2.4 SE). The presented findings indicate that pathological and functional changes in the left ventricle and atrium play a significant role in the pathogenesis of ascites in broilers. Severe dilation of the left atrium and pulmonary veins seen on postmortem examination, as well as regurgitant blood flow in the left atrium, demonstrated by Doppler study in ascitic birds, provide evidence that chronically elevated pressure in the left atrium is involved in the aetiology of pulmonary hypertension and ascites in fast-growing broilers.

The aetiology of hypoxaemia in chickens selected for rapid growth

In comparison to other classes of chickens, broilers selected for rapid growth tend to be hypoxaemic, and many develop congestive heart failure (CHF). In order to explain the physiological mechanisms associated with hypoxaemia in fast-growing broiler chickens (Gallus gallus), this study examined several basic physiological parameters including the blood gas profile in arterial [left atrial (LA)] and mixed venous [right atrial (RA)] blood, systemic oxygen extraction ratio, and intrapulmonary shunt fraction. These parameters were further studied in the context of blood flow in the pulmonary circulation, structural characteristics of the lungs, and cardiac function [measured as cardiac index (CI)]. Overall, broilers had lower arterial and mixed venous blood pO(2) levels and higher pCO(2) levels compared to leghorns. The cardiac index was lower in fast-growing and CHF broilers compared to leghorn chickens or feed-restricted broilers. Systemic oxygen extraction ratio (ER) and intrapulmonary shunt fraction were significantly higher in fast-growing broilers and birds with CHF (all P<0.01). Lungs of all broilers, but not leghorns, contained ectopic, irregular nodular formations located within air spaces. Broilers with clinical signs of hypoxaemia revealed the highest number of these formations in their lung. Taken together, the present findings indicate that key factors associated with the development of hypoxaemia in fast-growing broilers include: (1) high demand for oxygen as evidenced by high oxygen ER; (2) inadequate cardiac output (CO) to fulfill the higher oxygen demands, leading to severe depletion of O(2) in mixed venous blood; and (3) elevated intrapulmonary shunt fraction and possibly dead space associated with specific pathological and anatomical characteristics within the lung.

Effect of supplementing high levels of vitamin D3 on calcium homeostasis of steers fed barley-based finishing diets

The objective of this study was to evaluate the effect of supplementing high levels of vitamin D3 to steers fed barley-grain-based finishing diets on Ca metabolism. Fifteen Hereford steers (607 ± 12 kg) were individually penned and fed at 0800 and 1600 with a ration consisting of 90% barley-grain-based concentrate and 10% barley silage [dry matter (DM) basis]. Steers were randomly assigned to one of three treatments: 0, 2.5 or 5 million IU (MIU) of vitamin D3 steer-1 d-1 for 7 d. Daily blood samples were obtained for measurement of serum for total and ionized Ca, parathyroid hormone (PTH) and calcitonin and plasma for vitamin D3 and 25(OH)D3. Data were analyzed by repeated measures analysis and single degree of freedom contrasts. Feed intake was depressed relative to control animals by 18 and 37% for the 2.5 and 5 MIU D3 treatments, respectively. Relative to controls, total and ionized Ca increased (P < 0.05) by 8 and 19% and 6 and 18% for the 2.5 and 5 MIU D3 treatments, respectively. Serum PTH concentrations were reduced (P < 0.05) by vitamin D3 feeding with the greatest reduction seen with animals fed the 5 MIU treatment. Calcitonin values were not (P > 0.05) affected. Relative to controls, plasma vitamin D3 concentrations increased (P < 0.05) in a quadratic fashion over time with vitamin D3 supplementation, while that of 25(OH)D3 increased (P < 0.05) in a linear fashion. It was concluded that the increase in serum calcium was stimulated by a rise in plasma vitamin D3 and the resulting increased 25(OH)D3 concentrations, which have been shown to influence calcium absorption either directly or via induced synthesis of 1,25(OH)2D3. Key words: Calcium homeostasis, vitamin D3, cattle, beef tenderness

Lesions of the pericardium and their significance in the aetiology of heart failure in broiler chickens

The present study focuses on lesions of the pericardium commonly observed in fast growing broilers. These lesions are examined in the context of electrophysiological and functional changes associated with cardiac performance and patho-physiology in broilers succumbing to acute or chronic heart failure. Typical lesions involving the pericardium in fast growing broiler chickens included: (1) excessive pericardial effusion, (2) locally extensive or focal adhesions between parietal and visceral components of the pericardium, (3) fibrous deposits on visceral pericardium, and (4) thickened pericardium. Echocardiographic evidence indicated that severe pericardial effusion and/or adhesions may have a restrictive effect on heart pump function, where both diastolic and systolic function of the heart may be affected. Electrocardiographic data showed a strong trend indicating that pericardial adhesions may be associated with ventricular arrhythmia and increased risk of sudden death in fast growing broilers. Relatively high levels of matrix metalloproteinase MMP-2 activity have been found in pericardial effusions from affected chickens, suggesting a possible involvement of this enzyme in the aetiology of pericardial lesions. The present results indicate that pericardial lesions may be associated with biochemical, morphological, electrophysiological, and functional changes occurring in the hearts of broilers succumbing to acute or chronic heart failure and ascites.

Rapid HPLC method for measurement of vitamin D3 and 25(OH)D3 in blood plasma

The present work describes a novel, simplified high-performance liquid chromatography (HPLC) method for evaluation of vitamin D3 and its 25-hydroxy metabolite in blood plasma. The retrieval of the analytes from the blood plasma matrix is based on a single-step extraction using acetonitrile. The method is specific, sensitive, and ensures good reproducibility. The recovery of the analytes, precision, and reproducibility obtained using the present approach gave results comparable to or better than more complex, laborious, and time-consuming procedures. This method is suitable for evaluation of the host's vitamin D physiological status, as well as for rapid analysis of blood plasma samples in suspected cholecalciferol toxicity. With a significantly shortened time of analysis (10 minutes), the present method allows the possibility for processing of a large number of samples rapidly, efficiently, and at a low cost.

Adverse effects of dietary lupine in broiler chickens

This study describes the adverse effects of dietary lupines in broiler chickens for which lupine seeds (Lupinus angustifolius) in raw, dehulled, or autoclaved forms were used as a replacement for soybean meal (SBM) in practical diets. Test diets contained 35% SBM (control) or raw (40%), autoclaved (40%), or dehulled (35%) lupine seed meal. All diets were isocaloric (3,230 kcal/kg AME) and isonitrogenous (23% crude protein). Each diet was offered ad libitum to a group of 16 (four replicates with four birds per replicate) day-old male broiler chicks for 21 d. Chemical analysis of lupine seeds showed no detectable levels of mycotoxins, and total alkaloid contents were below 0.01%. Decreased food intake and growth rate were the main signs observed in all birds fed lupine-based diets. These adverse effects were observed during the first week and persisted throughout the trial. Acute signs of toxicity were observed in four chicks fed the diet containing raw lupine seed during the first week of exposure. Initial clinical signs included leg weakness, lack of coordination, and torticollis. In later stages, during Weeks 2 and 3, some birds fed lupine-based diets showed signs of muscle paralysis and skeletal deformity. Postmortem examination did not show gross pathological changes associated with the dietary treatments. Liver microsomal cytochrome P-50 content was higher (P < 0.05) in birds fed the raw lupine-based diet (mean 0.56 pmol/mg protein) in comparison with controls (mean 0.25 pmol/mg protein), which indicated a systemic effect. Based on the present results, it can be stated that high levels of some varieties of sweet lupines in broiler diets may cause significant adverse effects manifested as 1) decreased feed intake and growth rate in most of the birds, and 2) specific signs of acute and chronic toxicity in some individuals.

Ultrastructural and molecular changes in the left and right ventricular myocardium associated with ascites syndrome in broiler chickens raised at low altitude

The present study examines ultrastructural and molecular changes in ventricular myocardium associated with ascites cases in fast-growing broilers raised at low altitude. Extensive ultrastructural lesions were seen in the left and right ventricular myocardium of broilers with fulminant heart failure and ascites. Significant changes included lesions in the myofibril contractile apparatus, altered mitochondria, marked reduction in the myofibril component, and changes in the extracellular matrix (ECM) architecture. No lesions were observed in hearts of slow growing broilers, but mild to moderate changes (predominantly in the left ventriculum) were apparent in the hearts from some clinically normal, fast-growing broilers. SDS-PAGE profiles of washed myofibrils showed several distinctly different bands in preparations from left ventricular myocardium of ascitic birds. Western blot analysis of these samples revealed several fragments of myosin heavy chain, M-protein, and titin. Based on gelatinolytic activity, matrix metalloproteinases (MMP) in the cytosolic fraction of ventricular myocardium homogenates were identified as MMP-2. The relative activity of this enzyme appears to be considerably higher in preparations from broilers, particularly in the preparations from the left ventriculum of fast-growing broilers, in comparison to leghorns or slow growing broilers. The nature and distribution of the changes in the heart indicate that chronic cardiomyopathic process in the left ventricular myocardium occurs during the development of ascites. It is postulated that progressive deterioration of the left heart pump function caused by initial lesions in the left ventricular myocardium is a significant factor in the development of pulmonary hypertension and the pathogenesis of ascites in broilers raised at low altitude.

The effects of maternal thiamine nutrition on thiamine status of the offspring in broiler chickens

The response of broiler chickens to a wide range of dietary supplementation of thiamine to broiler breeder diet was studied in order to understand the effects of maternal thiamine nutrition on the status of thiamine indices in the offspring. Thiamine, and thiamine pyrophosphate (TPP) content, and alpha-ketoglutarate dehydrogenase (KGDH) activity were measured in hearts from 20 day old chicken embryos and from chickens at 1, 7, 14, and 21 days of age and in blood at 21 days of age. Total thiamine content in the heart of day old chicks was higher in comparison to 20 day old embryos. Maternal supplementation of thiamine increased heart thiamine in the offspring (p < 0.001), and increased the activity of KGDH in the hearts of day old chicks (p < 0.001), but not in the embryo. The TPP content in the heart increased in response to both maternal and offspring thiamine supplementation (p < 0.001), however the effect of broiler thiamine supplementation was largely independent from the maternal effect. The effect of maternal thiamine nutrition on the offspring's heart KGDH activity was apparent, but the responses to broiler supplementation were dependent largely on the maternal effect. Blood TPP content was not affected by maternal thiamine supplementation (p = 0.39), but thiamine supplementation in the offspring diets increased blood TPP (p < 0.001). Both maternal and offspring thiamine supplementation increased blood free base thiamine content (both p < 0.001). It is concluded from this study that maternal thiamine nutrition affects thiamine status indices and thiamine metabolism of the offspring.

The study of riboflavin requirement in broiler chickens

Riboflavin status indices in tissues (brain, liver, heart) and blood plasma, and performance parameters were studied in male and female broiler chickens in response to a wide range of dietary supplementation of riboflavin in order to establish the requirement for riboflavin in fast growing modern broilers. The birds fed riboflavin supplemented diets were increasing their body weight at a higher rate than those fed the unsupplemented diet, but this was apparent only during the first stage of growth (days 1 to 21). Supplementation of 2 mg riboflavin per kg was sufficient to support the maximum growth rate. Feed consumption was not affected by different levels of dietary supplementation of riboflavin. The supplementation of riboflavin in the diet increased (p < 0.001) plasma riboflavin level, but the magnitude of response decreased with age. The main component in the tissues was FAD, followed by FMN and riboflavin. Overall, the dietary riboflavin supplementation had highly significant (p < 0.001) effects on tissue FAD, FMN, and riboflavin status, but the effect of supplementation was clearly pronounced only at days 7 and 14, and thereafter the status of FAD, FMN, and riboflavin in the tissues did not differ between unsupplemented and supplemented birds. Neither FAD, FMN, and riboflavin nor GSSG-RED activity correlate with the level of supplementation. Saturation levels of riboflavin in the blood plasma and tissues, corresponded with dietary riboflavin levels of supplementation at 1 to 2 mg per kg. Based on the performance and biochemical data, the dietary requirement of riboflavin for fast growing broilers should be set at a level of 5 mg/kg. The currently recommended allowance of 3.6 mg riboflavin per kg of ration is not sufficient for modern breeds of broiler chickens.

Cellulitis in broiler chickens: epidemiological trends, meat hygiene, and possible human health implications

The present work evaluates trends in the incidence of cellulitis during the last decade using Canadian National Poultry Condemnation Records. In 1986, only 0.048% of the total slaughter broilers were condemned as a result of cellulitis lesions. Over the next 10 yr, steady increments in cellulitis condemnations were observed, and between 1986 and 1996, the percentage of cellulitis condemnation increased 11.8-fold. In 1996, more than 2.6 million broilers (0.568% of total slaughter) were condemned due to cellulitis; this constituted 30.1% of total condemnations, making it the number one condemnation category in 1996. In the context of dynamic increase in cellulitis, the problems concerning meat hygiene and possible health risk to the consumer are deliberated.

Progressive bradycardia, a possible factor in the pathogenesis of ascites in fast growing broiler chickens raised at low altitude

1. The first objective was to evaluate baseline heart rate (HR) responses in fast growing broilers fed ad libitum from 1 to 45d or subjected to a food restriction (85%, 70% and 55% of ad libitum from 7 to 21d) and a refeeding (22 to 45d) regimen in a normal thermal environment. The second was to evaluate HR and haematocrit responses in fast growing broilers reared at a low environmental temperature and fed ad libitum (A-L) from 1 to 42d, subjected to food restriction (70% ad libitum) between 7 to 21d and refed thereafter (R-R), or subjected to food restriction between 7 to 42d (R), and to follow the changes in normal birds and those prone to ascites. 2. The baseline HR in the normal thermal environment at 21 and 45d in birds fed ad libitum was lower (P < 0.001) than at 7d. The food-restricted groups had higher HRs at 21d than at 7d, with the differences significant (P < 0.01) for the 70% and 55% treatments. At 21d the HRs in restricted groups were significantly higher (P < 0.01) than in ad libitum-fed birds. After returning to ad libitum feeding the HRs in these birds tended to decline, with the differences significant (P < 0.05) for the 70% and 55% treatments. 3. In the birds exposed to cold, each feeding regimen produced distinct patterns of change in HR and haematocrit. Both feeding regimen and age had significant (P < 0.001) effects on the changes of both variables. Relative to 7d, on 14d and 21d the HRs decreased and haematocrits increased in all groups, but the rates of change were highest in the A-L and R-R birds. The first fulminant cases of ascites were observed during the third week in the A-L group and during the fourth week in the R-R group. None of the chickens from the R group developed ascites. Altogether, the incidence of ascites was 48% in the A-L group and 28% in the R-R group. 4. Among the birds exposed to cold, the ascitic birds had significantly (P < 0.001) lower HRs and higher haematocrits than normal birds from the same feeding regimen group. The time trends in the rates of change in HR and haematocrit were distinctly different (P < 0.001) for ascitic and normal birds. The change in feeding regimen from restricted to ad libitum in the R-R group resulted in a significant (P < 0.001) decrease in HR and increase in haematocrit. 5. In view of the evidence presented, it appears that hypoxaemia and tissue hypoxia in broiler chickens may be a result of circulatory insufficiency associated with progressive bradycardia rather than, as commonly believed, pulmonary insufficiency. In this situation the pulmonary hypertension may be a secondary symptom.

High incidence of cardiac arrhythmias in broiler chickens

A study was completed to characterize cardiac arrhythmias in broiler chickens. The data were collected from 505 (265 males and 240 females) commercial broilers. Electrocardiograph (ECG) readings were obtained from all birds between 7 and 9, 21 and 23, and 42 and 44 days of age. For comparison, ECG recordings were also collected from 180 broiler breeders at 3 and 8 weeks of age, and from 100 6-week-old Brown Leghorn and 100 6-week-old Barred Plymouth Rock chicks. The measurements included evaluation of heart rhythm, and incidence of ascites and of sudden death syndrome (SDS). Heart arrhythmias in broiler breeders or in the two other breeds examined were sporadic. Cardiac arrhythmias in broiler chickens were seen as early as 7 days of age. The incidence of arrhythmias increased with age. At 42-44 days of age 17% of the broiler population showed disrhythmia. The incidence was higher in male broilers (P < 0.012) in comparison to females. The most frequently observed disturbances of the rhythm were ventricular arrhythmias (VA), the most common being premature ventricular contractions (PVC). In most cases PVC occurred as one or two episodes, but in several birds, runs of three or more consecutive PVCs occurred. Unifocal PVCs were considerably more frequent than multifocal PVCs. Sustained ventricular tachycardia (VT) was least frequent. Heart-related mortalities were observed only in broiler chickens. There were 23 SDS cases (4.55% of the population) and 13 birds developed ascites (2.25% of the population). Male broilers had a higher incidence of SDS (P < 0.027) and ascites (P = 0.064) compared to females. Males represented 74% of all SDS cases and 77% of all ascites cases. Whereas three birds that died of SDS and one bird that developed ascites had a history of VA, five birds that developed ascites had a history of conduction block. It has been concluded that, compared to other chickens, the hearts of broiler chickens are considerably more susceptible to arrhythmias. Cardiac arrhythmias are involved in the pathogenesis of SDS and are likely in some cases of ascites.

Neurotoxicity and secondary metabolic problems associated with low to moderate levels of exposure to excess dietary sulphur in ruminants: a review

Problems associated with a low to moderate excess in dietary sulphur (S) intake in ruminants are being increasingly recognized. Comparing more recent reports with older data, there is an evident decrease in tolerance of cattle and sheep for even moderately elevated levels of dietary S, and an apparent drastic change in the clinical picture of chronic dietary S toxicoses. Outbreaks of polioencephalomalacia (PEM) in ruminants in association with excess dietary S have been reported in recent years throughout the world. Excessive levels of S-containing compounds in domestic ruminant animals' rations, and clinical problems associated with low to moderate levels of exposure to dietary S may be more common than previously thought. This review presents a comprehensive evaluation of the problems associated with excessive levels of S in ruminants' rations. Emphasis is placed on the recently increasing incidence of S-induced PEM. Secondary metabolic disorders associated with excessive intake of S are also discussed.

Malignant ventricular dysrhythmia in broiler chickens dying of sudden death syndrome

A flock of broiler chickens was monitored intensively for overt signs indicative of sudden death. Electrocardiographic tracing of terminal cardiac activity was obtained from six broilers succumbing to sudden death syndrome and from six control chickens which were killed by cervical dislocation. Normal sinus rhythm, heart rate and electrocardiogram (ECG) pattern with P, QRS, and T deflections were observed for two to three minutes in the control chickens. The ECG tracing from birds dying of sudden death syndrome showed no identifiable P, QRS, or T waveforms. Initial more regular oscillatory waves resembling ventricular flutter, changed to irregular, undulating waves characteristic of ventricular fibrillation. A straight line, indicating cessation of heart activity, appeared within four to six minutes of the onset of clinical signs. It was concluded that the sudden death syndrome is associated with an acute cardiovascular failure caused by a lethal cardiac dysrhythmia, ventricular fibrillation.

A study of electrocardiographic patterns in a population of commercial broiler chickens

A study was completed to characterize the electrocardiographic (ECG) patterns of male broiler chickens. Data were collected from 300 commercial broilers. ECG readings were collected from all birds between 12 and 15 days of age and then twice more at 10-day intervals. The measurements. included heart rate and rhythm, QRS complex duration, amplitude and mean electrical axis (MEA), incidence of ascites and incidence of sudden death syndrome (SDS). Eight birds died from SDS and 4 birds died from ascites. Twelve birds were condemned for ascites at the processing plant. The overall population heart rate declined with age. Birds that died of SDS had a higher heart rate, whereas those that developed ascites had a lower heart rate than the remainder of the population. The normal MEA was found to be between 0 degree and 180 degrees. On average 30% of birds showed left or right QRS axis deviation, and this pattern was observed in 14 of the 16 birds that developed ascites. Several types of cardiac arrhythmias were observed, the most common being premature ventricular contractions (PVC). The incidence of PVC increased with age, ranging from 1% at 12-15 days of age to 8.9% at 32-35 days of age. QRS axis deviation was present in 5 SDS birds. It is concluded that some 30% of the broiler flock tested was at risk of developing heart failure or heart-related disease.

Changing epidemiology of ascites in broiler chickens

Ascites has become a major economic problem in modern broiler operations world wide. Estimated losses to the global economy likely amount to hundreds of millions of dollars annually, however, accurate statistics are not available. Epidemiological information on incidence of ascites is scanty. The present work examines the condemnation records between 1986 and 1994 from federally inspected slaughtering plants in Canada. The analysis reveals that there has been a steady increase in ascites condemnation during this period. National average figures showed a nearly sixfold increase in condemnations due to ascites from 1986 to 1994. It is estimated that in Canada some 6–8 million chickens developed ascites in 1994. The present data have shown an alarming trend in the epidemiology of ascites. Key words: Chicken, broiler, ascites, condemnation, epidemiology

Role of thiamine status in sulphur induced polioencephalomalacia in sheep

The effects of excess dietary sulphur were studied in sheep supplemented and unsupplemented with thiamine. The diets contained either 0.19 per cent sulphur (LS) or 0.63 per cent sulphur (HS) in combinations with 14 mg kg-1 thiamine (LB1) or 243 mg kg-1 thiamine (HB1). A total of 56 two-month-old lambs were used. Groups consisting of nine, nine, 22 and 16 lambs were fed LS-LB1, LS-HB1, HS-LB1 and HS-HB1 diets, respectively for 14 weeks. Out of 22 lambs fed the HS-LB1 diet, seven lambs developed neurological signs between the third and eighth week of the trial. Two of these lambs died, three that were in extremis were euthanased, and two recovered completely. All clinically affected animals had extensive malacic lesions in the cerebral cortex, midbrain and brainstem. None of the lambs from the LS groups or HS-HB1 group developed clinical signs. Several clinically normal lambs from the HS-LB1 group had necrotic lesions in their brains at gross and microscopic examination. Supplementation with dietary thiamine prevented development of clinical signs, but did not totally prevent development of microscopic brain lesions. Brain thiamine concentration, transketolase activity and thiamine pyrophosphate (TPP) effect were not different (P greater than 0.05) among groups. There was a strong effect (P less than 0.0001) of dietary thiamine supplementation on blood thiamine concentration and TPP effect. Blood thiamine concentration was higher whereas TPP effect was lower in the thiamine supplemented sheep. Blood and tissue thiamine concentrations in sheep exposed to high dietary sulphur did not indicate either systemic or local thiamine deficiency per se. Increased TPP effect in sheep fed the HS-LB1 diet indicated mild to moderate metabolic thiamine deficiency. Thiamine inadequacy may be an effect of an increased requirement for thiamine in animals exposed to excess dietary sulphur.

The effects of thiamine and EDTA on biliary and urinary lead excretion in sheep

Relative efficacy of thiamine (B1) and/or calcium disodium ethylinediaminetetraacetate (EDTA) administration on lead (Pb) excretion via bile and urine was studied in Pb-loaded sheep. The sheep were administered B1 s.c., 75 mg/kg body wt., EDTA i.v., 110 mg/kg body wt., and a combination of B1-EDTA at rates as above. Each treatment was followed by 69 h sampling of blood, bile, and urine. Urinary Pb excretion increased following B1-EDTA greater than EDTA greater than B1 administration. Thiamine and B1-EDTA treatments increased biliary Pb excretion. Overall, B1, EDTA and B1-EDTA administration increased Pb excretion via bile and urine by 72%, 595%, and 842% respectively over basal level (mean +/- SE: 20.1 +/- 2.9 micrograms Pb/h). It has been concluded that thiamine enhances elimination of Pb from the body and this feature may be beneficial in chelation therapy.

The effects of copper status on thiamine metabolism in sheep fed a high sulfur diet

The effect of Cu status on selected aspects of thiamine metabolism was studied in sheep exposed to high dietary S over a period of 14 wk. Nine cross-bred 2-mo-old female lambs were used. The animals were divided into three groups (n = 3) and offered a basal diet containing 0.63% S (0.45% as sulfate) and 14 mg thiamine kg−1 DM. Copper and Mo were variable ingredients. Sheep in group 1 received a 14 mg Cu kg−1 DM diet, whereas those in groups 2 and 3 received a 6 mg Cu kg−1 DM diet. To precipitate Cu insufficiency, group 3 received an additional 20 mg Mo kg−1 DM diet. The concentration of blood thiamine tended to increase in sheep from group 1, but decline in sheep from group 3 which also had a lower concentration of Cu in plasma. In these groups, a similar trend was observed in thiamine and Cu concentrations of duodenal fluid. Liver thiamine tended to be higher (P = 0.09) in group 3 sheep than in group 1 and 2 sheep. However, the concentration of thiamine in the kidney and cerebral cortex did not differ among the groups. Copper concentration was lowest in the liver and brain, but highest in the kidney of sheep from group 3. The erythrocyte thiamine pyrophosphate (TPP) effect increased (P < 0.035) in sheep in groups 2 and 3 during the 8th week on the diet and in all sheep during the 13th week. We conclude that Cu plays an important role in the metabolism of thiamine in the gastrointestinal tract, as well as systemically. Key words: Sulfur, molybdenum, copper, thiamine, interactions, sheep

Ovine polioencephalomalacia associated with dietary sulphur intake

Fifty-six female crossbred two-month-old lambs were housed in individual cages, and fed a basic ration of barley (59%), soybean meal (5%), and alfalfa (32%) prepared to meet NRC nutrient requirements. Four percent of the diet contained a standard salt mix to which the factors inorganic sulphur (S) and thiamine (B1) were added. Four treatment groups were used: low sulphur and normal thiamine (0.19% S, 13.7 mg/kg B1) low sulphur and high thiamine (0.19% S, 243 mg/kg B1), high sulphur and normal thiamine (0.63% S, 13.7 mg/kg B1), high sulphur and high thiamine (0.63% S, 243 mg/kg B1). All animals had free access to water and were offered 1 kg/animal/day of diet for 14 weeks, when necropsy was undertaken. Seven lambs fed unsupplemented (normal B1) diets containing added sulphur developed clinical symptoms of polioencephalomalacia (PEM) between the 3rd and 7th week of the trial. Morbidity (P less than 0.013) and mortality (P = 0.08) differences were attributed to S administration. None of the B1 supplemented lambs developed clinical signs of PEM. Body weight and relative organ weights did not differ among treatment groups. Serial sections of all brains were examined grossly and microscopically. Nonparametric statistical analysis revealed sulphur related effects in the cerebrum, midbrain and hindbrain (P less than 0.0001), no thiamine-related effects or interaction between the factors were seen, except in the amygdaloid body. It was concluded that inorganic sulphur was associated with polioencephalomalacia, and that dietary thiamine may decrease the severity of lesions in some affected areas of the central nervous system.

Effects of high dietary sulfur on brain functions using evoked potentials technique

Brain stem auditory-evoked response (BAER) is a noninvasive technique used for detecting neurophysiological abnormalities of the brain stem along the auditory pathway. Brain stem auditory-evoked response recordings were obtained from subcutaneous skin electrodes from two control sheep and 22 other sheep fed high sulfur (S) diets with low or high concentration of thiamine (B1), copper (Cu), and molybdenum (Mo). At least four peaks (I,II,III,IV) of varied amplitude were observed in all animals. Neurophysiological abnormalities due to decreased conductivity and/or excitability of nerve fibers along the auditory pathway were found on the BAER recordings of sheep fed high S diet. Abnormalities of peaks and interpeak latencies within BAER recordings were related to histopathological observations of brain stem lesions. Lesions in the areas of the cochlear nuclei and lateral lemniscus were seen in conjunction with altered BAER components. However, abnormalities in BAER recordings and lesions in the brain stem also occurred in the absence of overt clinical signs. Analysis of interpeak latencies between peaks I and IV revealed significant differences among dietary groups. Sheep given diets low in Cu, Mo, and B1 were affected most. Factorial analysis indicated B1 and interactions among Cu, Mo, and B1 as significant factors influencing interpeak latencies.

Effects of diets of high sulphur content and varied concentrations of copper, molybdenum and thiamine on in vitro phagocytic and candidacidal activity of neutrophils in sheep

Candidacidal and phagocytic tests were performed on 34 female sheep fed high sulphur diets containing varied concentrations of thiamine, copper, and molybdenum for 14 weeks. Tests were conducted at weekly intervals for five weeks during the latter half of the experiment. The ability of polymorphonuclear leucocytes from sheep on diets unsupplemented with thiamine to kill phagocytosed Candida albicans was lower than those on diets supplemented with thiamine. The ability of polymorphonuclear leucocytes to phagocytose C albicans was lower in animals on low copper diets than in animals on high copper diets. Factorial analysis showed that thiamine supplementation significantly increased (P less than 0.0001) candidacidal but not phagocytic activity. By contrast, copper supplementation significantly increased (P less than 0.0005) the phagocytic activity with no effect on candidacidal activity. The observed detrimental effect of high sulphur intake on in vitro polymorphonuclear leucocyte function can mean that ruminants in areas where large quantities of sulphur are taken in with water and feed have compromised immune function due to lower copper and thiamine status and hence are at risk of increased susceptibility to infections.

Sulfur-induced polioencephalomalacia in sheep: some biochemical changes

The effect of high dietary sulfur (S) supplementation on blood thiamine (B1) concentration, biochemical indices of liver, muscle and kidney damage and selected plasma electrolytes was studied in six sheep. Three of these sheep received an additional 230 mg thiamine/kg diet (Group 2). After approximately 2.5-3 weeks on this diet, all three sheep in the non-B1-supplemented group (Group 1) showed loss of appetite and developed mild neurological signs: depression, intermittent signs of excitation and head pressing. Increases in blood B1 concentration and plasma creatine kinase (CK) and aspartate aminotransferase (AST) were observed during this time in all affected animals. Clinical signs lasted only for two to five days. Sheep in group 2 were clinically normal throughout the experiment, but all of these animals also had elevated blood B1 concentrations and plasma CK activity at the 3 wk sampling. Plasma magnesium concentrations of group 1 sheep were elevated at the 2.5-3 wk and 6 wk samplings but they declined significantly (p less than 0.05) to low normal levels thereafter. Magnesium concentrations of group 2 sheep were low at the beginning but progressively increased during the course of the experiment. At necropsy, brain lesions suggestive of polioencephalomalacia (PEM) were observed in all sheep but were most marked in group 1. It is speculated that PEM may be caused by a direct toxic effect of S, S metabolites or B1 antimetabolites in the brain rather than by an in vivo B1 deficiency per se.

High sulfur related thiamine deficiency in cattle: A field study

Following development of polioencephalomalacia in one of 105 cattle in a farm in southeastern Saskatchewan, a study was initiated to monitor thiamine (B(1)) and copper (Cu) status, and to evaluate interactive nutritional factors which may have been responsible for this occurrence. It was evident that a combination of high sulfur (S) and low Cu intake was responsible for the depletion of blood B(1) and plasma Cu. Supplementation with trace minerals alone resulted in a significant (p<0.05) improvement in both B(1) and Cu status of the herd. We recommend that herds exposed to high intakes of S be supplemented with Cu up to 50 mg/kg feed dry matter to alleviate potential deficiencies of B(1) and Cu.