Effect of heat-treated canola meal and glycerol inclusion on performance and gastrointestinal development of Holstein calves.

The objectives of this study were to assess the effect of using heat-treated canola meal (CM) and glycerol inclusion in starter mixtures on starter intake, growth, and gastrointestinal tract development in Holstein bull calves. In the first study, a protocol for the heat treatment of CM was evaluated by comparing commercial CM that was exposed to 0, 100, 110, or 120°C of heat treatment for 10 min. Following heat treatment, in situ crude protein (CP) ruminal degradability and estimated intestinal CP digestibility were assessed. It was observed that the degradable fractions of dry matter and CP in CM decreased linearly with increasing temperature of heat treatment. The estimated intestinal CP digestibility was greatest when CM was heated to 110°C. In the second study, 28 bull calves were used in a randomized complete block design. Calves were fed pelleted starters containing CM or CM that was heat-treated to 110°C for 10 min. Diets also contained 0 or 5% glycerol on a dry matter basis. The study lasted 51 d, ending on the first day of weaning. Starter intake, average daily gain (ADG), ruminal short-chain fatty acid concentrations, morphology of the rumen and small intestine, gene expression (MCT1, GPR41, GPR43, UTB, AQP3, PEPT1, PEPT2, ATB0+, and EAAC1) in the ruminal, jejunal, and ileal epithelium, and brush border enzyme activities in the duodenum, jejunum, and ileum were investigated. Few interactions between heat-treated CM and glycerol inclusion were observed. Feeding heat-treated CM did not affect starter intake. However, feeding heat-treated CM to calves tended to reduce ADG and decreased the weight of ruminal and jejunal tissue. Heat treatment did not affect gene expression or brush border enzyme activities in the small intestine. Glycerol inclusion tended to increase cumulative starter intake and increased cumulative body weight gain. Use of glycerol reduced ruminal pH and increased the concentration of ruminal short-chain fatty acids. Additionally, glycerol inclusion increased abomasal, duodenal, jejunal, and cecal digesta weights and tended to increase the weight of the jejunal tissue. Glycerol supplementation tended to downregulate the expression of MCT1 in the ruminal epithelium, and upregulated the expression of MCT1 in the epithelium of proximal jejunum. In conclusion, heat treatment of CM may negatively affect calf growth and gastrointestinal tract development. Glycerol inclusion may increase starter intake, ADG, ruminal fermentation, and intestinal development in calves when CM is used as a main source of protein in pelleted starter mixture.

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.

Changes in eggshell structure and predisposition of broilers to health problems: is there a common pathophysiology?

A study of broiler breeder eggs differing in eggshell matrix optical density was conducted to determine the association of eggshell structural quality and the risk of disease in broilers. A total of 10 000 eggs from a broiler breeder flock were examined according to the pre-established criteria, and allocated to groups classified as having a high or low density shell matrix. The eggs from respective groups were incubated and hatched in a commercial hatchery. Samples of unhatched eggs from each group were subjected to detailed examination to establish the cause of reproductive failure. First, quality chicks from each group were raised as separate flocks in a commercial broiler barn. Group performance, morbidity, and mortality were monitored throughout the growth period. All birds were processed in a commercial plant, and condemnation data were compiled. There were significantly more unhatched eggs, and fewer quality chicks in the group classified as having a low density eggshell matrix, in comparison to the high-density group. Embryo pathology accounted for a large proportion of the overall reproductive failure in both groups, with a large proportion of embryos showing anatomical anomalies. The eggs and embryos from the low-density eggshell matrix group were three times more likely to be infected. Significantly higher production losses associated with mortality/morbidity, and condemnations of carcasses at processing were observed in broilers from the low-density eggshell group compared with the high-density eggshell group. It is concluded that common metabolic/physiological changes in breeder hens associated with eggshell pathology may be also risk factors linked with predisposition of broiler chicks to some health problems.

Effect of day length on flock behavioural patterns and melatonin rhythms in broilers.

1. Ross × Ross 308 male broilers were used to study the impact of 14, 17, 20 and 23 h of light (L) on flock behavioural patterns and 24 h melatonin rhythm synchrony during the photophase. 2. Behaviour in two pens (n = 53) per lighting treatment was digitally recorded for 24 h in trial 1 (27-28 d of age (d 27)) and two (42-43 d (d 42)), and quantified using a scan sampling technique at 10 min intervals. Regression procedures were used to test flock trend analysis between behavioural (resting, standing, walking and feeding) variables and time during the photophase. 3. The presence of a flock melatonin rhythm was determined by radioimmunoassay of blood samples collected at 6 times for birds raised on 23L and 8 times for 14, 17 and 20L birds (n = 6 per time) over a 24 h period (d 21) in experiment 1. 4. Quadratic and linear relationships between time and behaviour during the photophase were frequent in 14L and 17L birds, sporadic in 20L birds and non-existent in 23L birds. Relationships were noted in inactive resting (d 27: 14L and 17L; d 42: 14L and 20L), walking (d 27: 14L and 17L), standing (d 27 and d 42: 14L, 17L and 20L) and feeding (d 27: 14L and 17L). A quadratic time × melatonin relationship existed in 14L, 17L and 20L flocks only. 5. Behaviour during the photophase and 24 h melatonin production indicates that flocks exposed to 23L do not develop synchronised rhythms, increasing the risk of suffering from sleep fragmentation.

Biochemical and physiological weaknesses associated with the pathogenesis of femoral bone degeneration in broiler chickens.

Femoral bone degeneration has been recognized as an important cause of lameness in broiler chickens for many years, but the pathogenesis of this condition has not been completely elucidated. The current work presents comprehensive analyses of changes associated with femoral bone degeneration based on findings from gross pathology, histopathology, biochemistry, and synchrotron-based imaging techniques. Gross lesions were predominantly seen in epiphysis and metaphysis of the proximal femur, and infrequently in distal femur, but we did not observe gross lesions in the diaphysis. Bone fractures were observed occasionally, but the most common lesions involved separation of articular cartilage of the femoral bone head, with progressive erosions of the subchondral bone. In advanced cases, on histopathological examination, changes in femoral bone were indicative of chondronecrosis and osteonecrosis. Computed tomography revealed that the degenerative process involves loss of trabecular bone. The course of the lesion development in the mineralized matrix appears to be coupled with increased bone resorption associated with excessive proliferation of pathologically altered osteoclasts. Light microscopy, Fourier transform infrared spectroscopy, and biochemical analysis provided consistent evidence that lowered protein content of the bone organic matrix is an integral component of femoral bone pathology, but these changes do not appear to be associated with excessive activity of matrix metalloproteinases. Taken together, our findings indicate that femoral bone degeneration is associated with structural changes occurring in both inorganic and organic matrix of the bone, but insufficiency in protein metabolism is most probably a primary aetiological factor in the natural history of femoral bone degeneration. However, it is important to stress that our findings do not negate the importance of bacterial infection in the evolution of this condition. Pathogens play a critical role in the progressive pathogenesis of this condition, which ultimately is manifested, in most instances, as femoral head necrosis.

Effects of dietary Cu, Mo and S on urinary Cu and Zn excretion in Simmental and Angus cattle.

This study determined the effects of dietary copper (Cu), molybdenum (Mo) and sulphur (S) on urinary Cu and zinc (Zn) excretion in cattle. Four Simmental and four Angus heifers were fed low (L) or high (H) levels (mg/kg DM) of Cu (5,40), Mo (1,10) and S (0.2,0.5%). Initially two of each breed was fed either LCu or HCu (2 mo). Then all eight animals were fed sequentially LCuHS (1.5 mo), HCuHS, HCuHMo and HCuHMoHS (2 mo each). Simmental had a higher urine flow, increased concentration and total excretion of urinary Cu and Zn compared to Angus, but only total Zn excretion was significantly higher. Urinary Cu excretion was greatest with the HCuHMoHS diet. Urinary Zn excretion significantly increased with HS but not HS in combination with HMo and/or HCu. This study, together with previously reported biliary excretion, allows a direct comparison of urinary and biliary Cu and Zn excretion responses to dietary Cu, Mo and S.

Vascular remodeling and its role in the pathogenesis of ascites in fast growing commercial broilers.

This study examined the putative role of blood vessel pathology in the development of ascites in broilers. Major blood vessels (aorta, brachiocephalic arteries, pulmonary arteries, and vena cava) from normal commercial male broiler chickens, and broilers that developed congestive heart failure (CHF) with or without ascites were subjected to gross and microscopic examination. On cross-section, grossly, the arteries from normal broilers and those showing dilated cardiomyopathy without ascites appeared circular, with firm wall tone characteristic of the normal artery. In contrast, the arteries from ascitic broilers appeared flaccid and lacked elasticity, which was evidenced by collapsing, ellipsoid cross-sectional arterial lumen owing to the structural weakness of the arterial walls. Microscopically, ascitic broilers showed thinning or occasionally total loss of elastic elements in the arterial wall, and reduced network density of the structural matrix of the vascular wall, as well as increased thickness of fibers in vena cava. The structural changes seen in the major arteries from ascitic broilers are maladaptive, and as such would definitively impose an increased hemodynamic burden on the already failing heart pump. The changes in veins are indicative of pathological remodeling conducive to increased permeability of the vascular wall, particularly in the situation when a poorly distensible structure is further subjected to wall stress associated with increased pressure and volume overload. Taken together, increased hemodynamic burden and reduced structural density of the venous wall constitute conditions conducive for seepage and accumulation of ascitic fluid.

Effects of dietary vitamin E and C supplementation on heart failure in fast growing commercial broiler chickens.

1. It has recently been shown that oxidative stress is involved in the pathogenesis of congestive heart failure (CHF) in broiler chickens. Vitamins E and C, common antioxidants, have been advocated for the prevention of heart failure in humans. The present study examines the effects of supplementation of these vitamins on incidence of CHF and prevention of oxidative stress in the myocardium. 2. Commercial male broilers were randomly allocated to three experimental groups and, respectively, offered commercial broiler diet (control), commercial diets fortified with vitamin E (960 IU/kg) or vitamin C (400 mg/kg). The broilers were monitored daily for overt signs of heart failure and clinical data including ECG and blood gas analysis were collected periodically. Lipid peroxidation was measured in cardiac tissues from apparently normal broilers and broilers developing CHF in each group using thiobarbituric acid reactive substances (TBARS) assay. 3. Overall, the incidence of CHF in broilers given diets fortified with vitamin E or vitamin C was not significantly different as compared to the control group. The incidence of overt signs of hypoxaemia was lower in the vitamin C group than in the control group. Lipid peroxidation was highest in broilers that developed CHF as compared to apparently normal broilers fed either vitamin E or C fortified diets. Neither vitamin E nor vitamin C was effective in preventing oxidative damage in broilers that developed CHF. 4. In conclusion, the present study confirmed that oxidative stress is involved in the pathogenesis of heart failure in broilers, but dietary supplementation of antioxidant vitamins did not prevent oxidative damage in broilers that developed CHF. Beneficial effects of vitamin C supplementation were evidenced by lower incidence of hypoxaemia, and the tendency to reduce the susceptibility of broilers to heart failure. However, vitamin E did not have any impact on clinical status or the incidence of CHF.

Putative cardiotoxic compounds extracted from meat meal as a potential risk factor for the development of heart failure in fast-growing commercial broilers.

Thermal processing of meat products generates cardiotoxic compounds capable of inducing heart failure in both humans and laboratory animals. Such compounds may be present in broiler diets because supplements such as meat meal (MM), which are commonly used in broiler rations, are rendered at high temperature. Our objective was to evaluate whether putative cardiotoxic compounds in MM increase the risk of heart failure in broilers. The treatment and control diets were prepared by mixing the condensed MM extract (equivalent to dietary MM inclusion of 25%) or placebo (condensed extraction medium) with commercial broiler feed, and the respective diets were offered to commercial male broilers randomly allocated to either treatment or control groups. Broilers fed a diet spiked with MM extract showed a higher incidence (P<0.05) of chronic heart failure (65.5%) in comparison with the control group (55.4%). Postmortem examination upon termination of the experiment revealed that, in comparison with control broilers, broilers fed diet containing MM extract showed higher incidence of lesions indicative of subclinical heart disease evidenced grossly by ventricular dilation and pericardial effusions, microscopically by changes characteristic of cardiomyocyte degeneration, and ultrastructurally by changes in contractile elements and in mitochondria. Measurements of cardiac high-energy phosphates revealed that broilers fed the diet containing MM extract had lower (P<0.05) levels of cardiac energy reserve as compared with birds fed control diet. We conclude that cardiotoxic factors that can induce patho-physiological changes in the heart are present in MM.

The role of oxidative stress in the development of congestive heart failure in a chicken genotype selected for rapid growth.

The present study examined the possible role of reactive oxygen species in the pathogenesis of heart failure in broilers. Data were collected from three groups of birds at various risk of heart failure: Leghorn chickens (resistant to heart failure), slow-growing feed-restricted broilers (low risk of heart failure), fast-growing ad libitum fed broilers (high risk of heart failure), and broilers with congestive heart failure (CHF). In the first part of the study, basic clinical parameters and ultrastructural changes were examined in the context of lipid peroxidation of the ventricular myocardium. This was followed by the study of in vitro changes in the activity of selected cytosolic enzymes (creatine kinase and lactate dehydrogenase) and mitochondrial enzymes (pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase) in the presence of oxidants (hydrogen peroxide or tertiary butyl hydroperoxide). The distinctive clinical feature in the fast-growing broilers and in the broilers with CHF as compared with slow-growing broilers or Leghorn chickens was a significantly lower heart rate (P <0.05). Electron microscopy revealed marked morphological changes in myocardial mitochondria in these broilers (i.e. fast-growing broilers and broilers with CHF). The level of malondialdehyde equivalents, an indicator of lipid peroxidation subsequent to generated oxidative stress, was significantly higher (P <0.05) in ad libitum fed broilers and was highest (P <0.01) in broilers with CHF. In vitro, the presence of oxidants had a detrimental effect on creatine kinase and alpha-ketoglutarate dehydrogenase activity, while lactate dehydrogenase activity increased. The activity of pyruvate dehydrogenase was not altered by oxidants. Our results indicate that the deterioration of heart function in fast-growing commercial broilers in our experimental model is associated with oxidative stress leading to lipid peroxidation of cellular and mitochondrial membranes, and decreased activity of myocardial creatine kinase and alpha-ketoglutarate dehydrogenase enzymes critical for energy synthesis and transformation pathways.

Sub-clinical necrotic enteritis in broiler chickens: novel etiological consideration based on ultra-structural and molecular changes in the intestinal tissue.

The present study revealed several previously not recognized etiological details in the development of necrotic enteritis (NE) in broilers. We provide evidence that the pathological process leading to mucosal epithelium necrosis follows morphologically distinct phases commencing at the basal domain of the mucosal epithelium and then progressively invading the entire lamina propria. Initially mucosal epithelium appears normal, but as the pathological changes progress throughout the lamina propria, the adjacent enterocytes begin to show features of necrotic cell death and the necrotic process of the epithelium progresses from being focal to locally extensive. Ultra-structural examination showed that primary changes occur at the level of basal and lateral domains of the enterocytes, whereas the apical domain of enterocytes remains intact even in the face of advanced necrotic changes. This indicates that the mucosal necrosis does not result from direct damage to the mucosal epithelium. Rather, the necrotic death of enterocytes is a consequential effect of the destruction of lamina propria, the extra-cellular matrix, and intercellular junctions. The nature of these morphological changes indicates that initiation of the pathological process leading to NE involves proteolytic factors affecting the extra-cellular matrix and cellular junctions. Further studies revealed that, indeed, the elevated activity of collagenolytic enzymes in the mucosal milieu and in intestinal tissue represents an integral component of the pathological process leading to NE. In the first instance we discovered that Clostridium perfringens strains isolated from field cases of NE secrete several potent collagenolytic enzymes. In the second instance we observed that, in comparison to controls, broilers challenged with C. perfringens isolated from field cases of NE show high levels of several collagenolytic enzymes in the intestinal tissue. A major component of the overall collagenolytic activity detected in the intestinal tissue was identified by zymography as matrix metalloproteinases (MMPs). Dominant activity was associated with MMP-2. We confirmed using immuno-histochemistry that this enzyme is expressed at high levels in mucosal tissue showing signs of NE. The high levels of collagenolytic activities, in particular associated with MMP-2, demonstrated in our studies are consistent with the nature of morphological changes observed primarily in extra-cellular matrix (ECM) at the basal domain of enterocytes, as well lateral domains of enterocytes. The lack of changes at the level of apical domain of mucosal epithelium indicates that the lipolytic aspect of alpha toxin in NE is not an essential factor in primary lesions development. Taken together, our findings indicate that the early lesions leading to NE are associated with virulence factors that induce proteolytic activity, rather than lipolytic activity.

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.

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.

Excessive dietary vitamin D supplementation as a risk factor for sudden death syndrome in fast growing commercial broilers.

Broiler diets are frequently fortified with vitamin D (D3) above the recommended levels in an attempt to prevent commonly occurring leg problems. Since the basal levels of dietary D3 are rarely known, there is a risk of over-supplementation. Over-supplementation of D3 has been shown to have detrimental effects on the heart. Sudden death syndrome (SDS) is a condition commonly observed in broiler flocks and is associated with acute heart failure. The present study examines the effects of excessive levels of vitamin D3 on cardiac health in fast growing broiler chickens. Commercial male broilers (Gallus gallus) were exposed to either a commercial diet or a commercial diet supplemented with D3. Throughout the trial all birds were monitored several times daily for overt signs of heart disease, and periodically electrocardiographic measurements were obtained. Morbidity and mortality data were collected daily. On day 32 a simulated stress challenge consisting of a single injection of epinephrine (100 microg/kg BW) was administered under continuous ECG monitoring. Broilers fed the high D3 diet were 2.5 fold more likely to succumb to acute heart failure and die of SDS (p<0.05). Electrocardiographic examination showed a higher rate of cardiac arrhythmia in birds fed the high D3 diet (22.6%), in comparison to those fed the control diet (11.8%). The stress challenge test revealed that broilers exposed to high dietary D3 were more susceptible to ventricular arrhythmia. Our findings indicate that over-supplementation of vitamin D increases the risk of SDS in broilers, and that the most likely mechanism is associated with increased susceptibility of the ventricular myocardium to arrhythmia.

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.

Effects of commensal bacteria on intestinal morphology and expression of proinflammatory cytokines in the gnotobiotic pig.

A germ-free neonatal pig model was established to determine the effects of bacterial colonization by different species on small intestinal morphology and proinflammatory cytokine gene expression. Two experimental groups of 16 pigs were aseptically delivered by cesarian section and allocated into 4 gnotobiotic isolators. Pigs were either maintained germ-free (GF), or were orally inoculated with either a single strain of nonpathogenic Escherichia coli (EC) or Lactobacillus fermentum (LF) or conventionalized with adult porcine feces (CV). After 13 days tissue samples were collected at 5 regions corresponding to 5%, 25%, 50%, 75%, and 95% of the small intestine (SI) length. In Experiment 2, the GF isolator became contaminated with Staphylococcus epidermidis (SE). In general, intestinal responses to bacterial colonization were similar among GF, LF, and SE pigs, and intestinal responses in EC pigs were more similar to CV pigs. Responses to bacterial colonization were most pronounced in the distal SI regions (50%-95%), suggesting that nonmicrobial factors may be more important in the proximal SI. Relative to CV pigs, the distal intestines of GF, LF, and SE pigs were characterized by long villi, shallow crypts, increased relative intestinal mass, and decreased lamina propria cellularity, whereas SI morphology was intermediate in EC pigs. Relative expression of proinflammatory cytokines interleukin-1beta (IL-1beta ) and IL-6 generally increased distally in the SI and was highest in EC and CV pigs. We observed regional variation in SI morphology and proinflammatory cytokine expression, which differed with bacterial species. This study demonstrates that bacterial species differentially affect intestinal morphology and expression of proinflammatory cytokines and suggests that neonatal bacterial colonization patterns may have long-term effects on intestinal health and development.

Effects of guar gum and cellulose on digesta passage rate, ileal microbial populations, energy and protein digestibility, and performance of grower pigs.

Dietary guar gum and cellulose were studied as purified soluble and insoluble nonstarch polysaccharide (NSP) sources, respectively. A control diet containing 14% cornstarch was formulated. A 7% guar gum, a 7% cellulose, and a 7% guar gum + 7% cellulose diet were formulated by adding the NSP to the control diet at the expense of cornstarch (wt/wt), forming a 2 x 2 factorial arrangement. The objectives were to determine whether guar gum and cellulose altered 1) the passage rate of digesta through the small intestine and total tract; 2) the digestibility of energy and CP, characteristics of the digesta, and microbial populations in the ileum; 3) plasma glucose and ghrelin concentrations; and 4) short-term voluntary feed intake and growth performance of grower pigs. In Exp. 1, 12 pigs (27.0 +/- 1.5 kg of BW) were fitted with an ileal T-cannula and were used in a 2-period change-over design, providing 6 observations per diet. Each period included 18 d: a 12-d acclimation period followed by 2-d feces, 3-d digesta, and 1-d venous blood collection periods. In Exp. 1, guar gum and cellulose slowed the passage rate of digesta through the small intestine by 26 and 18%, respectively (P < 0.05). Guar gum increased total tract retention time of the digesta by 14% (P < 0.05). Guar gum and cellulose increased the viscosity of ileal digesta by 72 and 76%, respectively (P < 0.05). Cellulose reduced ileal energy and CP digestibility (P < 0.05), but guar gum only tended to decrease ileal energy digestibility (P < 0.10). Guar gum and cellulose reduced total tract energy and CP digestibility (P < 0.05). At 60 min after feeding, guar gum decreased plasma glucose by 10% (P < 0.10). Guar gum interacted with cellulose to reduce plasma ghrelin before and after feeding (P < 0.05). Guar gum and cellulose interacted to increase ileal bifidobacteria and enterobacteria (P < 0.05); however, guar gum, but not cellulose, increased ileal clostridia (P < 0.05). In Exp. 2, 20 individually housed grower pigs (5 pigs per diet) had free access to the 4 diets used in Exp. 1 for 14 d. Guar gum and cellulose decreased ADG and reduced ADFI on d 0 to 14 (P < 0.05). In summary, increasing purified NSP in the diet reduced the passage rate of digesta, energy and protein digestibility, and feed intake, but increased ileal bifidobacteria and enterobacteria populations. The effects of cellulose were similar to those of guar gum. In conclusion, monitoring of dietary NSP is a critical factor to achieve predictable digestible nutrient intake and intestinal bacterial populations.

Effects of dietary protein source and level on intestinal populations of Clostridium perfringens in broiler chickens.

Two experiments were conducted to examine the effect of the level of dietary crude protein and protein source on intestinal populations of Clostridium perfringens in broilers. In experiment 1, 6 groups of 12 birds were fed diets containing 230,315 or 400 g/kg crude protein with soy protein concentrate (SPC) or low-temperature-dried fishmeal as the major protein sources in a 2 x 3 factorial arrangement of treatments. A significant interaction between protein source and level was observed where the number of C. perfringens present in the ileum and cecum increased as the level of crude protein in the diets increased from 230 to 400 g/kg in the birds fed fishmeal-based diets (P < 0.05) but not in the birds fed SPC-based diets. In experiment 2, the dietary treatments used were arranged in a 2 x 2 factorial arrangement with 2 levels of crude protein (230 and 400 g/kg) and 2 protein sources (SPC or fishmeal). The main effects of protein source and protein level significantly (P < 0.05) affected numbers of C. perfringens without interaction. Amino acid analysis of the diets showed that the glycine and methionine contents of the fishmeal diets were elevated compared with the SPC diets. This suggests that the level of crude protein, protein source, and amino acid content of diets affect the growth of C. perfringens in the lower intestinal tract of the broiler chicken and might be predisposing factors to outbreaks of clinical necrotic enteritis.

Hot topic: an association between a leptin single nucleotide polymorphism and milk and protein yield.

Allelic variation (C to T transition that results in an Arg25Cys) in the leptin gene has been associated with increased fat deposition in beef cattle. We report that this same genetic variant is also present in dairy breeds. Body fat reserves play an important role in sustaining high milk production in early lactation, when energy intake is limited. To test for an association between the leptin single nucleotide polymorphism and milk productivity, we genotyped 416 Holstein cows and compared lactation performance data using a mixed model. Animals homozygous for the T allele produced more milk (1.5 kg/d vs. CC animals) and had higher somatic cell count linear scores, without significantly affecting milk fat or protein percent over the entire lactation. The increase in milk yield is most prominent in the first 100 d of lactation (2.44 kg/d), declining to 1.74 kg/d between 101 and 200 d in lactation. The milk yield advantage, observed in cows homozygous for the T allele, could represent a major economic advantage to dairy producers.

Isolation and evaluation of immunological adjuvant activities of saponins from Polygala senega L.

We have identified saponins in the root of Polygala senega L., a plant indigenous to the Canadian prairies, which display immunopotentiation activity to protein and viral antigens. By two-step extraction and hemolytic activity-guided fractionation by silica flush chromatography six saponin fractions were generated and their HPLC profiles determined. Two dominant fractions, designated as PS-1 and PS-2, were tested for adjuvant activity in mice immunized with ovalbumin, and hens immunized with rotavirus. The resulting adjuvant activity was compared with that of Quil A saponin. The P. senega saponins increased specific antibody levels to the antigens, in both mice and hens. In mice, there was a preferential increase of the IgG2a subclass, and upon in vitro secondary antigen stimulation, high IL-2 and IFN-gamma levels were observed in spleen cell cultures from P. senega saponins-immunized animals. The saponins were tested for their toxicity by lethality in mice and were found to be less toxic at the same dose than their counterpart Quil A. The results of this study indicated the potential of P. senega saponins as vaccine adjuvants to increase specific immune responses.