PHOTOPERIOD

Photoperiod is defined as the hours of light to which the birds are exposed in a period of 24 hours. It is very important in poultry farming, since the metabolic activity and, consequently, the productive parameters, as well as the appearance of certain alterations, will depend on it.

Through lighting, suitable biorhythms can be obtained, which will have an important impact on the regulation of water and feed consumption, on hormonal production, as well as on the distribution of animals in the shed and on the homogeneity of the batches.

Therefore, the implementation of lighting systems that optimize biorhythms and, consequently, cause an improvement in production parameters and a reduction in mortality and certain pathologies is essential.

HOW DOES LIGHT INFLUENCE INDUSTRIAL BROILER BREEDING?

Prolonged periods of illumination in the photoperiod provide birds with more time for feed intake and digestion, which speeds up metabolism and growth, a desired effect in industrial farming.

However, excessively prolonged periods of light excessively accelerate the metabolic rate, which can lead to cardiovascular problems, such as ascites, that consequently increase mortality rate and locomotor problems, among others.

• Cardiovascular problems

In extended light periods (long photoperiods), the metabolic rate increases and so does feed and water intake, which helps to accelerate fattening. In this case, requirements for high oxygen levels also raise up.

As a consequence, the cardiac output is increased and, sometimes, the physiological capacity of the animal to provide oxygen levels can be exceeded, causing ascites syndrome and mortality increase. Therefore, proper lighting management becomes important, so that, on the one hand, animals grow as fast as possible and, on the other, prevent a metabolic excess that leads to death due to ascites. For this, it is necessary to maintain lighting that favors growth, but also to restrict it the minimum necessary to avoid increased mortality and the appearance of other alterations.

• Musculoskeletal disorders

Due to the fast growth of the broilers, musculoskeletal disorders can appear, mainly in the legs, such as tibial dyschondroplasia. In order to reduce these problems, it is very important to adjust the photoperiod and reduce the number of hours with light, because, in the dark, growth is limited. In addition, it is shown that a reduction of the light hours of the photoperiod during weeks two and three of the cycle leads to a reduction in musculoskeletal disorders, although the mechanisms are not fully defined.

LIGHT PROGRAMS IN BROILERS

The most common is that, during the first days, birds are provided with continuous light. In this way, the cycle begins with 24-hour photoperiods of continuous illumination in the reception of the chicks, which stimulates feed and water intake and, consequently, a good start of the breeding is guaranteed along with a good development of the digestive and immune system, as well as other organs. On the second day, an hour of darkness is applied, so that birds start to get used to the dark phase of the photoperiod.

Between days 5 and 7, when the chicks quadruple the birth weight, the dark hours are increased to about 6 hours, and the dark phase is progressively increased until about the third week. Then, the lighting hours are increased progressively again to promote growth in the final stages.

FACTORS TO TAKE INTO ACCOUNT IN LIGHTING PROGRAMS

When implementing a lighting program, several factors must be considered, some of them are included in the different international regulations. For example, regulations mention aspects related to light intensity, which should be at least 20 lux in 80% of the farm surface, although it is more important not to exceed maximum levels, to avoid causing stress to the birds. The obligation to maintain certain hoursof darkness, approximately 4 to 6, is also regulated, although this time differs according to international regulations.

The most important of these factors are:

• Light intensity

Light intensity is an important factor, since a high intensity is related to a greater activity of the birds. This greater activity is desired in the reception and acclimatization of the chicks to the farm and facilitates the fattening the first days of life. Therefore, in this initial phase the light intensity should be higher, and it will be reduced in later periods, once the birds have been acclimatized, so that they are more static, with less movement, which promotes fattening in the growing phases.

• Colour

Traditionally, to implement the different photoperiod programs in industrial broiler breeding, white, warm or cold light has been used. However, there are studies that show that green and blue spectra favor the fattening of birds, as well as immunity. Although, the color of the light in broiler chicken is not as important as in layers, where the red spectrum light produces an important hormonal stimulation that induces a higher egg production.

• Distribution

It is very important that the lighting systems are well distributed, so that the light reaches all parts of the shed. This avoids grouping of the birds in certain areas of the farm and competition for feeders and drinkers, which affects growth and homogeneity of the batches, as well as predisposes to the appearance of pathologies or locomotor disorders.

TYPES OF LIGHTING SYSTEMS

There are many types of lighting systems for poultry farms, all of them aimed at maintaining the lighting programs determined by the technician responsible for the farm.

There are different types of lamps such as incandescent, discharge or LED type, among others. All of them have different advantages and disadvantages, but the choice of one or another will depend on the availability and the decision of the technician, which should always be aimed at maintaining a homogeneous distribution of the lighting, as well as the intensity and spectrum required in each phase or each type of production.

For this, not only the type of equipment or lamps must be taken into account, but also the design and layout (the distance between the points of light and to the walls, the height, the number of lighting lines) and the characteristics for each phase, such as the spectrum or the intensity.

CONCLUSIONS

The photoperiod is very important in poultry industry because it has a direct effect on birds’ metabolic activity, the productive parameters and the appearance of certain, which depend on the hours of light and its intensity. It is, therefore, essential to design a lighting program that balances the activity of birds and the hormonal production, in order to optimize the level of production and minimize the possible arising problems. The responsible technician must take into account the different characteristics of the lighting equipment in order to implement a system that achieves adequate lighting times, intensity, spectrum and distribution for each phase and type of production.