P. D. Lewis

Poultry and coloured light

Poultry have four types of cone in the retina of the eye, and this means that they probably see colour differently from trichromatic humans. Notwithstanding the fact that humans and birds have maximum sensitivity in a similar part of the spectrum (545–575nm), poultry are likely to perceive light from various types of lamp at a different intensity from humans because they are more sensitive to the blue and red parts of the spectrum. Although colour has been confounded with illuminance in many trials, wavelength has an unquestionable effect on poultry production and behaviour. Growth and behaviour responses depend principally on retinal photoreception, whereas photosexual responses are mainly influenced by hypothalamic light reception. In turkeys and chickens growth under red illumination is inferior to that under blue or green light, and this may be a result of birds exposed to red light being more active and showing more aggression than birds exposed to shorter wavelength radiation. In contrast, the easier penetration of longer wavelength radiation to the hypothalamus makes red light more sexually stimulatory than blue or green, although the hypothalamic photoreceptors are more sensitive to blue/green light when illuminated directly. Egg production traits, however, appear to be minimally affected by wavelength.

Responses of domestic poultry to various light sources

More energy efficient and longer lasting lamps are being used to replace incandescent lighting in poultry houses. This paper reviews the responses of domestic fowl, turkeys and geese to various sou...

Photorefractoriness in broiler breeders: Sexual maturity and egg production evidence

1. Photorefractoriness was assessed in two lines of broiler breeders. In one trial, male-line and female-line pullets were reared on the floor and transferred to individual cages at 15 weeks. Birds were either maintained on 8-, 11- or 16-h photoperiods or transferred from 8- to 16-h photoperiods at 67 or 124 d. In the second trial, female-line pullets were concurrently housed in the same rearing facilities as trial 1 and transferred to adult floor-pens at 12 weeks. These birds were either maintained on 11- or 16-h photoperiods or transferred from 8- to 11-h or from 8- to 16-h photoperiods at 140 d. 2. In the cages, male-line and female-line birds responded similarly to the lighting treatments, but with the male-line maturing 1 to 2 weeks later than the female-line in each case. Birds on constant 11-h photoperiods matured 3 to 8 d earlier than constant 8-h birds, but 3 weeks earlier than constant 16-h birds. Birds photostimulated at 67 d matured at a similar time to constant 16-h birds, but almost 7 weeks later than those transferred from 8 to 16 h at 124 d. In the floor facilities, constant 11-h birds matured 3 weeks earlier than constant 16-h birds, but almost 2 weeks later than either of the photostimulated groups. Birds transferred from 8 to 16 h matured 4 d earlier than those transferred from 8 to 11 h. 3. Caged birds maintained on 16 h or transferred from 8 to 16 h at 67 d laid at least 24 fewer eggs, and had more hens not laying at 58 weeks, than birds maintained on 11-h days or those transferred from 8 to 16 h at 124 d. In the floor-pens, constant 11-h and both photostimulated groups produced about 20 more eggs to 56 weeks of age than the constant 16-h controls. 4. Collectively, these findings indicate that conventionally managed broiler breeders exhibit photorefractoriness. Additionally, a combination of photorefractoriness and controlled feeding appears to prevent broiler breeders from being photoresponsive until at least 10 weeks of age, and to cause some individuals still to be photoperiodically non-responsive at 18 weeks.

A model for predicting the age at sexual maturity for growing pullets of layer strains given a single change in photoperiod

A model is presented which will predict mean age at first egg (AFE) for pullets of laying strains reared under non-limiting environmental conditions but exposed to a single change in photoperiod during the rearing stage. An initial analysis of 12 previously reported trials involving a wide range of genotypes showed that the response to an increase in photoperiod is not simply the inverse of the response to an equal decrease in photoperiod applied at the same age. Maximum sensitivity to a reduction in photoperiod was found shortly before onset of lay, whereas maximum sensitivity to an increment in photoperiod was observed at around 10 weeks of age. Two experiments were conducted to provide further data. The first compared the effect of 3-h increases in photoperiod from 8 h to 11 h or from 11 h to 14 h with the double increment from 8 h to 14 h and also tested a reduction from 11 h to 8 h, all imposed at 17 weeks of age. AFE was advanced to a similar extent by the changes from 8 to 11 h and from 11 to 14 h (9.8 and 10.9 days respectively). Response to the double increment was not additive: AFE on this treatment was 13.3 days earlier than for constant 8 h controls. Reduction in photoperiod from 11 to 8 h at 17 weeks delayed AFE by 18.7 days compared with constant 11-h controls. In the second experiment, pullets of two strains were transferred from 8 to 16-h photoperiods and from 16 to 8 h at 5, 7, 9, 15, 17 and 19 weeks of age. Controls were kept on constant 8 and constant 16-h days. Transfer from 8 to 16-h photoperiods at 5 weeks of age had no effect on AFE. At 7 weeks there was a bimodal response with some pullets subsequently showing advanced maturity and others not. Maximum stimulation of early maturity (31 days on average for the two genotypes) was obtained at 9 weeks of age and response to stimulation declined linearly with age thereafter. The delay in AFE resulting from a reduction in photoperiod (16 to 8 h) increased linearly between 0 and 15 weeks. At 17 and 19 weeks, the response was bimodal, with some pullets maturing at the same age as long-day controls and others showing delayed maturity. Using all this evidence and some other unpublished data, a model is developed to predict AFE as a function of mean photoperiod and change in photoperiod during the rearing phase. Elements are incorporated to allow for the insensitivity of pullets younger than 50 days to an increase in photoperiod and the effect observed late in rearing when a change in photoperiod comes too late to alter AFE for the most precocious individuals in a flock. Two coefficients are required to adjust for genotype. One describes mean AFE for the genotype when reared on constant daylength and the other defines the rate at which age effects the response to a single change in photoperiod.

A model for the effect of constant photoperiods on the rate of sexual maturation in pullets

1. This paper reviews evidence from 15 experiments, reported over a span of 44 years, in which pullets were reared from hatching to sexual maturity on 2 or more constant photoperiods. 2. The evidence strongly indicates that earliest age at first egg (AFE) was observed when pullets were held on constant 10 h days (though earlier maturity is easily induced by increasing the photoperiod during rearing). The pair of equations which best describe the relationship between AFE (y, d) and photoperiod (x, h) are for x < or = 10 h, y = 175.8-1.731x; for x > or = 10 h, y = 155.5 + 0.301x. 3. This 2-straight-line model, hinged at 10 h, should be used in preference to curvilinear models published earlier, which wrongly predict that pullets reared on long days (14 h to 17 h) mature faster than birds reared on constant 10 h.

Constant photoperiods and sexual maturity in broiler breeder pullets

1. Broiler breeder pullets were maintained on 10-, 11-, 12-, 13-, 14- or 16-h photoperiods to determine the effect of constant photoperiods on sexual development in broiler breeders. The birds were fed to achieve a 2100 g body weight at approximately 17 or 20 weeks to see if the photosexual response was modified by rate of growth. 2. In both body weight groups, pullets maintained on 10 h were the first to reach sexual maturity (50 eggs/100 bird-d), and these and the 11-h pullets matured significantly earlier than any of the other photoperiod groups. Pullets maintained on 13 or 14 h matured latest, at about 3 weeks after the 10-h pullets, though both were only marginally later than the 12- or 16-h birds. These differences in maturation probably reflect the different rates at which photorefractoriness is dissipated in broiler breeders reared on photoperiods that vary in their degree of stimulatory competence. 3. There were no significant interactions among the photoperiods and the ages at 2100 g; faster-growing birds consistently matured about 10 d earlier than conventionally grown pullets.

Photoperiod and oviposition time in broiler breeders

1. Oviposition times were recorded for broiler breeder hens under 8-, 10-, 11-, 12-, 13-, 14- and 16-h photoperiods. 2. Mean oviposition time (MOT) was delayed relative to dawn by approximately 0·5 h for each 1-h increase in photoperiod up to 14 h, but was similar for 14- and 16-h photoperiods. However, the 0·5 h/h regression for the time when half the eggs were laid continued through to 16 h. 3. The rate of change in MOT for each 1-h increase in ≤14-h photoperiod was similar to that reported for early and modern egg-type hybrids, but, compared with modern genotypes, time of lay itself was 1 h later than white-egg and 2·5 h later than brown-egg hybrids. 4. At photoperiods ≤12·25 h, the number of eggs laid before dawn increased by 4·5% for each 1-h reduction in daylength.

Effects of environmental enrichment, fluorescent and intermittent lighting on injurious pecking amongst male turkey poults

1. Under commercial and experimental conditions domestic turkeys often cause injuries to pen-mates by repeated pecking, sometimes fatally. Environmental enrichment or lighting manipulations might be used to mitigate such injurious pecking. 2. This study examined responses to 4 treatments (2 rooms/treatment) of 8 groups of 100, non-beak trimmed, non-desnooded, male domestic turkeys from 1 to 35 d of age. 3. Birds of 1 treatment were reared under conditions approximating to commercial rearing (12L:12D incandescent, Control) whereas the experimental treatments were 12L:12D incandescent plus supplemental ultraviolet radiation, straw supplementation of litter, pecking substrates and visual barriers (Enriched), 12L:12D fluorescent lighting (Fluorescent), and 2(2L:3D):2L:12D incandescent (Intermittent). 4. Compared to control birds, the incidence of injuries caused by wing or tail pecking were both lower in the Enriched but not significantly different in the Fluorescent or Intermittent. 5. Injuries caused by head pecking did not occur in the Enriched rooms but were observed in at least 1 of the rooms with Control, Fluorescent and Intermittent treatments. 6. Despite considerable environmental differences between treatments, there was remarkable consistency within each type of injurious pecking in age at which injuries were 1st recorded (wing pecking, 9.38+/-1.31 d; tail pecking, 20.43+/-2.42 d; head pecking, 27.8+/-2.13 d). The roles of feather emergence, hierarchy formation in wild turkey poults and appearance of feathers are discussed as possible explanations of these consistencies.

Light intensity and performance of domestic pullets

Evidence from published trials is reviewed to investigate whether there is any need to change the recommended optimal light intensity for laying fowls from 5 lux. Although some recent trials have r...

Photoperiodic responses of broilers. I. Growth, feeding behaviour, breast meat yield, and testicular growth

1. A total of 7960 Cobb and Ross broiler males were reared in two trials to 35 d on various photoperiods between 2 and 21 h or under continuous illumination; a total of 444 birds were randomly selected at 35 d and retained for subsequent determination of breast meat yield and testicular weight at 40 or 54 d of age. 2. In both strains, feed intake and growth were positively correlated with photoperiod during the first 21 d, but afterwards feed intake was not significantly affected by photoperiods longer than 6 h and growth was negatively correlated with photoperiod beyond 12 h. Overall, to 35 d, there were no significant photoperiodic influences on either feed intake or growth for ≥6-h photoperiods, but significant depressions in feed intake and growth for photoperiods shorter than 6 h. Feed conversion efficiency was maximised by 12-h photoperiods, with decreases in efficiency above and below 12 h. Mortality was unaffected by photoperiod <12 h, but increased proportionately with photoperiod >12 h. The incidence of Sudden Death Syndrome (SDS) had an inverse relationship with photoperiod ≤10 h, but was positively correlated with photoperiod >10 h. The European Efficiency Factor was curvilinearly related to photoperiod, with the highest efficiency occurring at 12 h. Ross birds had significantly greater feed intakes but poorer feed conversion efficiencies than Cobb; differences in growth, overall mortality and the incidence of SDS between the strains were not significantly different. 3. By 5 d, birds given ≤15 h illumination had learned to eat in the dark, with the amount of feed consumed being inversely proportional to photoperiod; further increases in the amount of nocturnal feeding occurred between 5 and 20 d for ≤12-h photoperiods. The mean hourly rate of nocturnal feeding was consistently lower than diurnal feeding, irrespective of photoperiod. Nocturnal feeding patterns were similar for both genotypes. 4. Breast meat yield at 40 d was unaffected by photoperiod in Cobb birds, but significantly higher in continuously illuminated Ross birds than ≤21 h. At 54 d, breast meat yield was significantly higher in both genotypes given 21 h or continuous illumination and, overall, higher than at 40 d. 5. Testicular weights at 40 and 54 d of age increased with photoperiod in both genotypes to 12 or 15 h. Thereafter, weights plateaued for Cobb but decreased for Ross as the photoperiod was further extended to continuous illumination. 6. New EU welfare regulations come into effect on 30 June 2010 and these state that meat-chickens must have at least 6 h of darkness in each 24-h period, i.e. a maximum photoperiod of 18 h; compliance with the regulations should have no adverse effect on either performance or profitability.