Dietary thyroxine induces molt in chickens (Gallus gallus domesticus)

Thyroxine increases during a molt in wild and captive birds, and thyroidectomy prevents induction of molt. This trial examined the effect of dietary thyroxine on molt induction molt in chickens (laying hens, 59 weeks of age). In a completely randomized design (n=15 hens/replication; 6 replications/treatment), hens were randomly assigned to either a traditional molting program consisting of feed withdrawal (FWD), or to diets containing 40 mg thyroxine/kg diet (HT), 20 mg thyroxine/kg diet (LT), or 40 mg thyroxine from thyroactive iodinated casein/kg diet (TIC). The molting treatment lasted 7-13 d, until egg production reached 0%. After molt induction, birds had ad libitum access to the same diet, until egg production was re-initiated and maximized ( approximately 56 d). All treatments induced molt, based upon cessation of egg laying and regression of ovary and oviduct. Birds on FWD treatment lost more body weight during the molting period, but gained more after molt compared to thyroxine treatments (P<0.01 for each), although all body weights were similar when egg production was maximized. Data demonstrate that oral thyroxine, in purified or non-purified form, induces a molt and may enhance animal well-being by reducing the need for FWD.     

Bone response of broiler chickens (Gallus gallus domesticus) induced by corticosterone

Experiments were conducted with chickens exposed to corticosterone (CORT), with the aim of determining its effects on bone characteristics. At 7 d of age, the experimental birds were injected daily with CORT (4 mg/kg of body mass) for 1 week. CORT administration significantly decreased the body weight while increasing relative liver weight of the chickens and the bone parameters were also decreased. Histology and immunohistochemistry of type X collagen revealed that CORT reduced the lengths of proliferative and prehypertrophic zone in growth plate and the number of positive chondrocytes in the prehypertrophic zone. In conclusion exposure to CORT depressed the growth performance and retarded the longitudinal growth of the long bones by inhibiting the proliferation and differentiation of chondrocytes in growth plate in broilers.     

Oxidative stress induced by corticosterone administration in broiler chickens (Gallus gallus domesticus) 1. Chronic exposure

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.     

Episodic gonadotropin secretion in the mature fowl: serial blood sampling from unrestrained male broiler breeders (Gallus domesticus)

Forty-week-old male broiler breeders were used in two experiments. Males were reared as recommended by the breeder, housed in individual cages, and cannulated to facilitate blood sampling. In experiment 1, blood samples were collected at 10- min intervals for 4 h commencing the day of cannulation (Day 0) and for 12 h on each of Days 1 and 2. In experiment 2, blood samples were collected at 10-min intervals for 8 h on Day 1. After centrifugation, plasma was stored at -20 degrees C until LH, FSH (experiment 1 and 2), testosterone, and corticosterone (experiment 1) concentrations were determined by RIA. Different statistical methods used to identify hormone secretion profiles revealed a characteristic pulsatile pattern of LH and FSH in plasma. However, LH pulses were more frequent and had greater amplitude than FSH pulses. Less than 32% of the FSH pulses were associated with LH episodes. Conversely, the association between LH and testosterone pulses averaged 83% in birds with testis weight greater than 10 g. Concentrations of corticosterone tended to increase after cannulation and remained elevated for only 3-4 h. Our data indicate that LH, FSH, and testosterone secretion is pulsatile in male broiler breeders. Additionally, LH pulses are associated with testosterone episodes but not with FSH pulses. The pulsatile pattern of FSH secretion, which is unique from those of LH, in adult males suggests that FSH secretion is independently regulated in the adult male fowl.     

Plasma lipoprotein profiles in broiler chicks (Gallus domesticus): effects of early overfeeding

1. Twenty-eight day old broiler chicks gavage fed for 22 days consumed 40% more feed and gained 100-110 g more than control birds. 2. Normal feeding resumed on day 41, by day 63 feed intakes and body weights of overfed and control birds were equal. 3. Moderate differences in lipid compositions of LDL and VLDL were observed at 41 and 50 but not at 63 days. 4. In contrast to mammals where early over feeding predisposes to adult obesity, lipoprotein profiles and ad lib feeding patterns of chicks are not readily altered by dietary measures.     

Dexamethasone facilitates lipid accumulation and mild feed restriction improves fatty acids oxidation in skeletal muscle of broiler chicks (Gallus gallus domesticus)

Effects of dexamethasone (DEX) and mild feed restriction on the uptake and utilization of fatty acids in skeletal muscle of broiler chicks (Gallus gallus domesticus) were investigated. Male Arbor Acres chicks (7-days old, n = 30) were injected with DEX or saline for 3 days, and a feed restriction group was included. DEX enhanced circulating very low density lipoprotein (VLDL) level and the lipid accumulation in both adipose and skeletal muscle tissues. Compared with the control, liver-carnitine palmitoyltransferase 1 (L-CPT1) and AMP-activated protein kinase (AMPK) α2 mRNA level of M. biceps femoris (BF) were down-regulated significantly by DEX, while mRNA expression of lipoprotein lipase (LPL), fatty acid transport protein 1 (FATP1), heart-fatty acid binding protein (H-FABP), long-chain acyl-CoA dehydrogenase (LCAD), activities of LPL and AMPK in both skeletal muscles were not obviously affected. Feed restriction increased the mRNA expression of LPL, L-CPT1 and LCAD of M. pectoralis major (PM), and FATP1, H-FABP, L-CPT1 and LCAD of BF. In conclusion, DEX retards the growth of body mass but facilitates lipid accumulation in both adipose and skeletal muscle tissues. In contrast to the favorable effect of mild feed restriction, DEX did not alter the uptake of fatty acids in the skeletal muscle. The result suggests that DEX may promote intramyocellular lipid accumulation by suppressed fatty acid oxidation while mild feed restriction improved fatty acid oxidation in skeletal muscle, especially in red muscle. Glucocorticoids (GCs) regulated muscle fatty acid metabolism in a different way from energy deficit caused by mild feed restriction.     

Interaction of estrogen and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in immature male chickens (Gallus domesticus)

The interaction of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) and estrogen was studied in chickens to more clearly define this relationship in an avian species and its role in the enhanced sensitivity of female chickens to TCDD-induced wasting syndrome. Twenty male chickens (7-9 weeks old) were divided evenly into four groups: control (CTL, received the same volume of vehicle); estrogen-treated (E2, 1 mg/kg estradiol cypionate injections on days 1, 2 and 3); TCDD-treated (TCDD, single 50 microg/kg injection on day 4); and estrogen plus TCDD (E2+TCDD, as above), with measurements taken on day 14. The E2 group compared with the CTL group had decreased comb height (24%), comb length (26%) and adipose tissue (AT) lipoprotein lipase (LPL) activity relative to AT mass (51%), while liver mass and body weight gain were each increased by 28%. The TCDD group had increased liver mass (62%), reduced comb length (17%), and reduced AT LPL activity indexed to AT mass (70%) compared with the CTL group. Finally, the E2+TCDD group had 37% lower body weight gain and 30% larger livers relative to body mass compared with the E2 group, but were not significantly different from the TCDD group. These data show that TCDD antagonized several effects of exogenous estrogen in male chickens, while estrogen enhanced TCDD toxicity in a tissue-specific manner.     

Role of zinc in regulating the levels of hepatic elements following nickel toxicity in rats

This study was designed to determine the protective effects of zinc on the hepatotoxicity induced by nickel in rats. Female Sprague-Dawley (SD) rats received either nickel sulfate alone in the dose of 800 mg/L nickel in drinking water, zinc sulfate alone in the dose of 227 mg/L zinc in drinking water, and nickel plus zinc or drinking water alone for a total duration of 8 wk. The effects of different treatments were studied on activities of rat liver marker enzymes like alkaline phosphatase (ALP), alanine aminotransferase (ALT), and aspartate aminotransferases (AST) and on the status of essential elements in rat liver. The study revealed a significant increase in the activities of enzymes ALP and ALT in rats subjected to nickel treatment. Interestingly, zinc supplementation to rats treated with nickel brought back the raised activities of these enzymes to within normal limits. Further, the levels of elements in liver that include zinc, copper, selenium, and potassium were found to be significantly suppressed following nickel treatment, whereas the levels of iron and sulfur were elevated. However, zinc treatment alone did not cause any appreciable change in the concentration of these elements. To the contrary, when zinc was given to nickel-treated rats, the concentrations of zinc, copper, potassium, and phosphorus were not significantly different from that of normal controls, whereas the levels of iron, selenium, and sulfur were improved in comparison to nickel-treated rats but were not within the normal limits. The present study concludes that zinc has the ability to maintain the levels of hepatic elements and has bearing in regulating the liver functions by maintaining the activities of marker enzymes in conditions of nickel toxicity.     

Effect of Escherichia coli infection on growth and protein metabolism in broiler chicks (Gallus domesticus)

1. A controlled experimental Escherichia coli infection was developed in broiler chicks. 2. Infection with E. coli significantly reduced feed intake, altered growth of the whole body, eviscerated carcass, skeletal muscles, heart and liver. Organ weight and/or the proportions of organs within the body were affected. 3. Protein accumulation in the eviscerated carcass, extensor digitorum communis and sartorius muscles was severely inhibited by infection, and to a greater extent than body weight. 4. Failure of muscle tissue to accumulate protein was associated with a significant decline in protein synthesis, when measured in vitro (-48%; P less than 0.05) and in vivo (-42%; P less than 0.001). Protein degradation also declined (-28.7%), but to a smaller extent than protein synthesis. 5. Although the infected chicks showed no viable bacteria at day 12 after infection, chicks did not reach the same body weight as controls by day 30 after infection.     

Effects of ambient temperatures on blood viscosity and plasma protein concentration of broiler chickens (Gallus domesticus)

This paper describes the effects of ambient temperatures on whole blood viscosity and plasma protein concentration in broiler chickens. Whole blood viscosity and haematocrit, compared at 7 and 20°C, decreased significantly at or above 25°C of ambient temperature. However, no marked difference were found between 7 and 20°C or between the temperatures of 25, 30 and 35°C. The heat-induced decrease of whole blood viscosity was found after exposure for 1 h. These results suggest that the heat-induced decrease in blood viscosity is only a level change, which occurs between thermoneutral and high ambient temperature.     

Influence of selenium sources on age-related and mild heat stress-related changes of blood and liver glutathione redox cycle in broiler chickens (Gallus domesticus)

Selenium is an essential trace element that up-regulates a major component of the antioxidant defense mechanism by controlling the body's glutathione (GSH) pool and its major Se-containing antioxidant enzyme, glutathione peroxidase (GPX). Evidence has emerged suggesting that organic selenium, natural seleno-amino acids found in plants, grains and selenized yeast, maintains the antioxidant defense system more efficiently than inorganic selenium. Inorganic selenium is a pro-oxidant, whereas organic selenium possesses antioxidant properties itself. As a pro-oxidant, inorganic selenium is not suitable for animals or humans. Therefore, we examined the GSH–GPX system in broiler chickens and determined that organic selenium was indeed more beneficial than inorganic selenium. Chickens fed the organic selenium as Sel-Plex^®, a selenized yeast, had elevated GPX activity in both blood and liver in a thermoneutral environment and after heat distress. More importantly, the ability to reduce the oxidized glutathione (GSSG to 2 GSH) was enhanced and facilitated by maintenance of glutathione reductase activity. Organic selenium-fed chickens were less affected by mild heat distress than inorganic selenium-fed chickens, and this assessment was based upon less induction of heat shock protein 70 (hsp70) in organic selenium-fed chickens. Our results clearly show that heat distress, a potent inducer of oxidative stress and hsp70, can be partially ameliorated by feeding organic selenium. We attribute this observation to an enhanced GSH–GPX antioxidant system in organic selenium-fed chickens.     

Altered development and protein metabolism in skeletal muscles of broiler chickens (Gallus gallus domesticus) by corticosterone

Two trials were conducted to investigate the effect of corticosterone (CORT) on protein metabolism and the amino acid composition in muscle tissues of broiler chickens (Gallus gallus domesticus). In Trial 1, two groups of 30 broiler chickens were subjected to control or CORT treatment (30 mg/kg diet) from 28 to 39 days of age. In Trial 2, three groups of chickens of 28 days of age were randomly subjected to one of the following treatments for 7 days: CORT (30 mg/kg diet), pair-fed (maintaining the same feed intake as CORT treatment) and control treatments. The body mass gain and feed efficiency was significantly decreased by CORT treatment, while the food intake was decreased. The breast and thigh masses (% body mass) were significantly suppressed by CORT treatment, while the abdominal fat and liver masses (%) were obviously increased. The plasma levels of glucose, urate and total amino acid were significantly elevated by CORT treatment. The capacity for protein synthesis, estimated by RNA:protein ratio, were significantly suppressed by CORT in M. pectoralis major and M. biceps femoris. The 3-methylhistidine concentrations were significantly increased in both M. pectoralis major and M. biceps femoris of CORT chickens, compared to control but not the pair-fed chickens. The amino acid composition of M. pectoralis major and M. biceps femoris was not significantly affected by CORT treatment. In conclusion, the arrested growth in skeletal muscles induced by CORT administration has tissue specificity. The CORT treatment retards the growth of skeletal muscle by suppressed protein synthesis and augmented protein catabolism.     

Oxidative stress induced by corticosterone administration in broiler chickens (Gallus gallus domesticus) 2. Short-term effect

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.     

Novel function of the skin in calcium metabolism in female and male chickens (Gallus domesticus)

To study the role of the skin in differential calcium metabolism in White Leghorn chickens, we compared the composition of suction blister fluid (SBF) collected from cutaneous blisters with blood and serum in female and male animals in various physiological states. As an estimate for interstitial fluid (IF), SBF was used as a determinant of local cutaneous metabolism. Sample collection was carried out under ketamine–xylazine anesthesia. Eight chickens of both sexes were raised freely in similar environmental conditions and fed with similar food during their growth from juvenile to sexually mature and fully adult state. SBF, blood and serum were examined for concentrations of ionized Ca²⁺, Na⁺ and K⁺ with ion-selective electrodes (ISEs), and osmolalities by freezing point osmometry. pH and total protein content were also assessed. Our results showed that SBF of chickens is calcium-poor at the juvenile state and that it draws more Ca²⁺ in adult males than laying females of the same age. Interestingly, Ca²⁺ accumulation was observed also in females after laying had ceased. There was a positive correlation between blood and SBF Ca²⁺ in females but a negative one in males. In general, it was found that SBF of chickens was rich in Na⁺ and K⁺, was hypertonic compared to serum at the juvenile state and had a protein content of 36–47% of that in serum. Different from mammals, SBF in adult chickens was alkaline with the mean values of 8.7 ± 0.14 in females and 8.8 ± 0.06 in males. Age- and sex-related variability in cutaneous Ca²⁺ concentrations in chickens, and the differences of SBF composition between that of mammals point to a novel role of skin functions in avians. Possible functions of the skin as a dynamic calcium source balancing the free circulating Ca²⁺ levels and, also, as an excretory organ for Ca²⁺ are discussed.     

Differentiation of female primordial germ cells in the male testes of chicken (Gallus gallus domesticus)

In our previous studies, we demonstrated that female primordial germ cells (PGCs) have the ability to differentiate into W chromosome-bearing (W-bearing) spermatozoa in male gonads of germline chimeric chickens. In this study, to investigate the differentiation pattern of female PGCs in male gonads in chickens, three germline chimeric chickens were generated by injecting female PGCs into the male recipient embryos. After these male chimeras reached sexual maturity, the semen samples were analyzed for detecting W-bearing cells by PCR and in situ hybridization analyses. The results indicated that the female PGCs had settled and differentiated in their testes. A histological analysis of the seminiferous tubule in those chimeras demonstrated that the W-bearing spermatogonia, spermatocytes, and round spermatids accounted for 30.8%, 32.7%, and 28.4%, respectively. However, the W-bearing elongating spermatid was markedly lower (7.7%) as compared to the W-bearing round spermatid. The W-bearing spermatozoa were hardly ever observed (0.2%). We concluded that although female PGCs in male gonads are capable of passing through the first and second meiotic division in adapting themselves to a male environment, they are hardly complete spermiogenesis.     

Prostaglandin-dependent muscle wasting during infection in the broiler chick (Gallus domesticus) and the laboratory rat (Rattus norvegicus).

Systemic infection with Escherichia coli significantly decreased feed intake, slowed growth of the whole body and skeletal muscles, and severely inhibited muscle protein accumulation in both chicks and rats. Treatment with naproxen (6-methoxy-alpha-methyl-2-naphthaleneacetic acid), an inhibitor of prostaglandin production, decreased weight losses of body and muscle, and significantly inhibited muscle protein wasting in infected chicks and rats. E. coli infection increased net protein degradation by 44.8% (P less than 0.05) and prostaglandin E2 production by 148% (P less than 0.05) in isolated extensor digitorum communis muscle from chicks on day 2 after infection. Naproxen treatment significantly decreased net protein degradation and prostaglandin E2 production in infected chicks to values seen in muscles of healthy controls. Quantitatively and qualitatively similar results were seen in isolated rat epitrochlearis muscle.     

Effect of estrogen and 2,3,7,8-tetrachlorodibenzo-rho-dioxin (TCDD) on plasma fatty acids of immature male chickens (Gallus domesticus)

This study investigated the effects of 2,3,7,8-tetrachlorodibenzo-rho-dioxin (TCDD) and estrogen on plasma lipids in immature male chickens. Fatty acids were quantified in plasma collected on day 14 from chickens injected with either: Estrogen plus TCDD-1 mg estradiol cypionate /kg body wt. daily for 3 days and 50 microg TCDD/kg body wt. on day 4; Estrogen--1 mg estradiol cypionate/kg body wt. daily for 3 days and vehicle only on day 4; TCDD-vehicle only for 3 days and 50 microg TCDD/kg body wt. on day 4; or Vehicle--same volume of appropriate vehicle for 4 days. TCDD treatment alone increased the plasma concentrations of total triacylglycerides and of the specific fatty acids 14:0, 15:0, 18:0, 18:2n6, 18:3n3, 20:0, 20:1n9, 20:2n6, 20:3n6, 20:5n3 and 22:1n9, compared with vehicle treatment. The concentration of 22:6n3 was increased in all plasma lipid classes of the estrogen group compared with the vehicle group, but was not increased in the estrogen plus TCDD group. Overall, TCDD treatment alone increased plasma lipids, possibly as a result of decreased clearance or utilization; whereas estrogen plus TCDD treatment antagonized estrogen-induced increases in 22:6n3 but did not cause hyperlipidemia.     

红原鸡与家鸡的亲缘关系研究

对中国红原鸡滇地亚种和海南亚种与我国茶花鸡,泰和鸡和寿光鸡等地方鸡种以及芦花鸡,洛岛红等外国鸡种进行了血型（３个位点,１３个等位基因）,蛋白质（酶）多态（５个位点,１１个等位基因）和ＤＮＡ指纹分析,结果表明,红原鸡与茶花鸡（原始型品种）的亲缘关系较近;与泰和鸡,寿光鸡,芦花鸡,洛岛红（进化型品种）的亲缘关系较远,呈红原鸡－茶花鸡－泰和鸡,寿光鸡或芦花鸡,洛岛红这样一个进化阶梯,以上结果与国外资料（