Vertical temperature profiles at bird level in broiler houses.

1. The temperature in the close vicinity of commercial broilers was studied in relation to the setpoint temperature throughout the rearing period. 2. Mean temperature in the immediate environment of the chicks was 2.0 degrees C lower than the setpoint of 1 d of age. During the first week this initial temperature difference gradually rose to l.7 degrees C above setpoint. At 18 d of age a further rise to a mean difference of 4.0 degrees C above setpoint was measured. The difference then remained constant from 32 d of age until the end of the fattening period. 3. It was concluded that the chickens were actually brooded at 30 degrees C. During the rearing period the ambient temperature in the close vicinity of the broilers gradually declined to 26 degrees C. 4. During the finishing period, ambient temperature around the broilers was far above the value recommended for optimal food intake and growth. 5. These results are discussed in relation to heat generation and heat fluxes in the broiler houses.

Artificial light sources and their influence on physical activity and energy expenditure of laying hens.

1. The influence of fluorescent and incandescent artificial lighting in a 16L:8D day/night schedule on number and intensity of movements, and on total, resting and activity-related energy expenditure was investigated. 2. Fluorescent light showed the same positive correlation between light intensity and physical activity at all activity levels as was found previously for incandescent light. 3. Light-dependent physical activity under fluorescent light was higher than under incandescent light at illuminances of 5 lux and above, indicating the fowl's ability to perceive qualitative light differences. 4. Total and activity-related energy expenditure were positively associated with illuminance; resting energy expenditure was not influenced. 5. Total, resting and activity-related energy expenditure were not statistically significantly different between light sources. 6. The results are discussed in relationship to Teichmüller's concept of adequate lighting and the characteristics of the fowl's visual system.

Responses of broiler chickens to high-frequency and low-frequency fluorescent light.

1. The influence of the flicker frequency on physical activity and energy expenditure of broilers was studied using commercially available high-frequency (HF) and low-frequency (LF) fluorescent lamps in a 23L:1D lighting schedule. 2. Broilers were reared under and adapted to HF. They were alternately subjected to HF and LF during measurement of activity and energy expenditure. 3. In comparison with HF, LF inhibited activity (number and intensity of movements), but did not influence energy expenditure. 4. It was concluded that the 100 Hz flickering of low-frequency light is detected by broilers and has measurable behavioural effects upon them. 5. The results were discussed in relation to current knowledge of human and birds' critical flicker frequency and perception.

Physical activity and energy expenditure of laying hens as affected by light intensity.

The influence of light intensity using incandescent bulbs in a 16L:8D day:night schedule on the number and strength of movements and on total, resting and activity-related energy expenditure was investigated. Movements were classified into 10 activity levels of progressively increasing vigour. The number of movements at all activity levels was significantly positively correlated with the logarithm of the light intensity. Movements of low activity strength were less affected by increasing light intensities than vigorous movements. Activity-related energy expenditure was highly significant and positively affected by light intensity. A decrease of the light intensity from 120 to 1 lux may reduce total energy expenditure by 18%. A decrease in energy expenditure by 9% may be achieved by reducing the light intensity to about 15 lux, measured perpendicular to the main axis of radiation.

Automatic gravimetric calorimeter with simultaneous recording of physical activity for poultry.

An automatic calorimeter, based on gravimetric principles, for studies on the energy metabolism of the fowl, with simultaneous recording of the physical activity, is described. In order to reduce errors in the determination of heat production to below 3% a three hour experimental period is necessary. The length of this period in comparison to that of the Pettenkofer system is discussed. The relation between heat production and physical activity shows a good fit in a linear regression equation, from which resting heat production is derived. Up to 25% of the total heat production is related to physical activity, mainly during the day-time.

Glomerular filtration rate in intact and splenectomized running and swimming dogs.

The glomerular filtration rate (GFR) was measured using a continuous inulin infusion in control, treadmill running, and swimming experiments in intact and splenectomized dogs. There was a 20% increase in the GFR after swimming in the splenectomized dogs as compared to the corresponding value in the control trials (P less than 0.01). The GFR was not changed during or after running or during swimming. Possible mechanisms maintaining the GFR in intact and splenectomized dogs during exercise are discussed.

The respiratory quotient in indirect calorimetric measurements.

Respiratory quotients (RQ) smaller than 0.70 must be associated with partial oxidation of the biological substrates and storage of oxygen in the carcass or the excreta. An equation for the calculation of the amount of oxygen stored in relation to the RQ is described. The fluxes of N, C, H and O in the carcass of the fasting fowl were negative and compatible with the complete oxidation of the biological substrates. The amounts of these elements in the excreta corresponded with the nitrogenous excretion products, carbohydrates and minerals. No substantial oxygen storage could be demonstrated. The very low RQ values reported in the past would require a magnitude of oxygen storage which is incompatible with life.

Measurement of the respiratory metabolism of the fowl.

1. The occurrence of low respiratory quotients (RQ) in fowls and the reliability of oxygen consumption, carbon dioxide output and heat production data in indirect calorimetry were studied. 2. The RQ data from the gravimetric and the combined gravimetric-volumetric systems were essentially the same, while differences in O2 and CO2 between the systems were primarily due to variations in environmental temperature. 3. Fasting RQ was never less than 0.70 in these systems. 4. In the volumetric system the O2, CO2 and RQ data from the diaferometer were significantly different from the infra-red and paramagnetic analyses. 5. The CO2 values from the diaferometer were correct, but the O2 values were too low. In the specific analysers the reverse was seen, the paramagnetically-determined O2 values being correct and the CO2 values from infra-red analysis being too low. 6. Thus the fasting RQ values from the diaferometer were too high (0.762) and from the specific analysers too low (0.683).

Differentiation of phospholipases A in mitochondria and lysosomes of rat liver.

Highly purified mitochondria from rat liver contain a phospholipase A that catalyzes removal of 2-fatty acids, with a pH optimum above pH 8.0. Lysosomal preparations appeared to have two phospholipases A associated with them, one with a pH optimum at about pH 4.0, the second between pH 6.0 and 7.0. Mitochondrial phospholipase A hydrolyzed exogenous phospholipid as fast as or faster than endogenous phospholipid. The difference in specific radioactivity of (14)C-ethanolamine-labeled endogenous mitochondrial phospholipid before and after incubation indicates that a fraction of mitochondrial phosphatidyl ethanolamine is hydrolyzed more rapidly than the mitochondrial phospholipids as a whole. Acyl bond hydrolysis of exogenous and endogenous phospholipid by mitochondria was stimulated by free fatty acid, Ca(++), or in certain cases, monoacyl phospholipids or by treatments that disrupt the mitochondrial membrane. Of various fatty acids tested, lauric, myristic, oleic, and linoleic were most effective. ADP and ATP inhibited mitochondrial phospholipase, probably because they compete for Ca(++). Mg(++) also behaved as a competitive inhibitor; the effect was overcome by relatively little Ca(++).