Sham Birds Research Articles

Experimental Malaria Infection Affects Songbirds' Nocturnal Migratory Activity.

Migratory animals encounter multiple parasite communities, raising concerns that migration may aid transport of infectious disease. How migration affects disease spread depends fundamentally on how disease affects migration, specifically whether infection alters individuals' migratory physiology and behavior. We inoculated white-throated sparrows (Zonotrichia albicollis) with avian malaria parasites (Plasmodium sp.), monitored parasite loads for 5 wk as the birds reached spring migratory condition, and compared nocturnal migratory restlessness (Zugunruhe), body composition (fat, lean, and whole-body mass), and hematocrit among experimentally infected birds, sham-inoculated birds, and birds that were exposed to parasites but resisted infection. Migratory restlessness increased over time in the study, but the rate of change varied between sham (control) birds, infected birds, and birds that resisted infection. We were unable to detect any effects of malaria exposure on body condition. Our findings suggest that encountering parasites affects migratory activity, regardless of whether infection occurs or is resisted.

Protection of White Leghorn chickens by recombinant fowlpox vector vaccine with an updated H5 insert against Mexican H5N2 avian influenza viruses

Despite decades of vaccination, surveillance, and biosecurity measures, H5N2 low pathogenicity avian influenza (LPAI) virus infections continue in Mexico and neighboring countries. One explanation for tenacity of H5N2 LPAI in Mexico is the antigenic divergence of circulating field viruses compared to licensed vaccines due to antigenic drift. Our phylogenetic analysis indicates that the H5N2 LPAI viruses circulating in Mexico and neighboring countries since 1994 have undergone antigenic drift away from vaccine seed strains. Here we evaluated the efficacy of a new recombinant fowlpox virus vector containing an updated H5 insert (rFPV-H5/2016), more relevant to the current strains circulating in Mexico. We tested the vaccine efficacy against a closely related subcluster 4 Mexican H5N2 LPAI (2010 H5/LP) virus and the historic H5N2 HPAI (1995 H5/HP) virus in White Leghorn chickens. The rFPV-H5/2016 vaccine provided hemagglutinin inhibition (HI) titers pre-challenge against viral antigens from both challenge viruses in almost 100% of the immunized birds, with no differences in number of birds seroconverting or HI titers among all tested doses (1.5, 2.0, and 3.1 log10 mean tissue culture infectious doses/bird). The vaccine conferred 100% clinical protection and a significant decrease in oral and cloacal virus shedding from 1995 H5/HP virus challenged birds when compared to the sham controls at all tested doses. Virus shedding titers from vaccinated 2010 H5/LP virus challenged birds significantly decreased compared to sham birds especially at earlier time points. Our results confirm the efficacy of the new rFPV-H5/2016 against antigenic drift of LPAI virus in Mexico and suggest that this vaccine would be a good candidate, likely as a primer in a prime-boost vaccination program.

Effect of nucleus accumbens lesions on socially motivated behaviour of young domestic chicks

Behaviour of young domestic chicks when isolated from conspecifics is influenced by two conflicting drives: fear of potential predator and craving for company. The nucleus accumbens (Ac) has been suggested to influence social behaviour, as well as motivation in goal-directed tasks. In this study, the Ac of 1-day-old domestic chicks was lesioned bilaterally, using radiofrequency method. Open field behaviour before and after presenting a silhouette of a bird of prey was recorded, followed by a behavioural test to measure group size preference and social motivation of chicks. Ac-lesioned individuals emitted more distress calls and ambulated more in the open field test, however, they reacted to the predatory stimulus very similarly to control chicks: their vocalization was reduced and the intergroup difference in motor activity also disappeared. There was no difference between the lesioned and control chicks in the latency to approach their conspecifics in the social motivation test, and both groups chose the larger flock (eight) of conspecifics over the smaller one (three). Concerning the role of Ac in social behaviour, a difference between lesioned and sham birds was evident here only in the absence of detectable stimulus (predator or conspecifics). These findings may reflect either decreased fear of exposure to predators or increased craving for conspecifics suggesting that the likely function of Ac is to modulate goal-driven, including socially driven, behaviours, especially when the direct stimulus representing the goal is absent. This is in harmony with the known promotion of impulsiveness by Ac lesions.

The role of the pineal gland in the photoperiodic control of bird song frequency and repertoire in the house sparrow, Passer domesticus

Temperate zone birds are highly seasonal in many aspects of their physiology. In mammals, but not in birds, the pineal gland is an important component regulating seasonal patterns of primary gonadal functions. Pineal melatonin in birds instead affects seasonal changes in brain song control structures, suggesting the pineal gland regulates seasonal song behavior. The present study tests the hypothesis that the pineal gland transduces photoperiodic information to the control of seasonal song behavior to synchronize this important behavior to the appropriate phenology. House sparrows, Passer domesticus, expressed a rich array of vocalizations ranging from calls to multisyllabic songs and motifs of songs that varied under a regimen of different photoperiodic conditions that were simulated at different times of year. Control (SHAM) birds exhibited increases in song behavior when they were experimentally transferred from short days, simulating winter, to equinoctial and long days, simulating summer, and decreased vocalization when they were transferred back to short days. When maintained in long days for longer periods, the birds became reproductively photorefractory as measured by the yellowing of the birds' bills; however, song behavior persisted in the SHAM birds, suggesting a dissociation of reproduction from the song functions. Pinealectomized (PINX) birds expressed larger, more rapid increases in daily vocal rate and song repertoire size than did the SHAM birds during the long summer days. These increases gradually declined upon the extension of the long days and did not respond to the transfer to short days as was observed in the SHAM birds, suggesting that the pineal gland conveys photoperiodic information to the vocal control system, which in turn regulates song behavior.

Effects of egg oiling on ground-nesting double-crested cormorants at a colony in Lake Ontario: an examination of nest-attendance behaviour

Context We assessed the effects of egg oiling on ground-nesting double-crested cormorants (Phalacrocorax auritus) in the context of an emerging management strategy for the largest known cormorant colony on the lower Great Lakes. We designed the present study to answer specific questions in response to concerns raised by stakeholders and members of the public regarding this management technique. Aims The aim of the present study was to examine the behavioural response of adult cormorants to egg oiling. Prior work on this issue has focussed on population-response questions rather than the behavioural level. Consequently, detailed observations on how cormorants respond to egg oiling are lacking. Methods Using instantaneous and focal observations to measure behaviours, we compared Treatment nests (n = 24, 23) to Control (n = 24) and Sham (handled, but not treated; n = 24) nests. We observed nest attendance, incubation and mate-presence behaviour, and divided observations into pre-chick and entire-season categories for analysis. Key results Our study determined that egg oiling does not cause immediate nest desertion by adult birds; Treatment birds incubated their nests as long as did Sham and Control birds. We found no difference among the three groups in the proportion of time a mate was present during incubation for Control and Sham nests in the pre-chick period. We found that the total seasonal duration of nest attendance by Treatment birds was shorter than that for the birds in the other groups. Conclusions Both incubation and mate-presence data suggest that egg oiling did not measurably affect the behaviour of adult cormorants in the pre-chick period. Our study also suggests that Treatment birds attended their nest long enough to preclude re-nesting within the breeding season, although this may not apply for regions with longer nesting seasons. Implications Our study indicates that egg oiling, administered judiciously, may be an appropriate management technique for ground-nesting cormorants, although management targets must be clearly articulated.

The pineal clock affects behavioral circadian rhythms but not photoperiodic induction in the Indian weaver bird (Ploceus philippinus)

We investigated whether pineal is part of the circadian clock system which regulates circadian rhythms of activity and photosensitivity in the Indian weaver bird (Ploceus philippinus). Two experiments were performed. The first experiment examined the induction of testicular growth, and androgen-dependent beak pigmentation and luteinizing hormone (LH)-specific plumage coloration in pinealectomised (pinx) and sham-operated (sham) birds exposed to short day (8 h light: 16 h darkness, 8L:16D) and long day (16L:8D) for 9 months in the late breeding and early regressive phase (October), or the late regressive and preparatory phase (January) of the annual testicular cycle. As expected, short days were non-stimulatory, and long days stimulated testicular growth, beak pigmentation and plumage coloration. There was no difference in the response between pinx and sham birds subjected to short or long days in October, but the response was enhanced in pinx birds that were subjected to long day in January. In the second experiment circadian behavioral rhythms were studied (activity pattern in singly housed birds) in weaver birds first exposed at two different phases of the annual testicular cycle to a stimulatory photoperiod (12L:12D in preparatory phase or 13L:11D in early breeding phase) and then released into dim continuous light (LLdim). All birds showed synchronization to the light period before and after the pinealectomy; there was no difference in the response between pinx and sham birds. When released into LLdim, sham birds exhibited circadian rhythmicity continuously, whereas pinx birds lost circadian rhythmicity after some cycles. Considered together, these results suggest that circadian clock residing within the pineal gland regulates the circadian rhythm in activity, but not the circadian rhythm involved in photoperiodic induction of the Indian weaver bird.

Plasma taurine levels in broilers with pulmonary hypertension syndrome induced by unilateral pulmonary artery occlusion

Low plasma levels of taurine are associated with losses of cardiac sarcomeric proteins, leading to heart failure in mammals. Recently, it was proposed that cardiac taurine depletion serves to defend the heart against injury caused by regional ischemia in mammals. The role of taurine has not been well documented in broilers, particularly in relation to pulmonary hypertension syndrome (PHS; ascites). Three independent experiments evaluated plasma taurine in male broilers by utilizing the following treatments: unoperated controls (CONTROL; n = 10 in each experiment); sham operated (SHAM; n = 11, 12, and 10); or, unilaterally pulmonary artery clamped (PAC; n = 18, 29, and 24) that did (PAC-ascites) or did not (PAC-normal) develop ascites within 12 d postsurgery. Plasma samples were collected 9 and 11 d postsurgery in Experiments 1 and 2, respectively, and 2 d before and 4, 8, and 12 d after surgery in Experiment 3. Plasma taurine was analyzed by HPLC. Twelve days postsurgery, the birds were euthanatized, and ventricles were weighed for calculating the right:total ventricular weight ratio (RV:TV). The RV:TV of PAC birds (>0.35) consistently was higher (P < 0.01) than that of CONTROL and SHAM birds (<0.27 and 0.25, respectively). In Experiments 1 and 2, plasma taurine was higher (P < 0.05) in PAC-ascites (380 and 370 nmol/mL) than in SHAM broilers (183 and 186 nmol/mL), whereas CONTROL (262 and 278 nmol/mL) and PAC-normal (362 and 300 nmol/mL) broilers tended to have intermediate plasma taurine levels. In Experiment 3, PAC birds had higher (P < 0.05) plasma taurine at 8 and 12 d postsurgery when compared with presurgery levels, whereas plasma taurine was unchanged over time in CONTROL and SHAM birds. These results suggest cardiac taurine may be released into the plasma as a protective mechanism in response to the induction of pulmonary hypertension, hypoxemia, and right-side heart failure, similar to the mechanism reported for protecting cardiac muscle from ischemia in mammals.

Bursectomy and In Vitro Response of Adrenal Gland to Adrenocorticotropic Hormone and Testis to Human Chorionic Gonadotropin in Immature Male Chickens

This investigation was carried out to determine the effects of bursectomy on in vitro response of adrenal glands to adrenocorticotropic hormone (ACTH) and testes to human chorionic gonadotropin (HCG) in immature male chickens. One-day-old Single Comb White Leghorn male chicks were surgically bursectomized (BSX). Sham-operated (sham) chicks were used as controls. At 5 wk of age, adrenal cortical cells (ACC) from BSX and sham birds were incubated in vitro with various concentrations (0, 10−7, 10−6, and 10−5M) of ACTH for 2 h, and then corticosterone was measured in all supernatants. At 15 wk of age, Leydig cells from testes of both groups were incubated in vitro with HCG (3,000 IU/mL) for 3 h, and then testosterone was measured in all supernatants. Corticosterone concentrations in response to both 10−6 and 10−5 ACTH were significantly lower for BSX than for sham ACC. Leydig cells from sham birds produced significantly more testosterone than those of BSX birds whether or not the cells were stimulated with HCG. Furthermore, Leydig cells from sham birds, but not from BSX birds, produced significantly more testosterone when stimulated with HCG than when saline was added. These results indicated that the bursa of Fabricius or its products might have a stimulatory effect on the response of ACC and Leydig cells to ACTH and HCG, respectively.

Influence of ovariectomy and photostimulation on luteinizing hormone in the domestic turkey: evidence for differential regulation of gene expression and hormone secretion.

We have investigated the effects of ovariectomy (OVX) and photostimulation (PS) on anterior pituitary LH beta mRNA abundance and circulating levels of LH in the domestic turkey. The birds were divided into the following four treatment groups: non-PS SHAM, PS SHAM, non-PS OVX, and PS OVX. Photostimulation was initiated 7 days after OVX. Anterior pituitaries and blood samples were collected on Days 0, 1, 3, 7, 14, and 26 after PS. The experiment was terminated when the PS SHAM birds were laying eggs regularly. Photostimulation of intact birds induced an increase in both LH beta mRNA levels (Days 3, 14, and 26 of PS) and serum LH (Days 14 and 26 of PS; p < 0.05), while OVX of non-PS birds significantly elevated LH on Days 7, 10, 21, and 33 and LH beta mRNA levels on Days 7, 8, 10, 14, and 33 post-OVX. Circulating LH titers in the PS OVX birds were well above the levels in the non-PS OVX group (p < 0.005); however, LH beta mRNA abundance was not significantly greater (p > 0.05). Our results indicate that OVX and PS appear to be additive in stimulating LH secretion but do not have this effect on LH beta mRNA levels. We have hypothesized that gonadectomy induces near-maximal accumulation of LH beta mRNA and that therefore the subsequent stimulus of a long photoperiod has no additional effect. We suggest that increases in serum LH levels, beyond those of the OVX bird, may be controlled post-transcriptionally.

Influence of vagotomy in domestic fowls on feeding activity, food passage, digestibility and satiety effects of two peptides

The effects of bilateral vagotomy at the level of the proventriculus, in immature female fowls (VAG), on body weight, feeding activity parameters, rate of food passage, digestibility, and satiety effects of bombesin (BBS) and cholecystokinin octapeptide (CCK8), were compared with those in sham-operated controls (SHAM). SHAM birds gained weight at a greater rate postoperatively than before their operation, whereas VAG birds did not. Daily food intake did not change significantly as a result of the operation with either SHAM or VAG birds, and the only effect on feeding activity parameters was on the length of intermeal intervals, which increased in VAG birds. Rate of passage of the layers' mash diet was slower, and its apparent digestibility lower, in VAG than in SHAM birds. Short-term suppression of food intake, following intravenous injections of BBS (10 μg/kg) or CCK8 (10 μg/kg), did not differ between SHAM and VAG birds. The different postoperative weight gains may have been a consequence of different weights of food digested, and the difference in interval length was probably due to the different rates of food passage. The results of these experiments indicate that efferent information affecting rate of passage and digestibility travels via the vagus, but that afferent information concerned with initiation and termination of meals, and with satiety effects of BBS and CCK8, does not. Instead, such afferent information may travel via the intestinal nerve, which is unique to birds.

Bursectomy and Its Influence on Circulating Corticosterone, Triiodothyronine, and Thyroxine in Immature Male Chickens

This investigation was carried out to determine the effect of bursectomy on circulating corticosterone, triiodothyronine (T3), and thyroxine (T4) in immature male chickens. One-day-old Single Comb White Leghorn male chicks were surgically bursectomized (BSX). Sham-operated chicks were used as control. Blood samples were collected from different BSX and sham birds at 2, 3, and 4 weeks of age. Serum concentrations of corticosterone, T3, and T4 were measured using radioimmunoassays. Serum concentrations of corticosterone and T3 were higher in BSX than sham-operated birds at all ages. Concentrations of T4, however, were similar in both groups. It was concluded that the bursa, directly or indirectly, affected hormone secretion from the thyroid and adrenal glands.

Cigarette smoking impairs hepatic uptake of high density lipoproteins

The effect of chronic inhalation of cigarette smoke on hepatic uptake of high density lipoproteins (HDL) in White Carneau pigeons was examined. Four treatment groups included: 1) Shelf Control birds fed a chow diet and retained in their cages; 2) Sham pigeons fed a cholesterol-saturated fat diet and exposed to fresh air by a smoking machine; 3) Low nicotine-low carbon monoxide (LoLo) animals also fed the cholesterol diet and exposed to low concentrations of these cigarette smoke products; and 4) High nicotine-high carbon monoxide (HiHi) birds fed the cholesterol diet and subjected to high concentrations of these components. Livers from both smoke exposed groups contained significantly more triglyceride than those from Sham animals while livers from HiHi birds alone had elevated concentrations of protein. Liver slices from LoLo and HiHi pigeons incorporated significantly less HDL 3H free and esterified cholesterol and HDL 14C apoprotein from media during in vitro incubation than livers from Sham birds. Impaired hepatic uptake of HDL suggests a permanent alteration in liver function resulting from chronic exposure to tobacco smoke and may represent one mechanism by which cigarette smoking attenuates HDL's anti-atherogenic properties.

Cigarette smoke-induced depression in LCAT activity

The effect of acute inhalation of cigarette smoke on plasma cholesterol esterification by lecithin-cholesterol acyltransferase (LCAT) in atherosclerosis-susceptible White Carneau pigeons was examined. Pigeons were assigned to four treatment groups: (1) Shelf Control fed a chow diet and not exposed to smoke products; (2) Sham pigeons fed a cholesterol-saturated fat diet and exposed to fresh air by the Lorillard smoking machine; (3) low nicotine-low carbon monoxide (LoLo) animals also fed the cholesterol diet and exposed to low concentrations of these cigarette smoke products; and (4) high nicotine-high carbon monoxide (HiHi) birds fed the cholesterol diet and subjected to high concentrations of these inhalants. Both Control and Sham birds had significantly higher LCAT activity (percentage esterification per minute) than HiHi pigeons. Experiments designed to determine whether altered enzyme and/or substrate were responsible for depressed activity revealed no smoke-related modification in substrate efficiency. In addition, Sham and HiHi pigeons had similar concentrations of plasma-free cholesterol, high density lipoprotein (HDL) cholesterol, cholesteryl ester and phospholipid, and similar HDL phospholipid and cholesteryl ester fatty acid profiles. However, reduced LCAT activity in HiHi pigeons can be explained by (1) impairment of enzyme efficiency as estimated by in vitro analysis; and (2) in vivo reduction in levels of LCAT cofactor, HDL apoprotein A-I.

The influence of the sex of chickens on the effect of occlusion of the left pulmonary artery

In 5 male (M) and 10 female (F) chickens the left pulmonary artery was surgically occluded (ligated) at 36 days of age (PAO). In a second group of chickens (7 M and 6 F) of similar age a similar surgical procedure was followed, but the left pulmonary artery was not occluded (SHAM). A third group of chickens (10 M and 6 F) was kept as controls (C). When the birds were 72 days old PO 2, pH and haematocrit were measured in arterial blood, necropsies were performed and ventricular weights were obtained. SHAM birds showed no differences when compared to controls. All PAO birds had right ventricular hypertrophy (RVH) which was more marked in the males and 2 of the 5 PAO males had signs of right heart insufficiency. The ratio of the right ventricular weight to body weight was 0·60, 0·50, 1·37 and 0·82 (g per kg) for control M, control F, PAO M and PAO F respectively. The left ventricle of PAO birds was not affected. PaO 2 in the PAO birds was lower than in the controls. Haematocrit was higher in the PAO M than in the controls, but it remained unchanged in the PAO F. These findings indicate that increasing the blood flow through one lung in chickens produces right ventricular hypertrophy and hypoxaemia, probably as a consequence of pulmonary arterial hypertension. Furthermore, the effects of left pulmonary artery occlusion in males seem to be more severe than in female chickens.

The Effect of Cropectomy on Selected Reproductive and Physiological Characteristics of Laying Hens

Two-hundred and fifty Babcock B-300 pullets (18 weeks of age) were either cropectomized, sham-operated or used as unoperated controls in two experiments. Although feed consumption was slightly less in cropectomized birds than in control birds, the pattern of feed consumption in relation to time of day remained unchanged. Egg production and body weight of cropectomized birds were significantly lower than that of control or sham birds. Egg weight was not affected by cropectomy or the sham operation. Cropectomy had no influence on the pattern of serum calcium or on egg specific gravity in relation to time of day; however, serum calcium and egg specific gravity was consistently lower at each time interval measured throughout the day or night when compared to that of controls. The adverse effect of cropectomy on specific gravity of eggs and serum calcium indicated that the crop is an important organ in the laying hen. The crop appeared to serve as a storage depot for feed providing the bird with nutrients necessary for optimal shell quality during periods of non-consumption.

Effect of ultimobranchialectomy on the laying hen.

Ultimobranchialectomized (UBX) chickens were reared to maturity and through several months of normal egg production. The UBX hens consumed significantly less feed and produced smaller eggs with a trend toward reduced shell thickness. Plasma calcium, phosphorus and alkaline phosphatase activities measured at intervals throughout the eggshell formation cycle exhibited similar diurnal variations in both UBX and SHAM birds. However, the UBX birds had consistently lower values. These studies indicate no major influence of the ultimobranchial glands on normal calcium metabolism in the laying hen.

Effect of thymectomy and bursectomy on precipitin and natural hemagglutinin production in the chicken

1. Thymectomy of chickens during the first 3 days of age does not consistently affect precipitin production to bovine serum albumin when challenged at 6 to 9 weeks of age. In some cases, thymectomized groups did not differ in mean peak titer from controls; in some cases the response was significantly lower; in one case the response was significantly higher. This variation was not evident for the time necessary to clear antigen from the circulation. 2. Of intact and sham control birds 100% responded by producing precipitins, whereas 6% of the thymectomized birds did not give a detectable response. This frequency of negative responders was statistically significant. 3. There was a tendency for groups with greater amounts of residual thymic tissue to give higher mean precipitin titers. However, the titers of birds with no residual thymus fell in a range very similar to that of the controls. 4. The development of natural hemagglutinins was not affected by thymectomy. 5. Splenectomy performed from 2 to 10 days of age significantly delayed the appearance of precipitins but did not affect the mean peak titer. 6. Bursectomy at 1 to 2 days of age reduced the mean peak precipitin titers and the natural hemagglutinin titers drastically. Most birds did not give a detectable response.