Protein assimilation and metabolism studies are hindered by the lack of an adequate oral tracer, ... more Protein assimilation and metabolism studies are hindered by the lack of an adequate oral tracer, i.e., labeled proteins. We present a new and easily reproducible methodology for producing large amounts of egg proteins labeled with L-leucine-13C1. Laying hens were fed a 0.2% leucine-deficient food supplemented with 0.2% L-leucine-13C1 (99 atom %). At plateau, eggs containing highly enriched proteins were obtained. The 13C content of egg white relative to the total C content was 1.3371 atom %, corresponding to delta = 206%. The overall tracer recovery in egg proteins was high (40.2%), making this method financially attractive as well. Accurately measurable levels of 13CO2 in breath were obtained after ingestion of a physiological load of labeled egg white proteins. Thus, egg proteins with sufficient 13C enrichment and applicable for human protein assimilation and metabolism kinetic studies were produced in an easily reproducible and highly efficient manner.
Daily changes in the concentrations of plasma corticosterone, prolactin, thyroid hormones and som... more Daily changes in the concentrations of plasma corticosterone, prolactin, thyroid hormones and somatomedin C were measured in 28-day-old fat and lean lines of broilers produced by selection for high and low concentrations of very low density lipoproteins (VLDL). The effects of daily injections of corticosterone on the concentrations of these hormones and on fattening were compared in the two lines. The selection procedure had no effect on the concentrations of any of the hormones. However, daily rhythms in concentrations of plasma corticosterone, tri-iodothyronine (T3) and prolactin were less often observed in the fat line than in the lean line. No differences were seen between lines in the daily rhythms in plasma thyroxine (T4) and somatomedin C. Daily injections of 2500 micrograms corticosterone/kg body weight, in both lines, depressed mean concentrations of plasma prolactin, T3 and somatomedin C and body weight. This dose of corticosterone also increased abdominal fat pad and liver weights expressed as a percentage of body weight. The liver and fat pad responses to 2500 micrograms corticosterone in both lines were greater when the steroid was injected at the end rather than towards the beginning of the 14-h daily photoperiod. There was no difference between the lines in the fattening response to corticosterone. Lower doses of 100 and 500 micrograms corticosterone per day did not induce fattening or affect concentrations of plasma prolactin. They did, however, depress concentrations of plasma T3. Concentrations of plasma T4 were increased in both lines treated with 2500, but not with 100 or 500 micrograms corticosterone, towards the beginning of the daily photoperiod.(ABSTRACT TRUNCATED AT 250 WORDS)
1. Differences in responses to lipolytic agents have been investigated in vitro in abdominal adip... more 1. Differences in responses to lipolytic agents have been investigated in vitro in abdominal adipose tissue from lines of broiler chickens selected for body weight (GL, a 'fat' line) or for food efficiency (FC, a 'lean' line). 2. Dibutyryl cyclic adenosine monophosphate stimulated in vitro lipolysis, as measured by the glycerol release, by adipose tissue from GL or from FC chickens to the same extent. 3. Glucagon stimulated glycerol release from adipose tissue from FC chickens, but not from GL chickens. 4. Adipose tissue from GL chickens was much more sensitive to chicken growth hormone (GH) compared to FC chickens. 5. It is concluded that the selection criteria applied influenced the number of adipose GH and glucagon receptors, the number of adipose GH receptors being lower and of glucagon receptors being higher in FC chickens compared to GL chickens.
Previously, overall protein assimilation after the ingestion of a pure protein meal was studied. ... more Previously, overall protein assimilation after the ingestion of a pure protein meal was studied. In this study, the kinetics of protein assimilation in humans were investigated after the ingestion of a complex meal, which more closely represents a physiologically normal situation. Overall protein assimilation in humans after the ingestion of a pancake meal, containing 12 g of fat, 27 g of carbohydrate, and 19 g of protein, was evaluated in 26 normal volunteers. Both the egg white and yolk of L-[1-(13)C]-leucine-substituted eggs were used to make the batter. The labeled eggs were produced by feeding laying hens a standard chicken diet supplemented with 3 g/kg of L-[1-(13)C]-leucine (99%, mol:mol). High enrichment levels of protein with adequate labeling patterns were obtained in eggs from laying hens fed the L-[1-(13)C]-leucine-substituted diet. The isotopic enrichment of leucine at plateau was equal in egg white and yolk. The overall tracer recovery in egg proteins was 22.5%. The ov...
The health benefits of omega-3 polyunsaturated fatty acids (n−3 PUFA) are generally recognized. U... more The health benefits of omega-3 polyunsaturated fatty acids (n−3 PUFA) are generally recognized. Unfortunately, in most western countries, the recommended daily intake of these compounds is rarely met. Therefore, enrichment of commonly occurring foods can boost intake of these fatty acids. In this regard, eggs are an interesting target, as they form an integral part of the diet. Their n−3 PUFA profile can be modified through feed supplementation. A traditional n−3 PUFA source to be added to hens' diet is flaxseed, a plant source rich in α-linolenic acid. Alternatively, hens are often fed fish oil, which is rich in long chain n−3 PUFA eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). A more recent trend is feed supplementation with microalgae as a source of EPA and/or DHA. In this paper, recent scientific literature concerning n−3 PUFA enrichment in eggs is reviewed, giving an overview of advantages and disadvantages of the different approaches.
Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology, Jan 21, 2015
The 5'-adenosine monophosphate-activated protein kinase (AMPK) plays a key role in rapid meta... more The 5'-adenosine monophosphate-activated protein kinase (AMPK) plays a key role in rapid metabolic adaptations to maintain energy homeostasis in poultry. It remains unclear if AMPK is involved in muscular energy metabolism in broiler chickens. Hence, in the present study, seven-day-old male broilers were equally divided into three groups: fed ad libitum (control); feed-deprived for 24 h (S24); feed-deprived for 24 h and then refed for 24 h (S24R24). Compared to the control group, the plasma levels of glucose, insulin, T3 and triglycerides in the S24 group were significantly lower (P<0.05), whereas the uric acid levels were significantly higher (P<0.01). Except for glucose, refeeding for 24 h reversed the fasting-induced alterations in plasma metabolite. Fasting decreased the liver kinase B1 (LKB1), AMPK alpha 2 subunit (AMPKα2), and fatty acid synthase (FAS) mRNA levels (P<0.05) in M. pectoralis major (PM). Feed deprivation did not affect the phosphoryulated AKT, mammal...
What is the central question of this study? Prenatal protein undernutrition by albumen removal in... more What is the central question of this study? Prenatal protein undernutrition by albumen removal in an avian model of fetal programming leads to long-term programming effects, but when do these effects first appear and are these programming effects regulated by the same candidate genes as in mammals? What is the main finding and its importance? The present results indicate that prenatal protein undernutrition by albumen removal induces phenotypical and hormonal changes in the early posthatch period, when the mismatch between the prenatal and postnatal environment first arises, but these changes are not accompanied by an altered gene expression of the selected candidate genes. Studies of the chicken offer a unique model for investigation of the direct effects of reduced prenatal protein availability by the partial replacement of albumen with saline in eggs at embryonic day 1 (albumen-deprived group). The results were compared with mock-treated sham chicks and non-treated control chicks...
In chickens, metabolism is influenced by environmental factors and of particular interest nutriti... more In chickens, metabolism is influenced by environmental factors and of particular interest nutritional factors, such as diet quantity and composition. With respect to the dietary macronutrients, literature clearly shows that in isoenergetically formulated diets, the protein level has a pronounced effect on metabolism, whereas fat and carbohydrate concentrations play a limited role. A decreased dietary protein level results in depressed growth rates, with reduced carcass gains in both water and protein content. In spite of the lower protein retention in chickens fed low protein diets, the efficiency of utilization of dietary protein appears to be increased. This indicates an inverse relationship between protein intake and utilization, which is reflected in decreased circulating uric acid levels. In addition, feed intake is increased, at least when protein levels are slightly reduced, leading to an involuntary overconsumption of energy compared to protein. The chickens deal with this excess energy consumption by increasing de novo lipogenesis and fat deposition, which is supported by increased plasma triglyceride concentrations, and heat production is increased. In contrast to adult mammals, the dietary macronutrients have no effect on diet-induced thermogenesis, nor is there any relationship between diet-induced thermogenesis and feed intake. Plasma growth hormone levels are higher in chickens reared on a low protein diet, indicating a causal relationship between growth hormone secretion and protein efficiency. In spite of the increased growth hormone levels, plasma insulin-like growth factor concentrations are lowered in low protein reared chickens, and may be partially responsible for the reduced growth rate observed in these animals. Plasma corticosterone concentrations are augmented in chickens on low protein diets, despite a decline in the ACTH concentration. Finally, plasma T 3 and T 4 levels are well known to increase and decrease, respectively, with decreasing protein content, whereas the effects of dietary macronutrients on circulating leptin levels require more research.
Their higher production performance and feed conversion efficiency make today's chickens more sus... more Their higher production performance and feed conversion efficiency make today's chickens more susceptible to heat stress than ever before. The increasing proportion of poultry production in tropical and subtropical regions makes it necessary to reconsider the long-term selection strategy of today's commercial breeding programmes. Also, the importance of the potential use of Naked neck and Frizzle genes is accentuated. Nutritional strategies aimed to alleviate the negative effects of heat stress by maintaining feed intake, electrolytic and water balance or by supplementing micronutrients such as Vitamins and minerals to satisfy the special needs during heat stress have been proven advantageous. To enhance the birds' thermotolerance by early heat conditioning or feed restriction seems to be one of the most promising management methods in enhancing the heat resistance of broiler chickens in the short run. AERTS, J-M., BERCKMANS, D., SAEVELS, P., DECUYPERE, E. and BUYSE, J. (2000) Modelling the static and dynamic responses of total heat production of broiler chickens to step changes in air temperature and light intensity. British Poultry Science 41: 651-659. AIT-BOULAHSEN, A., GARLICH, J.D. and EDENS, F.W. (1995) Potassium chloride improves the thermotolerance of chickens exposed to acute heat stress. Poultry Science 74: 75-87. ALLEMAN, F. and LECLERCQ, B. (1997) Effect of dietary protein and environmental temperature on growth performance and water consumption of male broiler chickens. British Poultry Science 38: 607-610. ALMIRALL, M., COS, R., ESTEVE-GARCIA E. and BRUFAU, J. (1997) Effect of inclusion of sugar beet pulp, pelleting and season on laying hen performance. British Poultry Science 38: 530-536. Heterophil/lymphocyte ratio as a selection criterion for heat resistance in domestic fowls. British Poultry Science 38: 159-163. ARJONA, A.A., DENBOW, D.M. and WEAVER, W.D. (1988) Effect of heat stress early in life on mortality of broilers exposed to high temperature just prior to marketing. Poultry Science 67: 226-231. Early age thermal conditioning and a dual feeding program for male broilers challenged by heat stress. Poultry Science 80: 29-36. (2004) Physiological responses of broiler chickens to heat stress and dietary electrolyte balance (sodium plus potassium minus chloride, milliequivalents per kilogram). Poultry Science 83: 1551-1558. BOTTJE, G. and HARRISON, P.C. (1985) The effects of tap water, carbonated water, sodium bicarbonate, and calcium chloride on blood acid-base balance in cockerels subjected to heat stress. Optimum dietary arginine: lysine ratio for broiler chickens in altered during heat stress in association with changes in intestinal uptake and dietary sodium chloride.
Cholecystokinin (CCK) is a short acting satiating peptide hormone produced in the proximal small ... more Cholecystokinin (CCK) is a short acting satiating peptide hormone produced in the proximal small intestine. Daily CCK injection in rats initially inhibits food intake, but after several days, food intake is no longer affected, suggesting development of tolerance. Previously, we covalently coupled CCK to a 10 kDa polyethylene glycol (mPEG-OH) and showed that this conjugate, PEG-CCK 9 , produced a significantly longer anorectic effect than unmodified CCK 9 . The present study examined whether tolerance to the anorectic effect develops during long-term administration of PEG-CCK 9 . For 14 consecutive days, male Wistar rats (n = 12) received a daily i.p injection of 8 mg kg À1 of PEG-CCK 9 and a control group received a daily control injection of mPEG-OH. Body weight and food intake were monitored daily during the experiment. Effects on the pancreas were investigated. On each day, injection of PEG-CCK 9 induced an anorectic effect lasting 3-6 h, but failed to significantly reduce daily total food intake compared to controls. The body weight gain of the PEG-CCK 9 -treated animals was not different from controls. The PEG-CCK 9 -treated group had a significantly higher pancreas weight, mainly due to hyperplasia. In conclusion, PEG-CCK 9 continued to have a daily suppressive effect on food intake when administered for 14 consecutive days, showing there was no development of tolerance. ß
As it is for mammalian species, growth hormone (GH) is indispensable for normal growth and develo... more As it is for mammalian species, growth hormone (GH) is indispensable for normal growth and development of avian species. In contrast to mammals, exogenous GH administration has little, if any, potential for improving the growth rate and feed efficiency of rapidly growing broilers; it is more likely to do so in older birds. This is at least partly because of age-related changes in tissue GH-binding activity and GH-receptor mRNA expression. The effects of GH on lipid deposition depends on the age of the bird and pattern of GH administration. Pulsatile, but not continuous, GH administration to older broilers seems to reduce fat deposition. As in rats, the bioactivity of GH might also depend on the pulse-induced cyclicity in GH receptors and GH-binding proteins. In chickens, GH is also a very potent lipolytic hormone, but seems to have no diabetogenic effect, which is reported in mammalian species. Both insulin-like growth factors have apparently no growth-promoting effects in normal growing broilers, but seem to have opposite effects on fat deposition. In contrast to GH, both insulin-like growth factors have a marked hypoglycemic effect. Whether all these effects are direct effects, or are mediated by secondary mechanisms, awaits further investigations.
Cholecystokinin, produced in the proximal small intestine, is a short acting satiating peptide ho... more Cholecystokinin, produced in the proximal small intestine, is a short acting satiating peptide hormone. CCK-10, before and after mono-iodination, was previously coupled to 10kDa polyethylene glycol (PEG). The formed conjugates PEG10kDa-CCK-10 and PEG10kDa-[(127)I]-CCK-10 show after i.p. administration to rats a sustained food intake reduction during 8h in comparison to 2h for free CCK-10. The present study examined the blood pharmacokinetics of this pharmacological interesting molecule by means of PEG10kDa-[(123)I]-CCK-10 following intravenous, intraperitoneal, intramuscular and nasal administration and the biodistribution after i.p. administration. HPLC analysis with radiometric detection allowed the differentiation between inorganic iodide and the intact tracer in blood. Blood kinetics after i.v. injection was fitted to a bi-exponential with a distribution half-life of 15 min and with an elimination half-life of 8 hours for intact PEG10kDa-[(123)I]-CCK-10. The biodistribution studies showed a higher accumulation of the tracer for all administration routes in organs expressing CCK receptors localized in the gastrointestinal tract such as pancreas, duodenum and small intestine. No indication of blood brain barrier crossing for the conjugate could be observed independently of the administration route. Main clearance was via the urinary pathway.
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2006
Two trials were conducted to evaluate the effects of short-term administration of corticosterone ... more Two trials were conducted to evaluate the effects of short-term administration of corticosterone (CORT) on the induction of oxidative injury in broiler chickens (Gallus gallus domesticus). Twelve broiler chickens of 30 and of 40 days of age were respectively employed in Trial 1 and 2. Half of the chickens were administered subcutaneously with CORT (4 mg/kg body weight [BW] in corn oil), while another half served as controls (corn oil) in each trail. In Trial 1, a blood sample was obtained from each chicken immediately before administration and at 1 and 3 h after injection. In Trial 2, the liver and heart were obtained after 3 h of CORT exposure. Short-term administration of CORT resulted in enhanced proteolysis and gluconeogenesis. There were no obvious changes in lipid peroxidation status of the heart and liver, whereas a decrease in lipid peroxidation in the plasma was observed after acute CORT exposure. The significantly increased plasma nonenzymatic antioxidants (uric acid [UA] and total antioxidant capacity) in concert with the enhanced enzymatic antioxidant activity (SOD in heart) during short-term CORT administration indicate preventive changes to counteract the oxidative injury, and these may be tissue specific.
Protein assimilation and metabolism studies are hindered by the lack of an adequate oral tracer, ... more Protein assimilation and metabolism studies are hindered by the lack of an adequate oral tracer, i.e., labeled proteins. We present a new and easily reproducible methodology for producing large amounts of egg proteins labeled with L-leucine-13C1. Laying hens were fed a 0.2% leucine-deficient food supplemented with 0.2% L-leucine-13C1 (99 atom %). At plateau, eggs containing highly enriched proteins were obtained. The 13C content of egg white relative to the total C content was 1.3371 atom %, corresponding to delta = 206%. The overall tracer recovery in egg proteins was high (40.2%), making this method financially attractive as well. Accurately measurable levels of 13CO2 in breath were obtained after ingestion of a physiological load of labeled egg white proteins. Thus, egg proteins with sufficient 13C enrichment and applicable for human protein assimilation and metabolism kinetic studies were produced in an easily reproducible and highly efficient manner.
Daily changes in the concentrations of plasma corticosterone, prolactin, thyroid hormones and som... more Daily changes in the concentrations of plasma corticosterone, prolactin, thyroid hormones and somatomedin C were measured in 28-day-old fat and lean lines of broilers produced by selection for high and low concentrations of very low density lipoproteins (VLDL). The effects of daily injections of corticosterone on the concentrations of these hormones and on fattening were compared in the two lines. The selection procedure had no effect on the concentrations of any of the hormones. However, daily rhythms in concentrations of plasma corticosterone, tri-iodothyronine (T3) and prolactin were less often observed in the fat line than in the lean line. No differences were seen between lines in the daily rhythms in plasma thyroxine (T4) and somatomedin C. Daily injections of 2500 micrograms corticosterone/kg body weight, in both lines, depressed mean concentrations of plasma prolactin, T3 and somatomedin C and body weight. This dose of corticosterone also increased abdominal fat pad and liver weights expressed as a percentage of body weight. The liver and fat pad responses to 2500 micrograms corticosterone in both lines were greater when the steroid was injected at the end rather than towards the beginning of the 14-h daily photoperiod. There was no difference between the lines in the fattening response to corticosterone. Lower doses of 100 and 500 micrograms corticosterone per day did not induce fattening or affect concentrations of plasma prolactin. They did, however, depress concentrations of plasma T3. Concentrations of plasma T4 were increased in both lines treated with 2500, but not with 100 or 500 micrograms corticosterone, towards the beginning of the daily photoperiod.(ABSTRACT TRUNCATED AT 250 WORDS)
1. Differences in responses to lipolytic agents have been investigated in vitro in abdominal adip... more 1. Differences in responses to lipolytic agents have been investigated in vitro in abdominal adipose tissue from lines of broiler chickens selected for body weight (GL, a &#39;fat&#39; line) or for food efficiency (FC, a &#39;lean&#39; line). 2. Dibutyryl cyclic adenosine monophosphate stimulated in vitro lipolysis, as measured by the glycerol release, by adipose tissue from GL or from FC chickens to the same extent. 3. Glucagon stimulated glycerol release from adipose tissue from FC chickens, but not from GL chickens. 4. Adipose tissue from GL chickens was much more sensitive to chicken growth hormone (GH) compared to FC chickens. 5. It is concluded that the selection criteria applied influenced the number of adipose GH and glucagon receptors, the number of adipose GH receptors being lower and of glucagon receptors being higher in FC chickens compared to GL chickens.
Previously, overall protein assimilation after the ingestion of a pure protein meal was studied. ... more Previously, overall protein assimilation after the ingestion of a pure protein meal was studied. In this study, the kinetics of protein assimilation in humans were investigated after the ingestion of a complex meal, which more closely represents a physiologically normal situation. Overall protein assimilation in humans after the ingestion of a pancake meal, containing 12 g of fat, 27 g of carbohydrate, and 19 g of protein, was evaluated in 26 normal volunteers. Both the egg white and yolk of L-[1-(13)C]-leucine-substituted eggs were used to make the batter. The labeled eggs were produced by feeding laying hens a standard chicken diet supplemented with 3 g/kg of L-[1-(13)C]-leucine (99%, mol:mol). High enrichment levels of protein with adequate labeling patterns were obtained in eggs from laying hens fed the L-[1-(13)C]-leucine-substituted diet. The isotopic enrichment of leucine at plateau was equal in egg white and yolk. The overall tracer recovery in egg proteins was 22.5%. The ov...
The health benefits of omega-3 polyunsaturated fatty acids (n−3 PUFA) are generally recognized. U... more The health benefits of omega-3 polyunsaturated fatty acids (n−3 PUFA) are generally recognized. Unfortunately, in most western countries, the recommended daily intake of these compounds is rarely met. Therefore, enrichment of commonly occurring foods can boost intake of these fatty acids. In this regard, eggs are an interesting target, as they form an integral part of the diet. Their n−3 PUFA profile can be modified through feed supplementation. A traditional n−3 PUFA source to be added to hens' diet is flaxseed, a plant source rich in α-linolenic acid. Alternatively, hens are often fed fish oil, which is rich in long chain n−3 PUFA eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA). A more recent trend is feed supplementation with microalgae as a source of EPA and/or DHA. In this paper, recent scientific literature concerning n−3 PUFA enrichment in eggs is reviewed, giving an overview of advantages and disadvantages of the different approaches.
Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology, Jan 21, 2015
The 5'-adenosine monophosphate-activated protein kinase (AMPK) plays a key role in rapid meta... more The 5'-adenosine monophosphate-activated protein kinase (AMPK) plays a key role in rapid metabolic adaptations to maintain energy homeostasis in poultry. It remains unclear if AMPK is involved in muscular energy metabolism in broiler chickens. Hence, in the present study, seven-day-old male broilers were equally divided into three groups: fed ad libitum (control); feed-deprived for 24 h (S24); feed-deprived for 24 h and then refed for 24 h (S24R24). Compared to the control group, the plasma levels of glucose, insulin, T3 and triglycerides in the S24 group were significantly lower (P<0.05), whereas the uric acid levels were significantly higher (P<0.01). Except for glucose, refeeding for 24 h reversed the fasting-induced alterations in plasma metabolite. Fasting decreased the liver kinase B1 (LKB1), AMPK alpha 2 subunit (AMPKα2), and fatty acid synthase (FAS) mRNA levels (P<0.05) in M. pectoralis major (PM). Feed deprivation did not affect the phosphoryulated AKT, mammal...
What is the central question of this study? Prenatal protein undernutrition by albumen removal in... more What is the central question of this study? Prenatal protein undernutrition by albumen removal in an avian model of fetal programming leads to long-term programming effects, but when do these effects first appear and are these programming effects regulated by the same candidate genes as in mammals? What is the main finding and its importance? The present results indicate that prenatal protein undernutrition by albumen removal induces phenotypical and hormonal changes in the early posthatch period, when the mismatch between the prenatal and postnatal environment first arises, but these changes are not accompanied by an altered gene expression of the selected candidate genes. Studies of the chicken offer a unique model for investigation of the direct effects of reduced prenatal protein availability by the partial replacement of albumen with saline in eggs at embryonic day 1 (albumen-deprived group). The results were compared with mock-treated sham chicks and non-treated control chicks...
In chickens, metabolism is influenced by environmental factors and of particular interest nutriti... more In chickens, metabolism is influenced by environmental factors and of particular interest nutritional factors, such as diet quantity and composition. With respect to the dietary macronutrients, literature clearly shows that in isoenergetically formulated diets, the protein level has a pronounced effect on metabolism, whereas fat and carbohydrate concentrations play a limited role. A decreased dietary protein level results in depressed growth rates, with reduced carcass gains in both water and protein content. In spite of the lower protein retention in chickens fed low protein diets, the efficiency of utilization of dietary protein appears to be increased. This indicates an inverse relationship between protein intake and utilization, which is reflected in decreased circulating uric acid levels. In addition, feed intake is increased, at least when protein levels are slightly reduced, leading to an involuntary overconsumption of energy compared to protein. The chickens deal with this excess energy consumption by increasing de novo lipogenesis and fat deposition, which is supported by increased plasma triglyceride concentrations, and heat production is increased. In contrast to adult mammals, the dietary macronutrients have no effect on diet-induced thermogenesis, nor is there any relationship between diet-induced thermogenesis and feed intake. Plasma growth hormone levels are higher in chickens reared on a low protein diet, indicating a causal relationship between growth hormone secretion and protein efficiency. In spite of the increased growth hormone levels, plasma insulin-like growth factor concentrations are lowered in low protein reared chickens, and may be partially responsible for the reduced growth rate observed in these animals. Plasma corticosterone concentrations are augmented in chickens on low protein diets, despite a decline in the ACTH concentration. Finally, plasma T 3 and T 4 levels are well known to increase and decrease, respectively, with decreasing protein content, whereas the effects of dietary macronutrients on circulating leptin levels require more research.
Their higher production performance and feed conversion efficiency make today's chickens more sus... more Their higher production performance and feed conversion efficiency make today's chickens more susceptible to heat stress than ever before. The increasing proportion of poultry production in tropical and subtropical regions makes it necessary to reconsider the long-term selection strategy of today's commercial breeding programmes. Also, the importance of the potential use of Naked neck and Frizzle genes is accentuated. Nutritional strategies aimed to alleviate the negative effects of heat stress by maintaining feed intake, electrolytic and water balance or by supplementing micronutrients such as Vitamins and minerals to satisfy the special needs during heat stress have been proven advantageous. To enhance the birds' thermotolerance by early heat conditioning or feed restriction seems to be one of the most promising management methods in enhancing the heat resistance of broiler chickens in the short run. AERTS, J-M., BERCKMANS, D., SAEVELS, P., DECUYPERE, E. and BUYSE, J. (2000) Modelling the static and dynamic responses of total heat production of broiler chickens to step changes in air temperature and light intensity. British Poultry Science 41: 651-659. AIT-BOULAHSEN, A., GARLICH, J.D. and EDENS, F.W. (1995) Potassium chloride improves the thermotolerance of chickens exposed to acute heat stress. Poultry Science 74: 75-87. ALLEMAN, F. and LECLERCQ, B. (1997) Effect of dietary protein and environmental temperature on growth performance and water consumption of male broiler chickens. British Poultry Science 38: 607-610. ALMIRALL, M., COS, R., ESTEVE-GARCIA E. and BRUFAU, J. (1997) Effect of inclusion of sugar beet pulp, pelleting and season on laying hen performance. British Poultry Science 38: 530-536. Heterophil/lymphocyte ratio as a selection criterion for heat resistance in domestic fowls. British Poultry Science 38: 159-163. ARJONA, A.A., DENBOW, D.M. and WEAVER, W.D. (1988) Effect of heat stress early in life on mortality of broilers exposed to high temperature just prior to marketing. Poultry Science 67: 226-231. Early age thermal conditioning and a dual feeding program for male broilers challenged by heat stress. Poultry Science 80: 29-36. (2004) Physiological responses of broiler chickens to heat stress and dietary electrolyte balance (sodium plus potassium minus chloride, milliequivalents per kilogram). Poultry Science 83: 1551-1558. BOTTJE, G. and HARRISON, P.C. (1985) The effects of tap water, carbonated water, sodium bicarbonate, and calcium chloride on blood acid-base balance in cockerels subjected to heat stress. Optimum dietary arginine: lysine ratio for broiler chickens in altered during heat stress in association with changes in intestinal uptake and dietary sodium chloride.
Cholecystokinin (CCK) is a short acting satiating peptide hormone produced in the proximal small ... more Cholecystokinin (CCK) is a short acting satiating peptide hormone produced in the proximal small intestine. Daily CCK injection in rats initially inhibits food intake, but after several days, food intake is no longer affected, suggesting development of tolerance. Previously, we covalently coupled CCK to a 10 kDa polyethylene glycol (mPEG-OH) and showed that this conjugate, PEG-CCK 9 , produced a significantly longer anorectic effect than unmodified CCK 9 . The present study examined whether tolerance to the anorectic effect develops during long-term administration of PEG-CCK 9 . For 14 consecutive days, male Wistar rats (n = 12) received a daily i.p injection of 8 mg kg À1 of PEG-CCK 9 and a control group received a daily control injection of mPEG-OH. Body weight and food intake were monitored daily during the experiment. Effects on the pancreas were investigated. On each day, injection of PEG-CCK 9 induced an anorectic effect lasting 3-6 h, but failed to significantly reduce daily total food intake compared to controls. The body weight gain of the PEG-CCK 9 -treated animals was not different from controls. The PEG-CCK 9 -treated group had a significantly higher pancreas weight, mainly due to hyperplasia. In conclusion, PEG-CCK 9 continued to have a daily suppressive effect on food intake when administered for 14 consecutive days, showing there was no development of tolerance. ß
As it is for mammalian species, growth hormone (GH) is indispensable for normal growth and develo... more As it is for mammalian species, growth hormone (GH) is indispensable for normal growth and development of avian species. In contrast to mammals, exogenous GH administration has little, if any, potential for improving the growth rate and feed efficiency of rapidly growing broilers; it is more likely to do so in older birds. This is at least partly because of age-related changes in tissue GH-binding activity and GH-receptor mRNA expression. The effects of GH on lipid deposition depends on the age of the bird and pattern of GH administration. Pulsatile, but not continuous, GH administration to older broilers seems to reduce fat deposition. As in rats, the bioactivity of GH might also depend on the pulse-induced cyclicity in GH receptors and GH-binding proteins. In chickens, GH is also a very potent lipolytic hormone, but seems to have no diabetogenic effect, which is reported in mammalian species. Both insulin-like growth factors have apparently no growth-promoting effects in normal growing broilers, but seem to have opposite effects on fat deposition. In contrast to GH, both insulin-like growth factors have a marked hypoglycemic effect. Whether all these effects are direct effects, or are mediated by secondary mechanisms, awaits further investigations.
Cholecystokinin, produced in the proximal small intestine, is a short acting satiating peptide ho... more Cholecystokinin, produced in the proximal small intestine, is a short acting satiating peptide hormone. CCK-10, before and after mono-iodination, was previously coupled to 10kDa polyethylene glycol (PEG). The formed conjugates PEG10kDa-CCK-10 and PEG10kDa-[(127)I]-CCK-10 show after i.p. administration to rats a sustained food intake reduction during 8h in comparison to 2h for free CCK-10. The present study examined the blood pharmacokinetics of this pharmacological interesting molecule by means of PEG10kDa-[(123)I]-CCK-10 following intravenous, intraperitoneal, intramuscular and nasal administration and the biodistribution after i.p. administration. HPLC analysis with radiometric detection allowed the differentiation between inorganic iodide and the intact tracer in blood. Blood kinetics after i.v. injection was fitted to a bi-exponential with a distribution half-life of 15 min and with an elimination half-life of 8 hours for intact PEG10kDa-[(123)I]-CCK-10. The biodistribution studies showed a higher accumulation of the tracer for all administration routes in organs expressing CCK receptors localized in the gastrointestinal tract such as pancreas, duodenum and small intestine. No indication of blood brain barrier crossing for the conjugate could be observed independently of the administration route. Main clearance was via the urinary pathway.
Comparative Biochemistry and Physiology Part A: Molecular & Integrative Physiology, 2006
Two trials were conducted to evaluate the effects of short-term administration of corticosterone ... more Two trials were conducted to evaluate the effects of short-term administration of corticosterone (CORT) on the induction of oxidative injury in broiler chickens (Gallus gallus domesticus). Twelve broiler chickens of 30 and of 40 days of age were respectively employed in Trial 1 and 2. Half of the chickens were administered subcutaneously with CORT (4 mg/kg body weight [BW] in corn oil), while another half served as controls (corn oil) in each trail. In Trial 1, a blood sample was obtained from each chicken immediately before administration and at 1 and 3 h after injection. In Trial 2, the liver and heart were obtained after 3 h of CORT exposure. Short-term administration of CORT resulted in enhanced proteolysis and gluconeogenesis. There were no obvious changes in lipid peroxidation status of the heart and liver, whereas a decrease in lipid peroxidation in the plasma was observed after acute CORT exposure. The significantly increased plasma nonenzymatic antioxidants (uric acid [UA] and total antioxidant capacity) in concert with the enhanced enzymatic antioxidant activity (SOD in heart) during short-term CORT administration indicate preventive changes to counteract the oxidative injury, and these may be tissue specific.
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Papers by Johan Buyse