Behavioural and physiological fear responses in ducks: genetic cross effects

Mule duck, a cross between a Muscovy drake and a Pekin female, is reported by the farmers to frequently express fear behaviours, such as man avoidance. The genetic basis of fear responses in mule ducks was therefore investigated in this study. According to a previous experiment, the dominant effect of Pekin genotype was hypothesised; however, due to the absence of birds from the reciprocal cross, a superiority of the Pekin in additive effect could not be distinguished from a direct maternal additive effect. In order to clarify this, ducks from the mule genotype, the two parental genotypes (Pekin and Muscovy) and the reciprocal intercross (hinny) underwent a set of physiological and individual behavioural tests of fear. Both parental genotypes were highly fearful but exhibited responses of different patterns: Pekin ducks manifested a higher locomotor activity, whereas the Muscovy ducks showed a higher avoidance to man. Hybrids expressed higher panic responses and specific fear of man than the two parent breeds. Both hybrids expressed similar patterns and the maternal effects were not significant. Significant heterosis effects were found for most of the behavioural responses, in agreement with the fact that higher fear responses were expressed by the hybrids compared to the parental genotypes. A significant heterosis effect was also found for basal adrenal activity; hybrids having higher basal level than parental genotypes. Maximum capacity of adrenal response appeared to be determined by direct additive effects with a superiority of the Pekin genotype.     

Duck plague epizootics in the United States, 1967-1995

In 1967, the first confirmed diagnosis of duck plague (DP) in the USA was made from pekin ducks (Anas platyrhynchos domesticus) on commercial duck farms on Long Island, New York. Within 10 mo, DP was confirmed as the cause of death in migratory waterfowl on a Long Island bay. This paper reviews 120 DP epizootics reported from 1967 to 1995 that involved waterfowl species native to North America or were reported in areas with free-flying waterfowl at risk. Duck plague epizootics occurred in 21 states with the greatest number reported in Maryland (29), New York (18), California (16), and Pennsylvania (13). The greatest frequency of epizootics (86%) was detected during the months of March to June. At least 40 waterfowl species were affected with the highest frequency of epizootics reported in captive or captive-reared ducks including muscovy ducks (Cairina moschata) (68%), mallard ducks (A. platyrhynchos) (18%) and black ducks (A. rubripes) (14%). The greatest number of waterfowl died in three epizootics that involved primarily migratory birds in 1967 and 1994 in New York (USA) and 1973 in South Dakota (USA). The greatest number of DP epizootics reported since 1967 appear to have involved flocks of non-migratory rather than migratory waterfowl; therefore, in our opinion it remains unknown if DP is enzootic in either non-migratory or migratory waterfowl.     

Effects of ACTH, capture, and short term confinement on glucocorticoid concentrations in harlequin ducks (Histrionicus histrionicus).

Little is known about baseline concentrations of adrenal hormones and hormonal responses to stress in sea ducks, although significant population declines documented in several species suggest that sea ducks are exposed to increased levels of environmental stress. Such declines have been observed in geographically distinct harlequin duck populations. We performed an adrenocorticotropic hormone (ACTH) challenge to evaluate adrenal function and characterize corticosterone concentrations in captive harlequin ducks and investigated the effects of capture, surgery, and short term confinement on corticosterone concentrations in wild harlequin ducks. Harlequin ducks responded to the ACTH challenge with an average three-fold increase in serum corticosterone concentration approximately 90 min post injection, and a four- to five-fold increase in fecal glucocorticoid concentration 2 to 4 h post injection. Serum corticosterone concentrations in wild harlequin ducks increased within min of capture and elevated levels were found for several hours post capture, indicating that surgery and confinement maintain elevated corticosterone concentrations in this species. Mean corticosterone concentrations in wild harlequin ducks held in temporary captivity were similar to the maximum response levels during the ACTH challenge in captive birds. However, large variation among individuals was observed in responses of wild birds, and we found additional evidence suggesting that corticosterone responses varied between hatch year and after hatch year birds.     

Effects of ACTH, capture, and short term confinement on glucocorticoid concentrations in harlequin ducks (Histrionicus histrionicus)

Little is known about baseline concentrations of adrenal hormones and hormonal responses to stress in sea ducks, although significant population declines documented in several species suggest that sea ducks are exposed to increased levels of environmental stress. Such declines have been observed in geographically distinct harlequin duck populations. We performed an adrenocorticotropic hormone (ACTH) challenge to evaluate adrenal function and characterize corticosterone concentrations in captive harlequin ducks and investigated the effects of capture, surgery, and short term confinement on corticosterone concentrations in wild harlequin ducks. Harlequin ducks responded to the ACTH challenge with an average three-fold increase in serum corticosterone concentration approximately 90 min post injection, and a four- to five-fold increase in fecal glucocorticoid concentration 2 to 4 h post injection. Serum corticosterone concentrations in wild harlequin ducks increased within min of capture and elevated levels were found for several hours post capture, indicating that surgery and confinement maintain elevated corticosterone concentrations in this species. Mean corticosterone concentrations in wild harlequin ducks held in temporary captivity were similar to the maximum response levels during the ACTH challenge in captive birds. However, large variation among individuals was observed in responses of wild birds, and we found additional evidence suggesting that corticosterone responses varied between hatch year and after hatch year birds.     

Malonyl-CoA decarboxylase from the uropygial gland of waterfowl: purification, properties, immunological comparison, and role in regulating the synthesis of multimethyl-branched fatty acids.

Analysis of the acyl portion of the wax from the uropygial gland of muscovy duck, wood duck, (Cairininae subfamily) and Canadian goose (Anserinae) by combined gas-liquid chromatography and mass spectrometry showed that 2,4,6-trimethyloctanoic acid and 2,4,6-trimethylnonanoic acid were the major (~100%) components. Similar analyses of the wax from the glands of mallard and Peking duck (Anatinae) showed that 2- and 4-mono-methylhexanoic acids predominated (>75%) with no multimethyl-branched acids. The uropygial glands of the former group contained 20 to 100 times as much malonyl-CoA decarboxylase activity as those of the latter group. These results strongly support the hypothesis that this decarboxylase, by causing specific decarboxylation of malonyl-CoA, makes available only methylmalonyl-CoA for fatty acid synthesis, and thus causes the production of multimethyl-branched acids. Malonyl-CoA decarboxylase was purified to apparent homogeniety in 30% yield from the uropygial glands of muscovy and wood ducks. Properties of the enzyme from the ducks, such as S_20.w (7.8 S), molecular weight (190,000) subunit composition (4 × 47,000), amino acid composition, strict substrate specificity, pH optimum (~9.0), K_m (~33 μm), V (~80 μmol/min/mg), and inhibition by SH-directed reagents were similar to those observed with the decarboxylase from the domestic goose. Antiserum prepared against the goose enzyme cross-reacted with and inhibited the decarboxylase from the four genera of ducks and Canadian goose. Ouchterlony double-diffusion analyses showed fusion of precipitant lines with the enzyme from muscovy, wood duck, and Canadian goose, whereas spurs were observed with the enzymes from mallard and Peking ducks. Immunoelectrophoresis showed that the decarboxylases from muscovy and wood ducks were similar and that they were different from the enzyme from the domestic goose. It appears that during evolution, the subfamilies (Anserinae and Cairininae) which synthesize multimethyl-branched acids acquired the ability to produce a high level of malonyl-CoA decarboxylase, an enzyme which is also present in low levels in other organisms.     

Effects of heat stress on antioxidant defense system,inflammatory injury,and heat shock proteins of Muscovy and Pekin ducks: evidence for differential thermal sensitivities

Rising temperatures are severely affecting the mortality, laying performance, and meat quality of duck. Our aim was to investigate the effect of acute heat stress on the expression of heat shock proteins (HSPs: HSP90, 70, 60, 40, and 10) and inflammatory factors (nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2)) and antioxidant enzyme activity (superoxide dismutase (SOD), malondialdehybe (MDA), catalase (CAT), total antioxidant capacity (T-AOC)) in livers of ducks and to compare the thermal tolerance of Pekin and Muscovy ducks exposed to acute heat stress. Ducks were exposed to heat at 39 ± 0.5 °C for 1 h and then returned to 20 °C for 1 h followed by a 3-h recovery period. The liver and other tissues were collected from each individual for analysis. The mRNA levels of HSPs (70, 60, and 40) increased in both species, except for HSP10, which was upregulated in Muscovy ducks and had no difference in Pekin ducks after heat stress. Simultaneously, the mRNA level of HSP90 decreased in the stress group in both species. Morphological analysis indicated that heat stress induced tissue injury in both species, and the liver of Pekin ducks was severely damaged. The activities of several antioxidant enzymes increased in Muscovy duck liver, but decreased in Pekin duck. The mRNA levels of inflammatory factors were increased after heat stress in both duck species. These results suggested that heat stress could influence HSPs, inflammatory factors expression, and the activities of antioxidant enzymes. Moreover, the differential response to heat stress indicated that the Muscovy duck has a better thermal tolerance than does the Pekin duck.     

Genes involved in the establishment of hepatic steatosis in Muscovy,Pekin and mule ducks

Our main objectives were to determine the genes involved in the establishment of hepatic steatosis in three genotypes of palmipeds. To respond to this question, we have compared Muscovy ducks, Pekin ducks and their crossbreed the mule duck fed ad libitum or overfed. We have shown a hepatic overexpression of fatty acid synthase (FAS) and di-acyl glycerol acyl transferase 2 (DGAT2) in overfed individuals, where DGAT2 seemed to be more regulated. This increase in lipogenesis genes is associated with a decrease of lipoprotein formation in Muscovy and mule ducks, especially apolipoprotein B (ApoB) and Microsomal Triglyceride Transfer Protein (MTTP), leading to lipid accumulation in liver. In Pekin ducks, MTTP expression is upregulated suggesting a better hepatic lipids exportation. Regarding lipids re-uptake, fatty acid-binding protein 4 and very-low-density-lipoprotein receptor are overexpressed in liver of mule ducks at the end of the overfeeding period. This phenomenon puts light on a mechanism unknown until today. In fact, mule can incorporate more lipids in liver than the two other genotypes leading to an intensified hepatic steatosis. To conclude, our results confirmed the genotype variability to overfeeding. Furthermore, similar observations are already described in non-alcoholic fatty liver disease in human, and ask if ducks could be an animal model to study hepatic triglyceride accumulation.     

Adrenocortical response in the duck exposed to corticosteroid administration and salt loading

The functional zonation in the adrenocortical tissue of the duck was experimentally investigated after chronic administration of corticosteroids of different types (corticosterone, desoxycorticosterone, dexamethasone) and salt loading (chlorides of sodium and potassium). The cytomorphology of the interrenal cells belonging to subcapsular and central zones was explored by light- and electron microscopy and by biochemical analysis of plasma corticosterone. Corticoid-induced involution of the interrenal tissue, or hyperactivity elicited by salt loading were evident in both subcapsular and central regions of the gland. In the duck the adrenocortical tissue appears to be devoid of steroidogenic functional differentiation. The modifications of different cellular organelles and inclusions can be explained in the light of known concepts about corticosteroid metabolism. The depression of plasma corticosterone titre in corticosteroid-treated animals agrees with the image of cytological inhibition. The lowered corticosterone value in KCl-loaded ducks signifies increased peripheral metabolism of this hormone. The hypercorticosteronemia in NaCl-loaded ducks is probably related to activation of the nasal gland under osmotic stress.     

番鸭呼肠孤病毒和H9 亚型禽流感病毒共感染对番鸭胸腺免疫抑制作用

【目的】探讨番鸭呼肠孤病毒(muscovy duck reovirus,MDRV)和H9亚型禽流感病毒(H9 avian influenzavirus,AIV)共感染对番鸭胸腺免疫功能的影响。【方法】8日龄番鸭人工感染MDRV或/和H9 AIV,观察番鸭感染后发生率和死亡率、胸腺形态和显微结构变化,淋巴细胞增殖试验检测胸腺细胞增殖功能,RT-PCR检测MDRV或H9 AIV在番鸭胸腺的分布。【结果】H9 AIV感染后番鸭发病率低,无死亡;不影响胸腺的发育,胸腺病理变化不明显,但能显著抑制胸腺淋巴细胞增殖反应。MDRV单独感染番鸭生长迟缓,发病率80%,死亡率50%;胸腺萎缩,出现局限性坏死灶;对番鸭胸腺细胞增殖反应的有抑制作用,差异显著。共感染组番鸭生长迟缓,发病率90%,死亡率70%;胸腺萎缩,淋巴细胞减少,出现局限性坏死灶;对番鸭胸腺细胞增殖反应的有抑制作用,差异极显著。共感染组在病毒检出时间和检出率上均大于单一病毒感染组。【结论】H9AIV感染对胸腺的免疫抑制作用较弱,MDRV感染后对胸腺的免疫抑制作用较强,MDRV与H9AIV共感染在番鸭免疫反应抑制上有协同作用。     

Effects of short-term changes in electrolyte intake on the adrenal steroidogenic responses of juvenile mallard ducks (Anas platyrhynchos)

1. Adjusting the Na+ and K+ intake of juvenile mallard ducks caused the plasma concentrations of corticosterone (B) and aldosterone (Aldo) to increase independently of one another, but none of these changes in electrolyte intake had a significant effect on the deoxycorticosterone (DOC) concentration. 2. With the exception of DOC in birds consuming the control diet, the plasma concentration of each hormone, regardless of diet, increased significantly following exposure to stress. 3. Stress-induced increases in Aldo concentration were greatest in birds given diets containing low concentrations of Na+. 4. Unlike the mammal and some other species of birds, Na+ may be the primary secretagogue responsible for the regulation of both corticosterone and aldosterone synthesis in the mallard duck.     

Aflatoxin induced hepatocarcinogenesis in ducks

To assess the carcinogenic response of duck hepatic tissue, an experimental study was undertaken. Pure aflatoxin B₁, was administered to twelve white pekin ducks of two to three months of age at a dose rate of 0.04165 mg/kg body weight every third day for six months. There was reduction in body weight and haemoglobin level from the third month onwards. Total serum protein, albumin and globulin had a slow and gradual reduction and ESR was significantly increased from the third month. Serum enzymes (AST, ALT, GGT and ALP) were significantly increased from the Vlllth to XVth fortnights (Two weeks). Ten ducks developed hepatic tumours by 180th day. Four of them had neoplastic nodules on the 90th day. Histo-pathologically they were hepatocellular carcinoma (6), Cholangiocellular carcinoma (4) and Chronic hepatitis (2). There was moderate to severe expression of GGT and ALP in the liver tissue during neoplastic transformation.     

Host specificity of Cryptosporidium sp. isolated from chickens

The host specificity of Cryptosporidium sp. infecting chickens was evaluated by oral inoculation of oocysts into 6 different species of neonatal rodents, adult nude mice (athymic), neonatal conventional and gnotobiotic pigs, turkeys, muscovy ducks and bobwhite quail. Examinations of tissue sections, ileal mucosal smears, fecal flotations and stained feces failed to reveal any infections in the mammalian species examined. Oocysts were observed in the feces, and developmental stages were observed in tissue sections, of turkeys and muscovy ducks but not bobwhite quail. This study indicates that Cryptosporidium sp. infections in avian species are probably not a zoonotic threat to humans.     

Is domestication driven by reduced fear of humans? Boldness,metabolism and serotonin levels in divergently selected red junglefowl (Gallus gallus)

Domesticated animals tend to develop a coherent set of phenotypic traits. Tameness could be a central underlying factor driving this, and we therefore selected red junglefowl, ancestors of all domestic chickens, for high or low fear of humans during six generations. We measured basal metabolic rate (BMR), feed efficiency, boldness in a novel object (NO) test, corticosterone reactivity and basal serotonin levels (related to fearfulness) in birds from the fifth and sixth generation of the high- and low-fear lines, respectively (44–48 individuals). Corticosterone response to physical restraint did not differ between selection lines. However, BMR was higher in low-fear birds, as was feed efficiency. Low-fear males had higher plasma levels of serotonin and both low-fear males and females were bolder in an NO test. The results show that many aspects of the domesticated phenotype may have developed as correlated responses to reduced fear of humans, an essential trait for successful domestication.     

Correlations between brain catecholamines,neurosecretion, and serum corticoid levels in osmotically stressed mallard ducks (Anas platyrhynchos)

The effects of depleting brain catecholamines with a combined treatment of reserpine and alpha-methyl-p-tyrosine on serum corticosterone levels and release of immunoreactive neurophysin from the median eminence, in osmotically stressed and unstressed mallard ducks, were studied. Corticoid levels in salt loaded birds were more than three times that of unstressed birds. The combined treatment of reserpine and alpha-methyl-p-tyrosine significantly decreased the concentration of brain monoamines in all experimental groups and raised serum corticoid levels in non-stressed birds to the same level found in the osmotically stressed animals. Immunoreactive neurophysin in the zona externa of the median eminence was depleted in all birds subjected to either osmotic stress and/or reserpine treatment but not in unstressed control birds. These preliminary data indicate that catecholamines may exert an inhibitory influence on both ACTH release from the anterior pituitary and neurophysin from the median eminence and that these two events may in some way be interrelated in the duck.     

Hybridization between white-headed ducks and introduced ruddy ducks in Spain

The ruddy duck, Oxyura jamaicensis, was introduced to Great Britain in the mid-20th century and has recently spread to other Western European countries. In Spain, ruddy ducks hybridize with the globally endangered white-headed duck, Oxyura leucocephala. We assessed the effects of hybridization on the Spanish white-headed ducks, which constitute 25% of the global population of this species, using a panel of eight nuclear intron markers, 10 microsatellite loci, and mtDNA control region sequences. These data allowed parental individuals, F(1) hybrids, and the progeny of backcrossing to be reliably distinguished. We show that hybrids between the two species are fertile and produce viable offspring in backcrosses with both parental species. To date, however, we found no extensive introgression of ruddy duck genes into the Spanish white-headed duck population, probably due to the early implementation of an effective ruddy duck and hybrid control programme. We also show that genetic diversity in the expanding European ruddy duck population, which was founded by just seven individuals, exceeds that of the native Spanish white-headed duck population, which recently recovered from a severe bottleneck. Unless effective control of ruddy ducks is continued, genetic introgression will compromise the unique behavioural and ecological adaptations of white-headed ducks and consequently their survival as a genetically and evolutionary distinct species.     

Disruptive effects of glucocorticoids on glutathione peroxidase biochemistry in hippocampal cultures

Glucocorticoids (GCs), the adrenal steroids secreted during stress, compromise the ability of hippocampal neurons to survive various necrotic insults. We have previously observed that GCs enhance the hippocampal neurotoxicity of reactive oxygen species and, as a potential contributor to this, decrease the activity of the antioxidant enzyme, glutathione peroxidase (GSPx). In this report, we have studied the possible mechanisms underlying this GC effect upon GSPx in primary hippocampal cultures and have observed several results. (i) Corticosterone (the GC of rats) decreased glutathione levels; this was predominately a result of a decrease in levels of reduced glutathione (GSH), the form of glutathione which facilitates GSPx activity. (ii) Corticosterone also decreased levels of NADPH; this may help explain the effect on GSH as NADPH is required for regeneration of GSH from oxidized glutathione. (iii) However, the corticosterone effect on total glutathione levels could not just be caused by the NADPH effect, as there were also reduced levels of oxidized glutathione. (iv) Corticosterone caused a small but significant decrease in GSPx activity over a range of glucose concentrations; this occurred under circumstances of an excess of glutathione as a substrate, suggesting a direct effect of corticosterone on GSPx activity. (v) This corticosterone effect was likely to have functional implications, in that enhancement of GSPx activity (to the same magnitude as activity was inhibited by corticosterone) by GSPx overexpression protected against an excitotoxin. Thus, GCs have various effects, both energetic and non-energetic in nature, upon steps in GSPx biochemistry that, collectively, may impair hippocampal antioxidant capacity.     

Circadian rhythm and response to an acute stressor of urinary corticosterone, testosterone, and creatinine in adult male mice

In small laboratory species, steroid measures can be obtained more frequently and less invasively from urine than blood. Insofar as urinary levels reflect systemic levels, they could provide advantages particularly for measurement of glucocorticoids, whose blood levels react rapidly to handling and stress. In Experiment 1, urinary samples were collected from male mice every second hour over a 14:10 h light:dark cycle. Samples were analyzed via enzyme immunoassay for corticosterone, testosterone, and creatinine. Corticosterone had peak concentrations 1 h after light offset and a trough 1 h after light onset. Testosterone showed peak concentrations 5-7 h after light onset and lowest concentrations during the dark phase of the cycle. Creatinine showed some variation over the light-dark cycle, but steroid measures showed similar trends with and without adjustment for creatinine. In Experiment 2, mice were stressed via an injection at times close to the determined peak and trough levels of corticosterone. In urinary samples taken 90 min after injection, corticosterone was significantly higher in injected animals at both times relative to levels in control animals, but testosterone was unaffected by injection stress. In Experiment 3, serum and urine samples were collected from mice every sixth hour across the diurnal cycle. Corticosterone peaked in urine and serum immediately after light offset, and urinary measures predicted those in serum. These data indicate that urinary corticosterone reflects systemic levels in mice, document circadian variation in urinary testosterone, and indicate that circadian variation in creatinine is minimal, but potentially relevant in stressed animals.     

The effects of adrenalectomy and corticosterone replacement on maternal behavior in the postpartum rat

It is well known that the hypothalamic-pituitary-adrenal (HPA) axis is activated during stress. Recent work suggests it is also implicated in the regulation of "normal" behaviors. The present studies investigated the effects of adrenalectomy and of varying glucocorticoid concentrations on adult maternal behavior in primiparous rats. In two studies, rats in late pregnancy were adrenalectomized or given sham surgeries and were tested for maternal behavior. In the first study, primiparous rats were given 0, 25, 100, 300, or 500 microg/ml of corticosterone in their drinking water. In the second study, primiparous rats were given either control or corticosterone time-release pellets. Blood samples were taken to ensure that rats demonstrated levels of corticosterone in blood that were relative to doses received. In studies one and two, primiparous adrenalectomized rats showed slightly, but significantly, lower levels of some maternal behaviors, including licking and time in nest, than primiparous sham rats. Primiparous rats given higher doses of corticosterone replacement showed higher levels of these maternal behaviors than primiparous rats given lower doses of corticosterone. In conclusion, adrenalectomy decreases, but does not abolish, maternal behavior. Corticosterone replacement reverses these effects. Corticosterone is not necessary for the initiation or maintenance of maternal behavior but plays a role in the modulation of ongoing maternal behavior.