Hyperphagia induced by intrahypothalamic implants of mercury thioglucose

Rats implanted with intrahypothalamic cannulas prepacked with mercury thioglucose or gold thioglucose developed lesions of the ventromedial hypothalamus, were hyperphagic and gained significantly more weight than normal animals (p<0.01). Untreated cannulated animals and those implanted cannulas packed with gold thiomalate or mercuric chloride showed non-specific brain damage and were not significantly different from normal animals with respect to food intake or weight gain.     

Effect of different levels of diet methionine and metabolisable energy on broiler performance and immune system

Chickens were chosen by a factorial 2×2 and random design. Methionine levels of 1.2 and 0.45% were adjusted to 2800 and 3200 kcal/kg metabolisable energy (ME) in starters and 0.9 and 0.33% to 2800 and 3200 kcal/kg ME in grower period, respectively. Antibody titres and IgG in chickens by 1.2 and 0.9% methionine were significantly higher than low levels of methionine. Significant increases of total leukocyte, percentage of lymphocytes and heterophils were observed in chickens fed by high methionine levels. Significant weight changes of bursa and spleen were found in this case at 42 days of age. Chicken body weights were significantly increased by a high level of methionine and low level of energy. Higher feed intake was obtained at high methionine and low energy. It is concluded that inclusion of high levels of methionine and energy in broilers diet have a beneficial effect on humoral immunity and performance.     

Efficacy of early treatment with toltrazuril in prevention of coccidiosis and necrotic enteritis in chickens

In the present study, efficacy of the toltrazuril treatment for prevention of coccidiosis and necrotic enteritis was tested. Ninety-six 14-day-old commercial broiler chickens were caged and divided into eight groups (n=12), designated groups 1 to 8. Chickens of groups 1 to 6 were inoculated orally at 18 days of age with 25,000 oocysts of Eimeria tenella and 75,000 oocysts of Eimeria brunetti. At 22 days of age, chickens of groups 1 to 6 were infected with 10⁹ colony-forming unit Clostridium perfringens. Chickens of group 1 were treated with 75 parts/10⁶ toltrazuril in drinking water for 8 h on two consecutive days up to 12 h before Eimeria infection, while chickens of groups 2 to 5 were treated with the same dose of toltrazuril at 12 h, 36 h, 60 h and 84 h after Eimeria infection, respectively. The non-treated group 6 served as a positive control. Chickens in group 7 were treated with toltrazuril at 17 and 18 days of age, and those of group 8 remained uninfected and non-treated as a negative control. The feed conversion ratio was higher in the positive control compared with other groups. The mortality rates were 16.8% and 41.7% in the late toltrazuril-treated (at 84 h) and infected non-treated chickens, respectively. Lesions scores of necrotic enteritis or coccidiosis in infected, non-treated chickens were significantly more severe compared with negative controls (P<0.01) and late toltrazuril-treated (at 84 h) chickens (P<0.05). In conclusion, application of toltrazuril before Eimeria challenge protected chickens from coccidiosis and indirectly from successive necrotic enteritis caused by C. perfringens infection.     

The use of sodium pentobarbital for the study of immobility-related (type 2) hippocampal theta

A series of experiments investigated the effects of sodium pentobarbital on the dentate electroencephalographic (EEG) activity of rats and rabbits implanted with tungsten microelectrodes. Type 1 (movement-related) theta was abolished in both species and Type 2 (immobility-related) theta was abolished in the rat but remained intact and readily elicitable by sensory stimulation in the rabbit, following anaesthetic doses of pentobarbital. It was proposed that sodium pentobarbital may be useful for the investigation of mechanisms underlying the two types of theta and that the effect of pentobarbital provides further evidence for species differences in the way the hippocampal formation produces Type 2 theta.     

Opioid activation in the lateral parabrachial nucleus induces hypertonic sodium intake

Opioid mechanisms are involved in the control of water and NaCl intake and opioid receptors are present in the lateral parabrachial nucleus (LPBN), a site of important inhibitory mechanisms related to the control of sodium appetite. Therefore, in the present study we investigated the effects of opioid receptor activation in the LPBN on 0.3 M NaCl and water intake in rats. Male Holtzman rats with stainless steel cannulas implanted bilaterally in the LPBN were used. In normohydrated and satiated rats, bilateral injections of the opioid receptor agonist beta-endorphin (2 nmol/0.2 mul) into the LPBN induced 0.3 M NaCl (17.8+/-5.9 vs. saline: 0.9+/-0.5 ml/240 min) and water intake (11.4+/-3.0 vs. saline: 1.0+/-0.4 ml/240 min) in a two-bottle test. Bilateral injections of the opioid antagonist naloxone (100 nmol/0.2 mul) into the LPBN abolished sodium and water intake induced by beta-endorphin into the LPBN and also reduced 0.3 M NaCl intake (12.8+/-1.5 vs. vehicle: 22.4+/-3.1 ml/180 min) induced by 24 h of sodium depletion (produced by the treatment with the diuretic furosemide s.c.+sodium deficient food for 24 h). Bilateral injections of beta-endorphin into the LPBN in satiated rats produced no effect on water or 2% sucrose intake when water alone or simultaneously with 2% sucrose was offered to the animals. The results show that opioid receptor activation in the LPBN induces hypertonic sodium intake in satiated and normohydrated rats, an effect not due to general ingestive behavior facilitation. In addition, sodium depletion induced 0.3 M NaCl intake also partially depends on opioid receptor activation in the LPBN. The results suggest that deactivation of inhibitory mechanisms by opioid receptor activation in the LPBN releases sodium intake if excitatory signals were activated (sodium depletion) or not.     

Pathological and clinical effects of Eimeria tenella in partially immune chickens

Chickens were made partially resistant to Eimeria tenella by giving them several small doses of oocysts. Such chickens had severe lesions after challenge infection and had similar packed cell volumes and prothrombin times, but their body weight was only marginally affected compared with chickens having their first infection. Extracts were prepared from the caeca of partially immune and susceptible birds; the caeca used all had similar severe (grade 3) lesions. When these extracts were injected intravenously (i.v.) into coccidia-free chickens, sudden death occurred. However, the amount of “toxic” substances present in the caeca of chickens having their first infection with E. tenella was greater than that of caecal extract prepared from chickens previously exposed to the parasite. Extracts prepared from the caeca of chickens partially resistant to E. tenella also had lower thromboplastin activity. Chickens made resistant to E. tenella by repeated immunizing doses were not protected from the lethal effects of the caecal extract from E. tenella-infected chickens given i.v.Chickens inoculated intra-abdominally with caecal extract from E. tenella-infected chickens were slightly protected against the lethal effects of caecal extract i.v. and the pathogenic effects caused by the inoculation of oocysts.     

Inhibition of food intake by CRF in chickens.

The effect of intracerebroventricular (i.c.v.) injection of corticotrophin releasing factor (CRF) on food and water intake and on body temperature in chickens was determined. Both broiler and Leghorn type chickens were utilized in this experiment. A stainless steel guide cannula was surgically implanted into the right lateral ventricle of each bird. The i.c.v. injection of CRF significantly decreased food intake in both fed and overnight-fasted broilers and Leghorns. Water intake was decreased by CRF in Leghorns but not broilers. When CRF was injected into Leghorns given access to water, but not food, water intake was not affected. Body temperature was not affected by the i.c.v. injection of CRF. These results suggest that CRF acts within the central nervous system of chickens to decrease food intake while having no affect on water intake or body temperature.     

Alpha2-adrenergic activation in the lateral parabrachial nucleus induces NaCl intake under conditions of systemic hyperosmolarity

The inhibition of sodium intake by increased plasma osmolarity may depend on inhibitory mechanisms present in the lateral parabrachial nucleus. Activation of alpha(2)-adrenergic receptors in the lateral parabrachial nucleus is suggested to deactivate inhibitory mechanisms present in this area increasing fluid depletion-induced 0.3 M NaCl intake. Considering the possibility that lateral parabrachial nucleus inhibitory mechanisms are activated and restrain sodium intake in animals with increased plasma osmolarity, in the present study we investigated the effects on water and 0.3 M NaCl intake produced by the activation of alpha(2)-adrenergic receptors in the lateral parabrachial nucleus in rats with increased plasma osmolarity. Male Holtzman rats with stainless steel cannulas implanted bilaterally into the lateral parabrachial nucleus were used. One hour after intragastric 2 M NaCl load (2 ml), bilateral injections of moxonidine (alpha(2)-adrenergic/imidazoline receptor agonist, 0.5 nmol/0.2 microl, n=10) into the lateral parabrachial nucleus induced a strong ingestion of 0.3 M NaCl intake (19.1+/-5.5 ml/2 h vs. vehicle: 1.8+/-0.6 ml/2 h), without changing water intake (15.8+/-3.0 ml/2 h vs. vehicle: 9.3+/-2.0 ml/2 h). However, moxonidine into the lateral parabrachial nucleus in satiated rats not treated with 2 M NaCl produced no change on 0.3 M NaCl intake. The pre-treatment with RX 821002 (alpha(2)-adrenergic receptor antagonist, 20 nmol/0.2 microl) into the lateral parabrachial nucleus almost abolished the effects of moxonidine on 0.3 M NaCl intake (4.7+/-3.4 ml/2 h). The present results suggest that alpha(2)-adrenergic receptor activation in the lateral parabrachial nucleus blocks inhibitory mechanisms, thereby allowing ingestion of hypertonic NaCl under conditions of extracellular hyperosmolarity. We suggest that during cell dehydration, circuits subserving sodium appetite are activated, but at the same time strongly inhibited through the lateral parabrachial nucleus.     

Eating,drinking and temperature response of chicks to brain catecholamine injections

The effects of dopamine, norepinephrine and epinephrine on feed intake, water intake, water consumption and rectal body temperature (T_R) were investigated using broiler cockerels. Chicks were maintained in a thermoneutral environment with feed and water available ad lib. Solutions of dopamine, l-norepinephrine and l-epinephrine were prepared in concentrations of 33, 67 and 100 μg/10 μl in artificial cerebrospinal fluid and injected into the lateral ventricles. Dopamine and norepinephrine caused no effect on feed consumption while epinephrine caused a significant increase. Although norepinephrine had no effect on feed intake, it did precipitate a narcoleptic response which may have masked a stimulation of feed intake. Epinephrine and norepinephrine significantly decreased T_R while dopamine had no effect. Water consumption was not affected by any of the catecholamines. These results suggest that epinephrine and possibly norepinephrine are involved in neural control of feed intake, but not water consumption in chickens.     

5-HT2 and 5-HT3 receptors in the lateral parabrachial nucleus mediate opposite effects on sodium intake

The present study investigated the role of several 5-HT receptor subtypes in the lateral parabrachial nucleus (LPBN) in the control of sodium appetite (i.e. NaCl consumption). Male Holtzman rats had cannulas implanted bilaterally into the LPBN for the injection of 5-HT receptor agonists and antagonists in conjunction with either acute fluid depletion or 24-h sodium depletion. Following these treatments, access to 0.3 M NaCl was provided and the intakes of saline and water were measured for the next 2 h. Bilateral injections of the 5-HT2A receptor antagonist, ketanserin or the 5-HT2C receptor antagonist, mianserin into the LPBN increased 0.3 M NaCl intake without affecting water intake induced by acute fluid-depletion. Bilateral injections of the 5-HT2B receptor agonist, BW723C86 hydrochloride, had no effect on 0.3 M NaCl or water intake under these conditions. Treatment of the LPBN with the 5-HT2B/2C receptor agonist, 2-(2-methyl-4-clorophenoxy) propanoic acid (mCPP) caused dose-related reductions in 0.3 M NaCl intake after 24 h sodium depletion. The effects of mCPP were prevented by pretreating the LPBN with the 5-HT2B/2C receptor antagonist, SDZSER082. Activation of 5-HT3 receptors by the receptor agonist, 1-phenylbiguanide (PBG) caused dose-related increases in 0.3 M NaCl intake. Pretreatment of the LPBN with the 5-HT3 receptor antagonist, 1-methyl-N-[8-methyl-8-azabicyclo (3.2.1)-oct-3-yl]-1H-indazole-3-carboxamide (LY-278,584) abolished the effects of PBG, but LY-278,584 had no effects on sodium or water intake when injected by itself. PBG injected into the LPBN did not alter intake of palatable 0.06 M sucrose in fluid replete rats. The results suggest that activation of the 5-HT2A and 5-HT2C receptor subtypes inhibits sodium ingestion. In contrast, activation of the 5-HT3 receptor subtype increases sodium ingestion. Therefore, multiple serotonergic receptor subtypes in the LPBN are implicated in the control of sodium intake, sometimes by mediating opposite effects of 5-HT. The results provide new information concerning the control of sodium intake by LPBN mechanisms.     

Immunological tolerance in chickens hatching from eggs injected with cell-associated herpesvirus of Turkey (HVT)

Cell-associated herpesvirus of turkeys (HVT) was inoculated in ovo at various stages of incubation. Chickens hatching from these eggs were tested for anti-HVT antibodies by several serologic procedures including enzyme-linked immunosorbent assay, indirect immunofluorescence assays, and western blot. Viremic chickens that remained free of detectable antibodies were considered tolerant to HVT. Chickens exposed to HVT at embryonation day 14 or earlier had 6-33% incidence of tolerance. Tolerant chickens developed persistent HVT viremia. A preliminary challenge experiment provided circumstantial evidence that tolerant to HVT may be associated with reduced resistance to virulent Marek's disease virus. Tolerance to HVT did not influence the ability of the chickens to produce antibodies against an extraneous antigen or respond to a T cell mitogen.     

Vaccination of chickens against Newcastle disease with a food pellet vaccine.

The Australian, heat-resistant, a virulent V4 strain of Newcastle disease (ND) virus was selected for further heat resistance to give a variant designated V4-UPM. V4-UPM was sprayed on to food pellets which were fed to chickens in amounts calculated to give about 10(6) EID50 per chicken. Chickens vaccinated only once by feeding developed no haemagglutination-inhibition (HI) antibodies and were not protected against challenge with a viscerotropic velogenic strain of ND virus. Chickens given food pellet vaccine at 3 and 6 weeks of age developed HI antibodies and were substantially protected against parenteral and contact challenge with virulent ND virus. Similar protection was achieved when the V4-UPM vaccine was given intranasally on two occasions or when the vaccine virus was allowed to spread by contact from intranasally vaccinated chickens to nonvaccinated chickens. Heat resistant ND vaccine incorporated in food pellets may provide a method for protecting village chickens against ND in tropical countries.     

Feeding and locomotion responses to centrally injected nociceptin/orphanin FQ in chicks

Nociceptin/orphanin FQ (N/OFQ), the endogenous ligand of the opioid receptor-like receptor or nociceptin receptor (NOP), has been shown to induce feeding, locomotion, anti-stress and anxiolytic effects in rodents after central nervous system injection. In this study, the effect of intracerebroventricular (icv) injection of N/OFQ on feeding and locomotion behavior was evaluated in male broiler-type chickens. The icv injection of N/OFQ caused a moderate but significant increase in feed intake similar to the classical opioid peptides in rats. It also increased feed pecking frequency and feeding time 1 h after injection. Stepping, wing flapping and preening were not affected by N/OFQ. These results suggest that N/OFQ can act within the central nervous system of chickens to increase feed intake.     

Alpha 2-adrenoceptor blockade does not block feeding induced by neuropeptide Y in sheep

We tested the hypothesis that blockade of central alpha 2-adrenergic receptors would prevent neuropeptide Y (NPY)-induced feeding. Nine young female sheep were fitted with lateral ventricula cannulas. Bolus intracerebroventricular (ICV) injection of 3 nmol of NPY increased feed intake after 30 min between 45 and 153% in three experiments. A bolus ICV injection of 400 or 100 nmol of the alpha 2-antagonist, yohimbine, either 5 or 30 min before NPY injection, did not attenuate this response. Instead, yohimbine increased feed intake over NPY-induced feeding by 52 to 55%. We interpret these data as evidence that the putative NPY feeding pathway in feed-sated sheep is not dependent on the type of alpha 2-adrenergic mechanism which can be blocked by ICV injection of yohimbine.     

Behavior of haptoglobin in experimental allergic encephalomyelitis in chickens

Concentration of haptoglobin (Hpc) in serum of chickens with inflammation and allergic encephalomyelitis (EAE) was determined. Chickens with aseptic inflammatory state revealed 2.5 times higher concentration of Hpc while in the course of EAE only small increase was observed. Administration of immunomodulator--isoprinosine, resulted in elevation of Hpc level as compared to nontreated chickens.     

Eimeria: immunisation of young chickens kept in litter pens

Infection of chickens with an attenuated strain of Eimeria tenella gave good protection against challenge with the parent strain of this species. Chickens given an attenuated strain of E. acervulina var. mivati were protected against challenge with other pathogenic cultures of E. acervulina when kept in litter pens under conditions allowing reinfection. Two-week-old chickens, kept in litter pens, were given attenuated strains of E. tenella and E. acervulina and small numbers of oocysts (50-100) of E. brunetti, E. maxima and E. necatrix. Body weight gain was unaffected and resistance to challenge infection was demonstrated at 6 and 9 weeks after inoculation. In other experiments only a small proportion of 1 to 3-week-old chickens in each pen were given oocysts. Chickens placed in contact with these 'seeder' chickens were immunised against five species of Eimeria within a 2 to 4 week period. Similar experiments with 1-week-old chickens showed that these could also be immunised but the degree of parasitism during immunisation caused some weight gain depression. These results suggest that controlled immunisation against several species of Eimeria may be possible and further experiments are needed under conditions which more closely resemble those operating in the field.     

Eimeria: further studies on the immunisation of young chickens kept in litter pens

Chickens were inoculated with small numbers of oocysts of attenuated (E. tenella TA and E. mivati MA) and virulent strains of E. acervulina, E. brunetti, E. maxima and E. necatrix under conditions designed to permit reinfection. Chickens were immune to challenge with pathogenic laboratory strains 6 weeks after inoculation with either the homologous strains or attenuated derivatives. Immunity to challenge with heterologous strains was also achieved, except that it was incomplete with E. maxima. To obtain complete protection against heterologous challenge with E. maxima, it was necessary to immunise with several strains. Chickens immunised at 1 or 2 weeks of age showed a stronger immunity than birds immunised at 1 day old when challenged at 6 weeks of age. The effect of inoculating chickens with 0.1-10 times a standard immunising dose was examined. Chickens given 0.1-1 times the standard dose were substantially immunised but body weight gain was reduced with higher doses. The results show that controlled immunisation of 1- or 2-week-old chickens against six species of Eimeria is possible, and that a substantial degree of immunity develops within 2 weeks of exposure. This immunity was effective for at least 18 weeks.     

Protection of chickens against very virulent infectious bursal disease virus (IBDV) and Marek's disease virus (MDV) with a recombinant MDV expressing IBDV VP2.

To develop a herpes virus vaccine that can induce immunity for an extended period, a recombinant Marek's disease (MD) virus (MDV) CVI-988 strain expressing infectious bursal disease virus (IBDV) host-protective antigen VP2 at the US2 site (rMDV) was developed under the control of an SV40 early promoter. Chickens vaccinated with the rMDV showed no clinical signs and no mortality and 55% of the chickens were considered protected histopathologically after challenge with very virulent IBDV (vvIBDV), whereas all of the chickens vaccinated with the conventional IBDV vaccine showed no clinical signs and were protected. Chickens vaccinated with the CVI-988 or chickens in the challenge control showed severe clinical signs and high mortality (70-75%) and none of them were protected. Also, the rMDV conferred full protection to chickens against vvMDV just as the CVI-988 strain did, whereas 90% of the challenge control chickens died of MD. Antibody levels against IBDV and MDV following the vaccination increased continuously for at least 10 weeks. No histopathological lesions in the rMDV-vaccinated chickens and no contact transmission of the rMDV to their penmates were confirmed. These results demonstrate that an effective and safe recombinant herpesvirus-based IBD vaccine could be constructed by expressing the VP2 antigen at the US2 site of the CVI-988 vaccine strain.     

Variation in tolerance induction and oncogenicity due to strain of avian leukosis virus

Chickens were inoculated as embryos or orally at hatching with various doses of four strains of avian leukosis virus (ALV) subgroup A (RAV-1, RPL40, RPL41 and RPL42). Viraemia, antibody and tumours in chickens of various groups were compared; ALV shedding was determined, but only in chickens inoculated with virus at hatching. Results indicate that 95% to 100% of chickens embryonally inoculated with 105 infectious units of virus were viraemic at hatching, regardless of the strain of virus used. However, the incidence of viraemia in groups of chickens embryonally inoculated with 100 infectious units of virus varied, depending on the strain of virus, from 5% to 72%. All embryonally inoculated chickens, that had detectable virus at hatching and survived to 16 weeks of age were immunologically tolerant to the virus. ALV-induced tumours ranged from 4% to 47% depending on the strain of virus. Chickens inoculated orally at hatching did not develop immuno-logical tolerance to the virus; 13% to 76% of these chickens, depending on the strain of virus, had antibody by 18 weeks of age. ALV shedding in albumen of eggs or cloacal swabs at 42 weeks of age varied from 7% to 9%. Data from this study indicate that the strain of ALV may influence induction of immunological tolerance and tumours in embryonally inoculated chickens and induction of antibody in nontolerantly infected chickens. The data also suggest that chickens that are viraemic at hatching are probably incapable of breaking tolerance and developing antibody.     

Interaction between nociceptin/orphanin FQ (N/OFQ) and GABA in response to feeding

Nociceptin/orphanin FQ (N/OFQ) and gamma aminobutyric acid (GABA) agonists have been shown to increase feed intake in mammals and birds. In this study, the effect of intracerebroventricular (icv) injection of the potent NOP receptor agonists Nociceptin (1-13) NH(2), the GABA(A) receptor antagonist bicuculline, and the GABA(A) receptor agonist muscimol on feed intake in cockerels was investigated. The icv injection of N/OFQ and muscimol increases feed intake. The effect of N/OFQ on feed intake was strongly blocked by the injection of bicuculline whereas the effect of muscimol was stimulated by N/OFQ. These results suggest that N/OFQ may act at GABA(A) receptors or increases overflow of GABA in the brain of chickens to stimulate feeding.