Metabolism Of Chickens Research Articles

한국재래닭의 ADSL 유전자 내 단일염기변이를 이용한 경제형질과의 연관성 분석

Adenylosuccinate lyase (ADSL) deficiency is a disease of purine metabolism which affects patients both bioche- micall and behaviorally. An obstacle of this purine nucleotide cycle(PNC) can be caused brain functional disorder and growth disorder. So ADSL deficiency, which is associated with sever mental retardation, autistic features and energy metabolism. This study was performed to identify SNP on ADSL gene in chicken. The nucleotides were observed as T to C (7724 th nucleotide), C to T nd nucleotide), G to T (10108 th nucleotide), A to T (10356 th nucleotide), G to A(10375 th nucleotide), A to C (10402 nd nucleotide), A to T (12716 th nucleotide), T to A (12717 th nucleotide), C to T (15491 st nucleotide), C to T (15542 nd nucleotide) and C to T (15550 th nucleotide). The nucleotide substitutions at 15542 nd and 15550 th (GeneBank accession no. AY665559) were found as missense mutation (alanine valine, proline serine, respectively). This study will be useful for farther researches for identi- fying association between these SNPs and energy metabolism in chicken. The C15550T SNP showed three genotypes, CC, CT, TT by digestion with the genotype TT had significantly faster the first lay day (150.0) than CT (162.0, P<0.05) and genotype TT (150.0, P<0.05) had significantly higher the egg production rate than CT (172.4, P<0.05). According to result of this study, a C15550T was found to have a significantly effect first lay day and mean egg production. It will be possible to use SNP marker on selecting chicken to improve important economic traits, which is the first lay day and mean egg production.

Effects of energy restriction on thyroid hormone metabolism in chickens

Energy restriction induces changes in thyroid hormone economy in the form of a complex adaptation mechanism, in order to conserve energy storage and protein reserves. In the present work, thyroid hormone serum concentrations, hepatic deiodinase enzyme activities and hepatic deiodinase mRNA expression were examined after feed restriction and fasting. We demonstrate that during energy restriction, T 3 concentration is lowered due to a decreased T 4 activation and increased T 3 inactivation. We show that hepatic type-I deiodinase (D1) is not affected by energy restriction, however, hepatic D2 is decreased on both transcriptional and enzyme activity levels. Furthermore, hepatic D3 is increased after feed restriction in the liver. We also show that the hypothalamic feedback is not involved in the changes in serum T 3 and T 4 concentrations. Our data indicate that D2 enzyme contributes to the special hormone-exporting role of the chicken liver and this enzyme can be modulated by feed restriction.

Effects of simultaneous repeated exposure at high levels of arsenic and malathion on hepatic drug-biotransforming enzymes in broiler chickens

Groundwater contamination with arsenic is a major global health concern. The organophosphorus insecticide malathion has gained significance as an environmental pollutant due to its widespread use in agriculture, grain storage, ectoparasite control and public health management. The deleterious effects produced by arsenic or malathion alone are documented, but very little is known about the consequences of their coexposure. The aim of the current study was to examine the effects of repeated simultaneous exposure to arsenic and malathion on drug-biotransforming enzymes in the liver of broiler chickens. One-month-old broiler chickens were exposed daily to arsenic (50 ppm)-supplemented drinking water, malathion (500 ppm)-mixed diet or in a similar fashion coexposed to these agents for 28 days. At the term, changes in body weight, organ weights, and levels of hepatic cytochrome P450 (CYP), cytochrome b 5 , microsomal and cytosolic proteins; aminopyrine N-demethylase (ANDM), aniline P-hydroxylase (APH), glutathione S-transferase (GST) and uridine diphosphate glucuronosyltransferase (UGT) were assessed. Arsenic, malathion or their coexposure decreased the body weight gain and liver weight. Brain weight (relative) was increased with arsenic or malathion, but not with the coexposure. Treatment with arsenic decreased the CYP and cytochrome b 5 contents by 39 and 36%, than with malathion by 54 and 22% and the coexposure by 45 and 28%, respectively. The ANDM activity was decreased with arsenic (44%), malathion (23%) and the coexposure (32%). Arsenic (23%) and the coexposure (37%), but not malathion (14%), reduced the APH activity. The activities of hepatic microsomal and cytosolic GST were increased with all the three treatments [Arsenic (microsomal: 88% cytosolic: 113%), malathion (microsomal: 137%, cytosolic: 94%) and coexposure (microsomal: 140%, cytosolic: 148%)]. These treatments did not significantly affect the hepatic UGT activity, but reduced the hepatic microsomal (arsenic: 28%, malathion: 34% and coexposure: 43%) and cytosolic (17–19%) protein contents. The effects of coexposure on the activities of various phase I and phase II drug-biotransforming enzymes were almost similar to that of arsenic or malathion. This study provides evidence that repeated coexposure to arsenic and malathion may influence the extent of drug metabolism in chickens.

The effect of humic acid on zinc accumulation in chicken broiler tissues

Thirty-six selected male chickens were allocated into four groups C, HA, ZN, ZN + HA, and the experiment was initiated after 4 days of an adaptation period. Group C was fed a complete feed mixture without supplements. Group HA was fed the same diet with 500 mg of humic acid per chicken and day. Group ZN was loaded with 240 mg Zn (as 600 mg ZnSO&lt;sub&gt;4&lt;/sub&gt;) per chicken and day, and birds of the group ZN + HA were loaded as those of the latter group, with additional 500 mg of humic acid per chicken and day. The treatments were carried out for 10 days. Subsequently, the chickens were slaughtered and samples of liver, kidneys, leg muscles and blood were collected for Zn level assessment. The Zn levels detected in group C can be considered as the background value, found commonly in broiler chickens fed the complete feed mixtures enriched with trace elements. The following concentrations were detected (mg Zn/kg): 40.1 ± 13.4 in muscles, 81.0 ± 6.6 in kidneys, 72.2 ± 15.0 in liver, and in blood serum 1.04 ± 0.45 mg Zn/l. Increased Zn levels by 11 to 30% (&lt;i&gt;P&lt;/i&gt; &gt; 0.05) compared to group C were found in group HA in all tissues studied. The ten-day treatment with 600 mg ZnSO&lt;sub&gt;4&lt;/sub&gt; (240 mg Zn/day, i.e. 2 400 mg Zn per 10 days) resulted in increased Zn levels in all investigated tissues, significantly in kidneys (&lt;i&gt;P&lt;/i&gt; &lt; 0.01), liver (&lt;i&gt;P&lt;/i&gt; &lt; 0.01) and blood serum (&lt;i&gt;P&lt;/i&gt; &lt; 0.01). The mean levels 430.5 ± 159.0, 149.8 ± 41.9 and 57.9 ± 22.7 mg Zn/kg, and 4.14 ± 0.9 mg/l were found in liver, kidneys, leg muscles, and blood serum, respectively. After the same treatment with zinc sulphate together with humic acid (group ZN + HA), no significant changes of Zn levels in the investigated tissues were reported. Concentrations of the selected parameters of metabolism in chickens ranged within the reference limits; significant differences between experimental and control groups (cholesterol &lt;i&gt;P&lt;/i&gt; &lt; 0.05; lactate &lt;i&gt;P&lt;/i&gt; &lt; 0.05; calcium &lt;i&gt;P&lt;/i&gt; &lt; 0.01) were found sporadically.

Conjugated Linoleic Acid as a Key Regulator of Performance, Lipid Metabolism, Development, Stress and Immune Functions, and Gene Expression in Chickens

: It has been well documented from animal and human studies that conjugated linoleic acid (CLA) has numerous beneficial effects on health. In chickens, CLA exerts many effects on performance ranging from egg quality and yolk lipids to meat quality. Although there are several CLA isomers available, not all CLA isomers have the same incorporation rates into egg yolk: cis-9,trans-11 and trans-10,cis-12 CLA isomers are more favorably deposited into egg yolk than other isomers investigated, but of the two isomers, the former has a higher incorporation rate than the latter. CLA alters the amounts and profiles of lipids in plasma, muscles and liver. Furthermore, increased liver weight was reported in chickens fed dietary CLA. As observed in egg yolk, marked reduction in intramuscular lipids as well as increased protein content was observed in different studies, leading to elevation in protein-to-fat ratio. Inconsistency exists for parameters such as body weight gain, feed intake, feed conversion ratio, egg production rate and mortality, depending upon experimental conditions. One setback is that hard-cooked yolks from CLA-consuming hens have higher firmness as refrigeration time and CLA are increased, perhaps owing to alterations in physico-chemistry of yolk. Another is that CLA can be detrimental to hatchability when provided to breeders: eggs from these breeders have impaired development in embryonic and neonatal stages, and have increased and decreased amounts of saturated fatty acids and monounsaturated fatty acids (MUFAs), respectively. Thus, both problems can be fully resolved if dietary sources rich in MUFAs are provided together with CLA. Emerging evidence suggests that CLA exerts a critical impact on stress and immune functions as it can completely nullify some of the adverse effects produced by immune challenges and reduce mortality in a dose-dependent manner. Finally, CLA is a key regulator of genes that may be responsible for lipid metabolism in chickens. CLA down-regulates both expression of the gene encoding stearoyl-CoA desaturase-1 and its protein activity in the chicken liver while up-regulating mRNA of sterol regulatory element-binding protein-1.

Effects of dietary phytase on performance and nutrient metabolism in chickens

1. A broiler growth study was conducted to compare the effect of different concentrations of an Escherichia coli-derived phytase on performance, apparent metabolisable energy (AME), nitrogen (N), amino acid and mineral metabolisability, sialic acid excretion and villus morphology when fed to broiler chickens. 2. Female Ross 308 broilers (480) were reared in floor pens from 0 to 28 d of age. All birds were fed on nutritionally complete starter (0 to 21 d of age) and grower diets (21 to 28 d of age) with the exception that they were low in P (28 and 23 g/kg available P, respectively). These maize–soy diets were supplemented with 0, 250, 500 or 2500 phytase units (FTU)/kg feed. 3. Between 21 and 28 d of age, two birds from each floor pen were selected, and each pair placed in one of 32 metabolism cages (two birds per cage). Feed intake was recorded and excreta collected for the last 2 d of the feeding period, and AME, N, amino acid and mineral metabolisability coefficients and endogenous losses were determined following a total collection procedure. 4. Feed intake and weight gain increased in a linear manner in response to phytase dose, with an average increase of approximately 11·7 and 13·5%, respectively, compared with chickens fed on the low-P diet. Birds given diets with 2500 FTU weighed 6·6% more and had a 2·4% higher feed conversion efficiency (FCE) than those fed on diets containing 500 FTU. 5. Enzyme supplementation increased the intake of AME and metabolisable N by 10·3 and 3·9%, respectively, principally through increases in feed intake. Birds given enzyme-supplemented diets also improved their intake of metabolisable amino acids and P by approximately 14 and 12·4%, respectively, compared with birds fed on the control diet. Enzyme supplementation did not affect ileal villus morphometry of the birds. †Dr O. Oduguwa is visiting scientist from University of Agriculture, PMB 2240, Abeokuta, Nigeria.

Distinct features of dehydrocorticosterone reduction into corticosterone in the liver and duodenum of the domestic fowl ( Gallus gallus domesticus)

The mammalian 11-β hydroxysteroid dehydrogenase type 1 (11βHSD1) reduces glucocorticoids (GC) at C11 from the 11-keto-GC nonactive form to the 11-hydroxy-GC active form, an action essential for survival. Whereas GC metabolism at C11 and the role of 11βHSD1 are studied extensively in mammals, information about these in birds is scattered. Herein, we report the GC bidirectional metabolism in chickens. In hens’ liver and duodenal mucosa, 11βHSD1-like mRNA expression was detected; and 11βHSD1-like immunoreactivity was found linked to membranes of hepatocytes and duodenal enterocytes. With either NADH or NADPH, the membranal fraction of liver and duodenal mucosa converted dehydrocorticosterone (A) into corticosterone (B) with K m (1.1–8.7 μM) and V max (10–40 pmol/mg protein/min) values similar to those reported for mammalian 11βHSD1. In the presence of NADP + or NAD +, these membranal fractions oxidized B into A. With either NADPH or NADH, the cytosol of chicken liver and duodenal mucosa reduced A into B ( K m of 1.1 – 2.3 μM and V max of 260–960 pmol/mg protein/min). These cytosolic fractions did not convert any amount of B into A when incubated with either NADP + or NAD +. This may suggest that chicken liver and duodenal mucosa express 11βHSD1 that is a membrane-bound oxoreductase which uses both NADPH/NADP + and NADH/NAD + as cosubstrates. The substantial reduction of A into B (but no conversion of B into A) found in the cytosol is most likely executed by a unidirectional soluble reductase, different than 11βHSD1.

Effect of chronic oxidative/corticosterone‐induced stress on ascorbic acid metabolism and total antioxidant capacity in chickens (Gallus gallus domesticus)

The consequences of chronic corticosterone-induced stress (CCIS) on ascorbic acid (AsA) metabolism in chickens, an animal that syntheses the vitamin, are not known. This study was conducted to determine whether CCIS alters AsA synthesis, as measured by l-gulonolactone oxidase (GLO) activity, tissue AsA, lipid peroxides and tissue total antioxidant capacity (TAC). Stress was induced by dietary administration of corticosterone from 2 to 4 weeks of age and measurements were made at 0, 7 and 14 days post-treatment. Ascorbic acid synthesis was not influenced by CCIS but hepatic, cardiac, renal, bursal and duodenal AsA concentrations were significantly decreased and plasma TAC and uric acid concentrations were significantly elevated. Stress caused significant hepatomegaly and hepatic lipidosis but hepatic peroxides were not elevated despite the slight decrease in hepatic TAC. Tissue TAC varied in different organs. It was markedly elevated in the kidney, reduced by 49% in the spleen, and changes were not detected in the heart and duodenum even though AsA concentration was significantly decreased in all tissues. We conclude that CCIS caused a significant reduction in tissue AsA concentration but did not inhibit GLO activity. The change in AsA concentration was associated with increase, decrease or no change in TAC in tissues examined. The findings suggest that CCIS may alter AsA recycling, influx or turnover in different tissues of chickens.

The Effects of Dietary Chitosan on Liver Lipid Concentrations in Broiler Chickens Treated with Propylthiouracil

Chitosan, a polymer of glucosamine, decrease the absorption of dietary fat and then reduce the abdominal fat deposition in broiler chickens. Chitosan is digested by hens and broilers. Thus, chitosan may decrease lipogenesis and triglyceride (TG) synthesis in the liver. However, little research has been done to determine whether dietary chitosan regulate hepatic lipid metabolism in chickens. Administration of antithyroid agent such as propylthiouracil (PTU) induces excessive lipid deposition in livers of chickens. The present experiment was conducted to determine the effect of dietary chitosan on liver lipid concentrations in broiler chickens fed on PTU containing diets. Male broiler chickens at 14d old were fed on the basal diet based on corn and soybean meal or a PTU containing (0.03%) diets supplemented with or without 5% chitosan for 2 weeks. Administration of PTU increased (P<0.05) thyroid weight, liver weight and the contents of total lipid and TG in the liver. Dietary chitosan did not affect feed intake, body weight gain, feed efficiency, thyroid weight, liver weight and plasma TG concentration, but decreased (P<0.05) the contents of total lipid and TG in the liver regardless of dietary PTU treatment. These results suggest that dietary chitosan may not affect excessive lipid deposition in the liver induced by PTU, although a part of dietary chitosan may be absorbed and reduce lipogenesis and TG synthesis in the liver in broiler chickens.

Sequential Feeding Programs for Broiler Chickens: Twenty-Four- and Forty-Eight-Hour Cycles

Sequential feeding programs (Seq) of 2 feeds, 1 protein rich-energy poor and 1 energy rich-protein poor, during the same day or every other day were compared with a control complete diet for male broiler growth and body composition from 15 d to market weight. In experiment 1, BW gain and breast meat yield were significantly lower than those of controls for 24-h-cycle Seq with extreme protein content difference between the 2 feeds. BW gain and breast meat yield were higher than those of controls when feeds with moderate differences [feed moderately rich in protein (PM) = 26% CP; feed moderately rich in energy (EM) = 16% CP] were fed. Feeding periods that were half as long but changed twice as frequently gave less favorable results. In experiment 2, effects of allowing access to feed for different lengths of time were measured. The treatments in a 24-h cycle were a constant control diet, 50% PM-50% EM, 40% PM-60% EM, or 80% PM-20% EM decreasing to 40% PM-60% EM. Chickens fed 40% PM-60% EM had a 6% lower BW gain and a 3% higher feed/gain ratio and were fatter than those from other treatments. In experiment 3, male chickens fed a 48-h-cycle Seq of EM and PM every other day had the same BW gain, feed intake, and feed/gain ratio as controls. In experiment 4, five 48-h-cycle Seq with varying differences of energy and protein contents between EM and PM gave similar or slight reduction of performances compared with controls. A field trial with 8 flocks of broilers confirmed that feeding high and low protein feeds on alternate days resulted in performance similar to that from feeding a complete feed despite large day-to-day variations in lysine intake. Converse to shorter phases, Seq for 48-h cycles offers new opportunities for practical application and also for studies of short-term regulation of protein and lipid metabolism in chickens.

Systems-wide chicken DNA microarrays, gene expression profiling, and discovery of functional genes

The goal of our current consortium project is to launch a new era-functional genomics of poultry-by providing genomic resources [expressed sequence tags (EST) and DNA microarrays] and by examining global gene expression in target tissues of chickens. DNA microarray analysis has been a fruitful strategy for the identification of functional genes in several model organisms (i.e., human, rodents, fruit fly, etc.). We have constructed and normalized five tissue-specific or multiple-tissue chicken cDNA libraries [liver, fat, breast, and leg muscle/epiphyseal growth plate, pituitary/hypothalamus/pineal, and reproductive tract (oviduct/ovary/testes)] for high-throughput DNA sequencing of EST. DNA sequence clustering was used to build contigs of overlapping sequence and to identify unique, non-redundant EST clones (unigenes), which permitted printing of systems-wide chicken DNA microarrays. One of the most promising genetic resources for gene exploration and functional gene mapping is provided by two sets of experimental lines of broiler-type chickens developed at INRA, France, by divergent selection for extremes in growth traits (fast-growing versus slow-growing; fatness versus leanness at a similar growth rate). We are using DNA microarrays for global gene expression profiling to identify candidate genes and to map growth, metabolic, and regulatory pathways that control important production traits. Candidate genes will be used for functional gene mapping and QTL analysis of F2 progeny from intercrosses made between divergent genetic lines (fat × lean lines; fast-growing × slow-growing lines). Using our first chicken liver microarray, we have already identified several interesting differentially expressed genes in commercial broilers and in divergently selected broiler lines. Many of these candidate genes are involved in the lipogenic pathway and are controlled in part by the thyrotropic axis. Thus, genome-wide transcriptional profiling is a powerful tool used to visualize the cascade of genetic circuits that govern complex biological responses. Global gene expression profiling and QTL scans should enable us to functionally map the genetic pathways that control growth, development, and metabolism of chickens. This emerging technology will have broad applications for poultry breeding programs (i.e., use of molecular markers) and for future production systems (i.e., the health and welfare of birds and the quality of poultry products).

Preparation of Monoclonal Antibody Against Chicken Apolipoprotein B and Development of Enzyme Liked Immunosolvent Assay (ELISA) Method with the Antibody Aiming at the Optimization of Lipid Metabolism in Chickens

Apolipoprotein B (apoB) containing lipoproteins are major lipoproteins in blood and the elevated concentration in plasma may lead to increased transport of lipoproteins into adipose tissues resulting in the excessive fat deposition. Aims of the present study were to prepare monoclonal antibodies against chicken apoB and to development enzyme linked mmunosolvent assay (ELISA) methods with the antibody which would be provided for studies on lipoprotein metabolism in chickens. A monoclonal antibody, CAB4, was prepared using a purified chicken apoB and specific reactivity of the antibody was verified by Western blot analysis and immuno-precipitation of apoB in plasma and primary hepatocyte cultures in chickens. ELISA method with monoclonal anti-chicken apoB antibody developed in this study was applicable to measure apoB concentration in plasma and cell cultures within the range of 0 to 500ng/ml with the intra- and inter-assay variation of less than 10.6%. Using the present ELISA method, plasma apoB concentrations in broiler chickens starved for 8h were shown to be 0.44mg/ml against 1.02mg/ml in fed chicken counterparts. The monoclonal antibodies against chicken apoB and ELISA method developed in the present study could be potentially used for studies on the lipoprotein metabolism focusing on the optimization of lipid metabolism in chickens.

The combined effects of novel tocotrienols and lovastatin on lipid metabolism in chickens

Both lovastatin (a fungal product) and a tocotrienol rich fraction (TRF 25, a mixture of tocols isolated from stabilized and heated rice bran containing desmethyl [ d-P 21-T3] and didesmethyl [ d-P 25-T3] tocotrienols) are potent hypocholesterolemic agents, although they suppress cholesterol biosynthesis by different mechanisms. To determine additive and/or synergistic effects of both agents, chickens were fed diets supplemented with 50 ppm TRF 25 or d-P 25-T3 in combination with 50 ppm lovastatin for 4 weeks. Combinations of d-P 25-T3 with lovastatin were found most effective in reducing serum total cholesterol and low-density lipoprotein (LDL) cholesterol compared to the control diet or individual supplements. The mixture of TRF 25+lovastatin inhibited the activity of β-hydroxy- β-methylglutaryl coenzymeA reductase (21%) compared to lovastatin alone, which did not change its activity. Cholesterol 7 α-hydroxylase activity was increased by lovastatin (11%) and by lovastatin plus TRF 25 (19%). TRF 25+lovastatin decreased levels of serum total cholesterol (22%), LDL cholesterol (42%), apolipoprotein B (13–38%), triglycerides (19%), thromboxane B 2 (34%) and platelet factor 4 (26%), although high-density lipoprotein (HDL) cholesterol, and apolipoprotein A1 levels were unaffected. The mixture of TRF 25+lovastatin showed greater effects than did the individual treatments alone, reflecting possible additive pharmacological actions. The effects, however, of the d-P 25-T3/lovastatin combination were no greater than that of d-P 25-T3 alone, possibly indicating that d-P 25-T3 produced a maximum cholesterol lowering effect at the concentration used.

Dietary effects on bone quality and turnover, and Ca and P metabolism in chickens

The responses of skeletal health and blood calcium (Ca) and phosphorus (P) status to different dietary calcium and available P (avP) contents were examined in 2-week-old chickens. High avP content resulted in more inorganic P (Pi) and less ionised Ca (Ca2+) in the blood. Birds on low Ca and high avP diets showed a higher incidence of tibial dyschondroplasia and hypocalcaemic rickets and were therefore assumed to be hypocalcaemic. However the molar Ca:P ratio in bone was closer to the expected 1·67:1 in diets high in avP. No significant dietary mineral content effect was found on bone mineral content, or breaking strength, within the range of diets used. Results suggest that variations in molar Ca:P ratios in bone have little effect on mechanical competence, and that diets for this strain should be higher in Ca, and could be lower in avP, than current recommendations.

Effect of removal of caecal contents on nitrogen utilisation and nitrogen excretion in caecally ligated chickens fed on a low protein diet supplemented with urea

1. The effect of washing out the caecal contents on nitrogen utilisation and nitrogen excretion were examined in Single Comb White Leghorn cockerels fed on a 50 g/kg protein diet supplemented with urea. 2. Flushing out the caecal contents with saline in caecally ligated chickens produced a significantly increased nitrogen balance and increased nitrogen utilisation (P <0.05). 3. Washing out the caecal contents significantly decreased uric acid excretion but the treatment had no effect on urea and ammonia excretion. 4. Caecal bacterial contents were significantly decreased by caecal ligation and decreased further by washing out the caecal contents. 5. It is concluded that nitrogen metabolism in chickens is affected by possible changes in caecal fermentation produced by preventing substances from urine and digesta from entering the caeca.

Chickens fed with biomass of the red microalga Porphyridium sp. have reduced blood cholesterol level and modified fatty acid composition in egg yolk.

The biomass of the red alga Porphyridium sp.constitutes a unique combination of soluble sulfatedpolysaccharide that accounts for about 70% of thealgal dry weight, and various polyunsaturatedfatty acids (PUFA) such as arachidonic andeicosapentaenoic acid (AA, 20:4 ω6 and EPA,20:5 ω3). In view of earlier results in ourlaboratory showing a reduction in serum cholesteroland triglyceride levels in rodents fed with red algalbiomass, we set out to examine the influence of algalbiomass as a feed additive on the metabolism ofchickens, with an emphasis on blood and eggcholesterol levels. For that purpose, lyophilizedalgal biomass was fed to 12–13, 30-week-old, WhiteLeghorn chickens for 10 days at a proportion of 5% or10% of the standard chicken diet. Twelve chickensfed with unsupplemented diet served as the control. No differences in body weight, egg number, and eggweight were found between the algal-fed chickens (atboth concentrations) and the control. However,chickens fed with algal biomass consumed 10% lessfood for both groups, and their serum cholesterollevels were significantly lower (by 11% and 28% forthe groups fed with 5% and 10% supplement,respectively) as compared with the respective valuesof the control group. Egg yolk of chickens fed withalgae tended to have reduced cholesterol levels (by10%) and increased linoleic acid and arachidonic acidlevels (by 29% and 24%, respectively). In addition,the color of the egg yolk was darker as a result ofthe higher carotenoid levels (2.4 fold higher) forchickens that fed with 5% supplement. Theseresults encourage the development of an improvedchicken feed having dietary fibers and polyunsaturatedfatty acids.

Involvement of lipoic acid in plasma metabolites, hepatic oxygen consumption, and metabolic response to a β-agonist in broiler chickens

The present study was conducted to determine the role of alpha-lipoic acid (LA) in plasma metabolites, hepatic O2 consumption, and beta-adrenergic response in broilers. In Expt 1, 12-d-old female broiler chicks were divided into three dietary groups and fed on diets with or without LA (5 or 50 mg/kg) until 4 or 6 weeks of age, as a 2 x 3 factorial arrangement. The dietary LA had no effect on growth rates (body weight, abdominal fat, breast muscle, and liver). The higher level of LA increased plasma non-esterified fatty acid and decreased plasma triacylglycerol concentrations only at 6 weeks of age. A 42% increase in hepatic respiration was observed in the 4-week-old chickens given 50 mg LA/kg diet. In Expt 2, 3-d-old female broiler chicks were treated with or without dietary LA at 50 mg/kg. At 30 and 31 d old, isoproterenol (2 mg/kg body weight per h) was continuously infused into a wing vein for 2 h, and changes in plasma glucose, triacylglycerol, and non-esterified fatty acid concentrations were analysed. Isoproterenol increased plasma glucose over basal levels maximally at 60 min. Furthermore, the glucose increase in the LA-treated chickens was 35% greater than that of the controls at this time. Plasma non-esterified fatty acid and triacylglycerol concentrations were decreased by the isoproterenol infusion, regardless of LA administration. Therefore, the present study suggests that dietary LA has repartitioning effects on energy metabolism in chickens (although this depends on age-related metabolic state) and is a possible facilitator in the beta-adrenergic response of plasma glucose to a beta-agonist.

Hormonal Regulation of Stearoyl Coenzyme-A Desaturase 1 Activity and Gene Expression in Primary Cultures of Chicken Hepatocytes

Previous studies have provided evidence for the important role of liver stearoyl-CoA desaturase (SCD) in excessive adiposity in the chicken and suggest that the difference in SCD activity between fat and lean chickens could be explained by a difference in SCD1 gene expression. In the present study, the regulation of SCD1 gene expression was analyzed as the result of insulin and glucagon action, using primary cultures of 6-week-old chicken hepatocytes. Insulin increased SCD1 activity and mRNA levels, whereas glucagon decreased dramatically both the enzyme activity and the mRNA levels. Nuclear run-on transcription assays and mRNA stability investigations demonstrated that insulin and glucagon effects on SCD1 gene expression was primarily transcriptional. Furthermore, the results indicated that the glucagon-mediated inhibition of SCD1 gene transcription was more potent than just counteracting the insulin-mediated effect. These data represent the first demonstration that the glucagon effect on the SCD1 gene expression is primarily transcriptional. Moreover, among hepatic genes involved in lipid metabolism in chicken, SCD1 is the first gene shown to be regulated at the transcriptional level by insulin, in the absence of triiodothyronine. These data point out the potency of the growing chicken hepatocyte culture model in contrast with the embryonic cell culture model as regards the investigations of the insulin effect on gene expression.

Ligation of caeca improves nitrogen utilisation and decreases urinary uric acid excretion in chickens fed on a low protein diet plus urea

1. The effect of the ligation of the caeca on nitrogen utilisation and nitrogen excretion was examined in conventional chickens fed a diet containing 50 g protein/kg plus urea. 2. Ligation of the caeca significantly improved nitrogen balance and utilisation by up to more than 2 times as much as those of controls (P< 0.05). 3. The treatment significantly decreased uric acid excretion by 77 mg nitrogen/day (P< 0.01) and also total nitrogen excretion (P<0.05): the former decrease almost explained the latter. 4. No effect of the ligation of caeca on urea and ammonia excretion was observed. 5. It is concluded that nitrogen metabolism in chickens is affected by possible changes in caecal fermentation by preventing entry into the caeca of substances from urine and digesta.

The effects of ultraviolet light and cholecalciferol and its metabolites on the development of leg abnormalities in chickens genetically selected for a high and low incidence of tibial dyschondroplasia

Four experiments were conducted to investigate the effects of ultraviolet (UV) light exposure and several cholecalciferol metabolites on the development of tibial dyschondroplasia (TD) and other parameters associated with vitamin D metabolism in chickens selected for high (HTD) and low (LTD) incidence of TD. In Experiment 1, exposure of chickens to UV light reduced the incidence and severity of TD more in LTD chickens than in HTD chickens, as evident by the significant interactions (P < 0.10 and 0.04). In Experiment 2, the addition of cholecalciferol to diets that were deficient in cholecalciferol linearly decreased the incidence of vitamin D rickets and increased bone ash, but increased the incidence of severe TD. The LTD chickens had a higher maximal bone ash of 40.0 +/- 0.7% than did the HTD chickens, which had a maximal bone ash of 37.0 +/- 0.7%. In Experiment 3, the addition of 5 micrograms/kg of 25-hydroxycholecalciferol [25-(OH)D3], 1-alpha-hydroxycholecalciferol, or 1,25- dihydroxycholecalciferol decreased the incidence and severity of TD in the LTD chickens and had no effect on TD in HTD chickens. In Experiment 4, increasing dietary 25-(OH)D3 increased plasma 25-(OH)D3 levels in both lines, but HTD chickens had higher plasma 25-(OH)D3 levels at 20 and 40 micrograms/kg of dietary 25-(OH)D3. The incidence and severity of TD were reduced in the LTD chickens by dietary 25-(OH)D3, but little effect was noted in HTD chickens. The LTD chickens reached a maximal bone ash at 9.7 +/- 1.9 micrograms/kg and HTD chickens reached the same bone ash at 33.0 +/- 7.0 micrograms/kg. These results indicate that UV light and vitamin D metabolites are not effective in preventing TD in HTD chickens, but that altered vitamin D metabolism does exist between HTD and LTD chickens.