(Weaver and Siegel, 1968; Newberry et al., 1985, 1988) and feather pecking ... 6Hitachi, VT-L3OED, Hitachi House, Hayes, Middlesex, UB3 4DR,. UK. increases ...
The Effects of Color and Intensity of Light on Behavior and Leg Disorders in Broiler Chickens D. S. PRAYITNO,1 C.J.C. PHILLIPS,2 and D. K. STOKES School of Agricultural and Forest Sciences, University of Wales, Bangor, United Kingdom ABSTRACT Two experiments were conducted to investigate whether manipulating the wavelength and intensity of light could be used to increase activity and reduce locomotion disorders in meat chickens. The first experiment examined the effects of wavelength and intensity of light on bird activity. Male (n = 60) and female (n = 48) chicks were reared from Day 1 to 35 in red or blue light at three intensities. Walking, standing, drinking, aggression, and wing stretching increased with intensity in red but not blue light. In the second experiment, the effects of stimulating bird activity with bright red light in the early or late part of the rearing period on locomotion and leg disorders were examined. Male (n = 24) and female (n = 24) chicks were reared from Day 7 in either dim blue light to Day 55 (Treatment All Blue), or bright red light to Day 22, followed by dim blue light to Day 55 (Treatment Early Red), or dim blue light to Day 22, bright red light to Day 38, and dim blue light to Day 55 (Treatment Late Red). Bright red light
considerably increased walking, feeding and stretching, particularly when applied early in the growth period. There were residual effects on activity after the birds had returned to dim blue light. Red light increased growth when provided at the beginning of the rearing period, but decreased it when provided later. Bone strength was reduced in treatment Late Red, which appeared to be related to the lower body weights of birds in this treatment. Bone length, weight, and torsion were not affected by treatment, but the tibia plateau angle was reduced by Early Red light in female birds. In Treatment All Blue, there was a high incidence of gait abnormalities, which was reduced by Early and Late Red light. It is concluded that rearing meat chickens in bright red light increases activity, which reduces locomotion disorders in the late rearing period. It is preferable to provide the stimulatory light early in the rearing period.
(Key words: light, wavelength, intensity, broiler, activity) 1997 Poultry Science 76:1674–1681
INTRODUCTION As a result of breeding meat chickens for rapid growth of breast muscle, there is considerable strain on leg muscles and bones during the last half of the growing period (Lilburn, 1994). Leg disorders are common and include tibial dyschondroplasia (Lynch et al., 1992), angular and torsional deformities of the tibiotarsal and metatarsal bones (Haye and Simons, 1978), femoral head necrosis, and bone fractures (Gregory, 1991). Leg disorders are more likely when poultry are inactive. Laying birds in aviaries have been recorded to move seven times as far as caged layers, and have stronger tibias as a result (McLean et al., 1986). The breaking strength of caged layers can also be increased
Received for publication March 10, 1997. Accepted for publication July 15, 1997. 1Current address: Faculty of Animal Sciences, Diponegoro University, Semarang, Indonesia. 2Current address and address for correspondence: Department of Clinical Veterinary Medicine, University of Cambridge, Cambridge, CB3 OES, UK.
when the birds spend a short period each day on an exercise machine (Meyer and Sunde, 1974). A proposed mechanism for this effect is the mobilization of calcium from bone during decreased dynamic loading (Lanyon, 1984, 1987). Light stimuli affect the activity, reproduction, and growth of chickens (Phillips, 1992). Wavelength and intensity are believed to affect activity, but it has been difficult to isolate the effects of these two light characteristics. Light sources of different wavelengths may be perceived as being of different intensity, even if the photometric recording of intensity is the same for both sources, because the spectral sensitivity of the photometer is unlikely to have the same spectral sensitivity as the tested birds (Nuboer et al., 1992; Prayitno and Phillips, 1997). Similarly, the spectral composition of some light sources changes with intensity, which may affect the birds’ responses. Notwithstanding these limitations, there are suggestions in the literature that high intensity light increases activity (Weaver and Siegel, 1968; Newberry et al., 1985, 1988) and feather pecking (Hughes and Duncan, 1972; Appleby et al., 1992) in chickens, and that red light
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increases the time that chickens spend pecking at the floor and conspecifics (noninjurious) and wing stretching compared with blue and green light (Prayitno and Phillips, 1997). There are also several reports that red light reduces cannibalism, due to the birds’ inability to see the blood on injured birds (Bowlby, 1957; Schumaier et al., 1968; North and Bell, 1993). In turkeys, blue light has also been found to reduce activity compared with white, green, or red light (Levenick and Leighton, 1988). Light stimulation of activity could potentially be used to reduce the incidence of leg disorders in meat chickens. Increasing the light intensity has already been found to reduce the incidence of leg abnormalities (Newberry et al., 1988), such as angular deformities of the tibia and tarsus, enlarged hocks, and tibial dyschondroplasia (Classen et al., 1991). The authors are not aware of any reports of positive effects of wavelength manipulation on leg disorders. The work of Prayitno et al. (1997), that suggests that certain aspects of activity are increased in red light, may have been complicated by different perceived intensities of the colored lights. An operant conditioning test to equate the perceived intensity of different colored lights has been developed by Prayitno and Phillips (1997), and this was used in an initial experiment to distinguish the effects of intensity and color of light on the behavior of meat chickens. A second experiment used these results to investigate the effects of a stimulatory light regimen, applied either in the early or middle period of growth, on the incidence of leg disorders and the behavior of meat chickens.
MATERIALS AND METHODS
Experiment 1 A replicated experiment was conducted in a controlled environment using 60 male and 48 female Ross broiler chicks. On each of two occasions, 54 birds were sexed at 1 d of age and within sex were allocated at random to six cages in light proof chambers. The cages measured 1.5 × 0.8 m, and were constructed with a wire mesh floor and solid sides. They each contained nine chicks (five males and four females) and one feeder and drinker. From 1 to 14 d of age, a starter pellet with 230 g CP and 3,100 kcal ME/ kg was fed, followed by a grower ration with 150 g CP and 2,485 kcal ME/kg up to the end of the experiment. The six cages were used for six treatments in a twofactor factorial design, with two different colored lights, red and blue, and three different intensities, high, medium, and low. The red and blue lights were produced from filters3 selected for their distinct wavelength patterns (peak transmission at 415 and 635 nm, respectively). The
3Filter 120 (deep blue) and 106 (primary red), LEE Filters Ltd., Andover, Hampshire, SP10 5AN, UK. 4Quantum Sensor, Delta-T Devices Ltd., Burwell, Cambridge, CB5 OEJ, UK. 5Panasonic Infra red camera, WV-1450/B, Mitsushita Electric Industrial Co., Ltd., Uxbridge, Middlesex, UB11 1DD, UK. 6Hitachi, VT-L3OED, Hitachi House, Hayes, Middlesex, UB3 4DR, UK.
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mean ratio of red to blue light intensity was set at 1.0:3.3, because it had been found by psychophysical testing that the chickens perceived these two colors as being of equal brightness at this ratio (Prayitno and Phillips, 1997). Filters were applied over 40 W tungsten filament lamps that were each connected to a dimmer switch used to vary light intensity. The light output of the filtered lamps was measured by a quantum sensor4 connected to an integrator, taking 15 readings in each cage at a height of 20 cm above the floor. Recorded light intensities for low, medium, and high intensity lights were 12, 18, and 30 × 1020 photons for the red lights and 36, 60, and 108 × 1020 photons for the blue lights. The photoperiod used was 23 h light and 1 h dark between 1400 and 1500 h (23L:1D). The temperature in each chamber was maintained at 30 C for the first 4 d, and then reduced by 1 C every 2 d until it reached 21 C on Day 23, which was then maintained until the end of the experiment. Maximum and minimum temperatures were recorded in each cage daily. Behavior was recorded every 5 min for each bird during each of the 23 lit h of the day, using a TV camera5 connected to a time lapse video recorder.6 At 5-min intervals, each bird was classified as feeding, standing, sitting, dozing, or sleeping. Dozing was recorded when the chicken was sitting with neck withdrawn, the head motionless, and the eyes either half closed or slowly opening and closing. If the bird’s neck was fully recumbent and the eyes permanently closed, it was recorded as sleeping. We also recorded whether any of the following events occurred for each bird during each 5-min period: walking, drinking, floor pecking, pecking other birds, and wing stretching. Each bird was weighed at Day 1 and at the end of the trial on Day 35, with weight gain calculated from these two values. Feed consumption was measured daily for each cage.
Experiment 2 Twenty-four female and 24 male Ross broiler chicks were sexed at 7 d of age and within sex were allocated at random to 12 cages in three light-proof chambers. Each cage contained two female and two male birds, a feeder, and drinker. The temperature and photoperiod for each chamber were as described in Experiment 1. Three lighting treatments were selected to stimulate bird activity through a combination of color and intensity at two times in the growing phase. The experiment was divided into three periods for the purposes of applying light treatments: Period 1, Days 7 to 22; Period 2, Days 23 to 38; and Period 3, Days 39 to 55. The following three treatments were randomly allocated to the three chambers: 1) Treatment All Blue: dim blue (from Day 7 to 55); 2) Treatment Early Red: bright red (Days 7 to 22), followed by dim blue (Days 23 to 55); 3) Treatment Late Red: dim blue (Days 7 to 22), followed by bright red (Days 23 to 38), and then dim blue (Days 39 to 55). Red and blue light sources were the same as in Experiment 1. In order to stimulate activity in the red
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light, a mean intensity of 860 × 1020 photons was used for red light and 1.5 × 1020 photons for blue light. Gait Abnormalities. Each bird was assessed daily for locomotion disorders, using the following classification system: 0, normal movement; 1, intermittent detectable abnormality in gait; 2, permanent detectable abnormality in gait; 3, abnormal gait but able to walk; 4, only able to take one or two steps at a time; and 5, unable to walk. Bone Characteristics. At the end of the experiment, the birds were slaughtered humanely by neck dislocation. Bone length, weight, and strength were measured within 1 h of slaughter. Bone strength was determined by breaking the right and left tibia on an Instron 4301 tensiometer, using a three-point bend with supports 60 mm apart and a load applied at 50 mm/min to the mid point of the long axis of the bone (Knowles and Brown, 1990). The parts of the tensiometer that were in contact with the bone were covered in soft rubber tubing to avoid point stresses. The breaking strength was recorded as the peak load before the bone broke. A histopathological examination was made to assess the degree of tibiotarsal bowing in a ventrodorsal plane by calculating the tibia plateau angle (Lynch et al., 1992). The
long axis of the bone was established by drawing a straight line from the proximal to the distal end of the tibia. A second line was drawn perpendicular to the long axis bisecting the proximal extremity of the cnemial crest. The tibia plateau angle was measured between this perpendicular line and a line from the proximal crest across the surface of the condyles. Torsional measurements were made by comparing the transverse axes of the proximal and distal articular surfaces of each tibia, following the procedure of Duff (1985). Measurements were recorded as external or internal depending on the orientation of the distal relative to the proximal articular surface of the bone. Behavior. Behavior was recorded every 5 min for each bird during each of the 23 lit h of 1 d/wk, using the same procedure as in Experiment 1.
Statistical Analysis Broiler behavior and growth was tested for normal distribution before analyzing for statistical significance of treatment differences by analysis of variance, using a
TABLE 1. The behavior of broilers in red and blue lights of different intensity, Experiment 11 Statistics2
Treatment means Intensity
Red vs blue
Behavior
Color
Low
Medium
High
Feeding, min/h
Red
18.6
18.3
20.0
Standing, min/h
Blue Red
16.4 6.2
15.1 9.0
18.4 10.0
Sitting, min/h
Blue Red
7.7 10.2
7.1 9.7
7.4 10.7
Dozing, min/h
Blue Red
12.4 10.9
12.2 10.8
12.4 8.2
Sleeping, min/h
Blue Red
13.4 16.2
14.1 14.1
14.2 11.1
Walking, no./bird/h
Blue Red
8.1 3.7
9.4 4.5
7.6 4.8
Drinking, no./bird/h
Blue Red
3.2 1.57
3.7 1.61
3.5 1.62
Floor pecking, no./bird/h
Blue Red
1.55 1.24
1.53 1.15
1.58 1.15
Wing stretching, no./bird/h
Blue Red
0.98 0.32
0.97 0.33
0.98 0.45
Aggression, no./bird/h
Blue Red
0.18 0.07
0.18 0.07
0.26 0.16
Blue
0.03
0.03
0.05
1Four
Color × intensity
SED
P
SED
P
SED
P
0.29
