IMPACT OF LIGHTING PARADIGMS ON POULTRY PERFORMANCE
Dr. R. Sreeranjani
M.V.Sc., Scholar
Veterinary College and Research Institute, Namakkal
Tamil Nadu Veterinary and Animal Sciences University, Chennai
In India, one among the fast growing industry in agricultural sector is the poultry industry. In the last four decades, there was a tremendous transformation from rural backyard activity into a commercial industry. The standard package of practices in all areas resulted in the huge tremendous growth rate in egg (4-6% per annum) and broiler (8-10% per annum) production which in turn contributes 0.8% total GDP of India. The unidirectional genetic selection of birds for rapid body weight gain resulted in many complications like increased fat deposition, decreased egg hatchability, higher incidence of metabolic diseases, visual anomalies, skeletal deformities and circulatory problems together with other unprecedented natural calamities such as flood, rain, drought, etc.,
Like other livestock species, birds rely on both external and internal environment for their growth, development, production and reproduction. Beyond genetics, environment plays a crucial role in poultry production. All external environments are mostly associated with climatic seasons and affect the poultry farming either directly or indirectly. Change of climatic parameters like temperature, relative humidity, precipitation, light, etc., indirectly affect the crop availability and its production, thence environment acts as a key factor in controlling internal physiological metabolism of birds. As poultry birds are photoperiodic and hence varying lighting program and system are needed to be properly managed together with emergency, poultry breeding, nutrition, welfare and advancement of technology.
NEURAL CONTROL OF PHOTOPERIODISM
Reproduction is regulated by hypothalamic-pituitary-gonadal axis which involves the sensory detection of light signal by means of positive and negative feedback loop operated at different levels via specific neuropeptides or hormones. One of the main key hormone is melatonin, secreted by supra chiasmatic nucleus (SCN) of pineal gland establishes rhythmic and synchronization of many essential bodily functions viz., thermoregulation, feeding pattern, behaviour, circadian rhythm, locomotor and reproduction. Unlike other mammals, neural control of birds differs markedly. An increased sympathetic fibre from SCN reduces melatonin secretion by increasing norepinephrine (inhibitory). During scotophase (short exposure to light), increased melatonin secretion inhibit GnRH, prevent reproduction while photophase (long exposure to light) decreased melatonin secretion stimulate GnRH (FSH and LH), triggers reproductive process in birds. On and off switch of GnRH control sexual maturation resulting in subsequent maturation of gonads and production of sex steroids like estrogen and progesterone.
Various lighting paradigms like intensity, duration, quality (spectrum, source, colour) of light influence the growth, production and reproduction of poultry farming. All these parameters depend on age, type of housing, etc.
LIGHT INTENSITY
WELFARE
- Lowered light intensity reduce the activity (calm), feather pecking, cannibalism and mortality and boost the immunity and disease resistance.
GROWTH
- BROILER
- During early first seven days of post hatch period, light intensity of 20lux is needed and thereafter during growing period reduced to 5 lux
- Less than 5 lux units will not stimulate the retinal photorecptors, hence unable to release GnRH.
- More than 40 lux units resulted in decreased yield and dressing percentage.
- Intermittent photoperiod increases weight gain, FCR, carcass yield and decrease mortality rate.
- LAYER
- For pullets, 5 – 10 lux units is needed except during first week.
- During laying period, intensity of 30 lux then reduced to 5lux unit during peak production.
- Delayed photostimulation in pullets resulted in increased egg weight due to delayed sexual maturity. Conversely as age at first egg is decreased, more peewee eggs laid.
- Intermittent light during scotophase for a period of 45min stimulate midnight feeding resulted in increased calcium availability for eggshell formation.
- LIGHT DURATION
a.BROILER
GROWTH RATE
- Duration of day length has an impact on growth.
- During first seven days of post hatch period, 0L:1.0D is required.
- Upto 14days, 0L:8.0D. Thereafter increase the day light gradually 2 to 4 hour with subsequent decrease in darkness from 8 to 4 hours.
- At 28 days of age, 0L:4.0D.
- Around 35days, 0L:2.0D and more than 35days, 23.0L:1.0D.
- At all age group, the highest growth rate for 20hours of day light and reduced growth rate for 14hours of day light whereas 23hours of day light had a negative impact on the growth rate.
- At market age beyond 49days, breast carcass yield increases at 20hours of light.
FEED EFFICIENCY
- Higher feed conversion ratio is recorded on 12L:12D in two phases of 6L:6D periods than 12L:12D in one phase in 24hours period.
- Improved FCR with 14 hours of light due to lower metabolism and decreased maintenance requirement during darkness, limit the free access to feed and diminish the growth rate.
WELFARE
- Decreased mortality rate in two split period of 12L:12D than one period of 12L:12D
- LAYER
- During the early critical period of 0 to 7 days, 23 hours of light is required to stimulate early feeding and reduce mortality. At this stage chicks are photorefractory, hence need to be exposed to short days slowly to eight hours (weekly intervals) thereby allowing time for controlled sexual maturity. Intensive genetic selection for early lay has a negative impact on reproduction of laying hen which in turn alters the age of photostimulation. Beyond maturation and age at first egg, photostimulation is required to boost the production during early laying period.
- Pullets require 8 to 10 hours photoperiod. Less than 8 hours of light delays laying process due to insufficient feed intake, low body weight and poor metabolic status. If more than 12 h of light is used, it leads to juvenile photorefractoriness.
- At 16-22 weeks of age, 14 hours light is mandatory to initiate laying phase.
- During active laying period, more than 12 hour photoperiod is required to maintain hypothalamic-pituitary-gonadal axis for proper follicular stimulation. Commercially 14 hours of photoperiod increase the production (330 eggs per annum i.e., 22 pause days) rate.
- Abrupt photostimulation resulted in early onset of maturation and lay, compared to slow stepping up of light hours thereby increase the total number of egg produced. Gradual increase in photoperiod (15 to 30 min weekly) promotes optimum egg production and egg weight whereas decrease in photoperiod will terminate the active laying period.
LIGHT QUALITY
- SPECTRUM
A minimum of 50Hz of current with wavelength of 500 to 700 nm commonly installed in poultry houses and if the source and wavelength are inadequate for avian vision, social disorders like pecking may arise.
- SOURCE
For economic reason of prolonged shelf-life and conservation of electric current, now-a-days incandescent (INC) bulbs where replaced with compact fluorescent (CFL), high pressure sodium light and light emitting diode (LED) types. A defined spectrum of light should be maintained in poultry shed for optimum growth and reproduction. The modern light sources like CFL and LED lack uniform spectral output (flickering) may affect the welfare of birds.
- COLOUR
Retinal photosensitive of birds is different from other livestock and human as they can able to perceive ultraviolet (350 to 450 nm) in addition to blue, green and red light (3 times more).
EFFECT OF LIGHT QUALITY ON PERFORMANCE OF BIRDS
| PERFORMANCE | RED | GREEN | BLUE | DARK | WHITE |
| BROILER | |||||
| Growth rate and FCR | Not affected | Stimulates at early age | Stimulates in older birds | – | – |
| Welfare | Active | Calm | Calm | – | Active |
| Immunity | Improved | – | – | – | Improved |
| Disease resistance | Reduced | – | – | – | Reduced |
| Fear response | Calm | – | – | – | Calm |
| Hatchability | Increased | – | – | – | Increased |
| Chick anomalies | None | None | – | – | None |
| Fear response during isolation | Reduced | – | – | – | Reduced |
| LAYER | |||||
| Sexual maturity | Improved | Decreased | No effect | – | – |
| Egg production | Increased | Decreased | Decreased | Random | |
| Hatchability | Improved | – | – | – | – |
| Egg size | Decreased egg weight (after 30 weeks of age) | Increased | Increased size with decreased width and
length
|
– | Decreased size with increased width and
length |
| Egg Shell thickness and shell strength | Decreased | Increased | Increased | – | Decreased |
| Welfare | Calm Decreased distress | – | Calm | – | Moderate |
| Feed intake | Increased | Decreased Feeding time with increased Foraging time | – | Decreased | Increased |
| Feather pecking/cannibalism | No impact | Increased | – | – | No impact |
CONCLUSION
Domestic poultry are photo periodic unlike mammals. Lighting program or photoperiodism organise the reproductive axis apart from vision, welfare concern of birds associated with the emergence of advancement in poultry breeding, nutrition and product technology. Birds require optimum light spectrum with higher energy for proper stimulation of retinal neuro photoreceptors with red spectrum being the most effective. Management of lighting programmes in poultry farming can minimize the undesirable problems and maximize the productivity and economy.
Keywords: Broiler, layer, photoperiodism, hypothalamic-pituitary-gonadal axis, light intensity, duration, spectrum, colour, growth, welfare
