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Biomedical subjects

D Luger

Publications and source records attributed to D Luger.

9 recordsLinked to original sources
PubMed2004

Ventilation, sensible heat loss, broiler energy, and water balance under harsh environmental conditions.

Air velocity (AV) is one of the main environmental factors involved in thermoregulation, especially at high ambient temperatures. To elucidate the effect of AV on performance and thermoregulation of 4- to 7-wk-old broiler chickens, an experiment was conducted using 4 different AV (0.8, 1.5, 2.0, and 3.0 m/s) at constant ambient temperatature (35 +/- 1.0 degrees C) and RH (60 +/- 2.5%). BW, feed intake, and fecal and urinary excretions were monitored in individuals and were used to calculate the amount of energy expended for maintenance. Infrared thermal imaging radiometry was used to measure surface temperatures for the calculation of heat loss by radiation and convection. Brachial vein blood was collected for plasma osmolality and arginine vasotocin analysis. Broilers performed optimally at an AV of 2.0 m/s. Energy expenditure for maintenance was significantly higher under these conditions, suggesting the ability to direct a sufficient amount of energy to control body temperature, while maintaining relatively high growth rates. Convective heat loss increased significantly with increasing AV, whereas radiative heat loss was not affected. Sensible heat loss, expressed as a percentage of energy expenditure for maintenance, was significantly higher at 2.0 m/s compared with 0.8 m/s but significantly lower than that of 3.0 m/s. The high level of heat loss observed at 3.0 m/s probably affected body water balance, as supported by significantly higher plasma osmolality, arginine vasotocin concentration, and the hyperthermic status of these birds. It can be concluded that AV of 2.0 m/s enables broilers to maintain proper performance together with efficient thermoregulation and water balance under harsh environmental conditions.

Air Movements↗
PubMed2003

Erythropoiesis regulation during the development of ascites syndrome in broiler chickens: a possible role of corticosterone.

The ascites syndrome in broiler chickens is attributed to metabolic burdening, which results from intensive genetic selection for rapid growth coupled with exposure to extreme environmental conditions, such as low ambient temperature. These conditions impose on the broilers difficulties in fulfilling tissue demands for oxygen, and the birds exhibit a decrease in blood oxygen saturation and high hematocrit values. It is unknown whether the increase in hematocrit results from alteration in erythropoiesis or from fluid exudation out of the blood system to the abdominal cavity. The present study was conducted to examine the association between abnormal stress response and erythropoiesis process in ascitic broilers. Ascitic chickens revealed a uniquely continuous stress response: expressing an increase (P < or = 0.05) in plasma corticosterone concentration 2 to 3 wk before death. At 5 wk of age, ascitic broilers exhibited an increase (P < 0.05) in hematocrit, blood cell count, and packed cells and blood volumes, with no significant change in plasma volume. These results confirm an accelerated erythropoiesis process in ascitic birds. Increased blood cell production in ascitic birds was matched by an increase (P < 0.05) in the proportion of immature red blood cells (23%) in comparison with broilers that remained healthy (7%), and by decreased (P < 0.05) hemoglobin content relative to red blood cells. We conclude that continually increased corticosterone concentrations, as an inducer of erythropoiesis proliferation and differentiation arrest, in ascitic chickens, resulted in increased production of red blood cells (partially immature) with decreased hemoglobin content; this decrease in hemoglobin might have contributed to enhanced development of hypoxemia and to aggravation of the syndrome.

Animals↗
PubMed2001

Association between weight gain, blood parameters, and thyroid hormones and the development of ascites syndrome in broiler chickens.

The present study examined the association between thyroid hormones and the development of ascites on one hand and the ability to predict ascites from growth rate and hematocrit on the other hand. Ascites syndrome was induced in broiler chickens in two trials by exposing the chicks to low ambient temperature (Ta) and by supplying a pellet form of diet. Weight gain, hematocrit, hemoglobin, and plasma thyroxin (T4) and triiodothyronine (T3) concentrations were measured weekly for each bird, and comparisons were made between birds that eventually died from ascites and those that did not. Mortality from ascites amounted to 24.3 and 24.2% in Trials 1 and 2, respectively. Weight gain did not differ between ascitic and healthy chickens up to approximately 2 wk before death but was significantly lower in the ascitic broilers 1 to 2 wk before death. Hematocrit was significantly higher in broilers with ascites with the exception of ascitic broilers that died at the age of 7 wk (Trial 1). In ascitic broilers, T4 and T3 concentrations declined significantly during the week of death. The present findings raise the question of whether the association between low levels of thyroid hormones and the development of ascites is one of the physiological responses in the syndrome cascade, or whether the failure to maintain thyroid hormones concentration is one of the triggers of the syndrome initiation. This question requires further investigation. It can be concluded that a high rate of weight gain is not always a good predictor of ascites development. Hematocrit and thyroid hormones can provide a good indication but only during the last week of life, and not in all cases. None of these parameters, however, can predict the development of ascites at an early age.

Animals↗
PubMed1998

Thermoregulation in naked neck chickens subjected to different ambient temperatures.

1. Heterozygous (Na/na) naked neck chickens and their normally feathered (na/na) sibs, were exposed to constant ambient temperatures (Ta) ranging between 15 and 35 degrees C and 12h: 12h diurnal high:low temperatures of 15 degrees C:35 degrees C. 2. No significant effect of genotype was obtained in weight gain and food intake. However, the naked neck birds tended to gain somewhat more weight at high Ta and consume more food at low Ta. 3. At 35 degrees C Na birds showed better regulation of body temperature (Tb) and demonstrated considerably higher radiation from the neck. 4. The greater food intake of the naked neck chickens at 15 degrees C was associated with significantly higher packed cell volume, haemoglobin concentration, heart and liver size. These appear to involve both higher heat production and haemodynamic changes to accommodate the higher oxygen demands of the naked neck chickens at low Ta. 5. The results indicate the ability of the naked neck chickens, on the one hand to thermoregulate at low Tas and, on the other their slightly better capacity to maintain Tb at high Tas. However, no genotype advantage was obtained under diurnal cyclic temperature conditions.

Analysis of Variance↗
PubMed1978

The use of deep frozen, stored bovine blood for in vitro feeding of tsetse flies.

A method of blood preparation is described which resulted in the successful rearing of Glossina p. palpalis with in vitro feeding. Cells of defibrinated bovine blood were washed in 0.89% NaCl solution prior to deep-freezing. Cells and serum were stored (--28 degrees C) for up to four months. For feeding, both components were mixed in the volumetric proportion 1 : 1. Adenosine triphosphate was added at a concentration of 10-3 M to stimulate uptake of blood. Survival rate and mean weight of puparia remained constant over three generations while productivity increased.

Adenosine Triphosphate↗
PubMed1978

In vitro feeding in the rearing of tsetse flies (Glossina m. morsitans and G.p. palpalis, Diptera: Glossinidae).

The increasing demand for laboratory reared tsetse flies for research and biological control makes it necessary to develop effective and standardized tsetse fly feeding methods without using live animals for the daily blood uptake. The in vitro feeding technique, described in this paper, has been used for rearing G. m. morsitans by feeding them defibrinated equine blood through a silicone membrane. The results obtained for female longevity and productivity and mean weight of puparia are satisfactory. However, feeding defibrinated bovine blood results in significantly lighter puparia. A colony of G. p. palpalis feeding on defibrinated bovine blood is the only colony of this species that has been successfully maintained by in vitro feeding over several years. The survival rate of the females being fed defibrinated bovine, equine or porcine blood is equal. The number of larvae produced by females being fed defibrinated equine blood is significantly lower. Females younger than 50 days produce larvae which form a heavier puparia than females aged between 51 to 80 or 100 days, irrespective of blood source. Bovine blood used within the first 3 days after its collection leads to significantly higher mean weights of puparia than bovine blood used therafter. The increasing degree of haemolysis is most probably not the reason for this observation. A colony production model based on the performance of both species, G. m. morsitans and G. p. palpalis, fed in vitro, shows the importance of the first five age group periods (i.e. 45 to 50 days after emergence) for the overall performance of the flies. According to the results obtained, about 2,3 puparia per female are needed to maintain the same number of females in the colony. This level of production is reached in the fifth age group period. All larvae produced thereafter are available for colony expansion or experimental purposes. Rearing of both species with in vitro feeding is now a matter of routine.

Animal Feed↗
PubMedDate not supplied

Smoke out.

This year the EPA will finalize rules that will make medical waste incineration nearly a thing of the past. The author reports on an array of alternative approaches.

Decontamination↗