No abstract

A retinal laser ellipsometer has been developed by coupling a Fourier ellipsometer to a laser scanning system. The instrument has been used to assess the origin and the amount of change in the state of polarization of a laser beam that has double passed the retina around the optic nerve head of postmortemhuman eyes. Eight eyes with no history of glaucoma were studied. At 200 points around the optic nerve head of each eye the Mueller matrices of the retina were examined for the amount of retardation, the orientation of the optic axis, and the amount of dichroism. The degree of polarization preservation of the detected light varied between 50% and 87%. Little dichroism was found, and there was no obvious correlation to the physical arrangement of any retinal structure. However, there was a substantial amount of linear uniaxial birefringence with the optic axis perpendicular to the incident laser beam. Furthermore the calculated optic axis direction showed a strong correlation with the physical orientation of the radial symmetrically arranged retinal nerve fiber axons around the optic nerve head. The local distribution of the corresponding retardation values showed two maxima that coincided with the areas of the thickest retinal nerve fiber layer. These results support the hypothesis that the thickness of the form birefringent retinal nerve fiber layer can be assessed by ellipsometric methods.

The assessment of the condition of the retinal nerve fiber layer plays an important role for the early detection of blinding eye diseases like glaucoma. We describe the application of a scanning laser polarimeter for quantitative measurements of the retinal nerve fiber layer thickness in vivo. The measuring beam of the scanning laser polarimeter is focused on the retina and penetrates the birefringent nerve fiber layer. The retardation of the light double-passing the nerve fiber layer is proportional to its thickness and is measured at 256 by 256 positions within a field of view of 15 by 15 degrees. The measurement time is less than 1 second. During the measurement, the polarization effects of the anterior segment of the human eye are canceled by a cornea polarization compensator. The retinal retardation values are displayed as a color coded map of the retinal nerve fiber layer thickness distribution.

-In order to find out whether a reduction in load-bearing on chicken legs would modify the activity and leg bone tissue, an original suspension device was developed in order to alleviate half of the weight-load on the legs. Thirty-six 5 d-old male meat-type chicks were assigned to 12 groups, each of 3 birds: a control bird (C), a bird equipped with a harness (H) and one equipped with a harness and suspended from a balance (S). The counterweights of the balance reduced the load on the legs by 50%. Behaviour in the birds was recorded twice for a 22-hour period. The birds were slaughtered at 19 d of age. Their legs were then weighed and the humeri, tibiotarsi and femurs were used for computation of length, biomechanical stiffness and composition. Tibiotarsi were also used for histomorphometry. Body weight at 19 d of age was significantly higher in the C birds (642 g vs. 586 g in the H and S groups, P < 0.05). The distance travelled as measured in the second week of the experiment was greater in S birds (338 m per 22 h vs. 246 in the C group and 252 in the H group, P < 0.05). The length of the tibiotarsi and femora was greater in the S birds when corrected for body weight (P < 0.05). Bone stiffness, composition and histological parameters were not significantly different in the 3 groups. We thus concluded that a reduction in load-bearing on the legs of young chicks enhances locomotor activity and longitudinal growth of leg bones. Bone quality was not affected, probably due to the contradictory effects of increased exercise and reduced weight.

This study investigates the effect of different LED lighting colour temperatures on the preference behaviour of 4-week-old weaned piglets. A total of 32 piglets were housed in two replications in an experimental pen area with four identically equipped pen compartments connected two by two. Each pen unit offered a compartment set to a colour temperature of 3000 kelvin and another set to 6500 kelvin, at 80 lux during the day. Each piglet could freely choose between the two compartments by using a passageway. Over a period of five weeks, the behaviours “lying”, “eating” and “activity” were video recorded for 72 h during the 1st, 3rd and 5th week of the experiment. The location of the piglet in the pen and its behaviour were determined by using time sampling. In the first week, the piglets preferred the colour temperature of 3000 K to perform all behaviours. In the following weeks this preference decreased. Results also show that feed consumption and soiling of the pens were higher under 6500 K. Pigs can differentiate between the different colour temperatures and use them for different behaviours. This can be used to divide pens into functional areas in order to better suit the behavioural needs of pigs.

Summary Selection of broiler strains for high body weight has changed the anatomical characteristics and in connection to that, the pattern of locomotion. In addition, rapid growing broilers show a high incidence of leg disorders which compromise the walking ability of the birds. Differences in the patterns of locomotion between laying hens and broilers and between broilers with and without leg disorders can be demonstrated and quantified by gait analysis. The gait pattern was recorded by videotracking. Three points of the body ‐ the cloacal region and both feet joints ‐ were marked by small patches of reflecting foils. The vertical and horizontal movements of the marked points were recorded by a camera in posterior position, while the bird was walking on a treadmill. The camera was connected with a PC‐operated videotracking system1. The vertical and horizontal movements of the 3 marked points were recorded simultaneously and plotted against the time axis. Kinetograms show clearly the differences in the walking pattern between broilers and layers. Layers place the legs directly under the centre of gravity and, therefore, the body moves in a straight line. Broilers, in contrast, move the centre of gravity step by step laterally towards the position of the supporting leg. This pattern may be caused by the anatomical characteristics of broilers. Limping in broilers with leg problems can be measured by differences in the lateral and vertical movements of the right and left leg.

No abstract

Little is known on the effect of light on pig behaviour. The choice behaviour of weaned piglets kept under two different light-emitting diode (LED) illuminance levels was investigated: 32 piglets (in two batches) were housed in a preference test room composed of two identical double pen units. One side of the pen unit was permanently illuminated with 600 lux, while the other was darkened to almost 0 lux (~0 lx); by using a passageway, piglets could move between the two sides. The “lying”, “eating” and “activity” behaviours were evaluated during three days in the first, third and fifth experimental week based on video recordings and a 5-min time sampling method. At first, piglets preferred to stay in the 600 lux illuminated compartments. Then, this preference decreased for the “eating” and “activity” behaviours and reversed for the “lying” behaviour, with the darkened compartments being preferred. The results also show that pen soiling was higher under 600 lux, but feed consumption was not affected by the illuminance. Since pigs choose between the two illuminance levels to perform specific behaviours, illuminance could be used to divide the pens into functional areas and, thus, help in meeting pigs’ behavioural needs.