Development of drinking mechanisms in the chicken (Gallus gallus) (Aves)

Summary Development of the drinking mechanism from the day of hatching to the 4 week old chick was studied in relation to the growth of the oropharynx and drinking performance. Results indicate that due to scaling effects in the growing oropharynx, physical factors require the development of extra mechanisms. The swallowing mechanism to transport water from the pharynx into the esophagus during the tip up phase is already present in hatchlings, and does not change during ontogeny. The mechanism for water intake during the immersion phase changes considerably. Hatchlings display pecking behavior towards water. Week old chicks protrude the tongue far out, and the total volume ingested is sucked up by capillary action between the tongue, the floor, and the roof of the oropharynx. In 2 and 3 week old chicks the relative distance over which water is sucked up by capillarity decreases, whereas the volume of water pushed caudad by the tongue and bills increases. Laryngeal suction also develops in this period. At the age of 4 weeks chickens use the adult mechanism to drink. Most oropharyngeal elements increase two to three times in length and width during post hatching ontogeny. Due to these increases, water transport by capillarity alone does not suffice in the older age groups; therefore additional mechanisms such as pressure development by closing the bills and laryngeal suction must develop. Relative to the oropharyngeal length most elements grow isometrically. The width of the lingual alae and the larynx width, however, increase with positive allometry, which improves both capillary action as well as the transport of water during the tip up phase when the chicks grow older. The need to develop extra water transport mechanisms during growth due to scaling effects is shown to condition the radiation capacity of avian drinking mechanisms. Nidicolous birds are, however, not constrained by the need to have a properly operating drinking mechanism during the early ontogeny and may therefore have a better chance of developing alternativ drinking mechanisms then nidifugous birds.     

Ontogeny of magnetoreception in chickens (Gallus gallus domesticus)

Chickens are precocial birds, capable of moving independently from within a few hours of hatching, and thus provide a useful model to investigate the development of magnetoreception in young birds. Chicks show some sharply-timed behavioural changes at around 11 days of age that may be indicative of improvements in navigation ability around this age. We trained Young (<10 days, n = 7) and Old (11 days or older, n = 6) chicks to find a hidden imprinting stimulus behind one of four screens in a square arena. Once criterion was reached, the directional choices of chicks were recorded in unrewarded tests in the geomagnetic field and in an experimental field shifted by 90° clockwise. These tests were separated with rewarded training trials to avoid extinction. In the first, and the first 3 tests, no indication was found that chicks chose the correct unimodal magnetic direction. Instead, in all tests, Old chicks preferred the screens in the same magnetic axis as the training direction in tests in the geomagnetic and shifted experimental fields significantly more than Young chicks (P < 0.05). Choices of Young chicks were no different to chance in tests, whereas choices by Old chicks were significantly different from chance (P < 0.05). Our findings support the hypothesis that magnetoreception appears in the second week of life in the chicken. It is, however, unclear when a truly directional magnetic response (i.e. an unimodal, rather than axial, response in our test) develops that could be used by the chicks for accurate navigation.     

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.     

Mechanisms controlling vocalization-evoked stapedius muscle activity in chickens (Gallus gallus)

Summary The mechanisms involved in the vocalization-evoked stapedius muscle contraction in the chicken (Gallus gallus) were studied. The stapedius muscle EMG response is constantly associated with vocalization elicited by electrically stimulating the mesencephalic calling area. Stimulation of discrete points within the mesencephalic calling area elicits stapedius muscle EMG activity at low stimulus intensities, but does not evoke vocalization. The stapedius muscle EMG response remains unchanged after exclusion of both the syringeal and vagal afferent inputs. It is concluded that stapedius muscle activity is not driven by a neural reflex originating within the syrinx, but is elicited by a central drive.EBS-elicited stapedius muscle activity, identical in all respects to that obtained in an intact preparation, is present when vocalization is prevented by synringeal muscle denervation and tracheal occlusion. This rules out the possibility that stapedius muscle activation could be due to vocalization-linked afferent impulses other than vagal and syringeal ones. Stimulation of discrete points within the mesencephalic calling area can elicit separately vocalization and stapedius muscle activity. This finding is discussed in terms of the existence of two midbrain neuronal populations, projecting to the XIIth nucleus (controlling the syrinx) and to the VIIth nucleus (controlling the stapedius).Abbreviations EBS electrical brain stimulation - EMG electromyogram - ICo nucleus intercollicularis - MLd nucleus mesencephalicus lateralis pars dorsalis - OM tractus occipitomesencephalicus     

Genetic characterization of Bhutanese native chickens based on an analysis of Red Junglefowl (Gallus gallus gallus and Gallus gallus spadecieus), domestic Southeast Asian and commercial chicken lines (Gallus gallus domesticus)

The genetic diversity of Bhutanese chickens needs to be understood in order to develop a suitable conservation strategy for these birds in Bhutan. In this, work, we used microsatellite markers to examine the genetic diversity of Bhutanese chickens. Four Bhutanese chicken varieties (Black plumage, Frizzle, Naked neck and Red Junglefowl-like, corresponding to Yuebjha Narp, Phulom, Khuilay and Seim, respectively), two subspecies of Red Junglefowl (Gallus gallus gallus and Gallus gallus spadecieus), two varieties of Thai native chickens (Pradhu Hang Dam and Chee; Gallus gallus domesticus) representing the Southeast Asian domestic chicken, and two commercial lines (Broiler and Single Comb White Leghorn) were genotyped with 18 microsatellites that included 16 loci recommended by the FAO/ISAG for investigations of genetic variability in chickens. All loci were polymorphic, with the number of alleles ranging from six (MCW0111) to 23 (MCW0183). Substantial genetic variation was observed in all populations, with the Bhutanese native chicken Yuebjha Narp (Black plumage chicken) showing the lowest genetic variability. Despite extensive intrapopulation variation, the genetic differentiation among 10 populations was moderate. A neighbor-joining tree revealed the genetic relationships involved while principal component analysis showed that Bhutanese native chickens should be given priority in conservation efforts because of their genetic distinctiveness. Chee chickens are especially valuable as a reservoir of predomestic diversity, as indicated by their greater genetic variation and their position in the phylogenetic tree.     

Genome-wide expression analysis of roxarsone-stimulated growth of broiler chickens (Gallus gallus)

Roxarsone is a commonly used additive in chicken (Gallus gallus) industry. However, little is known on the intrinsic molecular mechanism via which the growth performance of birds improves. This study was therefore performed to investigate the expression profiles of genes induced by roxarsone. Fifty-six broiler chickens were divided into two groups, namely treated and untreated with roxarsone. The treated group was provided a diet of 45.4 mg/kg roxarsone medication and the other group acted as control. Data analysis showed that roxarsone consistently and significantly (P < 0.05) increased chicken growth performance. In addition to this a significant (P < 0.05) increase of arsenic residue in liver has been seen. Microarray expression analysis of 8935 genes in liver showed that 22 genes (10 up- and 12 down-regulated) had altered expression throughout the experimental periods. Two novel genes (GenBank accession no. GU724343 and GU724344) were cloned through rapid amplification of cDNA ends (RACE). Gene GU724343 was predicted to encode an unidentified protein and the second gene GU724344 was presumed to encode a new member of immunoglobulin-like receptor (CHIR) family. Our results suggested for the first time that the role of roxarsone could be mainly to modify the expression levels of cell growth, immunity/defense and energy metabolism associated genes, as a result promoting animal growth. Further research on these genes should help to increase the knowledge of improving animal productivity safely and effectively.     

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.     

Myocardial contractility in chickens (Gallus gallus): analysis of systolic time intervals

The avian cardiovascular system is of special interest because avian hearts are relatively larger than mammalian hearts, and activation of ventricular myocardium in birds has a "flash" pattern. Systolic time intervals and indices of myocardial contractility were examined in anaesthetized open-chest chickens by polycardiography, including synchronous recordings of electrocardiogram, phonocardiogram, and apex cardiogram. The asynchronous contraction time, isometric contraction time, pre-ejection period and ejection time were 26 +/- 3 (Mean +/- SD), 21 +/- 9, 47 +/- 12, and 83 +/- 23 ms, respectively, for heart rates of 260 +/- 57 bpm. The myocardial tension index, isometric contraction index and the pre-ejection period/ejection time ratio were 0.39 +/- 0.11, 0.42 +/- 0.10, and 0.54 +/- 0.14, respectively. A "flash" pattern of ventricular myocardial depolarization causes more rapid excitation and as a consequence shorter asynchronous contraction time of relatively larger chicken hearts compared with rabbit hearts. Inverse relation (P < 0.05) of the asynchronous contraction time to the heart rate in chickens is probably associated with the specific activation pattern of avian ventricles. Establishment of the values of systolic time intervals will facilitate a better understanding of cardiac function in birds. The obtained results are discussed in comparison with the rabbit. The indices calculated from the systolic time intervals show disadvantageous contractile function of chicken heart compared to rabbit heart.     

Depolarisation and repolarisation sequences of ventricular epicardium in chickens (Gallus gallus domesticus)

Activation and recovery sequences were mapped by means of 64-channel synchronous recording of extracellular potentials on ventricular epicardium in chickens. Ventricular epicardium was depolarized due to multiple breakthroughs. The recovery of ventricular epicardium occurs from the apex to the base of heart and does not repeat the activation sequence. Gradients of repolarisation exist over the ventricular epicardium in birds. Repolarisation pattern of ventricular epicardium depends primarily on intrinsic spatial heterogeneities of ARIs over epicardium.     

Material on experimental polyembryony in Gallus gallus domestica chickens

Cutting the blastodisc of nonincubated chick eggs in parallel and perpendicularly to the presumptive axis results in the development of twin embryos in 28% of cases. After tripsin and versen solutions were injected in various concentrations into the blastula cavity, the part of the developed twins was but negligible (5% and 3%, respectively). In all experimental groups embryos with different developmental anomalies were often occurrence, as well as various types of malformation were noted in twins. Histological investigation of embryos having teratomic character demonstrated double anlage of some organs in them. Formation of several neural tubes, chordae and hearts was noted. It is possible that in most cases somatic embryogenesis takes place, incompleted due to intensive processes of regulatory character at early embryogenesis in avian. Results of in vitro experiments for studying regulatory capability of early chicken embryos (mechanical trauma was performed in the embryo for this purpose) demonstrate a rather high degree of integration that should prevent processes of polyembryony to develop in the experiments.     

Differential autonomic nervous system response in obese and anorexic chickens (Gallus gallus)

Effect of reserpine on body weight (BW), feed intake (FI), brain and plasma catecholamine and indoleamine concentrations in high- (HWS) and low- (LWS) weight selected lines of chickens was investigated. Chicks from each line were assigned to three treatment groups and injected intraperitoneally with 0, 1.25, or 2.50 mg/kg of reserpine at hatch, and again at 5 weeks-of-age. Chick BW and FI were determined weekly. At 7 weeks-of-age, 12 males and females from each group were sacrificed for neurotransmitter analysis. In the HWS line there was a dose-dependent decrease in BW through 7 weeks-of-age, whereas in the LWS line BW decreased only through the first 2 weeks-of-age. In the LWS line, norepinephrine (NE), epinephrine, and 3,4-dihydroxyphenylacetate concentrations decreased in the brain in a linear and quadratic manner in response to reserpine, but not in the HWS line. Both lines showed linear decreases in dopamine levels in response to reserpine; however, serotonin was not affected by reserpine. Chickens in the HWS line had greater plasma NE, and lower 5-hydroxyindoleacetic acid than those in the LWS line. In conclusion, it appears that chickens from the HWS line were more sensitive to the BW reducing effects of reserpine than those from the LWS line, with the latter appearing to have greater sympathetic nervous system activity.     

Domestication effects on behavioural synchronization and individual distances in chickens (Gallus gallus)

Behavioural synchrony (allelomimetic behaviour), and inter-individual distances are aspects of social and anti-predator strategies which may have been affected by domestication. Chickens are known to adjust synchronization and inter-individual distances depending on behaviour. We hypothesized that White Leghorn (WL) chickens would show less synchronized behaviour than the ancestor, the red jungle fowl (RJF). Sixty birds, 15 female and 15 male WL and the same number of RJF (28 weeks old) were studied in groups of three in furnished pens (1 m × 2 m) for 24 consecutive hours per group, following 24 h of habituation. Video tapes covering 4 h per group (dawn, 9-10 am, 1-2 pm and dusk) were analysed. Red junglefowl perched significantly more, but there were no breed effects on the frequency or daily rhythm of any other activities, or on average inter-individual distances. Red junglefowl were more synchronized during perching and a tendency for the same was found for social behaviour. After performance of the two most synchronized behaviours, perching and comfort behaviour, individual distance increased more for RJF than WL. According to this study domestication of chickens appears not to have significantly altered the relative frequencies of different activities or average inter-individual distances, but have caused some changes in behavioural synchronization and maintenance of activity-specific inter-individual distances in chickens. The changes may indicate an adaptive response to captivity and domestication.     

Glucose and cationic amino acid transporter expression in growing chickens (Gallus gallus domesticus)

Tissue glucose transporter (GLUT1-3) and cationic amino acid transporter (CAT1-3) mRNA expression was determined in growing broiler chicks posthatch. In two experiments, tissues were either collected on days 1, 3 and 7 or days 1 and 14 posthatch. Heart and liver were the only tissues expressing a GLUT isoform on day 1. All tissues expressed a GLUT isoform on day 7 except for the thymus. Most tissues expressing a CAT isoform on day 1 decreased mRNA levels through day 7 (P<0.05), except for bursa CAT-1 which tended to increase (P=0.05). The thymus and spleen did not express any CAT isoform mRNA until day 7. The liver was the only tissue expressing GLUT-2 mRNA through day 14. On day 14, GLUT-1, CAT-1 and CAT-2 mRNA were differentially expressed across tissues (P<0.05). High-affinity GLUT and CAT mRNA expression was highest in the heart and bursa, respectively (P<0.05). Total CAT mRNA expression was greatest in the bursa (P<0.05). The thymus had the lowest high affinity GLUT and total CAT mRNA expression on day 14 posthatch. Therefore, T lymphocytes within the thymus may be most susceptible to glucose and cationic amino acid supply.     

中国红原鸡和泰国红原鸡遗传多样性分析

利用29个微卫星DNA标记对来自中国的红原鸡Gallus gallus spadiceus亚种和来自泰国的红原鸡Gallus gallus gallus亚种进行遗传多样性分析, 评估亚种内的遗传变异和亚种间的遗传分化, 结果表明: 共检测到168个等位基因, 每个位点的等位基因数从2到13不等, 所有位点平均的期望杂合度和PIC值分别为0.5780和0.53。中国和泰国红原鸡29个微卫星位点平均有效等位基因数分别为3.79和4.79, 平均基因杂合度为0.5379和0.6385, 两个红原鸡亚种均表现出较高的群体杂合度和丰富的遗传多样性。群体分化系数为19.4%(P<0.01), 两个红原鸡亚种间的Reynolds’遗传距离和Nm值分别为0.157和1.040。由此可见, Gallus gallus spadiceus亚种和Gallus gallus gallus亚种群体具有不同的群体遗传结构, 群体之间存在明显的遗传分化, 并不能将其认定为是同一亚种, 这也为中国家鸡具有独立的起源提供了一定的佐证。     

Parameters of the chicken genome (Gallus gallus)

As more information on the chicken genome is gathered, it is becoming increasingly more important to be able to correlate genetic and physical maps. Quantitation of the chicken karyotype is important in establishing parameters which define the genome. Here we report on the physical lengths of the chicken macrochromosomes and establish the DNA content of each, thus identifying implicitly how much of the genome is represented by the microchromosomal component. For the first time, genetic and physical data on the chicken karyotype are presented in relation to one another.     

Microstructure of matrix and mineral components of eggshells from White Leghorn chickens (Gallus gallus)

The avian eggshell is a composite structure of organic matrix and mineral (calcium carbonate) that is rapidly and sequentially fabricated in the oviduct in <24 hr. The eggshell is an excellent vehicle for the study of biomineralization processes and the role of the organic matrix in the mineral-matrix composite. The organic matrix components of eggshells from White Leghorn chickens (Gallus gallus) were examined by transmission electron microscopy (TEM) and optical microscopy. The mineral phase was analyzed by TEM, scanning electron microscopy (SEM), X-ray compositional microanalysis, and electron diffraction. Ultrastructural examination of the matrices within the calcified eggshell reveals a complex architecture that differs within each of the major zones of the eggshell: the shell membranes, the mammillary zone, the palisade region, and the cuticle. The mammillary layer consists of the calcium reserve assembly (CRA) and crown region, each with a unique substructure. TEM images show that the matrix of the CRA consists of a dense, flocculent material partially embedded within the outer shell membrane (a mostly noncalcified region of the shell). The mantle of the collagen fibers of the shell membranes is rich in polyanions (cuprolinic blue-positive), as is the CRA matrix. The CRA is capped by a centrally located calcium reserve body sac (CRB sac) that contains numerous 300–400 nm, electron-dense, spherical vesicles. Directly above the CRB sac is a zone of matrix consisting of stacks of interconnected vesicles (similar in morphology to CRA vesicles) that are interspersed with a granular material. The palisade region, the largest of the mineralized zones, contains hollow vesicles ∼450 nm (s.d. = 75 nm) in diameter, with a crescent-shaped, electron-dense fringe. An interconnecting matrix material is also found between the vesicles in the palisades region. The cuticle is composed of two layers, a mineralized inner layer and an outer layer consisting of only organic matrix. The bulk of the mineral within the eggshell is calcite, with small amounts of needlelike hydroxyapatite in the inner cuticle and occasionally, vaterite micro crystals found at the base of the palisade (cone) region. The well-crystallized calcite crystals within the palisade are columnar, typically ∼20 μm wide by 100–200 μm long; aside from numerous entrapped vesicles and occasional dislocations, they are relatively defect-free. The bulk of the matrix found in the palisade and crown regions are thought to be residual components of the rapid mineralization process. The unique matrix structure within the CRB corresponds to the region of preferentially solubilized calcite used by the developing embryo and the hydroxyapatite found in the inner cuticle may play a role in the cessation of mineral growth. © 1996 Wiley-Liss, Inc.     

Biological response of chickens (Gallus gallus domesticus) induced by corticosterone and a bacterial endotoxin

Experiments were conducted with chickens exposed to corticosterone and lipopolysaccharide (LPS) from Escherichia coli, with the aim of evaluating and differentiating their effects on endocrine, metabolic and immune response. Both, corticosterone and LPS significantly elevated plasma corticosterone concentrations and increased heterophil to lymphocyte (H/L) ratios 1 h, 3 h and 24 h post-treatments. Repeated exposure to corticosterone caused a prolonged elevation of plasma corticosterone concentration and H/L ratio. Data on blood metabolites demonstrated that corticosterone stimulated hyperglycaemia, hypercholesterolemia and hypertriglyceridemia. In contrast, LPS induced hypocholesterolemia and hypotriglyceridemia at 24 h post-injection. Weight gain and relative weight of the spleen and bursa were reduced in chickens treated with corticosterone. The LPS did not show any significant effect on weekly weight gain, but stimulated an increase in the relative weight of the spleen. Corticosterone initially stimulated antibody responsiveness to infectious bronchitis virus (IBV) vaccination, but thereafter the titres decreased. This was in contrast to LPS which depressed the antibody titre to IBV vaccination. It was concluded that the biological response of chickens induced by corticosterone could be differed from the response to LPS. The major difference occurred in metabolic, growth and immune activities. It appears that, both corticosterone and LPS differently alter physiological, metabolic and immunological responses of chickens through an activation of different molecular components (cytokines and chemokines) and neuroendocrine-immune network systems.     

The effects of feed restriction on plasma biochemistry in growing meat type chickens (Gallus gallus)

The effect of feed restriction on plasma hormones (triiodothyronine - T(3), thyroxine - T(4), and corticosterone), protein, lipid, carbohydrate, and mineral metabolism and activity of plasma enzymes (creatine kinase, alkaline phosphatase, aspartate aminotransferase, and alanine aminotransferase) were studied in meat type female chickens (Gallus gallus). Ad libitum fed birds were compared with those subjected to severe and moderate quantitative feed restriction from 16 to 100 days of age. Feed restriction elevated plasma T(4) and corticosterone levels and reduced T(3). A feed restriction-induced decrease was observed for plasma protein and albumin concentrations, but not for uric acid and creatinine. Total plasma lipids, triacylglycerols, cholesterol, high density lipids, and calcium were lower for the feed restricted chickens, in particular during the latter phase of the experiment. Concentrations of glucose and phosphorus were not altered by feeding treatment. Activity of alkaline phosphatase was significantly increased in restricted chicks from day 58. Significant changes of plasma biochemical parameters induced by severe and moderate quantitative feed restriction illustrate that limiting feed intake poses an intensive stress on meat type chickens during the rapid growth period. However, activities of creatine kinase, aspartate aminotransferase, and alanine aminotransferase were significantly higher in ad libitum fed chickens during this period. This elevation in enzymatic activity may be in response to tissue damage, indicating potential health and welfare problems also in ad libitum fed meat type chickens, resulting from selection for intensive growth.