K. Schwean-Lardner

Effect of light intensity on broiler production, processing characteristics, and welfare

Manipulation of light intensity is an important management tool affecting broiler production and well being. Despite considerable research on light intensity, there is still a debate on the optimum level to be used for intensively housed broilers. Two trials were conducted with the objective of investigating the effect of light intensity, within the practical levels at confinement barns (1, 10, 20, and 40 lx), on production, processing characteristics, and welfare of broilers raised to 35 d of age. Each light intensity treatment was replicated in 2 environmentally controlled rooms in each trial with 950 Ross × Ross 308 chicks per room. Data were analyzed as a randomized complete block design with trial serving as a block. All chicks were exposed to 40 lx of light intensity and 23 h of light for the first 7 d followed by treatment light intensity and 17 h of day length thereafter. Body weight and feed consumption were determined at 7, 14, and 35 d of age. At the end of each trial, 60 birds per treatment were processed to determine the detailed meat yield. Skeletal and footpad and ocular health were monitored at 31 and 32 d of age, respectively. Body weight, feed consumption, feed:gain ratio, and mortality were unaffected by light intensity. Carcass, thigh, and drum yield as a percentage of live weight decreased linearly with increasing light intensity. The 1 lx treatment resulted in heavier wings as a percentage of live weight. Light intensity had no effect on skeletal health, but ulcerative footpad lesions decreased linearly with increasing light intensity. Birds exposed to the 1 lx treatment had heavier and larger eyes. In conclusion, light intensity did not affect broiler production and mortality but did affect carcass characteristics. The 1 lx light intensity treatment had a negative effect on broiler welfare as demonstrated by increased ulcerative footpad lesions and eye size.

The effects of lighting programmes with twelve hours of darkness per day provided in one, six or twelve hour intervals on the productivity and health of broiler chickens.

Experiment 3 subjected 4 groups of three 40-dold broilers to alternating light intensities (5 and 100 lux) of 2-h durations. The activity of the broilers was recorded continuously for the duration of the experiments (1 d for experiment 1, 2 d for experiment 2 and 1 d for experiment 3) via top-view video-cameras describing the overall amount of movement on a group level as a function of time and light intensity. The analyses were hence based upon pen-level activity within each time unit and appreciated the autocorrelating repeated measures of activity. The activity of the birds changed very clearly with the light intensity as shown in the figure, with a significant increase in the activity of the birds during the 100 lux periods over the 5 lux periods (repeated measures analysis, F(1,5682)1⁄4 1738.77, P < 0.0001). The results from experiment 2 suggest that alternating light schedules enhance this effect of light intensity upon activity (repeated measures analysis, F(1,3051)1⁄4 710.35, P < 0.0001). When comparing the dynamic responses of broilers, using data-based mechanistic modelling (Aerts et al., 2000), the broilers responded fastest to the light change at 21-22 d of age (repeated measures analysis, F(2,81)1⁄4 25.08, P < 0.0001). Behavioural scan samples from experiment 1 showed no difference between the number of birds feeding and drinking in the different light intensities (ANOVA, F(1,14)1⁄40.04 and 0.44, P1⁄4 0.8533 and 0.5159, respectively). The results suggest that it may be possible to use changes in light intensity to control the activity of broiler chickens. The results also indicate that the variation in the activity level during an alternating light schedule is higher than in constant light, which may suggest more synchronisation of behaviour in the group. The increasing responsiveness of the broilers towards the end of the photoperiod may reflect an anticipation of the dark period probably enhancing the motivation for visually mediated behaviours such as foraging and increasing the reinforcing effects of light intensity during this period. Overall, the results provide the first evidence that it may indeed be possible to control activity of broiler chickens using step-wise changes in light intensity and also highlights the need to study the dynamics of behavioural responses in the future.

Effect of day length on cause of mortality, leg health, and ocular health in broilers

An experiment was conducted to study the effect of day length, sex, and genotype (Ross × Ross 308 and 708) on mortality causes, bird mobility, footpad health, and ocular size, with 4 trials within the experiment. Four graded day lengths were chosen to allow the study of relationship between day length and health parameters, including 14L:10D, 17L:7D, 20L:4D, and 23L:1D. The primary statistical tools used to assess the day length relationships were regression analysis (Proc Reg and RSReg of SAS). Data were also analyzed as a 4 (lighting program) × 2 (sex) × 2 (genotype) factorial arrangement. Total mortality, as well as mortality due to metabolic and skeletal disease, decreased linearly with increasing inclusion of darkness (7- to 32-, 7- to 38-, and 7- to 48-d periods). Infectious disorders were quadratically related to day length (7- to 48-d period only), with birds under 20L having the highest level. Day length was linearly or quadratically related to average gait score in a positive fashion, and the incidence of birds falling in painful gait score categories increased linearly with increasing day length. Average footpad lesion scores increased with increasing day length (28 and 35 d). The 23L photoperiod resulted in heavier eye weights than other lighting programs. Males had a higher mortality and morbidity rate and a higher average gait score than females. Average footpad score was lower for males than females (28 and 35 d). Overall mortality was higher for 308 than 708 broilers; hence, levels of specific mortality causes were higher. Average gait scores were lower for 308 than 708 birds in 2 of the 3 time periods measured and footpad lesions were higher. To conclude, many aspects of broiler health improve with decreasing day length.

Impact of daylength on the productivity of two commercial broiler strains

1. The impact of daylength on productivity in male and female broilers of two genotypes was studied in two replicated experiments. In each experiment, four lighting programs (14L:10D (14L), 17L:7D (17L), 20L:4D (20L) and 23L:1D (23L)) were used to study the relationships between productivity and daylength in two genotypes and both genders. 2. General Linear Model analysis was used to test for differences in daylength, genotype, gender and their interactions, and regression analysis to define relationships between productivity and daylength in experiment one and daylength differences in experiment two. 3. In experiment one, body weights at d 32 (P = 0·002) and d 39 (P = 0·011) were related in a quadratic fashion to daylength, with the heaviest birds raised under 20L. The growth curve at d 49 was similar in shape, and body weights under both 17L and 20L were significantly higher than under 14L and 23L (P < 0·001). In experiment two, data were similar, although the quadratic relationship was not significant. 4. Feed consumption was highest to d 39 or d 49 under 20L, and birds under 23L ate as much (d 39) or less feed (d 49) than under 17L. 5. Gain-to-feed efficiency (FCR) responded in a quadratic fashion, with maximum efficiency observed under the shortest daylength. 6. Mortality increased linearly with daylength for all time periods in both experiments.

Effect of day length on flock behavioural patterns and melatonin rhythms in broilers

Abstract 1. Ross × Ross 308 male broilers were used to study the impact of 14, 17, 20 and 23 h of light (L) on flock behavioural patterns and 24 h melatonin rhythm synchrony during the photophase. 2. Behaviour in two pens (n = 53) per lighting treatment was digitally recorded for 24 h in trial 1 (27–28 d of age (d 27)) and two (42–43 d (d 42)), and quantified using a scan sampling technique at 10 min intervals. Regression procedures were used to test flock trend analysis between behavioural (resting, standing, walking and feeding) variables and time during the photophase. 3. The presence of a flock melatonin rhythm was determined by radioimmunoassay of blood samples collected at 6 times for birds raised on 23L and 8 times for 14, 17 and 20L birds (n = 6 per time) over a 24 h period (d 21) in experiment 1. 4. Quadratic and linear relationships between time and behaviour during the photophase were frequent in 14L and 17L birds, sporadic in 20L birds and non-existent in 23L birds. Relationships were noted in inactive resting (d 27: 14L and 17L; d 42: 14L and 20L), walking (d 27: 14L and 17L), standing (d 27 and d 42: 14L, 17L and 20L) and feeding (d 27: 14L and 17L). A quadratic time × melatonin relationship existed in 14L, 17L and 20L flocks only. 5. Behaviour during the photophase and 24 h melatonin production indicates that flocks exposed to 23L do not develop synchronised rhythms, increasing the risk of suffering from sleep fragmentation.

Minimum light intensity threshold to prevent negative effects on broiler production and welfare

Abstract 1. Research focused on lower light intensity levels is required to set minimum standards appropriate for production and welfare of intensively housed broilers. The objective of this research was to study light intensity (0.1 to 10 lx) effects on Ross × Ross 308 and 708 genotypes. 2. Three experiments (35 d each) using 18 720 broilers were conducted with the initial experiment using two replicates of 0.1, 1, 5 and 10 lx. The second and third experiments examined 0.5, 1, 5 and 10 lx with treatments replicated twice in each experiment in a randomised complete block design with experiment acting as a block. In each experiment, mixed sex broilers from each genotype were housed in 6 equally sized pens per room. 3. In Experiment 1, the introduction of 0.1 lx at d 7 caused high levels of mortality and poor growth rate from d 7 to 14 and was discontinued. 4. In Experiments 2 and 3, increasing light intensity increased body weight gain (0–35 d) and feed intake (0–35 d) in a quadratic and linear fashion, respectively. Similarly, mortality corrected gain to feed ratio (FCR, 0–35 d) demonstrated a quadratic response with a maximum at 5 lx. Carcass, breast meat and skin, abdominal fat and drum skin, as a percentage of live weight, increased while drum bone and wing yield decreased in a linear fashion with increasing light intensity. Total carcass composition was unaffected by light intensity. 5. Genotype effects were numerous. No interactions were found between genotype and light intensity. 6. Ocular dimensions and the incidence of foot pad lesions decreased in a quadratic and linear fashion, respectively, with increasing light intensity. In contrast, welfare-associated gait score and mortality levels were not affected by light intensity. 7. It was concluded that performance, breast meat yield and bird welfare improved with increasing light intensity. The data support 5 lx as a minimum light intensity in broiler production.

The effect of toe trimming on behavior, mobility, toe length and other indicators of welfare in tom turkeys

Society is increasingly concerned about the welfare of animals kept for food production, for this reason, invasive procedures such as toe trimming in turkeys must be studied to assess the corresponding welfare implications and to ensure such procedures are acceptable for continued use. To this end, research was conducted to evaluate the welfare effects of toe trimming on toms raised to 140 d. The study used 306 Hybrid Converter toms, half of which were toe trimmed using a Microwave Claw Processor (MCP) which group are denoted T, and half of which were sham treated but not trimmed, which group are denoted NT. Turkey behavior was observed on d 1, 3, 5, and 133. Toe cross sections were taken every second day for 14 d after treatment and were used to histologically examine the healing process. Toe length, gait score, and bird stance were assessed on d 55, 84, 119, and 139. For the first 5 d after treatment, T birds demonstrated less active behaviors such as feeding, standing, walking and running (P ≤ 0.05), indicative of pain with the effect diminishing with age. At d 133, T turkeys stood more and walked less than NT birds (P ≤ 0.05). Gait score and bird stance were not affected by treatment. Trimmed toes were on average 91.9% of the length of NT toes and toe length was more variable (P ≤ 0.05) as a result of the trimming process. Histological examination indicated T toes had complete epithelium closure over the healthy tissue by d 8 and were fully healed by d 14. Although bird mobility and stance were unaffected by treatment, turkey behavior both early and late in the production cycle were suggestive of pain and balance effects; both indicators of reduced welfare as a result of toe trimming.

The impact of graded levels of daylength on turkey productivity to eighteen weeks of age

The impact of graded levels of day-length on the productivity of hens and toms was studied in two trials. Daylength treatments (trts) were 14 (14L), 17 (17L), 20 (20L), and 23 (23L) h and were started at 10 d of age. Turkeys (720 hens and 480 toms) were randomly allocated to 8 rooms (2 rooms per lighting trt) with six pens (3 hen--30 per pen and 3 tom--20 per pen) per room in each trial. Body weight (BW) was assessed at 0, 10, 21, 42, 63, 84, and 126 d of age; feed consumption (FC) was measured for the time periods between body weight determinations and feed efficiency (G:F; g of gain/g of feed) was calculated from BW and FC values. Birds were checked daily for mortality and culls, and affected birds were sent for necropsy. Data were analyzed according to a completely randomized block design with trial as the block and rooms nested within lighting trts. Regression analysis was used to study the relationship between dependent variables and daylength. Significance was declared at P≤ 0.05 and trends at P≤ 0.10. At both 21 and 42 d, body weight increased linearly with increasing daylength. At 84 d weights of toms decreased in a quadratic fashion and hen weights were unaffected. At 126 d, both tom and hen weights decreased linearly as daylength increased, with the magnitude of response gender dependent. Feed consumption corresponded with body weight changes, increasing for d 10 to 21, and 21 to 42 and decreasing for d 63 to 84, 84 to 105, and 105 to 126 with increasing daylength. Feed efficiency (G:F) was not affected by daylength for 10 to 84, 10 to 105 and 10 to 126 d periods. The incidence of mortality and culling was not affected by daylength for the 10 to 84 d period, but increased in a quadratic manner with increasing daylength for the 10 to 105 and 10 to 126 d periods. To conclude, daylength affects the growth and feed intake of turkeys in an age and gender-specific manner, and mortality and culling increase with longer daylength.

Effect of prolonged photoperiod on ocular tissues of domestic turkeys

OBJECTIVE The objective of this study is to investigate the structural and functional ocular changes that develop in turkeys exposed to a photoperiod of 23 h of light (23L) compared with a photoperiod of 14 h of light (14L). PROCEDURES Ten-day-old Nicholas heavy strain poults were exposed to either a 14L or 23L photoperiod. Between 16 and 18 weeks of age, equal numbers of turkeys per treatment group underwent ophthalmic examination (biomicroscopy, indirect ophthalmoscopy) (n = 14), refractometry (n = 20), keratometry (n = 20), tonometry (n = 20), and full-field electroretinography (ERG) (n = 14). Postmortem analyses included orbital magnetic resonance imaging (MRI) (n = 10) and light microscopy (n = 24) at 18 weeks of age. RESULTS Autorefraction revealed a median of -0.13 for sphere in both groups (P = 0.69), which is approximately emmetropia. The radius of curvature of the cornea was significantly higher (P = 0.0001) and the refractive power of the cornea was significantly lower (P = 0.0001) in the 23L group. The astigmatic power was significantly greater in the 23L group (P = 0.0001). Mean intraocular pressure did not differ between groups (P = 0.085). Turkeys from the 23L group had significantly larger globes in nasotemporal (P = 0.0007), dorsoventral (P = 0.015), and anterioposterior (P = 0.021) directions, and anterior chambers were more shallow (P = 0.0002). ERGs revealed the 23L group to have lower a- and b-wave amplitudes and significantly lower cone flicker amplitudes (P = 0.0008). Light microscopic examination revealed 23L turkeys to have significantly decreased numbers of nuclei in the outer nuclear layer (P = 0.0001) and inner nuclear layer (P = 0.0186), and decreased choroidal thickness (P = 0.0008). The prevalence of cataract in the 23L group was significantly higher (P = 0.001). CONCLUSIONS Exposing turkeys to a prolonged photoperiod induces significant ocular disease.

The impact of graded levels of day length on turkey health and behavior to 18 weeks of age

The impact of graded levels of day length on turkey health and behavior was determined in hens and toms raised to 18 wk of age. Birds were allocated to one of 4 lighting treatments (trt) providing 14 (14L), 17 (17L), 20 (20L), and 23 (23L) h of day length. Two time-replicated trials were completed with each, providing 2 rooms per lighting trt and each room having 3 hen (n = 720) and 3 tom (n = 480) pens. Data collection included gait score (GS), the incidence of footpad dermatitis (FPD), breast buttons and blisters, ocular size and pressure (males only), and behavioral observations (males only). Data were analyzed using SAS 9.3 based on a completely randomized design nested within 4 lighting trt. Regression analysis established relationships between response criteria and day length. Differences were considered significant at P ≤ 0.05 and trends noted at P ≤ 0.10. Gait score, FPD, and the incidence of breast buttons and blisters were assessed on 5 birds per pen at 11 and 17 wk of age. Average GS increased linearly with day length at 11 and 17 wk for both hens and toms, but the effect was larger in toms. Day length did not affect FPD, but more lesions and severe scores were found for hens than toms. The presence of breast buttons and blisters increased linearly with day length (11 wk) with the effect on blisters predominately seen in toms. Eye weight and size increased with increasing day length at 12 and 18 wk. Ocular pressure was not affected by day length. Infrared cameras recorded tom behavior over a 24 h period, and behaviors were classified over 10-min intervals using a scan sampling technique at 11 and 17 wk. Alterations in behavioral repertoire were observed with a linear increase in inactive resting and a linear decrease in standing, walking, preening, and environmental and feather pecking behaviors with increased day length. To conclude, day length affected bird mobility and incidence of breast blisters in an age- and gender-specific manner, and time spent inactive increased with longer day length.