Persistent reduction of hippocampal glutamine synthetase expression after status epilepticus in immature rats.

Mesiotemporal sclerosis (MTS), the most frequent form of drug-resistant temporal lobe epilepsy, often develops after an initial precipitating injury affecting the immature brain. To analyse early processes in epileptogenesis we used the juvenile pilocarpine model to study status epilepticus (SE)-induced changes in expression of key components in the glutamate-glutamine cycle, known to be affected in MTS patients. SE was induced by Li(+) /pilocarpine injection in 21-day-old rats. At 2-19 weeks after SE hippocampal protein expression was analysed by immunohistochemistry and neuron damage by FluoroJade staining. Spontaneous seizures occurred in at least 44% of animals 15-18 weeks after SE. As expected in this model, we did not observe loss of principal hippocampal neurons. Neuron damage was most pronounced in the hilus, where we also detected progressive loss of parvalbumin-positive GABAergic interneurons. Hilar neuron loss (or end-folium sclerosis), a common feature in patients with MTS, was accompanied by a progressively decreased glutamine synthetase (GS)-immunoreactivity from 2 (-15%) to 19 weeks (-33.5%) after SE. Immunoreactivity for excitatory amino-acid transporters, vesicular glutamate transporter 1 and glial fibrillary acidic protein was unaffected. Our data show that SE elicited in 21-day-old rats induces a progressive reduction in hilar GS expression without affecting other key components of the glutamate-glutamine cycle. Reduced expression of glial enzyme GS was first detected 2 weeks after SE, and thus clearly before spontaneous recurrent seizures occurred. These results support the hypothesis that reduced GS expression is an early event in the development of hippocampal sclerosis in MTS patients and emphasize the importance of astrocytes in early epileptogenesis.

Treatment experience, burden, and unmet needs (TRIBUNE) in Multiple Sclerosis study: the costs and utilities of MS patients in The Netherlands.

BACKGROUND: Multiple sclerosis (MS) is an important, highly disabling neurological disease, common among young adults in The Netherlands. Nevertheless, only a few studies to date have measured the burden imposed by MS on society in The Netherlands. OBJECTIVES: To estimate the cost and quality-of-life associated with MS in The Netherlands, while focusing on the burden of relapses and increasing disease severity. METHODS: MS patients in The Netherlands (n = 263) completed a web-based questionnaire which captured information on demographics, disease characteristics and severity (Expanded Disability Status Scale [EDSS]), co-morbidities, relapses, resource consumption, utilities, fatigue and activities of daily living (ADL). RESULTS: Most patients included in the study were receiving treatment for MS (76% of the sample). The mean cost per patient per year increased with worsening disability and was estimated at €30,938, €51,056, and €100,469 for patients with mild (EDSS 0-3), moderate (EDSS 4-6.5), and severe (EDSS 7-9) disability, respectively. The excess cost of relapses was estimated at €8195 among relapsing-remitting patients with EDSS score ≤5. The quality-of-life of patients decreased with disease progression and existence of relapses. CONCLUSIONS: The cost of MS in The Netherlands was higher compared to the results of previous studies. The TRIBUNE study provides an important update on the economic burden of MS in The Netherlands in an era of more widespread use of disease-modifying therapies. It explores the cost of MS linked to relapses and disease severity and examines the impact of MS on additional health outcomes beyond utilities such as ADL and fatigue. STUDY LIMITATIONS: Patients were selected from specialized treatment centers, therefore this sample may not be representative of the entire MS population in The Netherlands, i.e., few patients not receiving MS therapies were included. In addition, only a few patients with severe disability were included in the study sample; therefore, results for this disease severity sub-group should be interpreted with caution.

In vivo MRS and histochemistry of status epilepticus-induced hippocampal pathology in a juvenile model of temporal lobe epilepsy.

Childhood status epilepticus (SE) initiates an epileptogenic process that leads to spontaneous seizures and hippocampal pathology characterized by neuronal loss, gliosis and an imbalance between excitatory and inhibitory neurotransmission. It remains unclear whether these changes are a cause or consequence of chronic epilepsy. In this study, in vivo MRS was used in a post-SE juvenile rat model of temporal lobe epilepsy (TLE) to establish the temporal evolution of hippocampal injury and neurotransmitter imbalance. SE was induced in P21 rats by injection of lithium and pilocarpine. Four and eight weeks after SE, in vivo (1) H and γ-aminobutyric acid (GABA)-edited MRS of the hippocampus was performed in combination with dedicated ex vivo immunohistochemistry for the interpretation and validation of MRS findings. MRS showed a 12% decrease (p<0.0001) in N-acetylaspartate and a 15% increase (p=0.0226) in choline-containing compound concentrations, indicating neuronal death and gliosis, respectively. These results were confirmed by FluoroJade and vimentin staining. Furthermore, severe and progressive decreases in GABA (-41%, p<0.001) and glutamate (Glu) (-17%, p<0.001) were found. The specific severity of GABAergic cell death was confirmed by parvalbumin immunoreactivity (-68%, p<0.001). Unexpectedly, we found changes in glutamine (Gln), the metabolic precursor of both GABA and Glu. Gln increased at 4 weeks (+36%, p<0.001), but returned to control levels at 8 weeks. This decrease was consistent with the simultaneous decrease in glutamine synthase immunoreactivity (-32%, p=0.037). In vivo MRS showed gliosis and (predominantly GABAergic) neuronal loss. In addition, an increase in Gln was detected, accompanied by a decrease in glutamine synthase immunoreactivity. This may reflect glutamine synthase downregulation in order to normalize Gln levels. These changes occurred before spontaneous recurrent seizures were present but, by creating a pre-epileptic state, may play a role in epileptogenesis. MRS can be applied in a clinical setting and may be used as a noninvasive tool to monitor the development of TLE.

Fingolimod reduces direct medical costs compared to natalizumab in patients with relapsing-remitting multiple sclerosis in The Netherlands.

OBJECTIVE: To assess the costs of oral treatment with Gilenya® (fingolimod) compared to intravenous infusion of Tysabri® (natalizumab) in patients with relapsing-remitting multiple sclerosis (RRMS) in The Netherlands. METHODS: A cost-minimization analysis was used to compare both treatments. The following cost categories were distinguished: drug acquisition costs, administration costs, and monitoring costs. Costs were discounted at 4%, and incremental model results were presented over a 1, 2, 5, and 10 year time horizon. The robustness of the results was determined by means of a number of deterministic univariate sensitivity analyses. Additionally, a break-even analysis was carried out to determine at which natalizumab infusion costs a cost-neutral outcome would be obtained. RESULTS: Comparing fingolimod to natalizumab, the model predicted discounted incremental costs of -€2966 (95% CI: -€4209; -€1801), -€6240 (95% CI: -€8800; -€3879), -€15,328 (95% CI: -€21,539; -€9692), and -€28,287 (95% CI: -€39,661; -€17,955) over a 1, 2, 5, and 10-year time horizon, respectively. These predictions were most sensitive to changes in the costs of natalizumab infusion. Changing these costs of €255 within a range from €165-364 per infusion resulted in cost savings varying from €4031 to €8923 after 2 years. The additional break-even analysis showed that infusion costs-including aseptic preparation of the natalizumab solution-needed to be as low as the respective costs of €94 and €80 to obtain a cost neutral result after 2 and 10 years. LIMITATIONS: Neither treatment discontinuation and subsequent re-initiation nor patient compliance were taken into account. As a consequence of the applied cost-minimization technique, only direct medical costs were included. CONCLUSION: The present analysis showed that treatment with fingolimod resulted in considerable cost savings compared to natalizumab: starting at €2966 in the first year, increasing to a total of €28,287 after 10 years per RRMS patient in the Netherlands.

Prolonged increase in rat hippocampal chemokine signalling after status epilepticus.

Temporal lobe epilepsy (TLE) is one of the most common focal epilepsy syndromes. In a genome-wide expression study of the human TLE hippocampus we previously showed up-regulation of genes involved in chemokine signalling. Here we investigate in the rat pilocarpine model for TLE, whether changes in chemokine signalling occur during epileptogenesis and are persistent. Therefore we analysed hippocampal protein expression and cellular localisation of CCL2, CCL4, CCR1 and CCR5 after status epilepticus. We found increased CCL4 (but not CCL2) expression in specific populations of hilar astrocytes at 2 and 19 weeks after SE concomitant with a persistent up-regulation of its receptor CCR5. Our results show an early and persistent up-regulation of CCL4/CCR5 signalling during epileptogenesis and suggest that CCL4 signalling, rather than CCL2 signalling, could have a role in the epileptogenic process.

In vivo diffusion tensor imaging and ex vivo histologic characterization of white matter pathology in a post-status epilepticus model of temporal lobe epilepsy.

Although epilepsy is historically considered a disease of gray matter, recent diffusion tensor imaging (DTI) studies have shown white matter abnormalities in patients with epilepsy. The histopathologic correlate of these findings, and whether they are a cause or consequence of epilepsy, remains unclear. To characterize these changes and their underlying histopathology, DTI was performed in juvenile rats, 4 and 8 weeks after pilocarpine-induced status epilepticus (SE). In the medial corpus callosum (CC), mean diffusivity and axial diffusivity (MD and λ1) as well as a myelin staining were significantly reduced at 4 weeks. Only the λ1 decrease persisted at 8 weeks. In the fornix fimbriae (FF), λ1 and myelin staining were decreased at both time points, whereas fractional anisotropy (FA) and MD were significantly reduced at 8 weeks only. We conclude that SE induces both transient and chronic white matter changes in the medial CC and FF that are to some degree related to myelin pathology.

Glutamine synthetase deficiency in murine astrocytes results in neonatal death.

Glutamine synthetase (GS) is a key enzyme in the "glutamine-glutamate cycle" between astrocytes and neurons, but its function in vivo was thus far tested only pharmacologically. Crossing GS(fl/lacZ) or GS(fl/fl) mice with hGFAP-Cre mice resulted in prenatal excision of the GS(fl) allele in astrocytes. "GS-KO/A" mice were born without malformations, did not suffer from seizures, had a suckling reflex, and did drink immediately after birth, but then gradually failed to feed and died on postnatal day 3. Artificial feeding relieved hypoglycemia and prolonged life, identifying starvation as the immediate cause of death. Neuronal morphology and brain energy levels did not differ from controls. Within control brains, amino acid concentrations varied in a coordinate way by postnatal day 2, implying an integrated metabolic network had developed. GS deficiency caused a 14-fold decline in cortical glutamine and a sevenfold decline in cortical alanine concentration, but the rising glutamate levels were unaffected and glycine was twofold increased. Only these amino acids were uncoupled from the metabolic network. Cortical ammonia levels increased only 1.6-fold, probably reflecting reduced glutaminolysis in neurons and detoxification of ammonia to glycine. These findings identify the dramatic decrease in (cortical) glutamine concentration as the primary cause of brain dysfunction in GS-KO/A mice. The temporal dissociation between GS(fl) elimination and death, and the reciprocal changes in the cortical concentration of glutamine and alanine in GS-deficient and control neonates indicate that the phenotype of GS deficiency in the brain emerges coincidentally with the neonatal activation of the glutamine-glutamate and the associated alanine-lactate cycles.

Hippocampal Nabeta3 expression in patients with temporal lobe epilepsy.

Voltage-dependent sodium channels consist of a pore-forming alpha-subunit and regulatory beta-subunits. Alterations in these channels have been implicated in temporal lobe epilepsy (TLE) and several genetic epilepsy syndromes. Recently we identified Na(v)beta3 as a TLE-regulated gene. Here we performed a detailed analysis of the hippocampal expression of Na(v)beta3 in TLE patients with hippocampal sclerosis (HS) and without HS (non-HS) and compared expression with autopsy controls (ACs). Immunoblot analysis showed that Na(v)beta3 levels were dramatically reduced in the hippocampus, but not in the cortex of non-HS patients when compared to HS patients. This was confirmed by immunohistochemistry showing reduced Na(v)beta3 expression in all principal neurons of the hippocampus proper. Sequence analysis revealed no Na(v)beta3 mutations. The functional consequences of the reduced Na(v)beta3 expression in non-HS patients are unknown. Altered Na(v)beta3 expression might influence microcircuitry in the hippocampus, affecting excitability and contributing to epileptogenesis in non-HS patients. Further experiments are required to elucidate these functional possibilities.

Hippocampal distribution of vesicular glutamate transporter 1 in patients with temporal lobe epilepsy.

PURPOSE: Vesicular glutamate transporters (VGLUTs) are responsible for loading synaptic vesicles with glutamate, determining the phenotype of glutamatergic neurons, and have been implicated in the regulation of quantal size and presynaptic plasticity. We analyzed VGLUT subtype expression in normal human hippocampus and tested the hypothesis that alterations in VGLUT expression may contribute to long-term changes in glutamatergic transmission reported in patients with temporal lobe epilepsy (TLE). METHODS: VGLUT immunohistochemistry, immunofluorescence, in situ hybridization, Western blotting, and quantitative polymerase chain reaction (qPCR) were performed on biopsies from TLE patients without (non-HS) and with hippocampal sclerosis (HS) and compared to autopsy controls and rat hippocampus. VGLUT1 expression was compared with synaptophysin, neuropeptide Y (NPY), and Timm's staining. RESULTS: VGLUT1 was the predominant VGLUT in human hippocampus and appeared to be localized to presynaptic glutamatergic terminals. In non-HS hippocampi, VGLUT1 protein levels were increased compared to control and HS hippocampi in all subfields. In HS hippocampi VGLUT1 expression was decreased in subfields with severe neuronal loss, but strongly up-regulated in the dentate gyrus, characterized by mossy fiber sprouting. DISCUSSION: VGLUT1 is used as marker for glutamatergic synapses in the human hippocampus. In HS hippocampi VGLUT1 up-regulation in the dentate gyrus probably marks new glutamatergic synapses formed by mossy fiber sprouting. Our data indicate that non-HS patients have an increased capacity to store glutamate in vesicles, most likely due to an increase in translational processes or upregulation of VGLUT1 in synapses from afferent neurons outside the hippocampus. This up-regulation may increase glutamatergic transmission, and thus contribute to increased extracellular glutamate levels and hyperexcitability.

Haploinsufficiency of glutamine synthetase increases susceptibility to experimental febrile seizures.

Glutamine synthetase (GS) is a pivotal glial enzyme in the glutamate-glutamine cycle. GS is important in maintaining low extracellular glutamate concentrations and is downregulated in the hippocampus of temporal lobe epilepsy patients with mesial-temporal sclerosis, an epilepsy syndrome that is frequently associated with early life febrile seizures (FS). Human congenital loss of GS activity has been shown to result in brain malformations, seizures and death within days after birth. Recently, we showed that GS knockout mice die during embryonic development and that haploinsufficient GS mice have no obvious abnormalities or behavioral seizures. In the present study, we investigated whether reduced expression/activity of GS in haploinsufficient GS mice increased the susceptibility to experimentally induced FS. FS were elicited by warm-air-induced hyperthermia in 14-day-old mice and resulted in seizures in most animals. FS susceptibility was measured as latencies to four behavioral FS characteristics. Our phenotypic data show that haploinsufficient mice are more susceptible to experimentally induced FS (P < 0.005) than littermate controls. Haploinsufficient animals did not differ from controls in hippocampal amino acid content, structure (Nissl and calbindin), glial properties (glial fibrillary acidic protein and vimentin) or expression of other components of the glutamate-glutamine cycle (excitatory amino acid transporter-2 and vesicular glutamate transporter-1). Thus, we identified GS as a FS susceptibility gene. GS activity-disrupting mutations have been described in the human population, but heterozygote mutations were not clearly associated with seizures or epilepsy. Our results indicate that individuals with reduced GS activity may have reduced FS seizure thresholds. Genetic association studies will be required to test this hypothesis.

Reduced glutamine synthetase in hippocampal areas with neuron loss in temporal lobe epilepsy.

BACKGROUND: Increased levels of glutamate have been reported in the epileptogenic hippocampus of patients with temporal lobe epilepsy (TLE). This sustained increase, which may contribute to the initiation and propagation of seizure activity, indicates impaired clearance of glutamate released by neurons. Glutamate is predominantly cleared by glial cells through the excitatory amino acid transporter 2 (EAAT2) and its subsequent conversion to glutamine by the glial enzyme glutamine synthetase (GS). METHODS: The authors examined the hippocampal distribution of GS, EAAT2, and glial fibrillary acidic protein (GFAP) by immunohistochemistry in TLE patients with (HS group) and without hippocampal sclerosis (non-HS group), and in autopsy controls. In hippocampal homogenates the authors measured relative protein amounts by immunoblotting and GS enzyme activity. RESULTS: In the autopsy control and non-HS group GS immunoreactivity (IR) was predominantly found in glia in the neuropil of the subiculum, of the pyramidal cell layer of all CA fields, and in the supragranular layer of the dentate gyrus. In the HS group, GS and EAAT2 IR were markedly reduced in subfields showing neuron loss (CA1 and CA4), whereas GFAP IR was increased. The reduction in GS IR in the HS group was confirmed by immunoblotting and paralleled by decreased GS enzyme activity. CONCLUSIONS: Glial glutamine synthetase is downregulated in the hippocampal sclerosis (HS) hippocampus of temporal lobe epilepsy (TLE) patients in areas with severe neuron loss. This downregulation appears to be pathology-related, rather than seizure-related, and may be part of the mechanism underlying impaired glutamate clearance found in the hippocampus of TLE patients with HS.

Suppression of cortical spreading depressions after magnesium treatment in the rat.

The aim of this study was to investigate whether the neuroprotective properties of magnesium in cerebral ischaemia involve suppression of repetitive tissue depolarizations. Cortical spreading depressions (CSDs), evoked by cortical KCl application, and cardiac arrest-induced anoxic depolarization (AD) were measured by extracellular DC recording on intact rat brain. At 90 min after onset of CSDs saline, MK-801 (3 mg/kg) or MgSO4 (90 mg/kg) was given i.v. Latency time to AD was measured after 4 h. The frequency of CSDs was significantly reduced in animals treated with MgSO4 or MK-801. AD was significantly delayed by MgSO4 but not by MK-801. Our results suggest that suppression of depolarization by magnesium may play a role in its neuroprotective properties in cerebral ischaemia.

Required thermal thresholds during transport of animals.

Conditions (total complex of stressors) during the transport of animals vary strongly between and within transports. Adverse climatic conditions are stressors that animals have to face during transport. The thermoregulation of animals id discussed with respect to threshold values for optimal climatic conditions. These thermal thresholds depend on animal related factors and environmental conditions. The specific impact of transport conditions, such as food and water deprivation, high stocking density, high humidity and high air velocity, on thermal thresholds are described.

Heat production, body temperature, and body posture in west African dwarf goats infected with Trypanosoma vivax.

The relationships between heat production, body temperature, and body posture (standing/lying) were studied in goats suffering from trypanosomiasis. Sixteen goats were selected and infected with 1 x 10(6) Trypanosoma vivax parasites and 8 goats served as controls. In week 2, 4, and 6 after infection heat production, body posture, and body temperature were measured at 15-minute intervals. Heat production was higher (P < 0.01) in infected animals compared with control animals (342, respectively 306 kJ.kg- 0.75.d-1), body temperature was also higher (P < 0.001) in infected goats (39.78 degrees C, respectively 38.51 degrees C). The standing related energy costs per day were lower in infected animals (27 respectively 36 kJ.kg-0.75.d-1). Infected animals, therefore, masked part of the energy costs of infection by reducing the standing time. The heat production of infected animals was increased by 21 kJ.kg-0.75.d-1 per 1 degree C fever (7% increase). During periods of standing, body temperature increased with time, whereas during lying periods, it decreased. The number of standing periods was increased in infected animals. It was discussed whether postural behaviour is influenced by thermoregulatory mechanisms.

Development of metabolic partitioning of energy in young calves.

Modifications in thermal demand and energy partitioning in newborn calves were determined over time via indirect calorimetry. One-week-old calves were fed milk replacer at 70 and 110% of the metabolizable energy requirements for maintenance, at ambient temperatures of 7.5 or 19 degrees C, over two consecutive but separately monitored 7-d balance periods. During wk 1, N digestibility, energy digestibility, and energy metabolizability were lower than during wk 2. Heat production decreased, but retention of energy and fat increased, between balance periods. During wk 1, initial IgG concentration in serum was positively correlated with digestibilities of N and energy, and hemoglobin concentration was negatively correlated with heat production. Regression analysis revealed that predicted basal metabolic rate, efficiency of metabolizable energy use, and metabolizable energy requirements for maintenance were lower for wk 2 than for wk 1. Decreased energy utilization in calves on restricted feedings is related to an increase in the utilization of protein as an energy source. Young calves need at least 2 wk to adapt to the combination of new environmental temperature and low feeding amount. Metabolic partitioning of energy may indicate completion of the adaptation stage.

Effect of recombinant porcine somatotropin and monoclonal antibody directed to ovine somatotrophic hormone on nitrogen retention and immune parameters in pigs.

Single and combined effects of administration and withdrawal of recombinant porcine somatotropin (rpST) and an enhancing murine antiovine growth hormone monoclonal antibody (OA15) on nitrogen retention, and serological and immunological measurements in pigs were examined in a placebo-controlled experiment. Thirty-six barrows were allotted to one of four treatments: control, rpST, OA15, and OA15+rpST. The trial phase was four balance periods: a preperiod, two periods of treatment, and a postperiod. Weight- and nitrogen gain were higher for the rpST group by 13% (P < .01) and 15% (P < .001), for the OA15 group by 8% (P < .05) and 9% (P < .05), and for the OA15+rpST group by 25% (P < .001) and 20% (P < .001), respectively compared with the control group. During the postperiod, weight gain of the OA15- and the OA15+rpST group was 23% (P < .001) and 22% (P < .001) lower than that of the control group. Nitrogen gain during the postperiod was decreased by 19% (P < .01) for the OA15 group compared with the control group. Single or combined administration of rpST or OA15 did not affect (P > .10) cellular constituents in the blood of all groups during the periods of observation. Animals treated solely with rpST mounted a humoral immune response directed to rpST. This anti-rpST antibody response was, however, decreased (P < .01) in barrows treated with rpST and OA15 simultaneously. Also, a slight anti-rpST antibody response was noticed in barrows solely treated with OA15.(ABSTRACT TRUNCATED AT 250 WORDS)

Energy metabolism of growing pigs after transportation, regrouping, and exposure to new housing conditions as affected by feeding level.

An experiment was performed to evaluate alterations of energy metabolism with time in 10 groups of 16 barrows just after transportation. Ten-week-old pigs were fed at once (four groups; LF) or twice (three groups; MF) maintenance level (35 and 75 g.kg-.75.d-1, respectively), or allowed ad libitum access to feed (three groups; HF). The 13.5-d experimental period was divided into two balance periods. Heat production (HP) decreased with time. The changes in HP with time were different among feeding level groups (P < .001); the LF group had the greatest decrease. Metabolizable energy intake remained constant with time for the LF and MF groups and decreased for the HF group. Requirements for maintenance energy and efficiency of ME for growth decreased with time. Feeding level influenced (P < .001) energy retention (ER) during the total experimental period. The LF group had a negative ER (-65 kJ.kg-.75.d-1), whereas in the MF and HF groups positive values for ER were obtained (346 and 757 kJ.kg-.75.d-1, respectively). At all feeding levels, animals had a positive protein gain. The level differed between feeding levels (P < .001). Differences among groups (P < .001) were observed in energy retained as fat. Data from the present experiment show that young pigs are not in a steady state of energy metabolism during the 2 wk after transportation. During this period, the relationship between metabolic rate and feed intake alters with time.

Evidence of increasing thermal requirement in young, unadapted calves during 6 to 11 days of age.

Changes in thermal demand in restrictively fed, unadapted, young calves were studied during the first days after transportation. Twenty-three 6-d-old Holstein-Friesian male calves were assigned to one of four ambient temperature treatments: 5, 9, 13, or 18 degrees C. Calves were fed at a constant level below the maintenance requirement (300 kJ of ME.kg-.75.d-1). After arrival, heat production (HP) and energy and nitrogen balance were measured for each calf for 5.5 d. At ambient temperatures of 5 and 9 degrees C, HP was increased compared with temperatures of 13 and 18 degrees C (P < .001). As a consequence, energy retention was decreased at low ambient temperatures (P < .05). At temperatures of 5 and 9 degrees C, body fat mobilization was increased compared with that at temperatures of 13 and 18 degrees C (P < .001). Energy retained as protein was not affected by ambient temperature. During the experimental period, HP decreased with time. Ambient temperature affected this decrease (P < .001), indicating that the relationship between HP and ambient temperature changed with time. The rate of increase in HP below the lower critical temperature was not affected by time, averaging 9.5 kJ.kg-.75.d-1.C degrees-1. Lower critical temperature, however, increased with time by .89 C degrees/d (P < .05). The changing relation between HP and ambient temperature with time in young, unadapted calves after transportation is thus reflected in an alteration in thermal requirement with time.

Circadian rhythm in heat production of limit-fed growing pigs of several breeds kept at and below thermal neutrality.

Circadian rhythm in total and activity-free heat production (H and Hacf, respectively) was studied in Norwegian Landrace (N), Finnish Landrace (F), Dutch Landrace (D), and Great Yorkshire (Y) barrows. Animals, weighing 26 kg at the start of the study, were kept in groups for 18 2-d periods in climate respiration chambers at environmental temperatures (Tenv) between 11 and 26 degrees C. Measurements of H and physical activity of the pigs were done in 12-min intervals for 36 h per breed per Tenv. Feeding level of animals in a group was 93 g.kg-.75 x d-1 (2.5 times maintenance) and based on mean BW. Circadian rhythm in H and Hacf with data excluding the feeding periods was assessed using a sine wave with a 24-h periodicity per breed and per Tenv. With respect to H, the intercepts and amplitudes for the three Landrace breeds were similar, but the Y pigs had a lower intercept and a lower amplitude. The intercepts increased with decreasing Tenv. In N pigs, but not in F, D, or Y pigs, the amplitude increased with decreasing Tenv. With respect to Hacf, all breeds had similar intercepts and amplitudes. The Hacf varied less within a day than did H. In all breeds, the intercepts were increased with decreasing Tenv. The amplitudes were not affected by Tenv.

Effect of two-day temperature exposure of neonatal broiler chicks on growth performance and body composition during two weeks at normal conditions.

Newly hatched chicks were allotted to five different climatic treatment groups (28 to 32, 32 to 34, 34 to 35, 35 to 37, and 37 to 40 C) for 2 days after hatch during which feed and water were withheld. Their performance was measured for 2 wk and compared with control chicks kept under normal conditions. During the 2 days of climatic treatment, chicks lost weight of 5.3, 5.4, 6.7, 8.5, and 10.1 g, respectively, but control chicks grew 16.0 g. During 14 days of feed intake, chicks of the highest treatment group grew significantly less (217.5 g) than controls (267.7 g). Also, feed intake was significantly lower (292 versus 386 g). In the group exposed to 37 to 40 C, feed conversion decreased significantly from 1.43 to 1.37 g:g and mortality increased to more than 49%. Body composition of DM, protein, fat, and ash was also estimated. Chicks previously exposed to 37 to 40 C had significantly lower values for the gain in body components: DM (18.49 g), protein (7.13 g), fat (8.75 g), and ash (2.62 g) per chick at 2 wk. The ratios water:protein gain and fat:protein gain after posthatching heat exposure were decreased from 3.82 to 3.45 g:g and .76 to .67 g:g, respectively, whereas the ratio of gain in energy retention:weight gain was similar to that of controls.